ML20133F946

Transcript of ACRS Matls & Metallurgy & Severe Accident Subcommittees Joint Meeting on 970109 in Rockville,Md.Pp 1- 135

ML20133F946
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Issue date:	01/09/1997
From:	Advisory Committee on Reactor Safeguards
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ACRS-T-2088, NUDOCS 9701150074
Download: ML20133F946 (140)

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Official Trcnscript cf Prece dings Q

NUCLEAR REGULATORY COMMISSION VCI?ST-2088

Title:

Advisory Committee on Reactor Safeguards 3

Materials and Metallurgy & Severe Accident Subcommittees Joint Meeting TRO4 (ACRS) i Docket Number:

(not applicable)

RETURN ORIGINAL TO BJWHITE M/S T-2E26 415-7130 THANKS!

Location:

Rockville, Maryland O

Date:

Thursday, January 9,1997 11 4 970109 T-2088 PDR Work Order No.:

NRC-956 Pages 1-135 l/

og NEAL R. GROSS AND CO., INC.

Court Reporters and Transcribers 1323 Rhode Island Avenue, N.W.

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140112 AC18'B$$)$$y" yb DO NOTREMOVE FROM ACRS OFFICE

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UNITED STATES OF AMERICA 2

NUCLEAR REGULATORY COMMISSION 3

+++++

4 ADVISORY COMMITTEE ON REACTOR SAFEGUARDS (ACRS) 5 JOINT MEETING 6

MATERIALS AND METALLURGY 7

AND 8

SEVERE ACCIDENT SUBCOMMITTEES 9

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10 THURSDAY 11 JANUARY 9, 1997 12

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13 ROCKVILLE, MARYLAND

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V 14 The Subcommittees met at the Nuclear 15 Regulatory Commission, Two White Flint North, Room T2B3, 16 11545 Rockville Pike, at 12:30 p.m.,

Robert Seale, Acting 17 Chairman, Materials & Metallurgy Subcommittee, presiding.

18 COMMITTEE MEMBERS:

19 ROBERT L.

SEALE Acting Chairman 20 GEORGE E. APOSTOLAKIS Member 21 IVAN CATTON Member 22 MARIO H.

FONTANA Member 23 THOMAS S.

KRESS Member 24 DANA A.

POWERS Member fm s

Q 25 WILLIAM J.

SHACK Member NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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ACRS STAFF PRESENT:

2 Noel Dudley

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Sam Duraiswamy 4

John Larkin 5

Richard Savio l

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Mike Markley 7

Paul Boehnert 8

Amarjit Singh 9

10 ALSO PRESENT:

11 Ashok Thadani 12 Bob Jones i

13 Jack Strosnider I

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14 Gary Holahan 15 Tom King 16 Joe Murphy 17 18 19 20 21 22 23 24

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A-G-E-N-D-A 2

Acenda Item Pace I

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3 Opening Remarks, Acting Chairman Seale 4

4 Staff Opening Statement, Mr. Thadani 6

5 Use of PRA in the Regulatory Process 6

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Steam Generator Rule 28 1

7 Summary and Schedule for Next ACRS Meeting 116 8

9 10 11 12 13

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16 17 18 19 20 21 22 23 l

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P-R-O-C-E-E-D-I-N-G-S 2

(12:34 p.m.)

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3 ACTING CHAIRMAN SEALE:

The meeting will now 4

come to order.

This is a meeting of the ACRS Joint l

5 Subcommittee on Materials and Metallurgy and Sever 6

Accidents.

7 I am Robert Seale, Acting Chairman of the 8

Subcommittee.

9 The ACRS Members in attendance are:

Mario 10 Fontana, George Apostolakis, Ivan Catton, Thomas Kress, 11 Dana Powers, and William Shack.

12 The purpose of this meeting is to hold 13 discussions with representatives of the NRC staff to ex I

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14 gather information concerning the risk-informed, 15 performance-based rule and regulatory guide associated 16 with steam generator tube integrity.

The Subcommittee 17 will gather information, analyze relevant issues and 18 facts, and formulate proposed positions and actions as 19 appropriate, for deliberation by the full Committee.

20 Noel Dudley is the Cognizant ACRS Staff 21 Engineer for this meeting.

22 The rules for participation in today's meeting 23 have been announced as part of the notice of this meeting i

1 24 previously published in the Federal Register on December l

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25 24, 1996, and January 6, 1997.

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A transcript of the meeting is being kept and l

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will be made available as stated in the Federal Register 1

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3 Notice.

It is requested that the speakers first identify 4

themselves and speak with sufficient clarity and volume so 5

that they can be readily heard.

6 We have received no written comments or 7

requests for time to make oral statements from members of 8

the public.

9 Yesterday, we received a letter from the 10 Nuclear Energy Institute concerning the proposed steam 11 generator rule.

A copy of the letter has been provided to 12 each member of the Committee.

13 The ACRS last met with the staff to discuss

'\\m/p) 14 the proposed steam generator integrity rule on November 7, 15 1996.

Based on discussion with the staff and industry 16 during that meeting and previous meetings, we commented on 17 the proposed rule in a letter to the Executive Director 18 for Operations dated November 20,1 996.

19 The staff recently responded to our comments 20 in a letter dated January 2, 1997.

The staff concluded 21 that additional meetings of ACRS were appropriate to 22 further discuss the specifics of the proposed rulemaking.

23 Today, we plan to discuss the use of 24 probabilistic risk assessments in the regulatory process, C'i

( j 25 specific to the steam generator rule.

At a later meeting, NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHoDE ISLAND AVE., N W.

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we plan to review the technical basis and the regulatory l

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2 analysis associated with the rule.

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We will proceed with the meeting and I call l

4 upon Mr. Thadani of the Office of Nuclear Regulation to l

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begin.

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MR. THADANI:

Thank you very much.

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I just want to note first that the Agency is 8

moving forward in using risk-informed thinking in 9

essentially all of its activities.

Thus, the issue of 10 steam generator tube ruptures and the rule-making effort 11 is just one of many such activities.

12 It is pretty important to make sure that we 13 can share some thoughts on some of the broad issues and

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14 have a dialogue on that first and then to see how the 15 steam generator rule-making activity fits into that 16 framework.

17 I want to thank you also for having had a very 18 extensive dialogue with the staff on various documents 19 that we are preparing in support of using risk-informed in 20 our decision-making process.

21 In particular the letters that you sent us 22 August 15 and November 18 have been very helpful.

The 23 sense that we have is that we are moving together in these 24 areas.

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25 The letter that came on November 20 on the

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steam generator rule raised some questions in our minds.

2 It seemed to us that rather than sending letters back and 4

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rth it would be useful to have a dialogue.

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4 We do not have any prepared presentations l

5 today, but it would be helpful if I can just take a few l

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minutes and go over some of the upcoming activities and l

7 the background that has gotten us to where we are today.

8 First, in terms of the planned interactions 9

with the ACRS, the staff is revising the general 10 regulatory guide and the standard review plans.

The 11 previous draft was reviewed at senior management level 12 that includes the office directors and the comments have 13 been provided to the staff.

We expect a revised version j'~'\\

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14 to be available on January 17.

15 It is my expectation that that guide will be 16 fairly close to the final guide.

We have had enough 17 internal dialogue that I feel reasonably comfortable that 18 that is going to happen.

19 That report could then form the basis for 20 Subcommittee meetings on January 28 and 29; whether it is 21 one day or two days is up to you.

22 We will also provide to the ACRS the 23 application-specific reg. guides and standard review 24 plans, the first week in February.

O) 25 We will get the information to you before the

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1 full Committee meeting but of course I am not sure that 2

that makes a lot of difference.

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3 ACTING CHAIRMAN SEALE:

When you say 4

application-specific, do you mean to the steam generator 5

rule?

6 MR. THADANI:

No.

What I mean is we have a 7

number --

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8 ACTING CHAIRMAN SEALE:

Okay, I know which 9

ones you mean.

10 MR. THADANI:

I will come back to the steam 11 generator rule.

I am sort of going over all the documents 12 because they have relevance to what we are doing in terms of a number of rule-making activities, one of which is the 13

'V 14 steam generator rule.

15 ACTING CHAIRMAN SEALE:

Sure.

16 MR. THADANI:

My understanding is that then, 17 the February 20 and 21 meeting will cover the application 18 specific reg. guides and standard review plans and that 19 the Committee would meet in March with the view toward 20 sending a letter to the Commission.

21 That's the general schedule on these guides 22 and standard review plans that use risk-informed thinking.

23 The steam generator rule is sort of a little bit behind in 24 terms of the schedule.

O 25 We are expecting to get the regulatory

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analysis and the risk assessment in terms of the 2

activities on steam generator rule-making to you in the

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3 middle of February.

I understand that there will be a 4

meeting in the end of February to go over the steam 5

generator rule-making package.

6 That is the schedule that we are working on, 7

risk-informed guidance first and soon after, the steam 8

generator or application-specific aspects.

9 MEMBER APOSTOLAKIS:

So, I was handed here a 10 proposed agenda for the PRA Subcommittee meeting whicn is 11 now only one day, January 28.

The 29 and 30 will be steam 12 generators?

13 ACTING CHAIRMAN SEALE:

No.

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14 MR. THADANI:

No, I think the steam generator 15 rule discussion is in February.

j 16 MEMBER APOSTOLAKIS:

Oh, there will be no 17 Subcommittee meeting on this?

18 ACTING CHAIRMAN SEALE:

That is apparently 19 what I just heard.

Is that your understanding?

20 MR. THADANI:

That's because we are not 21 getting you the documents in time.

22 MEMBER APOSTOLAKIS:

Okay.

So that week the 23 only day that we have a Subcommittee meeting is January 24 28?

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25 MR. THADANI:

Yes.

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policy statement, in June, 1990, the Commission provided 2

significant guidance to the staff in a staff requirements 7s f

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3 memorandum which came out in June, 1990.

4 I basically made the point again, use these 5

concepts of safety goals and subsidiary objectives in a 6

generic manner.

And there were enough conservatisms built i

7 into these guidelines that one should not add significant 8

additional conservatisms to the decision-making process.

9 Another thought that came out, and quite 10 frankly I think it was a strong view of the advisory 11 committee, that operations aspects of plants should become 12 part of the decision-making process.

i 13 As we go through some discussion, that is in

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14 fact what we are also going to be doing; make sure that 15 cultural issues, which add uncertainties, are recognized 16 and understood in the decision-making process.

17 The Commission also issued the Severe Accident 18 policy statement which covered both the operating reactors 19 and the advanced lightwater reactors.

20 As far as the advanced lightwater reactors are 21 concerned, the Commission indicated the expectation that 22 these designs would be safer than the current version of 23 operating reactors.

24 I think in a way that is of some relevance O)

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ACTING CHAIRMAN SEALE:

I'd love for it to me 2

another day, but that is another story.

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4 EMBER APOSTOLAKIS; And we will have some

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documents before that, you say?

5 MR. THADANI:

January 17, we will get you the 6

documents.

7 The only difference there, George, is that 8

that document would not have gone through formal office j

9 concurrence process.

But as I said, we have had meetings 10 with the office directors participating and comments have 11 been provided to the staff.

1 12 Our expectation is that the revision is going 13 aid be very close to the final one.

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14 A little bit of background.

Back in 1986, the 15 Commission issued safety goals policy statement.

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16 the Commission discusses the qualitative and quantitative 17 health objectives and there is a discussion in there also 18 of the use of guidelines for regulatory implementation 19 considerations and that was the part that talked about the 20 frequency of one in a million of not getting to a large 21 early release.

That was the guideline in the document.

22 The Commission also indicated in that policy 23 statement that these objectives were to be used only in 24 the generic decision-making process.

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expectation that where appropriate and practical, we are 2

not to be looking for improving safety.

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3 In terms of the operating reactors Severe l

4 Accident policy indicated that as long as these plants 5

made our rules and regulations, that they were safe I

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enough, but that there were some uncertainties and it was 7

desirable to go take a look at individual plants.

8 That is really the genesis of the subsequent 9

generic letters that went out to the industry to conduct 10 individual plant examinations for internal and external 11 events to see if there were any outliers, so to speak.

12 In the recent policy statement on applications 13 of PRA, certainly took one step further and indicated that

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14 these concepts should also be used in terms of all the 15 decisions that the Commission makes.

16 There are some qualifiers in terms of data and 17 methods and so on.

Nevertheless, the direction the 18 Commission has given to staff and indicated to industry is 19 that that is the way we ought to be proceeding.

20 The expectation is that such use of these 21 techniques, carefully applied techniques, will lead to 22 better decisions.

The concept was that the decisions 23 should be complementary, that is the process should 24 include consideration of deterministic factors and l

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25 probabilistic factors.

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One needs to be sure one understands that the 2

underlying rationale for whatever requirement there is, if

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one is going to change that requirement, then one needs to i

4 have full understanding of the background as well as the 5

implications of that change.

6 So, in the draft regulatory guide, we laid out 7

the basic principles.

Let me give you what they are.

8 The plants are to meet the current regulations 9

and if they don't then there are two options.

One is to 10 go back and see if the regulation needs to be revised.

11 Or, if it is a plant-unique issue, then one would provide 12 plant-specific justification for that change.

13 Here is the fact, also, that when one conducts

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14 risk-assessment, it ought to reflect the plant 15 configuration, as is, including procedures and other 16 things.

17 As you know, we have identified some 18 differences in terms of what is in the documentation 19 versus the plant configuration, as it exists.

We are 20 trying to be sure that if the PRAs are based on documents 21 that those documents really have to reflect the plant.

22 That has to be carefully considered when one is performing 23 risk-assessment.

l 24 It is our intention to make sure as we go on

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that the analysis that we are seeing is, in fact, i

2 reflecting the plant configuration.

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3 The concept of barriers should be maintained.

4 When I say barriers, it is the fuel cladding, the reactor 5

coolant pressure boundary, containment.

If there are 6

issues that impact more than one barrier, one would want i

7 to pay much, much more careful attention to a number of 8

issues, including the uncertainties in those assessments.

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9 A good example are steam generator tubes 10 because the tubes form not only the boundary in terms of 11 reactor coolant pressure boundary, but they also can l

12 provide a pathway for bypassing the containment.

13 So, a potential failure of one barrier, one f

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14 component can lead to breaching two barriers, so to speak.

15 So, the idea is to be careful, particularly 16 when you are going through some relaxation of some 17 requirements, one has to be careful of what the impact is 18 going to be in terms of the barriers that we have out 19 there.

20 The other central element in this is to make 21 sure that when we are going forward and approving 22 relaxations that these changes, estimated changes are very j

23 small in terms of either core damage frequency or large 24 early release of some factor that represents potential

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25 risk to the public.

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1 ACTING CHAIRMAN SEALE:

When you say small, l

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with the respect to the existing assessment of what the 1

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risk is?

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4 MR. THADANI:

Yes.

The staff would be using a 1

5 number of factore Small in this case, let's say we are 6

talking about 10" per reactor year core damage frequency.

7 Not that that is where we want to see all the plants, but 8

that is the expectation that we ought to be there, be 9

better than that.

10 ACTING CHAIRMAN SEALE:

Yes.

11 MR. THADANI:

In the context of 10",

one would 12 say, suppose a licensee comes in with a change and the 13 change is on the order of delta CDF change of 10-6, we l

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14 would think that is pretty small.

But as you get 15 estimates that go higher and higher, the issue of 16 uncertainties become more and more challenging as to how 17 far the analysis has to go.

18 The staff will of course use in decision-19 making process some of the other guidance that exists.

20 First would be when do we impose back fits, that means 21 what do we mean when talk about substantial additional 22 protection.

23 ACTING CHAIRMAN SEALE:

Yes.

24 MR. THADANI:

Clearly we don't want aid get j

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fits.

2 You wouldn't want to relax and then turn 3

around and impose a back fit in the same area; that 4

wouldn't make sense.

5 So, you have to have some range that has to be i

6 below substantial additional protection range and this is 7

basically derived from two areas.

One is core damage 8

frequency and the other is potential for loss of 9

containment.

That is in the regulatory analysis 10 guidelines document, NUREG/BR-0058.

11 There is actually a matrix in there that 12 defines change in core damage frequency versus potential 13 for early containment failure.

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18 MEMBER APOSTOLAKIS:

But, I guess we have to 19 understand better what the word principles means.

For 20 example, suppose a licensee with a proposed change and the 21 technical arguments are very good, convincing and so on.

22 They demonstrate that it will save significant amounts of 23 money.

24 Do you see your staff rejecting it on the

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damage frequency?

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2 MR. THADANI:

Yes, the potential exists for 7_

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3 rejecting it if the impact on core damage frequency is j

4 still fairly substantial.

5 The issue is cost is very important in terms 6

of priorities that one would assign for our reviews.

7 Recognize that we get about 1,000 to 1,200 requests for 8

amending licenses.

Clearly, we don't expect that for 9

every amendment one would go through a rigorous 10 quantitative analysis.

We necessarily have to prioritize 11 where we pay our attention.

12 One factor in that prioritization would be 13 cost aspects.

But the decision would still have to be

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14 made; if there is substantial impact on safety, then one 15 may well reject it.

16 What we are going to try to do is provide a 17 little flexibility in terms of not just calculated 18 results; there will be other factc rs that have to be built 19 in.

20 I was at a plant recently where -- And I 21 looked before I went at what the IPE results were saying.

22 It had a very low calculated core damage frequency, well 23 below 10~5 There were many rooms it was difficult to go 24 in either because of high radiation or contamination e-(g) 25 concerns which means that people have to suit up to go in NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

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and take manual action.

That introduces a type of 2

uncertainty that is very difficult to quantify.

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Questions come up about performance of the 4

plant, perhaps the plant is on the Commission's category 5

watch list.

That is reflective of culture, safety culture 6

and so on.

That has to be a consideration when you are 7

talking about making changes that are significant and 8

there is a substantial changes in core damage frequency, 9

it is quite possible that the Commission would not want to 10 approve it.

11 MEMBER APOSTOLAKIS:

But it is possible that 12 they would?

13 MR. THADANI:

Oh, yes.

Now we are talking q

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14 about getting into an arena of uncertainties.

If the 15 plant operation has shown problems over a sustained 16 period, then that would have to take that into 17 consideration in the decision-making process.

18 I don't think you can layout black and white 19 rules for that.

I think it is very important that the 20 decision-making process have some hard rules and some 21 flexibility in terms of other issues to be considered.

22 Another factor to consider would be how close 23 are those changes getting to the concept of substantial 24 additional protection that we talked about in our back fit (n,)

25 decisions.

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If plant X comes in with a proposed change.

2 Let's say the change in core damage frequency is 5 x 10-5 l

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3 When I go back to my thought process that says if the 4

estimated core damage frequency from the sequence is 5 x 5

10-5, I can probably justify imposing a back fit because 6

there are two parts to a back fit consideration.

One is 7

substantial additional protection and the other is cost 8

effectiveness.

That is another place where large costs 9

can play a part.

10 But the logic has to hang together.

He can't 11 have an environment where we are relaxing and imposing 12 back fits in similar areas.

13 MEMBER KRESS:

Ashok?

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14 MR. TRADANI:

Yeah?

15 MEMBER KRESS:

Back fits are generally for a 16 set of plans; more than one.

17 MR. THADANI:

Not necessarily.

We can do 18 plant-specific back fits.

By and large, though, you are 19 right.

If you look at the auxiliary feedwater issue from 20 many years ago, we ended up with a very small number of 21 plants, about four, where we said we were going to impose 22 a back fit.

23 MEMBER KRESS:

Well, it seems reasonable to 24 have an environment in which you impose back fits on a

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individuals.

That was the point I was trying to work up 2

to.

I was trying to explore your concept of whether or

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3 not the two are compatible.

4 MR. THADANI:

In fact I think that is true.

5 It could be that when we impose back fits, based on some 6

generic analysis, in the past rules, and plant X turns out 7

to have capability that is close enough to the underlying 8

intent of the rule.

