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W ASHINGT ON. D. C. 20555 June 28,1982 MEMORANDUM FOR:
Ron Hernan, Midland Plant Licensing Project Manager FROM:
D. C. Fischer, Staff Engineer QU$hn SUBJECT STEAM GENERATOR OVERFILL PROTECTION At the Midland Subcommittee meeting held on June 2,1982, representatives of the applicant estimated that the cost of adding a safety grade _high level trip on each steam generator at Midland cost somewhere in the range of a quarter to a half of a million dollars per unit (total installed