Then I would think you would write an 9

exemption or grandfather certain plants.

10 We have a regulation called 50-12 which lays 11 out the guidelines for anyone to come in and request an 12 exemption from that specific regulation.

13 MEMBER APOSTOLAKIS:

You made the point, Ashok

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20 I think that is reasonable.

21 But I would like to point out that that 22 argument works both ways.

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23 MR. THADANI:

Yes.

24 MEMBER APOSTOLAKIS:

Sometimes you do a

.A (N.s) 25 calculation and realize that you are allowing increases in t

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risk.

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2 Well, there many be unquantifiable benefits.

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3 For example, what if, as a result of the change, the l

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burden on operators is eased?

What if the culture at the l

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plant changes.

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So I think that we should apply this approach 7

to both places.

So, a proposed numerical increase of core 4

8 ds.nage f requency of 5 x 10 is not necessarily the actual 9

change if you include these benefits that you have in 10 other areas.

11 So, the qualitative part works in both ways.

12 MR. THADANI:

I completely agree with you.

13 That is why we are going to have to be very careful that O't

(_)

14 numerical analyses or the bottom line estimates don't just 15 driver every decision.

16 MEMBER APOSTOLAKIS:

Exactly.

17 MR. THADANI:

So, I agree with you that it 18 works both ways.

19 We have to make sure that the guide calls out 20 these factors so that the reviewer is introduced to every 21 concept so that we don't inadvertently leave out some 22 important factors.

23 MEMBER APOSTOLAKIS:

And that is very 24 important because as you know several people have

('O 25 expressed concern about this new road that we are taking j

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22 1

and that the agency is about to relax its requirements and 2

allow increases in risk.

3 MR. THADANI:

That's right.

I think there are 4

a number of factors.

As I indicated we get about 1,000 to 5

1,200 requests for amendments to licenses, some of which 6

would increase risk.

And we have approved them in the 7

past.

In fact there is a regulation, 50.59 which was 8

written for the industry for them to make decisions on 9

making changes to a structure system, components or 10 procedures as they are described in the FSAR.

They have 11 to meet certain criteria.

12 The key is there an unreviewed safety question 13 which means can this change lead to an increase 10

(_/

14 probability of an accident or increase in consequences?

15 When you can't meet those criteria you come in 16 under different part of the regulations for the NRC to 17 review and approve the change.

18 So, I think it should be recognized that there 19 are some changes that we make to these licenses that do 20 invariably lead to, I think very small, increases in risk.

21 So, we clearly think that it is okay for some 1

22 small increases in risk where properly justified.

But we 23 want to be sure that the message is not that while small 24 increases are okay, the industry as a whole can

()

25 systematically increase risk.

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23 l

l 1

Clearly it is not the Commission's intent that l

2 each plant that is below, let 's say 10-*, to make changes 7-eb 3

to get up to 10-4; that is the wrong message.

1 4

We need to use these techniques to better 5

learn the plant operation which I think has been done 6

through IPEs and IPEEEs.

7 But then, from these results there were some 8

areas where the licensees have made improvements or are 9

considering making improvements.

10 I think that that is the right way to go.

Our 11 goal is going to see if that in fact is indeed being to be l

12

done, 13 ACTING CHAIRMAN SEALE:

I have a comment, if I b

V 14 may.

15 MR. THADANI:

Please.

16 ACTING CHAIRMAN SEALE:

Early when this 1

17 process first began, one of the revelations that comes is 1

18 an awareness of the importance of going from bounding to 19 best-estimate analyses in the quantification of risk.

We 20 run into this in a myriad of things.

We were having 21 conversations this morning in other areas where that 22 difference becomes very striking and puts very real 23 requirements on calculational capabilities that we have 24 never had before.

OQ 25 MR. THADANI:

Yes.

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ACTING CHAIRMAN SEALE:

Now, you are saying, i

2 and I would agree with you, in the overall evaluation in l

/~%

3 the kinds of changes that we are talking about, there is 4

not only this quantitative evaluation component, but there 5

may well be other parts of the equation which at this time 6

are perhaps much more subjective and will require the best 7

of the intuition and understanding and judgement of the 8

people involved.

9 I think that one of the real requirements that 10 you have is to be able to apply those ideas effectively 11 while at the same time not propagating a climate in which 12 the degradation in the expectation of the quality of the 13 quantitative part of the assessment would be accepted.

(s/

14 MR. THADANI:

There is no question, and you i

15 will see in the regulatory guide, robustness of analysis 16 is very important.

17 MEMBER CATTON:

A lack of robustness in 18 analysis should be reflected in uncertainty.

19 MR. THADANI:

No, no.

I think treatment of 20 uncertainty --

21 MEMBER CATTON:

You can't separate them.

22 MR. THADANI:

That is what I am saying.

You 23 have to do uncertainty analysis to get a better sense of l

l l

24 where the reality might exists.

You need to know what

/s

, ( )

25 that range is.

t NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W (202) 2344433 WASHINGTON, D C. 20005-3701 (202) 234-4433

25 1

ACTING CHAIRMAN SEALE:

But what I think he is i

2 saying is, if your analysis is less rigorous, then you 7-

! U l

3 will probably have to accept a wider uncertainty placed on 4

the results of that analysis.

5 MR. THADANI:

It would, yes.

6 ACTING CHAIRMAN SEALE:

And if you can live 7

with the broader uncertainty, then okay.

8 MR. THADANI:

And in fact you are saying the 9

same thing.

10 ACTING CHAIRMAN SEALE:

If you cannot, 11 somebody has to spend some money to tighten it up.

12 MEMBER APOSTOLAKIS:

The problem with this 13 though is that these uncertainties are usually not

/m 14 quantified.

What the PRA reports is the uncertainty on

~-

15 things that have already been quantified in the PRA.

16 I have yet to see a PRA where they say there 17 are all these qualitative things that we haven't taken 18 into account, so we will stretch the high end of the 19 distribution to go up.

20 So, in principle, Ivan, I think what you said 21 is correct.

But in practice, it does not happen.

22 MEMBER CATTON:

Right.

23 MEMBER APOSTOLAKIS:

Which brings up another 24 interesting point.

What we are saying here is we look at

{)s 25 the distribution that we get from the PRA and knowing all q_

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l 4

26 l

l 1

these qualitative factors we follow another distribution i

2 in our mind, which we don't really quantify and then we s

1 i

)

\\)

3 make decisions based on that.

1 4

Now, I have heard many times in the past that j

5 we should not even attempt to quantify things that are not 6

in the PRA now because only trouble can result.

7 But if this is the state of affairs, it seems 3

to me that there is an incentive to try to quantify thinga 9

that are not already in the PRA because they will be

]

1 10 included in the decision-making process anyway.

11 MR. THADANI:

That's right.

That's exactly 12 right.

13 Let's say I am Licensee X and I want O(_)

14 relaxation and I have two parts that I would like 15 relaxation on; part A and part B.

16 I calculate and see that the change in core 17 damage frequency for example is 10-7 under part A.

Under 18 part B you are calculating 10-6 or higher, whatever the 19 numbers.

20 Licensee X may choose to just come in with 21 part A with much less detailed analysis for part A.

The 22 licensee then has to make their own cost-benefit decision.

23 How much do I need to spend on much more rigorous analysis 24 if I want to push the envelope.

t

/N I

t,N-)

25 I think you are right; that is what it is l

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27 l

1 going to have to come down to.

2 I can't believe that next year we are going to l

7-

\\ '/

i 3

see 1200 license applications, each one with rigorous 4

analysis because many of them should be relatively easy to 5

deal with.

6 But I do imagine that a subset of that would 7

require rigorous analysis for us to go forward.

8 We are going to track these changes that we 9

approve, on a plant by plant basis, because we really do 10 need to know what is happening as a function of time in 11 this industry.

12 I think we talked about the general guides and 13 the thinking that is behind these guides.

We got approval

(^x

(

\\/

14 from the Commission to delay sending these guides to them 15 until March of this year; the initial schedule was 16 December.

17 I believe that the general guide and the 18 standard review plan are the key.

Once we can make sure 19 there is agreement on those, then the application-specific 20 would be easier.

21 Another element is going to be siting.

While 22 we are not talking about doing calculations to level 3 23 type of risk assessment, there are deterministic factors 24 that one needs to consider in the decision-making process.

/3(,,)

25 Siting could be one of those.

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28 1

Steam generator rule, just a little bit of l

2 background.

s l I

)

3 If you look at most of our recent regulations,

~

4 station blackout, anticipate transient without scram 5

pressurized thermal shock, in all of these recent rules we 6

have been using risk analysis to see whether there is 7

substantial improvement in safety and how far should one 8

go in imposing new requirements.

9 The steam generator tube issues have a long 10 history.

We had unresolved safety issues, A-345.

We did 11 a number of analyses including risk analyses, trying to 12 get a sense of what the risk might be in terms of core damage frequency and trying to gauge if there would be 13

\\\\--

14 substantial releases or not.

15 While there were some recommendations on what 16 the industry might want to do, and some of those have, in 17 fact, been adopted, the key point was that the risk to 18 public was not high enough that we should impose back 19 fits.

It was based on operating experience and the 20 analyses that we could do in the mid '80s time frame.

And 21 I think it was late '80s when the NUREG document was 4

22 published.

23 What's changed?

Why are we talking about a l

24 rulemaking on stream generator tubes?

Two things, O,

! ()

25 basically.

One is that we are seeing different NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1023 RHODE ISLAND AVE., N W.

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29 1

degradation mechanisms than we had been considering in the 2

past.

And it's pretty clear that our requirements needs l /~.)

3 to be based on what is actually happening.

What is 4

actually happening is different than what we thought and t

5 our criteria were really based on the past degradation 1

6 mechanisms in terms of being able to size the degradation 7

level and the rate at which degradation might get worse.

8 Those are the issues that we didn't really have to deal 9

with in the earlier years.

10 The second issue related to can the tubes 11 withstand high pressure, high temperature conditions?

Why 12 should we be worried about that?

If you step back, the 13 Agency has spent literally hundreds of millions of dollars A

t

\\

\\m /

14 in trying to understand containment performance under 15 severe accidents.

16 One big factor there was the high pressure 17 melt scenarios.

Things like dry containment heating and 18 so on.

We wanted to be sure that the design margins that 19 were there would be sufficient that if these challenges 20 are considered credible the containments can actually 21 handle these challenges.

Fortunately the margins I think 22 have played a very big role -- margins and containment i

designs played a very big role in resolving some of those 23 24 issues.

! (A) 25 What we have not done until recently has been l

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30 1

to see are there pathways other than containment that 2

could lead to potentially large releases?

And for high

,_N

'A 3

pressure melt sequences we are,looking at containment 4

response, surely the steam generator tubes are also seeing 5

those conditions.

That's sort of the genesis we ought to 6

look because that's the pathway that bypasses the i

7 containment.

8 We didn't really know how the tubes would l

9 behave and that's what led to some of the work at Argonne 10 to get a little better understanding of the tube 11 performance under high temperature and high pressure 12 conditions.

13 Now, if I can go back, anytime we are fx_/

14 considering a rulemaking, we really do have to make sure 15 that rulemaking is risk informed and now, to the extent we 16 can, performance based.

We do need to consider both 17 factors.

18 In terms of risk informed decisions, we do use 19 the NUREG-0058 guidance that I talked about, changing core 20 damage frequency and containment impact.

That's the part 21 we look at and that's what we are looking at in terms of 22 the steam generator tube issues.

We will do some generic 23 analyses once we are, we believe that substantial 24 improvement could be achieved and we still have to do cost A(,)

25 benefit analysis.

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31 l

1 The cost benefit analyses are based on 1

2 actually looking, trying to estimate what the releases

(

tl G l

3 would be and converting them in terms of person rem and 4

assigning some values for those calculated doses to i

5 public.

That's the same approach that we are using for 6

the steam generator tube rulemaking.

It's nothing 7

different.

And it is in fact consistent, we are trying to 8

make sure that it is consistent.

The thinking that goes 9

there, the system -- the thinking that goes into 10 developing these regulatory guides.

That's why it's very 11 important to first make sure we understand what the 12 framework is and how did this rule fit it.

13 The approach on this rule is not any different em

((>)

1 14 than the approach we've used on other rulemaking 15 activities recently.

I want to be sure that we are not 16 saying that the severe accidents become part of the so-17 called definition of design based acc'idents.

That's not 18 what we are saying.

19 If we are considering severe accidents, we 20 still have to look at issues of substantial protection and 21 cost benefit.

We have to be able to support that in fact 22 that those changes are going to lead to improved safety.

23 Now, we have risk analyses and the regulatory I

24 analyses are ongoing now.

I have, I think the middle of

-w l (,)

25 February we hope we will have documents that you will see l

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32 1

in support of whatever we end up with in terms of the 4

2 rulemaking package.

What we do not believe is appropriate O

3 is to walk away from really fully understanding what the 4

risks might be.

I think that is a central issue.

We 5

think that we -- we may conclude that the risk is low 6

enough and that's okay.

But we ought to look at the whole 7

envelope, all aspects.

The alternative, I'm afraid, would 8

be rulemaking now and potentially another rulemaking in 9

five or ten years.

I hope that's not how we end up.

10 So our intention clearly is to understand the 11 envelope more completely.

12 MEMBER APOSTOLAKIS:

So, if I may interrupt.

13 You said earlier that this rule is developed using the

/\\

i k

4

's /

14 philosophy that you have been using, but then you 15 recognized that severe accidents have to be taken into 16 account.

Right?

17 MR. THADANI:

Yes.

18 MEMBER APOSTOLAKIS:

Doesn't that de facto 19 force you to change the philosophy?

I mean, you might as 20 well attack the issue of risk informed rulemaking, you 21 know --

22 MR. THADANI:

In fact, that's really what you 23 are doing.

24 MEMBER APOSTOLAKIS:

Okay.

/~.

(,)

25 MR. THADANI:

You are attacking the old NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

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33 i

1 philosophy.

If you look at station blackout, we did 2

exactly the same thing.

We attacked the old philosophy I,h

\\#

3 and we said "There is no reason why one cannot take credit 4

for non-safety systems.

They are there.

They may be 5

equally reliable."

The real issue should be reliability, 6

and not necessarily a component of the system is under 7

either the so-called Appendix B coverage or not.

It 8

should really be functionality / reliability issue.

9 MEMBER APOSTOLAKIS:

Is it true, Ashok, that 10 this will be the first rule to be issued under the new 11 philosophy of risk informed and performance based --

12 MR. THADANI:

Yes, but I do want to -- let me 13

-- I'm hesitating a little bit.

The Agency has in its

/~T l

(_)

14 backfit decisions, has been risk informed for many years.

15 MEMBER APOSTOLAKIS:

Yes.

16 MR. THADANI:

What is different now, I think, 17 is there are two parts, that we ought to use these 18 techniques not just for backfit considerations, but for 19 all decisions.

And that we really need some 20 infrastructure because we've been pretty ad hoc in the 21 past.

We need to be systematic.

We need to have the same 22 guidance that everybody has.

It should be clear to l

23 industry and NRC public, what we are doing and how we are 24 going about conducting this business.

So that's the other

(~N.

()

25 new part, I'd say.

l l

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l

L 34 1

MR. HOLAHAN:

And the other rulemaking that's 2

on a -- at least a close schedule is the shut down rule, t

1 3

and I think it also has the risk informed and performance 4

based elements to it.

l 5

MEMBER CATTON:

Then I guess fire is coming 6

along right after that.

7 MR. HOLAHAN.

Well, I think --

8 MEMBER CATTON:

There are three of them that 9

are in the --

10 MR. HOLAHAN-I think it will be a little 11 longer to do the fire protection rule.

12 MEMBER CATTON:

Fire might be easier.

13 MR. THADANI:

Let me put it this way.

There

/

kl 14 is still ongoing debate on if there is going to be a m

15 revised rule in terms of fire, what the scope of that 16 rulemaking should be, and we will wait and see how that 17 dialogue ends up.

18 MEMBER CATTON:

In that case there is 19 guidelines for some 13 countries that already have it, 20 anyway.

21 MR. THADANI:

Yes.

22 MEMBER CATTON:

I'd like to just comment a 23 little bit.

I think risk needs to be coupled to the 24 regulation by a clear and understandable path.

I think it (Gj 25 has to be.

Even if it's done with words, it still has to NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

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35 1

be connected.

2 In the steam generator case you have 1150.

f3 i

\\

3 You might argue that what they did with the steam l

4 generator tube rupture in the connecting it to the public 5

was weakly done, highly conservative and I think that is 6

the case.

But you could fix that if you wanted to.

7 And once you have dcne that you need to 8

connect the regulation to the probability of failure.

9 What this requires I think is a delineation of the insult 10 along with uncertainty as well as resistance to the 11 uncertainty.

And it's -- you have uncertainty on both 12 sides.

13 MR. TRADANI:

Yes.

,O s-14 MEMBER CATTON:

And you have it both with 15 respect to what the tube will do given an insult, but you 16 have to treat the insult in its distribution.

Because if 17 you don't we always come to the conclusion that it doesn't 18 fail, and that's not right.

19 MR. THADANI:

I agree with you --

20 MEMBER CATTON:

Good.

21 MR. THADANI:

-- that the challenge has to be 22 looked at in that way as well.

23 MEMBER CATTON:

And when I heard that they 24 were only going to change the heat transfer coefficient s

)

25 plus or minus five percent, I don't think there is an i

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i 36 1

experimentalist in the world who would agree with that l

2 under the most ideal conditions.

l \\,- )

l 3

MR. THADANI:

No, but I think one of the 4

things I would certainly agree with you that the insult to 5

the challenge has to be looked at with its distribution 6

because 7

MEMBER CATTON:

And again, these are difficult 8

problems because it's just a matter of putting it together 9

in a scrutable way.

10 MR. THADANI:

Yes.

I would just comment that 11 NUREG-1150 did not fully consider this case.

So I just 12 want to make sure --

13 MEMBER CATTON:

Cure, I mean there is the q

x.)

14 pathway from the tube to the outside that was treated too 15 conservatively in my view.

And if you are going to do it, 16 you really need to look at it again or accept that 17 conservatism.

18 MR. THADANI:

In terms of --

19 MEMBER CATTON:

Dana is going to tell me I'm 20 wrong.

21 MR. THADANI:

-- the ACRS letter, I forget, 22 that was November letter or August letter, I forget.

I've 23 sort of, in my view was right on the mark suggesting the 24 use of core damage frequency and large release with some 7.sv) 25 maybe, you know, there may be some reasonable way to go at i

(

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l 37 1

it.

And that's all we are trying to do.

We are trying to i

2 be careful that we don't -- as you go further and further

-s/T 3

out the uncertainties get pretty significant and broad, l

1

(

4 You go from core damage to containment performance 5

releases to health effects.

It gets pretty challenging.

l l

6 We are trying to keep the focus on designs and l

7 not to get as caught up in terms of what the weather 8

conditions might be, you know, kai over 2 factors and so

\\

9 on.

It just gets, is that necessary for a number of 10 decisions?

I don't think it is necessary for a lot --

1 11 MEMBER CATTON:

You can certainly bring those 12 things in in terms of ranges and uncertainties.

i 13 MR. THADANI:

You can do that -- if we are f3 i

4 V

14 imposing a backfit.

What I'm suggesting two parts.

If we 15 are imposing a backfit we do that, actually.

We do look 16 at ranges and calculations because we have to come up with 17 some idea of person rem, so to speak, so we do do that.

18 MEMBER CATTON:

Absolutely.

19 MR. THADANI:

What I'm talking about is when 20 you go for a small change license amendment change or 21 something, I mean it would be an overkill so to speak.

We 22 can analyze the issue to demise I think.

23 So I guess most of our focus is to still use 24 some judgement on the ability to maintain core coolability m

l 25 or ability to maintain the integrity of the containment 1

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38 1

and if there are pathways that go around that, to pay 2

careful attention to those.

That's, that continues to be

,_s l

's 3

the approach in terms of backfits.

But we take the next 4

step to understand better releases that might be --

1 1

5 MEMBER CATTON:

As soon as you start talking l

l 6

about risk based, risk informed or whatever pair of words i

7 you want to use, I think you have a requirement that's 8

incumbent on you to clearly state and document your 9

position.

Because what happens is that in these 10 judgements, the judgement arena, we talk about it until we 11 agree, have a glass of beer or whatever.

Not a bad idea, 12 right?

13 MR. THADANI:

Yes, right.

fm )

t\\_/

14 MEMBER CATTON:

But once we have a -- Bill, 15 I'm sorry, a glass of milk.

16 MR. THADANI:

Is it -- how about 6:00?

17 MEMBER CATTON:

Once you have agreed then the 18 whole basis has a tendency to disappear.

I think you have 19 to have documentation that supports your view, whether 20 it's heavy analysis or a little analysis or whatever.

It 21 needs to be put on the table.

22 MR. THADANI:

Absolutely, I --

23 MEMBER CATTON:

And that's what has been 24 missing in the past.

If the new approach does nothing

()

25 more than require that Ashok Thadani took this position l

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39 1

based on this reasoning.

2 MR. THADANI:

See I might disagree with you if t

3 you generalize we --

4 MEMBER CATTON:

You don't want to put your 5

name on it.

6 MR. THADANI:

Well, let me tell you.

If you 7

say we haven't done that in the past, I don't think that's 8

fair.

I think we have actually done that.

9 MEMBER CATTON:

Not that I can --

10 MR. THADANI:

If you go back to, as I said, 11 the recent regulations you will find is pretty good 12 documentation and enumeration of what is expected, is 13 fairly scrutable.

I think, over the last several years, I O

14 think we've done a pretty good job in terms of new 15 regulations.

If you can say prior to that, I would 16 probably agree with you and that's what causes difficulty 17 sometimes and understanding what was the rationale, what 18 was the margin, and what was expected.

19 MEMBER CATTON:

I'm referring more to the 20 implementation.

21 MEMBER APOSTOLAKIS:

And the presentation, I 22 think.

The way things are presented.

23 MEMBER CATTON:

Yes, well that's a part of it 24 too, but the, you suggest that in many times these are gO Q

25 going to be on plant specific basis.

That's where it NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

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40

]

l 1

starts to come unstuck because the people that agree that j

i 2

this is the risk informed thing to do don't document it.

('~~'#

\\

3 MR. THADANI:

What -- see that's the whole 4

idea behind making sure we have these guides and standard 5

review plans.

6 MEMBER CATTON:

Absolutely.

7 MR. THADANI:

That lead people the right path 8

of decision-making and the scope and depth of reviews.

9 Our resources are limited.

We do have the --

10 MEMBER CATTON:

That's when I think everybody 11 seems to overlook the beauty of considering uncertainty.

12 You can do a relatively simplistic analysis and you get a i

13 certain uncertainly spread associated with it.

And then l'3

(_,/

14 you can decide whether you want to put the money in to 15 reduce it or just live with it.

And if you have it in 16 front of you, you know what you are doing.

17 And you are the one who brought up this melt 18 injection.

If we had done this at the front end we 19 wouldn't have spent those millions of dollars because most 20 of those early analyses were based on 100 percent of the 21 core in zero time --

22 MR. THADANI:

That's right.

23 MEMBER CATTON:

That was a mistake.

And a 24 simplistic risk evaluation would have led us to conclude

. ()

25 that it was a much lesser insult.

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41 1

MR. THADANI:

Okay so what I was going to get 2

was -- with that it was helpful on any issues that are

\\

\\

/

3 significant enough, instead of writing you a letter why 4

don't we just sit down and talk about what issues may be 5

of concern.

6 MEMBER APOSTOLAKIS:

You briefed the 7

Commissioners on October 3rd, right?

On the steam 8

generator order?

9 MR. THADANI:

Yes.

10 MEMBER APOSTOLAKIS:

Mr. Dudley was there and 11 he submitted a summary to us.

He says here Mr. Thadoni j

12 indicated that the proposed rule would be precedent 13 setting.

Is that correct?

(hU 14 MR. THADANI:

I said it was precedent setting 15

-- I hope I didn't use precedent setting.

What I -- what 16 I said was -- well, I don't remember exactly so --

17 MEMBER APOSTOLAKIS:

But do you agree with 18 that sentence?

19 MR. THADANI:

Maybe you are quoting me out of 20 context you know?

21 (LAUGHTER.)

22 MR. THADANI:

What a reliable source told him 23 that --

24 MEMBER APOSTOLAKIS:

I am not trying to see O()

25 whether you used those words.

But do you agree with the NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

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42 1

message?

2 MR. THADANI:

Yes, on this one because what 1 Ch O

3 was trying to make sure the Commission understood was that 4

we had taken a hard look at the steam generator tube 5

issues before.

6 MEMBER APOSTOLAKIS:

Okay.

7 MR. THADANI:

And we didn't consider this 8

piece.

And that we believed we ought to consider it if we l

9 are really and truly going forward with risk informed 10 thinking in our decisions.

l l

11 MEMBER APOSTOLAKIS:

Okay.

Now the reason why l

12 that caught my eye is because it seems to me that it would 13 be better for all concerned to separate the individual

\\_/

14 issue of regulating steam generators from the broader 15 issue of developing risk informed and performance based i

16 rules.

And discuss the latter first, come up with some 17 sort of agreement.

At least maybe at the principle level.

18 MR. THADANI:

Yes.

19 MEMBER APOSTOLAKIS:

And then say now let's 20 take these ideas and try to implement them to the steam 21 generators.

Because I am afraid that if we are given 22 again a document like, or more than one document regarding 23 steam generators, the discussion really is not focused.

24 Because, you know, sometimes you try to make an argument im (v) 25 regarding the performance based element and then somebody NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

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43 1

explains to you in terms of steam generators that this 2

doesn't apply, and not all of us are experts on steam 7-b 3

generators so we have to shut our mouths.

4 So why don't we separate the two.

Now that 5

probably will cost some time, but I think in the long run 6

maybe it will be better.

7 MR. THADANI:

If you look at the timing, what 8

you will see is we will be looking -- the Commission will 9

be looking for a letter from you certainly by the March 10 time frame on the reg. guides and the general standard 11 review part.

And probably it's a month or two months 12 later a letter on steam generator rule.

13 So it is actually following.

Y /'

14 MEMBER APOSTOLAKIS:

Okay.

I 15 MR. THADANI:

So that's one of the things we 16 wanted to be sure was that when you have agreement on 17 principles then you see our reapplying principles in an 18 appropriate way to the regs. rulemaking.

19 MEMBER APOSTOLAKIS:

Ah, but there is a 20 difference though.

The other documents refer to proposed 21 modifications.

So we have a set of principles that you --

22 MR. THADANI:

Yes.

23 MEMBER APOSTOLAKIS:

-- decided earlier and so 24 on, but I think the issues are different here.

Aren't (j

25 they?

I mean, in one case somebody comes with a NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

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44 1

modification and says, you know, I'm arguing that I should 2

be allowed to do this.

In the other case you are issuing

(,.\\

3 a rule --

1 4

MR. THADANI:

Right, right.

5 MEMBER APOSTOLAKIS:

And you find requirements 6

and so on and so on.

So I don't think we have discussed, 7

at least not to the extent that I recollect, the 8

principles that would apply to this particular issue.

And 9

we have a cryptic paragraph in our letter that talks about 10 functions and goals and all that.

We can spend two or 11 three hours discussing that, how long we would do that and 12 how long we would --

13 MR. THADANI:

Yes.

.Q (s'

14 MEMBER APOSTOLAKIS:

The difficult part in my 15 opinion is the performance part.

16 MR. THADANI:

Oh I agree with you.

17 MEMBER APOSTOLAKIS:

Not so much the risk 18 informed.

19 MR. THADANI:

Well, I also think so, but there 20 is not unanimity in terms of whether one should consider a 1

21 revision of the rule with attention to all aspects that 22 could contribute to public health and safety.

So there 23 are some differences of views on that.

i 24 What I want to be sure is that we are not O(v) 25 changing the concept of what we call, is there a 4

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45 1

substantial enhancement to safety.

That's, we are not 2

doing it differently than we have done before.

We are

'\\"')

3 going to use the same kinds of guidelines.

4 What I'm saying is that we have some 5

experience with that.

We use those guidelines and then 6

for relaxations and so on, we have to be careful that the 7

two concepts are not inconsistent.

There needs to be some 8

consistency in decision-making.

So to that extent, I 9

think you are right, the reg. guides and so on need to be 10 looked at carefully.

But I think the guidance to the 11 staff is very clear for how to make decisions on 12 substantial improvement in safety, what factors to 13 consider, and cost benefit analysis.

I think that's

/"N l

\\

(/

14 clear.

15 It seems to me, what you have to be sure is 16 what we do there is not inconsistent with what we are 17 proposing in the guides.

I mean, that would not be 18 appropriate, if we do that.

19 MEMBER SHACK:

Well, that is part of the 20 problem I think philosophically here though.

In the steam 21 generator rule, we have been looking and focusing on what 22 you are requiring, and we haven't seen the "why" documents 23 yet.

24 MEMBER APOSTOLAKIS:

That's right.

e^

(3) 25 MR. THADANI:

Okay, we need to -- that's --

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46 1

MEMBER SHACK:

So this is sort of a kind of a 2

trust me argument, you know.

These performance criteria

(,_s) 3 are consistent with the risk analysis.

4 MR. THADANI:

Okay, I think --

5 MEMBER APOSTOLAKIS:

We'11 tell you later.

l 6

MEMBER SHACK:

We haven't seen tbc risk i

7 analysis, you know, we are trusting you at the moment.

8 MR. THADANI:

Okay, I think then that's a very 1

9 fair question because we have to make sure we are making 10 the technical case.

Otherwise -- we can't go with trust l

11 me because five years from now we would find ourselves in 12 difficult spot.

13 ACTING CHAIRMAN SEALE:

You run into Ivan's (3

b 14 documentation problem.

But --

15 MR. HOLAHAN:

I'd like to add something on 16 this point before we leave it.

17 ACTING CHAIRMAN SEALE:

Yes.

18 MR. HOLAHAN:

I remember at some of the early 19 subcommittee -- the PRA Subcommittee meetings, this issue 20 came up about the relationship between the reg. guide and 21 other documents like the regulatory analysis guidelines.

22 And I think it's fair to say that we haven't thought it 23 through and we haven't really developed a reg. guide that 24 applies to things other than applications.

n 25 But the way the philosophy has been developed, NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

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47 1

I think ultimately we will find out that these key 2

principles that we have laid out I think do apply to rule fs

(

)

3 changes and other, you know, regulatory programs.

Now, 4

the numerical criteria may be different.

And I think they 5

do have to be consistent and compatible in some way.

Not 6

necessarily numerically equal.

I think there is some 7

range where you don't what the, sort of overlap between 8

what you require and the burden that you relieve.

9 But in terms of the principles I think you 10 find that they will eventually apply to both cases.

And 11 what we have now in the regulatory analysis guidelines 12 addresses the risk numbers and the dose values and allows 13 some general consideration of uncertainties, but it j'~)%

k-14 doesn't tell you very much about the defense in depth and 15 engineering margins.

And I think that's probably the area 16 where these, where the PRA reg. guide, in fact it is more 17 than the PRA reg. guide.

It's a guide for converging 18 engineering analysis and PRA analysis.

And I think what 19 we do here will ultimately affect how regulatory analysis 20 and rulemaking are done.

21 MEMBER APOSTOLAKIS:

Yes, I agree that a large 22 part of what we have discussed would apply to rulemaking 23 too.

There may be other principles that you may want to 24 consider. And I think a problem also is the, maybe it's (y) 25 part of the documentation, but the presentation really.

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1 48 l

1 The argument.

How do you make your case?

And that is 2

very important, in my opinion, to show --

,.s t

3 MR. HOLAHAN:

It's clear that the burden of 4

proof is different.

1 5

MEMBER APOSTOLAKIS:

I'm sorry?

6 MR. HOLAHAN:

The burden of proof is quite 7

different --

8 MEMBER APOSTOLAKIS:

Yes.

9 MR. HOLAHAN:

In the two cases.

10 MEMBER CATTON:

But the presentation --

11 MR. HOLAHAN:

It shifts.

12 MEMBER CATTON:

-- I don't want to keep going 13 back to fire but that's where people have worked very hard CN

(_ /

14 at this.

And it's pretty well acce'pted by everybody that 15 gets involved, a clear statement of objective, functional 16 requirement, performance, detail, documentation.

It's 17 just that simple.

It's clean.

18 MEMBER APOSTOLAKIS:

And that's what I would 19 like to discuss.

A simple --

20 MEMBER CATTON:

Each item.

21 MEMBER APOSTOLAKIS:

To see that what means.

22 MEMBER CATTON:

The objective is safety.

23 That's easy.

And through something like NUREG-1150 or 24 whatever, you can make a statement on the actual

(~)x 25 requirements for this thing that is buried in this system.

(

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49 1

What it has to be. And once you've done that you can take l

2 it out and do with it as you wish because the requirement

,_s

/

\\

3 for its performance came directly from your risk l

4 evaluation.

It's a simple structure.

5 I don't think it came easy to these people 6

either, that this five step or six step process came 7

following probably 20 years of people fooling around with 8

how to do it.

9 ACTING CHAIRMAN SEALE:

I don't want to let us 10 get too far afield from a problem that you brought up a 11 little -- or you may not have known you brought it up a 12 little bit earlier, but you did.

I've been reminded by 13 our staff engineer here that an April letter on the steam

/^%

(_)

14 generator tube issue would not be responsive to the 15 schedule we have right now, Commissioner.

We need to do 16 that earlier.

17 MR. THADANI:

The -- Jack help me on this one.

18 MR. STROSNIDER:

Well, the schedule -- I'm 19 sorry, Jack Strosnider, NRR.

We did brief the Chairman, I 20 don't remember the exact date, but we did -- we got a 21 change in the schedule with which we plan to forward the j

l 22 draft rule to the Commission.

And that is roughly two j

l 23 months after completion of the general reg. guide on risk l

i 24 informed applications.

So we are talking now about the O) 25 April time frame.

(

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501 1

ACTING CHAIRMAN SEALE:

Okay.

r 2

MR. THADANI:

When we briefed the Chaire, wit, l s)

\\"/

3 and we spent, I can assure you, we spent, paid close 4

attention to the schedules.

And on the steam generator 5

rule issue we met with the Chairman and we laid out the 6

reasons why, and it was agreed that we could delay the 7

date from what was, I think, the end of February to the 8

end of May.

And so that, I believe, gives us enough time.

9 ACTING CHAIRMAN SEALE:

Okay.

10 MR. THADANI:

And the tracking list -- I 11 believe on the tracking list a revised date shows up on 12 the tracking list.

I think.

13 MEMBER APOSTOLAKIS:

Which item are we f~)l C

14 discussing on the agenda by the way?

I am a bit confused 15 now.

Are we on Item 5?

Where are we?

16 MR. THADANI:

Yes, yes, Item 5, Item 5.

17 MEMBER APOSTOLAKIS:

So are we done with this?

18 ACTING CHAIRMAN SEALE:

No, we are not.

19 Carlier he had said it indicated the timing between these 20 two things, and my concern was --

21 MEMBER APOSTOLAKIS:

No, I understand that.

22 But there was a lot of discussion of the steam generator 23 rule.

So are we on five now?

24 MR. THADANI:

This issue on schedule relates O.

Q 25 to that.

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51 1

MEMBER APOSTOLAKIS:

Yes, I understand the 2

schedule -- the ' discussion, the agenda, because we, I

-~

3 don't recall discussing defense in depth, CDF versus LERF, 4

are we skipping those or are we coming back to those?

5 MR. THADANI:

No, no, we can come back.

I 6

just wanted to make sure all of our --

7 MEMBER APOSTOLAKIS:

Okay, I just wanted to 8

make sure.

9 MR. THADANI:

I just wanted to go over the 10 broadness --

11 MEMBER APOSTOLAKIS:

Okay.

12 MR. THADANI:

-- and the scope of where we 13 are, where we are going.

,O

'~ I 14 MEMBER APOSTOLAKIS:

So, just to understand it 15 better.

Do you think that it would be useful to discuss 16 how one would approach risk informed performance based 17 rulemaking in a generic sense, independently of the steam 18 generator rule?

Or do you think we should do it in that 19 context and that we have discussed it enough in the 20 context of the reg. guides that Gary is preparing?

21 MR. THADANI:

Yes, my own sense it that the, 22 our new requirements, generic requirements, in terms of 23 risk informed thinking, I think is reasonably clear what 24 the guidance to the staff is.

And that's in fact what we (n_)

25 do.

We do have to follow the Commission guidance, and NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W (202) 234-4433 WASHINGTON. D C. 20005-3701 (202) 234-4433

52 1

that's what we are doing.

The only point I was trying to 2

make was, what we are doing in the guides is to make sure

,s

(' ')

3 that we are, there is some consistency and compatibility 4

in the decisions that we make with that guidance.

5 There is several -- there is a reason I went, 6

why I went through some of the policy statements.

Policy 7

statements, some of the guidance documents, really what we 8

would follow in our decisions.

And when there is a staff 9

requirements memorandum that has guidance and it says 10 that's what the staff ought to be doing.

And so the 1990 11 staff requirements memorandum laid out some things.

12 Now if you want to change, that's okay, but we 13 go back to the Commission and say we propose that we ought g

'\\m,)

14 to do things differently.

An example would be, there was 15 a concern, I believe in that staff requirements i

16 memorandum, of not suballocating goals.

But it may be 17 that suballocating goals in the context of performance 18 based thinking may not be too bad.

19 Functioning -- functionality of a system, 20 which is suballocation, if one is going to use that, then 21 performance based thinking --

22 ACTING CHAIRMAN SEALE:

Well certainly the 23 idea that you don't allow all the risk to accumulate in j

l 24 one particular initiator is a form of suballocation.

O).

25 MR. THADANI:

Sure, sure.

,\\~-

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53 1

MEMBER APOSTOLAKIS:

But still, when you say 2

the conditional probability of the tube failing should not

,_s

/

1

' ('")

3 exceed point one, that's a de facto allocation, isn't it?

4 MR. THADANI:

Yes it is.

Yes it is.

But 5

that's reasonably consistent with the guidance that we 6

have from the Commission.

Now, let me give you another 7

example, 10 ~4 core damage frequency.

If we say, well for 8

internal events, we will say 3 x 10-5, for external events, 9

3 x 10~5 and sabotage and something which is not quantified 10 11 ACTING CHAIRMAN SEALE:

Uncertainty is 4 x 10~

12 5

13 MR. THADANI:

That's right.

That's a no no n

14 unless we go back to the Commission and say that is what 15 we are doing.

And in some cases, it may not be 16 unreasonable to do that.

17 MEMBER APOSTOLAKIS:

Well, there are several 18 ways 19 MR. THADANI:

Yes, yes.

20 MEMBER APOSTOLAKIS:

-- in which you can do 21 this.

For example, you don't have to specify numbers, you 22 may again state principles.

That you don't want one 23 sequence to dominate everything or --

24 MR. THADANI:

Yes.

.r'{sf 25 MEMBER APOSTOLAKIS:

So, but it seems to me NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE N W.

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54 1

that the de facto location is really not the best way to 2

proceed.

We have to look at it from the top down.

,_.s

(

)

Q' 3

MR. THADANI:

Yes.

4 MEMBER APOSTOLAKIS:

That we have a goal, or 5

two goals.

Now, as we go down the PRA, or to the left, it 6

depends on how you look at the diagram, how do we want the 7

risk to be distributed?

8 MR. TRADANI:

Yes, very good.

See we, the 9

number of decisions you probably have to make, you have 10 some guiding principles.

We said defense in depth.

I 11 talked about barriers.

And, in reality that's what we are 12 doing.

If pressurized thermal shock, use that as an 13 example.

If one says that the frequency of getting to

/'N 1

(s/

14 certain pressure and temperature conditions that the 15 vessel is going to see, is 104, just for the sake of 16 argument, and the conditional probability of vessel 17 failure is 1.

Even if let's postulate for sake of 18 argument that's not a large lead.

Is that okay?

Because 4

19 what that safs frequency of vessel failure is 10 That 20 may not be okay because now you are -- somewhere you have 21 to bring in this concept that we do make mistakes and we 22 ought to build in some balance in designs.

So there ought

{

23 to be some consideration of results.

24 MEMBER CATTON:

What you are suggesting is if j

I

/~N

(

)

25 you appropriately consider defense in depth, you shouldn't I

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i

55 1

be allowed to relax.

2 MR. THADANI:

That's right.

If you f_s 3

appropriately consider defense in depth, then you should 4

not -- you are in an ideal situation.

5 MEMBER CATTON:

Now that's going to be 6

difficult to do.

You want to move to risk based or risk 7

informed and what that really means is that you state the 8

allowable risk and then that's what they have to abide by.

9 They have the liberty to eliminate one of these defenses.

10 MR. THADANI:

But you see that's what we are 11 saying.

We don't believe that's the right place to be.

12 MEMBER CATTON:

But if you want risk based 13 then you have to go back and say " Gee, the risk really is o

s 14 such and such when I consider defense in depth."

15 MR. THADANI:

yes.

16 MEMBER CATTON:

And now you cannot do that 17 anymore.

18 MR. THADANI:

I guess --

19 MEMBER CATTON:

Didn't 1150 try to do this?

20 MR. THADANI:

But I guess -- I want to make 21 sure we don't disagree on basic issues.

You, it's 22 important to do calculations as well as you can to try and 23 understand what the risks might be to the public.

24 MEMBER CATTON:

And put a statement of O)

(,

25 uncertainty NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE, N W.

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56 l

1 MR. THADANI:

And then you go on and take the l

2 next step.

Even if you say your calculations show you i

'\\ l l

3 that frequency of let's say certain releases is 10-*,

but 4

it comes from one accident that knocks out everything.

5 You then better pay very close attention to what the 6

unknowns might be and is that the right place to be?

7 So, I'm saying decision-making must include a 8

lot more than numerical results.

9 MEMBER CATTON:

It has to include uncertainty.

10 That's what uncertainty is all about.

11 MR. THADANI:

True, true.

12 MEMBER CATTON:

So if you' properly treat the 13 uncertainty and carry it through to the end point the O)

(,,

14 decision maker has everything he needs.

15 MR. THADANI:

But as George said earlier, I 16 have yet to see -- I also have yet to see a risk 17 assessment that fully explores all different types of 18 uncertainties.

19 MEMBER CATTON:

I agree.

20 MR. THADANI:

There are some that you can 21 calculate.

There are others you don't know how to 22 calculate.

23 MEMBER CATTON:

But what you want, I think, is 24 that if you lay it out simply like I tried to do, you can fx

(

)

25 point to where these uncertainties are.

If you don't know NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

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t l

57 l

1 the answer you either accept it or your spend some money.

l l

2 And then it's clear and it's on the table in front of you.

3 MR. THADANI:

That I clearly agree with you.

I 4

We need to say why is it that you want vessel to be able 5

to withstand this -- and --

6 MEMBER CATTON:

And of course you wind up 7

accepting expert judgement or analysis or whatever in 8

order to get your conclusion.

But it's in front of you.

9 MEMBER APOSTOLAKIS:

Now this NUREG report 10 that provides the risk basis for the steam generator rule, 11 is that available now?

12 MR. THADANI:

No, I think -- what's the 13 schedule Jack?

r k_,xl 14 MR. STROSNIDER:

There is a draft that's being 15 viewed now and is being worked on, and the schedule is to 16 try to get that to you by the middle of February.

17 MEMBER APOSTOLAKIS:

Okay.

18 MR. STROSNIDER:

That was the -- mid-February 19 to try to get to you the draft, the NUREG on risk and also 20 the regulatory analysis.

21 ACTING CHAIRMAN SEALE:

Will that then be 22 basically the package that we will be expected to comment 23 on?

24 MR. STROSNIDER:

Yes.

-s

)

25 ACTING CHAIRMAN SEALE:

Okay, so what we have q

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58 1

now and those two additional element.t?

2 MR. STROSNIDER:

This is the part that Dr.

,-)

('^'

3 Shack indicated you hadn't seen yet.

4 ACTING CHAIRMAN SEALE:

Right, right.

Okay.

5 MEMBER APOSTOLAKIS:

So it seems that in the 6

first quarper of 1997 we will revolutionalize the 7

regulatory process.

8 MEMBER CATTON:

Maybe, George.

9 ACTING CHAIRMAN SEALE:

And that's what a lot 10 of people are afraid of.

11 MR. THADANI:

Let me say evolution -- let me 12 say the following.

When we say end of March, end of March 13 is when this information goes to the Commission.

We have

/^'N

(~ l 14 a briefing for April lith or some such thing.

And, how 15 long the Commission would take before saying "Let's go out 16 publish for public comment, I don't know."

17 ACTING CHAIRMAN SEALE:

What's your cue there 18 you are giving --

19 MR. HOLAHAN:

I thought for George we would 20 make it a row-volution.

21 (LAUGHTER.)

22 MR. STROSNIDER:

Let me add one thing with 23 regard to the package, if I could.

There was a lot of 24 discussion about documentation and rationale for what goes (O

25 into the regulations.

A lot of that is also documented in

,j NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE.. N W.

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59 1

the Statement for consideration.

The NUREG report that 2

documents a risk assessment may not get you all the way to fs

(

)

3 what actually goes into the rule, and for all the 4

regulations that are promulgated there is a Statement of 5

Consideration that goes with it and there is a large 6

effort that goes into that.

So that's another thing I 7

will have to see at what point you want to look at that.

8 Because that sort of bridges the gap between the risk 9

assessment and what goes into the rule.

10 ACTING CHAIRMAN SEALE:

Well, I know that a 11 lot of the people who are attending here today are 12 interested in any word that any of us might say.

But that 13 in particular they are concerned about the schedule with

(~~)

\\/

14 respect to the steam generator rule.

And I think this 15 fairly well defines the time line that we are on then, 16 assuming that the April day will in fact be acceptable as 17 a time for us to have our letter in.

)

I 18 MR. DUDLEY:

The only reason I was concerned 19 was to support the staff's schedule and what that --

20 ACTING CHAIRMAN SEALE:

Yes, right, so that's 21 where that stands.

We still have some other things on the 22 agenda we wanted to talk about today.

Is there anything i

23 else you want to say about the steam generator rule in 24 particular while are are on the subject?

(_)j

(

25 MR. THADANI:

No, that's basically all I NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHOOE ISLAND AVE., N.W.

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60 1

intended to say.

I was looking to make sure that November 2

20th letter that I was not sure what the thrust was in one i

3 area, and that is I'm not sure if you intended for us to 4

get into health effects issues or not.

I couldn't tell 5

from the letter.

6 It's not our intent to go that far.

We are 7

going to be doing some calculations to be able to see what 8

kind of releases there might be, and for cost benefit 9

purposes, analysis purposes.

10 ACTING CHAIRMAN SEALE:

And these will include 11 the effect of post-rupture attenuation of the release.

12 MR. THADANI:

We would do the best analysis we i

13 can.

O)

(_

14 ACTING CHAIRMAN SEALE:

Okay.

15 MR. THADANI:

But that's really a requirement 16 for us --

17 ACTING CHAIRMAN SEALE:

Spatially post l

\\

18 rupture, not time-wise post rupture.

19 MR. THADANI:

No, I understand your point.

20 And I guess what I'm saying is we are going to do as good 21 analysis as we can, and because, I mean, to be able to do 22 cost benefit analysis we really need that information 23 anyway.

l 24 MEMBER CATTON:

Well, there's been a lot of

()

25 cost benefit analysis done, and some of it's not too good.

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l 61 1

But if you are going to use the word risk, you need to 2

somehow couple the performance requirement of the tube to

[-s) 3 risk, even if it's a tenuous connection.

And that 4

connection needs to be clearly stated.

5 MR. THADANI:

I think we do need to say yes, 6

if I can give a simple answer.

7 MEMBER CATTON:

Analysis not risk.

8 MR. THADANI:

Yes, I mean --

9 MEMBER CATTON:

And it could well be that the 10

.1 or whatever it is is a number that's too small.

11 MR. THADANI:

Could be.

12 MEMBER CATTON:

But that's why I think that 13 connection is all important.

\\_/

14 MR. THADANI:

But I want to be sure that --

15 MEMBER CATTON:

I don't think it's too small 16 but --

17 MR. THADANI:

No, no, by the way, based on 18 some limited information that I'm familiar with,

.1 may 19 not be an unreasonable value to tse.

See we want to make 20 sure, we want to be careful, we have two things, 21 uncertainty and variability.

22 MEMBER CATTON:

That's right.

23 MR. THADANI:

Plants out there are different.

24 Let's be honest.

They are different. They are operated

()

25 differently.

The condition of the tubes is different.

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62 1

when you make a generic decision, it has to recognize the 2

issue of variability.

And sometimes that leads to a 7,,k) 3 conservative decision, and that's when we go back to what 4

Tom said earlier that then the individual licensee can 5

come in and say, " Wait a minute, you don't understand what 6

I have."

7 And we have to, if we state our underlying 8

bases properly, what is the intent of the rule?

What 9

level of safety we are trying to achieve?

If we do that 10 well, then the licensee that has, say three pumps instead 11 of two pumps, simplifying something, could come in and say 12

" Wait a minute.

I have a better system.

I meet the 13 intent of whatever you said.

I don't need to do any

[)

\\/

14 more."

15 ACTING CHAIRMAN SEALE:

-- some guys with 16 large dry containments did that.

1 17 MR. THADANI:

That' right.

That's an example.

18 MEMBER APOSTOLAKIS:

Ivan was talking about i

19 the relation of risk to the rule.

And I must say I really 20 liked the framework that the industry presented at our 21 meeting where they started out with the accident sequences 22 and they said "Now which ones of these involve the steam l

23 generator and then go down."

I think that would make a 24 very convincing case for whatever numbers you want to (h

(,/

25 choose and whatever, and where to put the performance NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

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63 l

1 criteria.

Because that really places the issue in the l

l 2

broader context of risk.

.3

(

)

%/

\\

3 MEMBER CATTON:

Right.

l I

I 4

MEMBER APOSTOLAKIS:

And then you can say, but 5

there may be other sequences that are not there, or all 6

the mechanisms are not there.

But at least you start out 7

by something that is familiar, it is related to risk, and 8

then you work your way down to the specifics.

I really 9

liked that.

10 MEMBER CATTON:

AP600 is a good example.

At 11 the outset they were going to put their relief valves 12 inside the containment in a pool.

A lot of this would go 13 away.

Because you would go through it and say " Gee, it

\\~/

14 doesn't matter."

A severe accident it won't impact it.

15 Because of the conclusions that they came to and they took 16 a look at it, they just put them back outside because it 17 didn't make any difference.

18 But if you were doing it from a risk j

19 perspective from the outset, they would have left them 20 outside.

21 MEMBER APOSTOLAKIS:

Okay.

22 ACTING CHAIRMAN SEALE:

Jack, do you have 23 another comment?

24 MR. STROSNIDER:

I wanted to make two r~N

()

25 comments.

I think one is that when you see the risk NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

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i 64 1

assessment that the staff is preparing, it is along the j

2 traditional lines of looking at various events and

,_s

( 'b 3

following them from initiation through -- so you can --

4 you know, like I said earlier it was pointed out you l

5 haven't had a chance to see that yet so --

l 6

MEMBER APOSTOLAKIS:

But I meant something 7

else.

I'm sure if you have a report that looks at risk 8

you will look at the sequences.

I think that presentation 9

is extremely important too.

So, even in the rule I would 10 like to see some sort of an argument or sequence that goes 11 that way.

I don't know whether legalistically you can do 12 that, but that really would be a good --

13 MR. THADANI:

See that is generally the

,r 5 k,)

14 purpose of Statement of Considerations, not the rule s

1 15 itself, but the Statement of Consideration.

j l

16 MEMBER APOSTOLAKIS:

Okay, y s, I have --

17 MR. THADANI:

Which lays out what it is trying l

l 18 to do.

19 MR. STROSNIDER:

The other comment I wanted to 20 make was going back to the dose calculations and the 21 discussion about attenuation or scrubbing in the steam 22 generators.

I just wanted to point out that for value 23 impact analysis, you may need to go that level of detail, 24 but it's also possible you may not.

And the first place

()

25 you might start there is with some bounding calculations.

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65 1

So I'm not sure exactly at this point what 2

assumptions are made in the value impact analysis with

)

~

3 regard to that particular parameter, but I want to point 1

)

4 out, you know, I don't want expectations to get up that 5

necessarily there is going to be a great detailed 6

evaluation of that.

It will depend on what the reg impact 7

analysis tells us we need to do.

8 MEMBER CATTON:

Well, if you just start with 9

1150, they didn't do that part very good.

It's, whatever l

10 answers you get are quite conservative.

And if you come 1

11 to a number that everybody can live with, then you are 12 done.

If you don't like the number you revisit and the 13 risk approach clearly delineates where the sticking points

-m

\\m)1

/

14 are.

That's why I like it.

15 MR. THADANI:

Yes, and I think you can, if it 16 turns out that for the sake of argument, that the dominant 17 accident sequence is extended loss of main and auxiliary 18 feedwater system, there is no heat sink basically.

If 19 that's the dominant accident sequence, then you generally 20 know what the secondary conditions are for an accident and 21 maybe you can say if that's, I don't need to do more 22 sophisticated analyses in that case.

And that may be good 23 enough.

24 But I think we still have to be able to say r"N j

()

25 technically why what we have done is reasonable.

We still i

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66 1

have to just to do that.

And if we are making some 2

conservative assumption, I think it's our job to explain 7y t

i 3

why that's onay.

4 MEMBER CATTON:

In the past we've just 5

essentially assumed that the steam generator tube opens up 6

into the atmosphere.

7 MR. THADANI:

No, I think in this analysis my 8

understanding is one would look at whether the secondary 9

side is open --

10 MEMBER CATTON:

Yes.

11 MR. THADANI:

And that performance of those 12 valves under those conditions would be clearly an issue.

13 ACTING CHAIRMAN SEALE:

There is also some (O

d K/

14 attenuation though on the secondary side, too.

15 MR. THADANI:

Yes, can one in absence of 16 information, if it is an important safety issue, I think 17 the right thing to do is to make a conservative decision.

18 We have to say that we looked and we think that's the 19 right.

20 ACTING CHAIRMAN SEALE:

We have about an hour 21 left.

And the schedule calls for a break shortly.

And I 22 was wondering if it wouldn't be very worthwhile for us at 23 this point to say what we are going to talk about in that 24 remaining hour so we make sure we get everybody's base.

O) l, 25 And then we can --

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67 l

1 MEMBER POWERS:

Well, have we really answered 2

the question of whether this should go to the risk --

V 3

accident consequences?

4 ACTING CHAIRMAN SEALE:

They have told us what 5

they intend to do.

I don't think we responded to it.

And 6

we may want to discuss that some more.

1 7

MEMBER POWERS:

It strikes me at least one of 1

8 the members has a response.

9 ACTING CHAIRMAN SEALE:

Okay.

All right.

10 Perhaps, well, what else are you going to talk about in 11 this additional hour?

12 MR. THADANI:

I didn't plan to talk about 13

'anything else.

/^\\

G')

i 14 ACTING CHAIRMAN SEALE:

Well, we would like to 15 go back and talk about defense in depth a little bit more.

16 MR. THADANI:

Certainly.

17 ACTING CHAIRMAN SEALE:

And the CDF versus 18 LERF versus dose question.

19 MR. THADANI:

Okay.

20 ACTING CHAIRMAN SEALE:

I guess you've 21 answered the allowable risk versus, or allowable increases 22 versus risk neutrality question as well as you can at this 23 point.

24 MR. HOLAHAN:

I would just add one thing to rs

()

25 that subject.

To remind you that even though the staff, NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W (202) 234-4433 WASHINGTON, D C. 20005-3701 (202) 234-4433

68 1

with the Committee's support, made some recommendations to 2

the Commissioners.

We haven't officially really heard 7s I

)

\\#

3 back from the Commission on that subject.

4 ACTING CHAIRMAN SEALE:

I understand, yes.

5 MR. HOLAHAN-So that remains --

6 ACTING CHAIRMAN SEALE:

That's still hanging 7

out there, but our positions are basically unchanged from 8

the original intent.

9 MR. HOLAHAN:

Yes.

10 ACTING CHAIRMAN SEALE:

Well, why don't we 11 raise this question of -- well, okay, we'll take the 12 break.

13 MR. HOLAHAN-Yes, I think so.

(_-

14 ACTING CHAIRMAN SEALE:

For 15 minutes.

We'll 15 be back at 25 after.

And right afterwards I'd like for us 16 to go into this question of risk that is of individual 17 risk.

Tom do you want to do that?

18 MEMBER KRESS:

Yes.

19 ACTING CHAIRMAN SEALE:

Okay.

And then we 20 will go from there.

21 (Whereupon, the foregoing matter went off the 22 record at 2:15 p.m.

and resumed at 2:32 p.m.)

23 ACTING CHAIRMAN SEALE:

I'm, I'm sorry to be a 24 little bit late.

I just got enchanted with the fact that C's

( )

25 my flight's been canceled, but.

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69 1

(Laughter.)

2 MEMBER CATTON:

Well, you better call the (3

\\

i

~~'

3 Hyatt, then.

4 ACTING CHAIRMAN SEALE:

Anyhow.

Tom, you had 5

a concern you wanted to raise?

6 MEMBER KRESS:

What was it?

7 (Laughter.)

l 8

ACTING CHAIRMAN SEALE:

You know what it was.

9 (Asides.)

10 MEMBER POWERS:

You were going to tell us that 11 the plants vary by location as well as the configuration 12 and operation.

13 MEMBER KRESS:

That's right.

That, that I

')

(-)

14 think you make a big mistake in this business of risk-15 based, risk-informed, performance-based world, if you 16 don't really start off thinking site-specific parameters.

17 Health effects, and wind, and population.

18 And that it may not be as difficult to factor 19 that into your thinking as you might think.

I'm working 20 on ways to do that, but when you, when you back off, to 21 get a -- well, for example, the conditional containment 22 failure probability, or the conditional tube rupture, in 23 this case, in this, the steam generator tube.

24 That, the way you get that is by backing down m

25 from the health effects, and the site population, using, NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHoDE ISLAND AVE., N W.

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1 70 J

1 1

for example, maybe the safety goals.

The qualitative, 2

health objective part of the safety goals.

<~s

(

)

3 And that, I really think you have to do that.

~'

4 And then that's the, where you get the justification from j

5 the point one.

And then --

l 6

MR. TRADANI:

If I can just --

7 MEMBER KRESS:

Yes.

8 MR. THADANI:

-- a quick comment.

I said I 9

was going to stick back, and Gary and Joe are going to 10 address some of these issues.

But I think the -- that 11 there's a time and place, it seems to me, where you're 12 probably right, one ought to look at those things.

13 But the, as long as the objective is defined

('~)\\

\\-

14 reasonably well, what is it that we're trying to achieve, 15 the Commission indicated to the staff, a number of 16 documente, what kind of an approach one ought to use.

17 And one element of that was to configure this 18

-- remember the large early release.

Then, there was a 19 lot of debate.

So, are you going to do this site by site, 20 and what does that mean.

What implications there might 21 be, and such analysis.

22 The, the staff made a number of attempts at 23 trying to define that.

And, and the ACRS was, was fully 24 aware.

In fact, you sent a letter to the Commission on

(

s i

25 that subject.

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71 1

And what we ended up with was probably the 2

best way to deal with the issue is to try and establish p_ )

5

J 3

something that's representative of the potential for large 1

4 early release.

5 And that's how, if you remember, in 1993, we 6

finally went to the Commission with that definition, which 7

sort of became, subsequently, part of the regulatory 8

analysis guidelines.

9 So, we, we did, did, I believe the Commission 10 did address that aspect, and concluded that it was best to 11 proceed in this manner.

Because it does really focus them 12 on the design itself.

Issues which are sort of manageable j

13 in the analysis scheme.

A 14 The, the issue of uncertainties is, is, also s-15 gets more complicated when you don't have the facts.

16 MEMBER KRESS:

Certainly.

Well, I've been 17 looking at the issue of large early release, and 18 conditional containment failure probability.

They're 19 related.

20 MR. THADANI:

Yes.

21 MEMBER KRESS:

And what I've found out, and 22 what some reports of fellows, ACRS fellows found out is 23 that, that, if you start from -- let's just use the early 24 fatality QHOs, as a starting point.

()x 25 MR. THADANI:

Okay.

(

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72 1

MEMBER KRESS:

And, and assuming that were 2

some sort of an acceptance, risk acceptance criteria.

You 3

will find out, then, that, if you back that into some 4

reasonable definition of a large early release, that that S

number, that release of it, some fraction of fission 6

product inventory.

7 MR. THADANI:

Yes.

Yes.

8 MEMBER KRESS:

And that number will be site, l

9 plant-rpecific, to meet that.

So, you have a, for each 10 plant and each site, you have a different number for that, 11 to meet that QHO.

12 MR. THADANI:

Yes.

13 MEMBER KRESS:

So, and so that, if you wanted

,a i

)

\\_/

14 to use the top level QHO, in backing it into a large early j

15 release, and a conditional containment failure criteria 16 also.

The same applies to that.

17 You would either have to have specific values, 18 plant-specific values for each of them, or you would have 19 to have a bounding value that bounds all sites, or you 20 would have to have a representative value that represents 21 sites, or you would have a, site-specific values for it.

22 Then, I think --

23 MR. THADANI:

Yes.

I think --

24 MEMBER KRESS:

I don't know what your

(,)

lI, philosophy is, on how --

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73 1

MR. THADANI:

I guess the Commission laid out 2

its philosophy in, there was the recognition -- let me 7s

(

)

~'

3 step back again.

There was a reason why I started out by 4

alking about safety goals.

5 Because the Commission basically has been 6

looking at -- if you look at quantitative health 7

objectives, and, and that, if you use that as, let's say, 8

the criterion for decision, presumably that could mean you 9

could have a frequency of core damage of may ten to minus 10 two, or something.

Il But that would say every few years, it would 12 be okay to have a core damage event, which, of course, is, 13 is not, not a tenable situation.

,O

\\~s/

14 MEMBER KRESS:

Yes.

Well, I,

I like elevating 15 the CDF to, to --

16 MR. THADANI:

Yes.

So, --

17 MEMBER KRESS:

-- a fundamental also.

18 MR. THADANI:

So, if I can go back to what you 19 did, in terms of the hierarchy that the ACRS had proposed, 20 going from qualitative, quantitative objectives to release 21 guidelines, core damage frequency considerations.

22 Because you had the five or seven step 23 hierarchical approach, and, in fact, one of the factors i

24 you pushed was operation of a plant, and, I.think you o)

I

(,

25 said.

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74 1

And so, what the Commission did in the, in the i

2 decisions the Commission made was to say we recognize

,. s

/

s

)

s 3

that, when we talk about something like a large early 4

release or large release, frequency of one in a million, 5

we recognize that's conservative, if you compare that to, 6

to the quantitative health objectives.

7 MEMBER KRESS:

Yes.

8 MR. THADANI:

The Commission recognized that.

9 I think it was a, it's a very conscious decision that we, 10 we want to get down to a fairly low level, in terms of 11 potential for large release.

12 And they said, and the SRM then said -- let me 13 back up.

They, that's why they said was that core damage s

14 subsidiary objectives are okay to use for decisions.

15 But they were, they were basically 16 acknowledging that the subsidiary objectives, if you meet 17 those, then there's no, no doubt, basically, that you'll l

18 meet the quantitative health objectives.

That recognition l

19 was there because these were conservative factors.

j 20 And so then, the question was well, what is 1

21 the large early release?

And keep in mind, it's a 22 release.

So, that's when you moved in, and tried to get 23 away from site-specific considerations, to say, if you can 24 show that the potential for release from, let's say, the

('D

(_j 25 reactor site is, is low enough.

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751 1

clearly low enough, for a large release.

That's what the 2

Commission said.

3 Then, you, you don't get into further 4

discussions and consideration of factors that could 5

influence the health effects and so on, because you have 6

enough confidence that, by choosing these criteria, you 7

know you're going to not exceed the quantitative health 8

objectives.

9 Just, it cuts out, it gives you less 10 information, I would agree with you, but it cuts out a 11 component that was not deemed to be critical.

12 MEMBER KRESS:

I, I'm not proposing that you 13 can't do that.

What I'm saying is whatever you define the

()

w_

14 large early release as needs to be based on the early 15 health, early health objectives.

16 MR. THADANI:

Yes.

17 MEMBER KRESS:

So that you sure enough can 18 justify your statement that if, if you meet this value, 19 along with the CDF, then --

20 ACTING CHAIRMAN SEALE:

You don't exceed it.

21 MEMBER KRESS:

You don't exceed it for any 22 site.

23 ACTING CHAIRMAN SEALE:

Yes.

Tom, why don't 24 you --

t 25 MEMBER KRESS:

And this is what I was --

%/

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76 1

MR. MURPHY:

Tom, let me offer a couple of 2

points on that.

What you say is clearly right.

What we

()

l

("i j

3 have to do, when we pick a number for large early release, 4

is be able to relate it, relate it back to why we picked 5

that number.

6 And what's the logic behind that in the 7

logical framework.

And that we will do.

And that we're 8

trying to express, in terms of the, the general reg 9

guides, for the PRA applications.

10 The, the advantage of a large early release, 11 to me, is -- it has a lot of, a number of disadvantages, 12 which you already told us.

But the advantage is that we 13 lose a big chunk of uncertainty.

,r h I

i

'ul 14 For instance, we have never done a complete 15 uncertainty analysis of the consequence models in the, in 16 NUREG 1150.

17 MEMBER KRESS:

Yes.

18 MR. MURPHY:

I suspect the uncertainty there 19 is going to be quite large.

The, we get into, you know, 20 questions of the linear hypothesis and everything else, as

,/

21 you get into that.

It's a very difficult subject.

22 MEMBER KRESS:

One could, one could finesse 23 the --

24 MR. MURPHY:

The --

,x

'(j 25 MEMBER KRESS:

One could finesse those NEAL R. GROSS COURT REPORTERS AND TRANSCR!BERS 1323 RHODE ISLAND AVE., N W.

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77 1

questions by recognizing that the safety goal policy 2

statement said to use mean values.

~s

(

')

3 MR. MURPHY:

Yes.

i 4

MEMBER KRESS:

Now, now --

5 MR. MURPHY:

But even there, you --

6 MEMBER KRESS:

-- there are those of us who 7

would argue you can't arrive at a mean without knowing 8

what the uncertainty is, but.

9 MR. MURPHY:

Yes.

10 MEMBER KRESS:

But there are others that would j

11 argue that the number that you get out of a, quote, "best 12 estimate" calculation may be representative.

13 MR. MURPHY:

If the number that you put into A

t\\.m) 14 that best estimate calculation is close to the mean of the 15 distribution --

16 MEMBER KRESS:

But, it --

17 MR. MURPHY:

Experience tells me that you, the 18 answer will also be close to the mean.

19 MEMBER KRESS:

Yes, but you can't do that, 20 because --

21 MR. MURPHY; However, if you happen to be 22 close to the median and not to the mean, that's not going l

l

(

23 to be true.

24 MEMBER KRESS:

Yes.

(A) 25 MR. MURPHY:

So, --

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t l

78 1

1 MR. THADANI:

If you assume normal 1

l 2

distributions, I'll agree with you.

p_

N jl 3

MEMBER KRESS:

Yes, but --

4 MR. THADANI:

Otherwise.

5 MR. MURPHY:

The other advantage that you have 6

of this is that you come up with a stability and some 7

uniformity in your regulatory practice.

It is difficult, 8

I think, for, for the licensees, it will be difficult for 9

the inspectors, if each plant in the country has a l

10 different standard to meet.

11 MEMBER KRESS:

But that's --

12 MR. MURPHY:

Because their site --

13 MEMBER KRESS:

But that's --

(h.

\\J 14 MR. MURPHY:

Their site parameters are 15 different.

16 MEMBER KRESS:

Yes.

But that's, that's 17 penalizing those plants that have chosen well on their 18 site.

19 MR. MURPHY:

It does, except for one thing.

20 It would, I guess they say, except for one thing.

If you, 21 the discussion that went through earlier.

We made a point 22 of saying that, as you approached the large early release l

23 limits, that you'll have, as guidelines in, in the reg 24 guides.

' O) 25 That one of the things that would be

(

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79 l

l 1

considered, as to whether we would take action as you

(_

2 start approaching those limits is siting.

So, we'll bring 3

it in in a qualitative way.

4 MEMBER KRESS:

I see.

All right.

My, my real l

5 point was, I'm not objecting to using a large early I

6 release in definition.

I 7

MR. MURPHY:

Yes.

8 MEMBER KRESS:

I'm, I'm, in fact, 'i '

i 9

advocating it.

I just think it has to be clearly defined, i

10 and its definition needs to be site-encompassing.

11 MR. MURPHY:

Okay, 12 MEMBER KRESS:

And it needs to be based on the l

i 13 qualitative health objectives, and objectives for early

, ()

(_,/

14 fatality.

15 MR. MURPHY:

Yes.

l 16 MEMBER KRESS:

And, and, when you put that up, 17 you can actually define a large early release that would 18 do that for you.

19 And, in order to do that, you have to consider

]

l 20 the site-specific meteorology, the population, and, and 1

21 the population distribution.

You have to consider it in 22 how you back that definition out.

I 23 MR. KING:

Let me --

24 MEMBER KRESS:

I mean, I don't think it's good

()

25 enough just to say one in a million.

I, I think you need NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

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l l

1 to say why is this good.

l 2

MR. KING:

Let me make two points on that.

(

\\

\\

\\

l 3

This is Tom King, research staff.

In the draft reg guides 4

you've seen, we do have a LERP criteria or guideline in 5

there.

The value we had chosen in the drafts you had seen 6

was ten to the minus fifth per reactor year.

7 You haven't seen the basis as to why we came 8

up with that, but the basis ie derived from the early 9

fatality QHO, looking at NUREG 1150 results, which include 10 site characteristics, population, weather, and so forth, 11 and working backwards to come up with that ten to the 12 minus fifth.

13 Now, why don't we do one for each site?

If iC 14 you recall, about five or six yearr ago, the Commission 15 embarked on a, on a program to decouple siting from plant 16 design.

They didn't want, you know, to have less safe 17 designs on remote sites, and, or vice-versa.

That they 18 were trying to set --

19 ACTING CHAIRMAN SEALE:

Yes.

20 MR. KING:

-- siting requirements and design 21 requirements.

Really, when you put the two together, 22 you've got an acceptable match.

23 So, I think, on that basis, we've taken the 24 position that, whatever these guidelines are, they apply

,a

)

25 across the board to the designs.

They're not matching, or NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

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tailoring them because of the site that that design, l

2 particular design happens to be on.

3 So, I think that's another piece of 4

information that, you know, we need to be aware of.

That, 5

as a constraint, a guidance from the Commission.

6 ACTING CHAIRMAN SEALE:

Yes.

7 MEMBER KRESS:

As part of that study, there 8

was an IRAC that was written, and, by Sandia, and I've 9

forgotten the title of it.

Or its NUREG number.

But, but 10 it basically took a standardized, sized reactor, and put l

11 it on every site, to be the best.

l 12 MR. KING:

Yes.

13 MEMBER KRESS:

And used a source term.

(D

\\s) 14 MR. KING:

Yes.

15 MEMBER KRESS:

In fact, they varied the source 16 term, actually.

17 MR. KING:

Yes.

18 MEMBER KRESS:

And, with site-specific 19 meteorology and site-specific population, calculated the 20 health effects, using CRAC.

21 MR. KING:

Yes.

22 MEMBER KRESS:

At the time, CRAC was what was l

23 the, the code.

Now, that would be an appropriate place, I 24 think, to do what I'm talking about, rather than NUREG C)\\

25 1150's set plans.

You've got every site there, already (s-NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

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82 l

l 1

characterized.

i 2

MR. KING:

Yes.

We have the site information.

l 7~b 3

That's no problem.

4 MEMBER KRESS:

And you could use that 5

information.

I'm, I've, one of the things I'm working on 6

now is how to use that information to actually develop a 7

large early release, for definition, that would encompass 8

all the sites.

And we've, and backing it up from the, 9

from, the early fatality health objectives.

10 MR. KING:

Yes.

Well, --

11 MEMBER KRESS:

Using that information in that 12 document.

13 MR. KING:

I think --

['T i

\\'

14 MEMBER KRESS:

That's what I'm recommending.

15 MR. MURPHY:

That, that document clearly gives 16 us an idea of the spread that's associated with, with the 17 standard release of various sites.

18 MEMBER KRESS:

And it's quite large.

19 MR. MURPHY:

But, and it's, it's -- yes, it 20 is.

Because some of the sites are in the middle of 21 nowhere, and some are in large population centers.

22 MEMBER KRESS:

Yes.

23 MR. MURPHY:

By the same token, though, do you 24 really want to get to the point where you're so closely

,/~T

(,/

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criteria, or tied to the population growth in the, in the 2

nearby county?

[s) 3 MEMBER KRESS:

No.

I.

4 MR. MURPHY:

Which that could lead you into.

5 And we definitely don't want to be in that kind of a --

6 MEMBER KRESS:

Yes.

7 MR. MURPHY:

-- of a mode.

So, we have to i

8 find the balance between it.

9 MEMBER KRESS:

Sure.

10 MR. MURPHY:

We think the qualitative 11 application we're suggesting is that balance, but, you 12 know, we'd be glad to hear your thoughts.

13 MEMBER KRESS:

Well, my, my point is that if

^\\

rU 14 you want to pick a number for a large early release, a 15 criteria --

16 MR. HOLAHAN:

Yes.

17 MEMBER KRESS:

-- you've got to have a basis 18 for that.

19 MR. HOLAHAN:

Yes.

20 MEMBER KRESS:

And that, and the basis I'm 21 talking about puts it on a firm basis.

22 MR. KING:

Yes.

23 MEMBER KRESS:

Related to the QHO and the 24 sites, and then you can, I mean, you've got to pick a p) 25 number.

And you can put in some qualitative thoughts into

+

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this, too, when you pick that number, and you know what i

I 2

the basis of it, and how it relates to it.

(~'\\

'_]

\\

3 That's all.

I'm not saying you can let it 4

vary with time, due to population, or you, or you make it 5

site-specific even.

Just make it site-encompassing.

6 That's, that's the tack I'm working on, the recommendation 7

I'm working on.

8 MR. KING:

Okay.

Well, I think we've taken a 9

step to do that.

I think we haven't gone back and looked 10 at every site, and taken the NUREG 1150 sites, and backed 11 out the ten to the minus fifth number.

You're suggesting 12 we take a more refined look at it, and that can certainly i

13 be done.

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k~

14 MEMBER KRESS:

And I think there's an easy way 15 you can do that.

16 ACTING CHAIRMAN SEALE:

Well, you can 17 obviously see that's an area where we're going to want to 18 look at details when the time comes.

Where did Mario go?

19 MEMBER SHACK:

He stepped out a minute ago.

20 ACTING CHAIRMAN SEALE:

Okay.

He was, he had 21 another question he wanted to raise.

22 MEMBER CATTON:

He's worried about his 23 airplane.

24 ACTING CHAIRMAN SEALE:

Okay.

I guess I can

/~T

( )

25 forgive him for that.

He wanted, he had a question he l

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wanted to raise with, with you, Jack, about tne steam

)

2 generator rule, progress, and so forth.

,, 3 l

i s~/

3 Do you guys want to talk a little bit more 4

about risk, about defense-in-depth?

5 MR. THADANI:

I guess -- Gary, do you want to?

6 MR. HOLAHAN:

I can, I can say a few things, 7

and others can, can jump in.

8 ACTING CHAIRMAN SEALE:

Okay.

9 MR. HOLAHAN:

The, the approach we're 10 developing in the PRA reg guide identifies five 11 principles, and one of those is preservation or 12 maintenance of adequate defense-in-depth.

13 And, if you remember, when we had discussions O

V 14 with, I think, both the full committee and the 15 subcommittee on these subjects, there was a lot of 16 discussion of how do you treat the engineering issues, 17 and, and PRA issues, and how do you, how do you save 18 yourself from getting, really, two separate analyses, and 19 then adding them together at the end.

How do you do a 20 more integrated analytical approach?

21 ACTING CHAIRMAN SEALE:

Yes.

22 MR. HOLAHAN:

And it was, I think, largely as 23 a result of one of those meetings that the staff sort of l

l l

24 revised some of its approach.

And saying, rather than 1 Oy) 25 doing two separate analyses, one engineering analysis that l

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86 1

has sort of a traditional defense-in-depth built into it, 2

and a separate PRA analysis.

,,\\

I\\~_)

3 That we'd establish some principles up front, 4

and those principles could be shown to be met through 5

either a PRA analysis or an engineering analysis, or maybe 6

some combination of the two, just depending upon the i

I 7

circumstances.

8 ACTING CHAIRMAN SEALE:

Yes.

9 MR. HOLAHAN:

And then we did that, and we 10 tried to lay out, lay out those principles, and we spent l

11 some time talking about what are, really, our fundamental 12 principles, and what are sort of our lower tier 13 expectations.

,/~~Ni V

14 We identified, you know, some measure of risk 15 as being a fundamental safety measure, but also defense-16 in-depth separately being a fundamental principle.

Now, 17 the way, the way we are approaching this.

18 We're saying defense-in-depth, whether it's, 19 it's seen as physical barriers, as Mr. Thadani mentioned, 20 the cladding in the systems, or whether it's viewed as 21 functional barriers, prevention, mitigation of 22 containment, emergency preparedness.

23 Those issues can be addressed in the l

l l

24 engineering analysis, showing a strong containment, or, or O

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one, level two, level three analysis all show some balance 2

in the, where the risk is coming from.

(\\ ')

3 So, at the moment, I would say we see defense-That's in-depth as being fundamental to our approaches.

4 5

one of the reasons why, I think, we're reluctant to have 6

decision-making go directly to health effects.

I think, 7

in doing so, you lose some of the defense-in-depth a

concept.

9 So, whether it's rulemaking or approving 10 license amendments, I think having a fundamental principle 11 addressing defense-in-depth says you shouldn't, you 12 shouldn't be making decisions based solely on, on the 13 health effects.

O Th'ere have to be some intermediate decision k/

14 points that are related to your, your layers of defense-15 16 in-depth.

17 And, in the PRA context, I think core damage frequency and large early release helped serve those 18 19 purposes.

And, you know, when you see the next version of 20 the reg guide, I think, you know, it even strengthens 21 that, that viewpoint.

22 MEMBER CATTON:

You can't really separate 23 defense-in-depth and risk, or even if you stop at, at the core damage frequency, there's still some defense-in-24 r~N

(

)

25 depth.

You've gone through the clad, and now you're going NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

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1 through the vessel.

l

\\

2 MR. HOLAHAN:

Yes.

(_T

/

/

3 MEMBER CATTON:

So, I think as soon as you 4

talk about, talk in terms of probabilities, or risks, or 5

wherever you want to stop the ball game, whatever defense-6 in-depth is along the path you have included.

7 It's only when you do engineering analysis by 8

itself that you have to treat separately one defense and j

l 9

then the next.

But I think, in that sense, moving towards 10 the, the risk, informed risk base gets rid of the 11 question.

12 MEMBER APOSTOLAKIS:

Not really, though.

13 Because I think, the way I see this is as follows.

Again, I

(_/

14 you have to consider what's in the PRA and what's not in 15 the PRA.

16 MR. THADANI:

Right.

17 MEMBER APOSTOLAKIS:

Okay.

So, regarding 18 first, the first one, what's in the PRA, I think -- well, 19 you quantify what you have, as you say.

20 MR. HOLAHAN.

Right.

21 MEMBER APOSTOLAKIS:

But then, this notion of 22 spreading the risk, and all of that.

If you don't want 23 minimal cut set, having one component --

24 MR. HOLAHAN:

Right.

O

(,/

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89 1

be 99 percent of the risk.

2 MR. HOLAHAN:

Right.

G 3

MEMBER APOSTOLAKIS:

Because then you don't 4

have defense-in-depth.

5 MR. HOLAHAN:

Right.

6 MEMBER APOSTOLAKIS:

Now, if you discover 7

that, --

8 MR. HOLAHAN:

Right.

9 MEMBER APOSTOLAKIS:

-- after the fact, you 10 may want to do something about it.

11 MR. HOLAHAN:

Yes.

12 MEMBER APOSTOLAKIS:

Or, when you issue a 13 rule, you may want to do something in advance.

,rx

)

e'v' 14 MR. HOLAHAN:

Right.

15 MEMBER APOSTOLAKIS:

And I, but I think that 16 the concept in, in that domain is more or less 17 straightforward.

What is not clear to me is how we will 18 implement defense-in-depth, in the outside PRA, for things 19 that are not in the PRA.

And I think, just by stating the

)

20 principle, Gary, maybe that should, that would not be

)

I 21 enough.

I don't know.

22 I don't know how far you can go in a generic 23 sense.

And, because that's when, also, you start getting 24 into issues like controlling the process, like controlling rh

, ( )

25 a,

prescriptive programmatic issues.

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1 MR. HOLAHAN:

Yes.

I i

2 MEMBER APOSTOLAKIS:

But how far do you go in s

3 all of that?

That's really an issue, and I don't think 4

that anybody really has the answer to, to control these 5

non-quantifiable factors or issues.

6 And how do you apply defense-in-depth there?

7 I don't know.

I mean, you might say gee, we've been doing 8

it for years, so we have an idea how to do it.

9 MEMBER FONTANA:

Well, before --

10 MEMBER APOSTOLAKIS:

It could be a license, 11 though, to, to be arbitrary.

12 MEMBER FONTANA:

Can I, before -- excuse me.

13 Before time runs out, I'd like to bring this back to the

(

\\

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14 steam generator for a second.

15 In, in analyzing these things from top-down on 16 a risk basis, of, you, the distinction between design 17 basis and non-design basis gets blurred.

18 MEMBER APOSTOLAKIS:

Yes.

19 MEMBER FONTANA:

In fact, there really 20 shouldn't be any, and, if you're doing it properly, you 21 should be able to identify which areas the break point 22 comes or there's very, very detailed quality assurance, 23 and qualifications, and so on, and which areas the, the 24 risk is low enough that, that you don't.

i 7%,)

25 So, now, and applying these high level ideas i

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91 1

to the steam generator issue, I think, is going to raise a 2

lot of stakes, and similar to what we've been talking

,_s i

's 3

about here.

4 And not only that, but how do you apply 5

defense-in-depth to the steam generator issue, because 6

that is one of the stickier ones.

And I just wanted to be 7

sure that we discussed this the next time that we got 8

together.

9 MR. STROSNIDER:

Actually, if I might.

10 MEMBER FONTANA:

Yes.

11 MR. STROSNIDER:

This is Jack Strosnider, NRR 12 staff.

I wanted to comment on this just a little bit, 13 because I think the steam generator rule is a place where

,F'N (m) 14 we're trying to come to grips with exactly this issue.

15 And just to briefly summarize, and we can go 16 over this again in future presentations, but I think our 17 intent, at least, is to establish performance criteria, 18 given that this is a performance based rule, which have 19 some foundation in risk-assessment.

20 So that, if these performance criteria are 21 satisfied, we're comfortable that we have an appropriate 22 level of risk.

All right.

23 Then we get to the defense-in-depth issue, 24 though.

And, if you recall, in the rule, there's a (m) 25 section which we refer to basically as some programmatic NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

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elements.

2 And what we've said is, in order to 7

l I

3 demonstrate, in order to meet the performance criteria, 4

all right, you need to have a balanced program which looks 5

at inspection, cube repair, pri..ry to secondary leakage, 6

mitigation, which could be lowering temperature or other 7

elements.

8 And what we've said is you need to have all of 9

those in a good program.

Now, one might argue that I 10 could accomplish my performance criteria using just one of 11 those elements in my program, all right.

12 But our, you know, our perspective on that is 13 that doesn't provide defense-in-depth.

And this is not in k.s2 14 teras of barriers now, but it's in terms of --

15 MEMBER FONTANA:

Yes.

16 MR. STROSNIDER:

-- of providing defense-in-17 depth, in the mitigation and other areas.

So, that's i

18 where we use, frankly, some judgment, but we, we, you 19 know, I think it's well-founded to say that you need to 20 have a well-balanced program to maintain defense-in-depth.

21 And that was our rationale and our basis for including 22 that in the rule.

23 MEMBER FONTANA:

And that's, too, where you 24 have some real difficulty in trying to quantify it in 25 terms of PRA-type numbers, NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

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MR. STROSNIDER:

It is -- I agree.

It is very

'2 difficult to quantify the contribution of any one of those

('"/

3 elements.

4 And, in fact, what we did in the rule was we 5

simply said a good program will have these elements.

At 6

that point, it becomes performance-based, what they're 7

supposed to accomplish.

All right.

8 And, again, trying to, trying not to be 9

prescriptive in those elements, but to say that each one 10 of these should contribute, you know.

11 MEMBER CATTON:

And so the way you did that is 12 you, you gave a probability of failure number to the steam 13 generator tube, right?

You said it was

.01.

/3 r

a

'v' 14 MR. STROSNIDER:

Right.

15 MEMBER FONTANA:

You didn't demonstrate it was 16

.01.

I don't see a connection between the --

17 MR. STROSNIDER:

-- purposes.

18 MEMBER CATTON:

The number you've chosen can 19 be very difficult to demonstrate.

l 20 MR. STROSNIDER:

Well, there's -- no.

{

21 There's, there's a difference here.

I mean, we i

22 established some performance criteria.

I think five times 23 ten to the minus second, for example, conditional, 24 conditional on main steam line break.

/~(

25 MEMBER CATTON:

I don't think the number's NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

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l 94 t

1 what's important.

I 2

MR. STROSNIDER:

No.

And I agree, l

7-t 1

~

3 MEMBER CATTON:

Do you --

4 MR. STROSNIDEP:

But the point there is that's 5

a, that's a high level performance goal.

Now we're 6

talking about how you accomplish it.

7 MEMBER CATTON:

But, before you --

8 MR. STROSNIDER:

What we're saying is you need 9

to have these elements of defense-in-depth.

You can't 10 have one thing that's going to, that's going to make sure 11 you attain that performance goal.

You need to have all 12 these elements in the right balance.

{

13 MEMBER CATTON:

But, now, that performance i

\\l 14 goal, the number that you chose, should have been pulled 15 out of a PRA somehow.

16 MR. THADANI:

But I think --

17 MEMBER CATTON:

To tie all this --

18 MR. THADANI:

I think, let me see if I can't 19 give you -- I don't think we know if you take each element 20 of the, the package on rulemaking, non-destructive 21 examination, and there are lots of unknowns, and we've 22 been pushing to make sure the techniques for understanding 23 what's going on are improved, and that those improved 24 techniques are used.

(O

_,/

25 Now, what we have done is let's take a look at NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS l

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the experience out there, which is based on today's 2

requirements, basically.

And we said really, the risk to O

3 public health and safety is not very high.

4 We did that.

That's what unresolved safety 5

issue A-3, 4,

5 did.

It came out somewhere in the range 6

of frequency of ten to the minus five to ten to the minus 7

six of core damage from these.

Maybe it was a little 8

lower in some cases.

9 MEMBER CATTON:

Yes, but these had the --

10 MR. THADANI:

But --

11 MEMBER CATTON:

-- influence.

12 MR. THADANI:

But what I'm saying is that's 13 the, the best you could do, looking at integral

,o km 14 information that we had available up to that time period.

15 MEMBER CATTON:

Well, you haven't had any 16 severe accidents.

17 MR. THADANI:

Right.

18 MEMBER CATTON:

Okay.

19 MR. TRADANI:

Right.

That's the best we could 20 do.

We, we did that analysis.

We said, with today's 21 requirements -- I can't tell you how much contribution 22 came from each piece of the requirements, but, in 23 totality, we said the risk is low enough now, now.

I 24 MEMBER CATTON:

Now, to keep it at that (3

( )

25 number, you go back through your PRA and say gee, the NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

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performance of this piece must be.

2 MR. THADANI:

Right.

Right.

You could, you (D

3 could do that.

4 MEMBER CATTON:

That closes the problem.

5 MR. THADANI:

But, but what I was trying to 6

say was where, I guess, Mario's question went, in the 7

context of severe accident consideration and design basis 8

consideration.

9 I just want to be very clear that what we're 10 doing, in terms of this rulemaking, is picking on the 11 piece that has not been dealt with in the past, the high 12 temperature effects on materials.

13 And what we're saying is, if these are the new (D

\\m /

14 requirements on the industry, then we have to put them in 15 one of three classes.

Is it under adequate protection, or 16 is it enhanced protection?

17 Anything new that we go out and impose on 18 industry we have to meet certain standards.

We have to 19 meet the backfit rule.

20 And what we're saying is we believe these are 21 enhancements in safety, so they should be supported by 22 cost-benefit analysis.

As you know, under adequate 23 protection, cost is not a factor.

24 MEMBER CATTON:

Yes, but the first thing you (m) 25 have to do, then, is to show what it is.

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MR. THADANI:

Okay.

2 MEMBER CATTON:

If you can't show what it is, p-U 3

how can you carry the discussion any further?

4 MR. THADANI:

Yes, but -- no.

I, I don't 5

disagree.

That's what I'm saying.

6 MEMBER CATTON:

I think, as soon as you start 7

using risk anywhere in your statements, in order to move 8

away from prescriptive, what's the responsibility both on 9

the part of the, the enforcer, and -- I picked that word 10 up at the prior meeting, they used the word enforcer.

I l

11 know you guys don't like that, but.

12 (Laughter.)

1 13 Enforcer --

ID

%./

14 MR. THADANI:

Only when we take enforcement 15 action.

16 MEMBER CATTON:

Actually, it puts --

17 ACTING CHAIRMAN SEALE:

Well, the enforcee.

18 MEMBER CATTON:

It puts certain requirements 19 both on the, on the enforcer and on the applicant, on both 20 sides.

And you just have to know more in order to get the 21 relief you want.

There's a price you have to pay.

22 MR. THADANI:

Yes.

23 MR. STROSNIDER:

It's like --

24 MEMBER CATTON:

In this case, the price is 0

1( )

25 what's the number.

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98 1

MR. STROSNIDER:

But I'd like to make a i

2 comment on this, because you indicated that the

/-s)

(

1

'~'

i 3

performance criteria need to come out of a risk l

4 assessment.

l 5

MEMBER CATTON:

If you want to call it risk.

6 MR. STROSNIDER:

The, and the performance 7

criteria that you presented in, in the draft regulatory 8

guide, the performance criteria for spontaneous rupture 9

and for, for conditional rupture and main steam line 10 breaks came out of prior risk assessments.

11 MEMBER CATTON:

Okay.

12 MR. STROSNIDER:

NUREG-0844.

The portion we 13 are working on is the severe accident thermally induced O

\\s /

14 portion, and that's the, that's the part we're still 15 working on.

16 But I would go further and make one point.

17 You could, if you had the rigorous risk assessment, you 18 could go in and actually probably say that, from a risk 19 perspective, you could accept a higher cor'itional 20 probability of failure and still show that risk is 21 acceptable.

22 MEMBER CATTON:

Absolutely.

23 MR. STROSNIDER:

All right.

But that's where, 24 again, you know, we look at that and say are you

/~.

(,)

25 maintaining defense-in-depth if you do that?

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99 1

some concern about driving the conditional probability 2

failure so high that we think we lose the balance in

-)

3 defense-in-depth.

4 So, you know, there's some judgment involved 5

at that point, but that's how those numbers that are in 6

the rule are developed.

We have not totally come to grips i

7 with the thermally induced severe accident portion.

8 MEMBER CATTON:

I understand that.

1 9

MR. STROSNIDER:

That you haven't seen.

10 MEMBER CATTON:

But anyway you cut it, you're i

11 going to make a change.

You either have to argue that 12 it's not going to increase risk, or that it doesn't do 13 anything, or that risk will be -- I mean, you have to say A

(,/

14 something about that, or else you can't call it risk.

15 MEMBER APOSTOLAKIS:

They claim they do that 16 in the NUREG that we have not seen.

17 MEMBER CATTON:

They do, they do in a lot of 18 them.

I'm not sure what they've done with the, the 19 thermal performance part.

We'll find out.

20 ACTING CHAIRMAN SEALE:

Well, that's going to 21 be something we'll have to look for.

George, you had?

22 MEMBER APOSTOLAKIS:

I think we're discussing 23 several issues at the same time.

24 ACTING CHAIRMAN SEALE:

I think you're right.

(~ha 25 MEMBER APOSTOLAKIS:

One of the issues is --

t l

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ACTING CHAIRMAN SEALE:

You're probably right.

1 2

MEMBER APOSTOLAKIS:

-- you know, how do you 3

set criteria and so on.

But you said something 1

4 interesting earlier, which I think really we ought to 5

think about.

You said we have the criteria of 0.1 for 6

individual tube rupture, right?

7 And then we also want to tell them what would 8

be the elements of a good program that would make sure 9

that we get the 0.1.

Was, did I understand that 10 correctly?

11 MR. STROSNIDER:

We have, and we've tried to 12 cast it in the context of a performance-based regulation.

13 We indicate that a program would have certain elements.

(/

14 And I will acknowledge that's somewhat prescriptive.

We 15 don't indicate, or we're not prescriptive in exactly what 16 those elements are.

17 For example, we say you have to do in-service 18 inspection.

All right.

And we say you have to do tube 19 plugging.

But there's flexibility in how --

20 MEMBER APOSTOLAKIS:

Right.

21 MR. STROSNIDER:

-- the licensees would do 22 that to accomplish the goal.

But then there are actually, 23 if you look in the rule, some, what I'll characterize as 24 mini-performance goals, which say well, you know, you (G,)

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101 l

1 end of cycle, you still meet the performance goals.

That 1

2 is, the factors of safety.

/-s')

3 If you don't meet the performance goal, we i

4 would go back and say well, what happened?

Was this a 5

problem in that your inspection fell down, and you didn't 6

find it?

Are you plugged at too high a level?

Or, your 7

inspection method wasn't qualified well enough?

All 8

right.

So, see where the, where the program broke down.

i 9

But we, the point I was making earlier is that 10 we believe you need all those elements to provide some 11 defense-in-depth, because we know that inspection alone 12 won't do it, we know that primary or secondary leakage 13 monitoring alone won't do it.

You need those combination Ak-14 of things to really effectively accomplish what you want s

15 to do.

16 MEMBER APOSTOLAKIS:

So, there must be 17 something about this 0.1, this particular situation, that 18 makes you think that way.

Is it because you don't believe 19 that, that one can demonstrate convincingly that they have 20 satisfied the criterion without really having this program 21 in place?

22 If I take a, a piece of equipment that's not 23 very important, and I have a long statistical record with 24 it, and I show you statistical records, and I calculate i

rm( )

25 that the, the corresponding number is 0.5.

It's less than NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

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102 1

0.1.

Everybody's happy.

l 2

MR. STROSNIDER:

Yes.

7--

I I

3 MEMBER APOSTOLAKIS:

I don't need to have a

(

4 program in place.

So, what is it in this particular case l

l 5

that is not as convincing in this example, so you feel the i

6 necessity of imposing these requirements programmatic 7

requirements?

8 Because, I mean, you mentioned that there is 9

flexibility as to how to meet the individual requirements, 10 but I would say, well, flexibility also might be to say 11 you guys come and show to me that it will be less than 12 0.1.

13 Now, you may decide to do it by showing to me f'8 i

i

\\>

14 that you have a program in place, by showing some 15 statistical evidence showing some calculations.

But it's 16 up to you.

So, I'm raising now the flexibility to a 17 higher level.

18 So, what is the process that makes us decide 19 at which level we want to impose requirements?

I think 20 that's a key issue that has to be resolved, if we want to 21 move ahead with performance-based regulation.

22 Because, you know, I think the ACRS has, is on 23 record that the performance criteria should be imposed at l

24 as high a level as possible, assuming that the highest O(

i

,/

25 level, of course, core damage, or.

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103 1

MR. HOLAHAN:

Can I, let me make a few general 2

comments, because I'm not, I haven't really thought S

\\-

3 through this case with the steam generator rule.

j 4

But, in the reg guide, we have a section on 5

performance monitoring strategies, and we do identify a 6

hierarchy among the possible ways of doing performance 7

monitoring.

And I think that one -- we gave, we gave six 8

layers, but I think you could develop a different scheme.

9 And, in effect, if you look at that scheme, I 10 think it answers your question, because what it would say 11 is, if you have abundant data being generated under real 12 demand type situations, then you don't need any sort of 13 program at all.

You have real monitoring.

/'N 14 But there are other situations in which you're 15 using some surrogate.

You're getting information, but 16 it's not exactly under demanding situations.

17 There are even other circumstances under which 18 you're getting very little information.

The example I 19 keep coming back to is a seismic qualification of 20 equipment.

Okay.

Plants are out there.

We have 2,000 21 reactor years of experiences, and we have no, basically no 22 data on, for nuclear power plants on seismic.

23 So, in that case, where you have rather poor 24 information being provided on a, from performance

(_)

25 monitoring, then you need a program.

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MEMBER APOSTOLAKIS:

Okay.

2 MR. HOLAHAN:

And so I think, and there's a g)

('"

3 whole gradation among those, to say how much program you 4

need, I think, is how little performance information 5

you've got.

I mean, you've got to balance those.

6 MEMBER APOSTOLAKIS:

So, it's an issue, 7

really, of the uncertainty that I kept referring to, in 1

8 the result.

9 MR. HOLAHAN:

Yes.

10 MEMBER FONTANA:

Let's, let's take it down to, 11 again, to steam generator tubes.

You have a lot of l

12 requirements on how to inspect the tubes, and identifying 13 flaws, and that sort of thing.

'\\

V 14 And, as far as I know, there's not much data 15 on how the flaw configuration affects the response of that

)

l 16 tube to a, a high temperature, high pressure challenge.

17 MR. HOLAHAN:

Yes.

18 MEMBER FONTANA:

Now, having a program that, 19 that goes into great detail on how you inspect the tubes 20 is not going to affect the, the response of that, of that 21 steam generator, as far as you know, as much as doing 22 something else, like make sure, making sure the primary 23 system is depressurized.

So, --

24 MR. HOLAHAN:

And I think the rule would allow im

(~.s) 25 either approach.

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105 1

MEMBER FONTANA:

It has, it would have to, I 2

guess.

3 MR. HOLAHAN:

Yes.

4 MEMBER FONTANA:

Because you don't have any 5

information on the other.

6 MEMBER APOSTOLAKIS:

But, but did you use this 7

kind of reasoning in your development of the program?

8 MR. STROSNIDER:

Yes.

Those, those are 9

exactly the considerations we've been considering.

10 MEMBER FONTANA:

Or keeping the steam 11 generator full of water.

12 MEMBER APOSTOLAKIS:

The question is --

13 MEMBER FONTANA:

Or gas.

hCl 14 MEMBER APOSTOLAKIS:

-- how far down do you 15 go, right?

16 MR. HOLAHAN-Yes.

17 MEMBER FONTANA:

It depends on how far down do 18 you have to go.

19 MEMBER APOSTOLAKIS:

Yes.

20 MR. HOLAHAN My recollection is --

21 MEMBER APOSTOLAKIS:

Because it's --

22 MEMBER FONTANA:

No.

23 MR. HOLAHAN:

My recollection is the draft of 24 the rule allows an alternative, which says, if you can get

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106 1

challenge to the tube'below ten to the minus six per year, 2

then you don't have to, you know, worry about its response fs

(

)

3 to those demands.

4 MEMBER CATTON:

So, you see, that would allow 5

them to go the other route, which is DF factors from the 6

top of the steam generator and everything.

It wouldn't?

7 No?

8 MR. JONES:

No.

Bob Jones, staff.

No.

9 MEMBER CATTON:

You're still going to assume 10 the steam generator tube bursts out in the atmosphere?

11 MR. JONES:

No.

12 MR. HOLAHAN:

No.

13 MR. STROSNIDER:

The objective is, is to n\\

i\\_/

14 maintain the, the containment bypass frequency consistent 15 with, with the Commission surrogate safety goals.

16 MEMBER CATTON:

All right.

17 MR. STROSNIDER:

So, and not get into doing 18 all these calculations, which we feel have a great degree 19 of uncertainty, and, in addition, we think would, would i

20 reduce this defense-in-depth concept we've been talking 21 about.

And part of --

22 MEMBER CATTON:

It isn't exactly defense-in-23 depth.

24 MR. STROSNIDER:

Well.

Going to violation of 7

(,/

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l l

107 l

1 as maintaining defense-in-depth.

I 2

MEMBER SHACK:

Wouldn't you rather prevent the N/

3 accident, Ivan, rather than demonstrating that the, its 4

consequences aren't as bad as you think they are?

l 5

MEMBER CATTON:

Well, of course.

6 MEMBER SHACK:

But the thing is, as long as 7

you're, as long as, as the judgment --

8 MEMBER CATTON:

You use the word risk, and you l

9 combine it either with based, or informed, or whatever, 1

10 and now you work your way down, and what you have is a 11 performance requirement for the tube.

l 12 MEMBER SHACK:

Yes.

Yes.

13 MEMBER CATTON:

It's only performance based

[ )

\\_/

14 regulation if it's tied back to the risk.

And that's the 15 part that I don't --

)

16 MEMBER SHACK:

It is, well, if you want to 17 argue that, --

18 MEMBER CATTON:

Because we're going to impose 19 defense-in-depth.

20 MEMBER SHACK:

Yes.

21 MEMBER CATTON:

Where, where we're putting 22 defense-in-depth in place is that we're not going to let 23 you take credit for the decontamination that could take 24 place in the top of the steam generator, or, or wherever, m

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If that kind of a NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

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i 108 l

1 clea

"- 4.ement is made, then I don't have anymore problem 2

with it.

1

,~s

\\

'j

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3 MEMBER FONTANA:

I do.

4 MEMBER CATTON:

Now, you still may have to 5

argue about the probability of failure of the tube.

6 MR. HOLAHAN:

Yes.

7 MEMBER CATTON:

But at least the defense-in-8 depth question is taken care of.

That is the defense-in-9 depth.

Is not allowing credit for decontamination in the 10 separator, and the cycle, and so forth.

11 MEMBER FONTANA:

No.

12 MEMBER APOSTOLAKIS:

No.

That would be a new 13 interpretation of defense-in-depth, in my opinion.

V 14 MEMBER CATTON:

I've been --

15 MEMBER APOSTOLAKIS:

A conservative approach.

16 MEMBER CATTON:

Well.

17 MEM.BER APOSTOLAKIS:

Conservatism and defense-18 in-depth are not the same thing, I don't think.

19 MEMBER CATTON:

Probably not.

20 MEMBER APOSTOLAKIS:

No.

21 MEMBER CATTON:

No.

22 MR. JONES:

Ivan, the way the steam generator 23 rule is written, or the reg guide, which says how you meet 24 the severe accident part, basically it starts from a

,a

(

)

25 premise that, if you meet ten to the minus six, large NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

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109 i

1 early release is acceptable.

2 MEMBER APOSTOLAKIS:

Okay.

,_s

! /

i

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3 MR. JONES:

And then you can do it by either 4

demonstrating that the challenge is, is not there.

5 MEMBER APOSTOLAKIS:

Yes.

6 MR. JONES:

That you don't have a dry high 7

pressure, high temperature condition, or do a risk 8

analysis that looks at the challenge and the conditional 9

failure probability of the steam generator.

10 And have, and have even -- in doing that, how 11 you assure you meet that back end, if you use the 12 probability of, the conditional probability of failing the 13 tube may be related to what your program is, and what data p(_)

14 you have in order to size, detect, and repair flaws.

15 So, you have a, you know, it is flexible in 16 how you accomplish that goal.

But the goal is ten to the 17 minus six.

If we do not account for attenuation.

I will 18

-- that's just flat out clear, at this point.

19 MEMBER CATTON:

If you took the large early 20 release approach, you could bring decontamination into the 21 picture, couldn't you?

Because isn't large early release 22 in magnitude?

23 MR. JONES:

No.

i l

l 24 MEMBER CATTON:

No?

rm

(

)

25 MR. JONES:

Not as we define it.

(

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110 1

MR. STROSNIDER:

But, to summarize this, we'd 2

be basing the performance criteria on failure of the fuel,

/T

\\~')

3 failure of the steam generator tubes, failure of the 4

containment.

5 And I asked the question where did my defense-6 in-depth go.

If we're going to give up two of the 7

barriers with some frequency, okay, the argument is well, 8

that's certainly, you know, I want to keep the third one.

9 MEMBER CATTON:

I'm not asking to give up 10 anything.

I just want to make sure that --

11 MR. STROSNIDER:

But --

1 l

12 MEMBER CATTON:

-- whatever --

)

13 MR. STROSNIDER:

But I think there's a r~N

?

)

\\_/

14 difference in what you're saying.

15 MEMBER CATTON:

If it's clear and you can 16 interpret it, and everybody knows what you mean.

l 17 MR. STROSNIDER:

Well, we agree with that, and 18 that needs to be well-documented.

I guess one other point 19 I'd make, though, is, is that we have, and I think it's 20 more than semantics.

We, we have the discussion about 21 risk-based versus risk-informed.

l 22 MEMBER CATTON:

Yes.

l l

23 MR. STROSNIDER:

And I think one of the things 24 in your letter suggested that, if you had a rigorous risk n()

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l

l 111 j

l l

1 then you would determine where you want to put margins.

i 1

l 2

MEMBER CATTON:

Okay.

1 (

\\

\\

3 MR. STROSNIDER:

In the ideal world, there's 4

no argument with that, all right.

What we have done may l

5 not be ideal, but I would characterize it as rigorous i

6 informed.

Okay.

We do that analysis to the extent we 7

can.

8 But, more importantly, where we establish 9

performance criteria, we go back and do enough risk 10 assessment, or look at risk assessments that have been 11 performed, to give ourselves confidence that it, you know, 12 maintains the correct level of risk.

And I think there's 13 really a difference between risk-informed and risk-based.

/s i

\\

A s/

14 And, again, getting back to risk-based, you s

15 may, you may completely lose defense-in-depth, because you 16 could drive some of these parameters to conditional 17 failure of probability one on tubes, as, as I said 18 earlier, in which case, you know, defense-in-depth, you 19 could argue you've lost that.

20 MEMBER APOSTOLAKIS:

Well, let me, let me 21 change the argument here.

If you have the programmatic 22 requirements that you're putting in the rule in place, why 23 do you need the 0.1 conditional probability of failure?

24 What does that add to anything?

7m

, (j 25 MR. JONES:

George, let me answer that.

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112 l

1 me try from slightly different view than what Jack would.

l 2

The original failure criteria is basically based on

,!(

)

3 historical d.ata.

And, to some extent, we're saying the 4

historical failure rates are acceptable.

l 5

On the other hand, we know that tubes are 6

degrading differently than what a lot of that historical 7

data has been based on.

And we're plugging them under 8

certain indications today.

9 As we move forward with the rule, they're 10 allowed to come up with alternative criteria as to where 11 to plug, beyond where our database is based on.

So, now, i

12 we no longer know what that database is.

13 So, we would say, for those, the program has k.-

14 to have a certain ISI element, inspection element.

You've 15 got to be able to characterize it to some degree, so you 16 come up with some understanding as to what the failure 17 rate is.

18 So, some of the detail of what the 19 requirements are, but we have some qualifications, and 20 other things down in there, is inherent in there, but, in 21 a sense; those programmatic requirements all are 22 considered in trying to demonstrate you meet your failure 23 criteria.

24 And then, to assure that, we use the

(~N,

( p/

25 performance monitoring, and I forget the, the fancy NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

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113 1

buzzword in the rule, but it's basically what, after you 2

open up the steam generator, and see what's left, and what

,s C.

3 you find and, and repair, to try to project and see what 4

you actually came up with, to make sure that you're 5

maintaining that level of --

6 MEMBER APOSTOLAKIS:

Yes.

7 MR. JONES:

That's there.

8 MEMBER APOSTOLAKIS:

I guess the point I want 9

to make is we all have this mindset that the PRA numbers 10 are not very good, and there's always something left out, 11 and we have to impose additional requirements.

So, I'm 12 reversing the argument.

13 If I impose these requirements, why do I need fm k_

14 the PRA number?

Why isn't it good enough to have the 15 programmatic requirements?

What is it that the PRA number 16 of 0.1 brings into this that is not already in the 17 programmatic requirements?

18 MR. STROSNIDER:

Okay.

If you -- with regard 19 to the programmatic requirements that are in the rule, and 20 in the regulation, they are performance based, in the 21 nense that we're not telling people this is the inspection 22 probe you have to use, this is the level you have to 23 repair the tube at.

24 What you're suggesting is sticking with

(%)

/

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114 1

that we currently have, which says go in and do this 2

inspection, plug at 40 percent.

n i

i '!

i 3

And it's a very prescriptive process which 4

does not allow for changes in technology, improvements in 1

l l

5 inspection methods, or changes in, in degradation methods, 1

l 6

and that's one of the things we wanted to get away from.

t 7

The --

8 MEMBER APOSTOLAKIS:

But, wait.

i 9

MR. STROSNIDER:

The programmatic elements 10 that we have in this rule, as, as they're written, they're 11 not directly related, okay, quantitatively related to the 12 performance goal that you wait to achieve.

13 They're more of these are the things we're AU 14 aoing to look at, if you don't meet the performance goal.

15 We'Ic going to come in and look at these areas, and see 16 how you performed in them.

17 In a sense, they're, they're basically there 18 for enforceability and for establishing the expectations 19 of, you know, what areas people need to be looking at to, 20 to accomplish these goals.

I don't know if that helps.

21 MEMBER APOSTOLAKIS:

Well, it certainly does, 22 but.

Don't get me wrong.

I mean, I'm not advocating 23 going back to, you know, overly prescriptive approach we 24 used to, we still have.

O l \\ )

25 ACTING CHAIRMAN SEALE:

Somebody was about to i

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115 1

say sold, I think.

2 (Laughter.)

! ]\\

\\'

3 MEMBER APOSTOLAKIS:

But, but what I'm, what 4

I'm trying to do is, is attack a little bit the approach 5

that says PRA numbers are soft and no good, so we have to 6

have additional requirements.

7 MR. STROSNIDER:

Yes.

8 MEMBER APOSTOLAKIS:

And I'm changing the 9

argument to say, if I impose the additional requirements, 10 maybe I don't need the PRA number.

Now, what, why am I 11 doing that?

Because I think, I mean, my point of view is 12 that we should impose the minimum number of requirements 13 to do our job, to assure public health and safety.

A N.

14 So, if I start with a PRA number, and this is 15 broader than just the steam generator, than I am going to is it that that number represents?

h.ask myself what IA l'7 MEMBER CATTON:

Yes.

18 MEMBER APOSTOLAKIS:

What is it that's left 19 out?

Do I need anything else to supplement this 20 particular regulation?

And I'm saying apply the same 21 thing to the prescriptive regulations.

22 If I have this program in place, do I need a 23 PRA number at this level?

Maybe I need it at one of the 24 higher levels.

It all comes down to how much do these

,-( )

25 requirements overlap.

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And, by asking the second question, namely, if 2

I have the program in place, do I need the PRA number, I 7_

(

3 think maybe you will see the problem in a different light.

4 That's all I'm saying.

5 Because, you know, I'm sure they overlap.

6 And, in this case, maybe they don't overlap a lot.

I 7

don't know.

So, I will, we will discuss that at later 8

meetings.

9 ACTING CHAIRMAN SEALE:

Well, I think the, the 10 witching hour is almost on us, that we've all agreed to.

11 Some people have had flights that have survived the i

12 weather, so far anyway.

But I want to do something before 13 we quit.

O

\\_sl 14 I'd like to go around the table quickly, and 15 have each member of the Committee identify things they 16 would like to hear about in one of the meetings, whatever 17 it may be, whichever one it may be, that are going to be 18 scheduled to follow this, George, do you want to start?

19 MEMBER APOSTOLAKIS:

I don't want to, but I 20 will.

21 ACTING CHAIRMAN SEALE:

All right.

22 MEMBER APOSTOLAKIS:

My main, main problem 23 with the document I read last time was that it was not 24 clear to me what role risk assessment played in the rh

(,)

25 various requirements that are there.

And I --

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ACTING CHAIRMAN SEALE:

Is this with regard to 2

the steam generator?

3 MEMBER APOSTOLAKIS:

No, just in general, yes.

4 ACTING CHAIRMAN SEALE:

Okay.

5 MEMBER APOSTOLAKIS:

I have been told several 6

times that there is this NUREG report that will clarify 7

alot of things, so I would like to have an opportunity to 8

read that report well in advance of a subcommittee or a 9

full committee meeting, so I will be able to, to then ask 10 more intelligent questions.

11 Because I think this particular rule really 12 would be impossible, and we have to be very careful how we 13 do things.

Frankly, those last five pages of the, of the C'\\

kI 14 document I saw last time turned me off completely.

15 I mean, PRA was an add on, added new 16 requirements.

You know, that's the thing that the 17 utilities don't like, and I don't like.

I'm sure a lot of 18 other people don't like it.

19 That PRA is there only to create new 20 requirements.

That we keep everything else in the rule, 21 and we just add this.

That may be the wrong perception, 22 but that's a perception.

And, as you know, we live by our 23 perceptions.

24 So, that's really what I would like -- I would p)

(

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l 1

me a key here, to understanding what the approach of the 2

staff was to this.

/-s\\

N_Y 3

ACTING CHAIRMAN SEALE:

Ivan, do you want to 4

make any comments?

5 MEMBER CATTON:

I'll just sort of reiterate 6

what I said earlier.

I think the steps are clear.

You 7

need to have clearly stated objective, functional 8

requirement, performance requirement, and these are very i

9 short, and then you need verification, acceptable 10 solution, which could be prescriptive.

11 You could just say something.

It needs to be 12 thus and so.

And an, an allowance for alternative 13 solutions, which could be purely PRA.

[~N 14 And, again, if you want to impose defense-in-15 depth, you can carry the 0.1 final barrier failure right 16 through to the steam generator tubes, because it is a 17 barrier if the other is open.

18 But I think, if you do that, you should 19 include the SRVs, the safety relief valves and their 20 failure, because that's a part of that pathway to the 21 outside that has been left out.

22 So, the 0.1 could well be the higher number in 23 the steam generator tube, and still meet the defense-in-24 depth criterion.

(q_)

25 And I'm just perplexed with the use of the NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

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119 I

word risk when it's not connected to the regulation in 2

some sort of a direct way.

And you could make the

' ')

t 3

connection just by making a statement.

i 4

That 0.1 is good enough for the containment, l

5 and therefore, to keep risk at where we think it is, 0.1 6

is what's going to be used for the tube.

It, it ought not 7

be hidden.

It should be right up front, what it is.

8 And, if I were writing the rule, I would have 9

six sections, and that would be the six items that I 10 mentioned, objective, functional requirement, performance 11 requirement, verification, alternative methods that are 12 allowed.

Finito.

That's all.

Finito.

13 ACTING CHAIRMAN SEALE:

That's not in English.

f'T

()

14 (Laughter.)

15 MEMBER FONTANA:

I've already said, but I'll 16 reiterate a little bit.

And that is, as you apply these 17 high level risk approaches, it is a very difficult 18 problem.

It seems like you picked the worst thing you 19 possibly could, using the steam generator rule as the 20 place to apply this.

21 It, I think it would be very interesting and 22 instructive to identify those things that come from a top 23 level risk requirement, and then, as you work into 24 specifics and apply those things which they don't apply, fs

(

)

25 in which you have to do something else, identify those sm-NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

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120 1

things which you call defense-in-depth and try to identify 2

the basis for why you did somethirig like that.

,_s T

)

~'

3 And I think that would be very instructive, 4

because you, you know, you can talk about the high level 5

right way of doing things in the best of all worlds, and 6

then, when you get to the nuts and bolts, you start 7

stripping threads and things like that.

8 So, identifying those things which are 9

trackable to the high level requirements and id* tifying 10 those that just don't work, I think would be very useful.

11 That's all for me.

12 ACTING CHAIRMAN SEALE:

Dana?

13 MEMBER POWERS:

I think we're going to spend a

()

14 lot of time working on this high risk.

But the 15 performance part of it has got to be addressed at some 16 point.

17 As I go through the document and look at it, 18 my first reaction is just I have awful hard time knowing 19 what my design to standard is here.

What, what I'm 20 supposed to have by the end of the day, that is going to 21 get me through.

22 So, if we talk about some of those things, and 23 we have opportunity, something that can help me understand 24 what is, exactly this document is going to look like, or rm t

)

25 this program is going to look like, and what standards s,

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121 1

it's being designed to, that would help me a lot.

2 MEMBER CATTON:

That's the performance

,o

(

)

'^#

3 requirement?

4 MEMBER POWERS:

It's the performance part of 5

it.

6 MEMBER CATTON:

Yes.

i 7

MEMBER POWERS:

I just, it's just that I sit 8

there and say now, if I had to do this, what am I supposed 9

to do?

And, in some cases, it's very helpful.

It says go 10 look at the EPRI documents.

11 And, if you put those in, that's okay.

But, 12 in a lot of cases, it lacks those things.

And I'm just 13 not sure what I'm being told, what standard I'm being held o) 4

)

C/

14 to here.

15 And, since I don't have a very clear tie to 16 evaluating risk, I don't know what I have.

And maybe it's 17 there, maybe it's not.

That's, that's the part that I,

18 that hasn't been touched on already, that I think I have 19 troubles with.

20 MEMBER CATTON:

And, actually, in this case, 21 it's a ratchet, isn't.i t, because the containment failure 22 is 0.1, conditional containment failure is 0.1.

23 If the tube is held to 0.2.

you've got the.

24 the SRVs that are still between you and the atmosphere, rh

!.vl 25 and they have to fail first.

So, it's really the product NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

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of the two that should be 0.1.

2 MEMBER POWERS:

But the containment 0.1 7~

6 a

\\,J 3

doesn't have a good basis.

4 (All at once.)

5 MEMBER POWERS:

I wouldn't look at defense-in-6 depth quite that way, because, when you look at barrier 7

concepts for defense-in-depth, you have to have multiple 8

independent barriers.

It's difficult to sit down and 9

argue that tube and SRV are, constitute independent j

10 barriers.

11 MEMBER CATTON:

They are independent.

12 MEMBER POWERS:

No.

Failure of one can lead 13 to failure of the other.

l 7U 14 MEMBER CATTON:

Well, see, what they're doing 4

15 now, Dana, is failure of one leading to a 0.1 probability 16 of failure of the second.

And that may be more than they 4

17 really need.

Anyway, I just raised the issue.

18 MEMBER POWERS:

Yes.

19 MEMBER CATTON:

That, in this case, there are 20 two barriers.

I mean, it's not just the containment wall 21 that you look at.

You have the steam generator tube, and 22 then you have the SRV.

23 MEMBER APOSTOLAKIS:

But that brings up a --

24 MEMBER POWERS:

Well, I think you're right

/3

(,)

25 that the safety relief valve's open if you vent the, if NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

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i 123 1

you blow the tube.

I, I don't -- I think that probability l

2 is one.

(

)

3 MEMBER CATTON:

I don't know, I don't know 4

about that.

5 MEMBER POWERS:

Well, I --

6 MEMBER CATTON:

Well, but what we're trying to 7

do, Dana, is avoid the I thinks.

8 MEMBER POWERS:

I think NUREG 1150 used 0.2 9

million, which is close enough to one.

10 MEMBER APOSTOLAKIS:

That, that triggers my 11 memory.

I wanted to ask earlier who within the agency is 12 keeping track of the very high level of these various 13 contributions or requirements, and make sure they are l /~h s

\\_ /

14 cons.istent.

1.5 That, that's, you know, the issue we're 16 discussing now, of you have a requirement on a particular 17 issue, say, 0.1 or

.01, something else on something else, 18 something else on something else.

19 Who looks at, at all of these and says gee, 20 you know, if I take all of these, the core damage i

21 frequency is ten to the minus two?

That high level i

22 thinking.

Joe?

23 MR. STROSNIDER:

Ah, good question.

24 MEMBER APOSTOLAKIS:

Something that.

p t

i 25 MR. STROSNIDER:

I think you have to

%)

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124 1

recognize, before I give you the, the obvious answer, the 2

thinking in the reg guide is evolving.

)

1

\\

/

3 It's, it would be wrong to express right now 4

that, if you took the current version of the regulatory 5

guides and the current version of the steam generator 6

rule, you'd find complete coherence.

7 If you did, it would be a miracle, because I 8

think the, the, and I mean this quite literally, the 9

latest version of the regulatory guide is supposed to be 10 finished at 3:30 this afternoon.

And I know Jack hasn't 11 faxed it into his --

12 MEMBER APOSTOLAKIS:

I can wait for five 13 minutes.

(~\\

\\s /

14 MR. STROSNIDER:

-- yet.

So, there's an 15 evolution going on.

I think one thing that is clear 16 coming out of this is a commitment that we have to make 17 internally, and the utilities are also going to have to 18 make.

To track what the risk is of an individual plant is 19 a function of time, and we'll both have to do that.

20 Their job will be more difficult, because they 21 will have to look at the changes that have been made that 22 affect the risk, some of which don't require approval from 23 the NRC.

So, it's broader than just looking at what, what 24 the submittals to the NRC are.

/~N

()

25 We, in turn, are going to have to look at the, NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

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125 1

at what all our rules are saying, and how they affect the 2

whole game, so that we are not then requiring either 3

something ridiculous or something that's unsafe.

~

4 So, who's doing it right now?

Well, right 5

now, we're not regulating that way, and so we'll, probably 6

nobody, except collectively, everybody that's been at this 7

table --

8 MEMBER APOSTOLAKIS:

Yes.

9 MR. STROSNIDER:

-- worries about that all the 10 time, so I think, among us, we, we have that feeling 11 without a formal program to do so.

But, as we get into 12 this, clearly, we're going to have to do something along 13 that line.

g3

\\--

14 MEMBER APOSTOLAKIS:

Okay.

15 ACTING CHAIRMAN SEALE:

Tom, do you have any 16 additional comments or questions that you want to raise at 17 the next meeting?

18 MEMBER KRESS:

I don't know if they're 19 different or additional, but.

I am quite interested in 20 how one arrives at.05 I think we mentionen. for the tube 21 failure, and so I'm quite interested in that.

22 How one allocates bypass, with respect to the 23 ordinary containment failure.

Well, if ordinary 24 containment failure is summed over all the, and weighted

,a

)

25 over all the sequences, this 0.1, what allocation, how is NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

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126 1

does one allocate the bypass effects within that?

2 The other thing I have a little problem with 7-(

i 3

right now is how does one take the criteria from tube 4

plugging, based on the findings of the inspection or the 5

leak rates, voltage criteria or the leak rate criteria.

6 How does one translate that into a probability of tube 7

failure?

8 I'm not sure I've -- is that supposed to be in 9

the NUREG?

10 MR. STROSNIDER:

Well, to give you a very 11 brief summary, there, there are some modes of degradation 12 where we have sufficient data to calculate that sort of 13 probability.

Outside diameters stress corrosion cracking

,O.

.(_/

14 with a voltage base criteria is one where we have that.

15 There are others where we don't.

16 MEMBER KRESS:

Yes.

37 MR. STROSNIDER:

And that's why there are 18 deterministic criteria in the reg guide, as well as 19 probabilistic.

20 MEMBER KRESS:

Okay.

You don't really, you're 21 not able really to go from there to probability yet?

22 MR. STROSNIDER:

Not in, not in, --

23 MEMBER KRESS:

Yet.

24 MR. STROSNIDER:

Really -- not, not in every

("%

(,)

25 case.

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MEMBER KRESS:

That's why it's risk-informed, 2

and you can go to these performance criteria.

If you want

(

4 3

to go, you can back off and use performance criteria.

4 MR. STROSNIDER:

That's right.

5 MEMBER KRESS:

Because you can't really do 6

this.

I have a problem with that.

7 MR. STROSNIDER:

Yes.

8 MEMBER KRESS:

Because I think that's the 9

essence in performance.

10 MR. STROSNIDER:

We're trying to create a 11 framework where people could develop the data and the 12 methodologies to do those calculations.

And a large part 13 of that 60 or 70 page reg guide is how you do that.

/~s

_/

14 MEMBER KRESS:

Okay.

15 MR. STROSNIDER:

So.

16 MEMBER KRESS:

And, in the meantime, you hope 17 your performance criteria are sufficient to give you 18 acceptable risk?

l 19 MR. STROSNIDER:

Well, yes.

In the meantime, 20 we have deterministic criteria which are based on the 21 years of experience we've had to this point, which, which 22 have, we believe, maintained adequate level of risk.

To l

23 go beyond those, you have to develop these additional 24 models and database.

n(,)

25 MEMBER KRESS:

That's the only --

l NEAL R. GROSS I

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128 1

MEMBER POWERS:

Jack, Jack, when you, they use 2

the word mechanism in these various documents, both you

\\.,I 3

and the industry.

4 Maybe it's not really a mechanism that has to 5

be identified.

It's just that the flaw has to look like 6

it came from some mechanisms that you have enumerated.

Is 7

that right?

8 MR. STROSNIDER:

True.

Although, you know, if 9

you get into details, different corrosion mechanisms might 10 have different growth rates.

11 MEMBER POWERS:

That's right.

But we're not 12 even, we're not even, when I find an axially oriented 13 crack on the outside, that is enough to class it as a

(~%

(s /

14 mechanism.

I don't have to know absolutely that that came 15 from stress relation cracking.

16 MR. STROSNIDER:

Well, when you start looking 17 at the integrity of the tube, and the idealization of the 18 defect type, it may not, it's probably not all that 19 dependent upon what the mechanism is.

So, we have to be 20 careful.

If, if you look at a fatigue crack.

21 MEMBER POWER.S:

Yes.

22 MR. STROSNIDER:

That's --

23 MEMBER POWERS:

That was the next one I was 24 going to ask you.

()

25 MR. STROSNIDER:

The fatigue crack.

If, if I NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

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129 1

take a crack that was developed, it's macroscopic size.

2 One by fatigue, and one by the sort of circumferential p

/

T i

/

3 cracking that we're, we're see at the top of the tube 4

sheet.

5 They have significantly different structural 6

responses, because the fatigue crack is a coplanar flaw 7

with, with no ligaments in it.

The stress corrosion crack 8

has a lot of small ligaments, which can significantly 9

increase the load carrying capability.

10 MEMBER POWERS:

Yes.

11 MR. STROSNIDER:

So, in some cases, the 12 mechanism is important, and --

13 MEMBER POWERS:

But the question is I,

I found

/

s V

14 this macroscopic crack on the outside, and I said well, 15 and I found it by an ultrasonic or an eddy current 16 technique.

So, I don't know too much about ligaments and 17 detail morphology here.

18 It, in the rule, it's adequate for me just to 19 say okay, I'm going to proceed as though that were a 20 stress corrosion crack.

21 MR. STROSNIDER:

Now, I think, in fact, 22 there's, there's some discussion, I believe, with regard 23 to verifying the type of mechanism that you have, and this 24 could, this could require removing tubes, for example, --

A i

)

25 MEMBER POWERS:

Yes.

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130 1

MR. STROSNIDER:

-- and doing some

,- y 2

examination.

Another alternative that's been laid out in

?

\\

(_/

3 the, in the reg guide is to use what we've, the in situ 4

pressure test, where you actually get a direct 5

measurement.

6 You may not know exactly what the degradation 7

mechanism is, but, but you demonstrate that it will 8

withstand a certain pressure.

9 MEMBER POWERS:

That's right.

But I've got a l

10 problem with forecasting in the rule, and I --

11 MR. STROSNIDER:

I don't know what's coming up 12 next, that's right.

13 MEMBER POWERS:

And --

rs O )'

i 14 MR. STROSNIDER:

Form of degradation.

15 MEMBER POWERS:

And, you know, I find 50 16 cracks, 50 cracked tubes.

I pull one of them.

Sure 17 enough it's a stress corrosion crack, crack, but it may 18 well be one of the other 49 is, is actually a fatigue 19 crack.

20 But it's okay for me to proceed as though they 21 were stress corrosion cracks.

It's, what really matters 22 to you is location, orientation, and shape.

i l

23 MR. STROSNIDER:

No.

Actually, --

24 MEMBER POWERS:

Rather than the actual

()j

(

25 mechanism.

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i 131 1

MR. STROSNIDER:

-- I'd suggest that the l

l l

2 mechanism isn't working.

l

(

)

3 MEMBER POWERS:

You think it isn't?

'~'

4 MEMBER SHACK:

The growth rates operate l

l 5

differently when he does his operational assessment in the 6

next cycle.

7 MEMBER POWERS:

You see where my problem is?

8 ACTING CHAIRMAN SEALE:

Sure.

9 MEMBER POWERS:

I mean, the only way you can 1

10 find out whether the, what the cracks are is you have to 11 pull every single one of them.

12 MR. JONES:

It's also one of the reasons that 13 we have things like leakage monitoring in the program, r~ s k,_ l 14 because we know we can't, we will not necessarily make 15 every call absolutely right.

16 MEMBER POWERS:

Yes.

17 MEMBER SHACK:

So, if we're wrong, that will 18 hopefully give you pre-warning before you have a failure.

19 Or, it may lead to a failure, and your whole thing, or 20 your whole construct keeps you within the kind of expected 21 spontaneous failures you've observed historically.

22 MEMBER POWERS:

Yes.

But, again, you proceed 23 as though you know what those cracks are, based on your, 24 your limited sample.

You don't have to absolutely attest

[)

25 on a stack of bibles that that is --

s_-

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132 1

MEMBER SHACK:

No.

Well, the, the intent is, 2

number one, to provide reasonable assurance.

That doesn't

,s

(' )

3 mean you pull every tube, obviously.

And the second part, 4

which I think Bob pointed to, and we've been talking about 5

this afternoon, is defense-on-depth.

6 We know that in-service inspection and tube 7

plugging may not catch every form of degradation.

In 8

fact, you could have a new form show up between cycles, or 9

you could have new sparks which, which may not, you may 10 not be lucky enough to find it during the outage.

11 So, you have primary, secondary leakage.

You 12 have defense-in-depth methods.

13 MEMBER POWERS:

Well, I think I --

O)

\\_

14 MEMBER SRACK:

Which gets back to why you have l

15 all --

16 MEMBER POWERS:

-- understand.

17 MEMBER SHACK:

-- those program elements in 18 the rule.

19 MEMBER POWERS:

I, I think I understand the 20 point you're making there.

I will make one other point.

21 Every time you use the word reasonable assurance I wish 22 you'd tell me what reasonable assurance was.

Because it 23 differs, as you go through the document.

24 MEMBER CATTON:

It's a fuzzy feeling.

p) t 25 ACTING CHAIRMAN SEALE:

Warm fuzzy.

Bill?

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133 1

MEMBER POWERS:

Okay.

I mean, that's, that's 2

when I get to the, that's where I get into the trouble p.

t' 3

with I don't know how to design this thing.

4 They don't tell me exactly what reasonable 5

assurance is.

In, in a couple of places, you do.

You say 6

this will all get explained to you in section C.22-34, 7

But a lot of times you don't.

8 MEMBER CATTON:

But, if they're prescriptive 9

and they tell you that the conditional failure of that 10 tube shall be less than 0.1, now you have a design 11 criteria.

12 MEMBER POWERS:

Yes, I do.

And, and that's 13 wonderful when you can do thut.

/'%

l

\\

kl 14 MEMBER CATTON:

That's --

15 MEMBER POWERS:

I think the instances where 16 you can do that are far rarer than the instances where you i

17 have to use son.e rounder term to define what reasonable 18 ' assurance is.

19 MEMBER CATTON:

I would agree with that.

So, 20 it's our job to help them tighten it up.

21 ACTING CHAIRMAN SEALE:

Without making it 22 overly prescriptive.

23 (Laughter.)

24 ACTING CHAIRMAN SEALE:

Bill?

Q(%

25 MEMBER SHACK:

Yes.

I guess one of the things NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

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134 i

1 1

I have a question about is, is what one does with this 2

five times ten to the minus three spontaneous probability.

, - ~

, e a

3 Since it comes from mechanisms, you don't really know or 4

are able to understand, what are you supposed to do to 5

demonstrate that you're going to meet it?

6 The other one is this question that came up 7

of, you know, there seems to be agreement on the

.05, and 8

we'll, we'll believe that comes out of the risk 9

assessment, and then there's the 20 percent to each 10 mechanism kind of distribution.

11 And the defense-in-depth argument for that one 12 escapes me a little bit, and, you know, and I'd like to 13 see that one discussed for just a little bit more.

C\\

k-)

14 ACTING CHAIRMAN SEALE:

Okay.

Anything else 15 from anyone else?

16 (No response.)

17 ACTING CHAIRMAN SEALE:

Well, I believe we've 18 gotten the, the gist of what some of the questions are.

19 I'm not sui 2 rr learned a lot more today than we already 20 knew, I must'say.

I do appreciate the problem of, of 21 timing these two rules.

22 Certainly, the -- the two efforts, but 23 certainly the tendency of them to run together in, in some l

24 of the discussions doesn't help a lot.

We'll try to help f%()

25 you, and you help us in keeping them separate, as we go NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N W.

(202) 234 4433 WASHINGTON, D C. 20005-3701 (202) 234-4433

135 1

forward.

2 I would remind the members of the committee

(,_ )

k/

3 that we have here a copy of a letter from Mr. Modine from 4

NEI to, to the Chairman of the Committee on, their 5

comments on the meeting that we had last November.

6 And there's an attachment to that, which is 7

really quite, quite detailed, and I would urge you all to 8

take a look at that, for the industry's perspective.

I i

9 assume you folks have a copy of this letter as well..

If 10 not, let's make sure they have one, and we'll.

11 MR. JONES:

Well, I looked at the cc:, and the 12 copy went to Bryan Sheron, so.

13 ACTING CHAIRMAN SEALE:

Okay.

Fine.

That's

,/ s (m) 14 correct.

You're right.

I'm sorry.

Does anyone from the 15 industry want to make any comments?

Anybody else?

16 (No response.)

17 ACTING CHAIRMAN SEALE:

Well, we're waiting 18 for the revelation, then, and, with that anticipation, I 19 guess, I'll say the subcommittee meeting is adjourned.

20 (Whereupon, the foregoing ACRS joint 21 subcommitee meeting went off the record at 22 3:48 p.m.)

23 24

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+

CERTIFICATE This is to certify that the attached 3

proc. edings before the United States Nuclear Regulatory Commission in the matter of:

I Name of Proceeding:

ACRS - MATERIALS AND METALLURGY &

SEVERE ACCIDENT JOINT SUBCOMMITTEES l

MEETING 1

j Docket Number:

N/A j

P.! ace of Proceeding:

ROCKVILLE, MARYLAND were held as herein appears, and that this is the original transcript thereof for the file of the United States Nuclear 4O j

Regulatory Commission taken by me and, thereafter reduced to typewriting by me or under the direction of the court 4

reporting company, and that the transcript is a true and i

accurate record of the foregoing proceedings.

b 87 W

TORBETT RINER Official Reporter 1

Neal R. Gross and Co.,

Inc.

l_

f INTRODUCTORY STATEMENT BY THE CHAIRMAN OF THE MATERIALS & METALLURGY AND GEVERE ACCIDENTS JOINT SUBCOMMITTEE 11545 ROCKVILLE PIKE, ROOM T-2B3 ROCKVILLE, MARYLAND JANUARY 9, 1997 The meeting will now come to order.

This is a meeting of the ACRS Joint Subcommittee on Materials & Metallurgy and Severe Accidents.

q I am Robert Seale, Acting Chairman of the Subcommittee.

j The ACRS Members in attendance are:

Mario Fontana, George Apostolakis, Ivan Catton, Thomas Kress, Dana Powers, and William Shack.

The purpose of this meeting is to hold discussions with representatives of the NRC staff to gather information concerning the risk-informed, performance-based rule and regulatory guide 3

associated with steam generator tube integrity.

The Subcommittee will gather information, analyze relevant issues and facts, and formulate proposed positions and actions as appropriate, for deliberation by the full Committee.

s j

Noel Dudley is the Cognizant ACRS Staff Engineer for this meeting.

The rules for participation in today's meeting have been announced as part of the notice of this meeting previously published in the Federal Register on December 24, 1996, and January 6, 1997.

A transcript of the meeting is being kept and will be made 1

available as stated in the Federal Register Notice.

It is requested that the speakers first identify themselves and speak i

with sufficient clarity and volume so that they can be readily heard.

We have received no' written comments or requests for time to make oral statements from members of the public.

Yesterday we received a letter from the Nuclear Energy Institute concerning the proposed steam generator rule.

A copy of the letter has been provided to each member of the Committee.

The ACRS last met with the staff to discuss the proposed steam generator integrity rule on November 7, 1996.

Based on discussion with the staff and industry during that meeting and previous meetings, we commented on the proposed rule in a letter to the Executive Director for Operations dated November 20, 1996.

The d

staff recently responded to our comments in a letter dated January s

2, 1997.

The staff concluded that additional meetings ACRS were 4

j

!{O appropriate to further discuss the specifics of the proposed i

rulemaking.

Today we plan to discuss the use of probabilistic risk lV assessments in the regulatory process, specific to the steam generator rule. At a later meeting we plan to review the technical basis and the regulatory analysis associated with the rule, i

t l

We will proceed with the meeting and I call upon Mr. Thadani of the Office of Nuclear Regulation to begin.

i 4

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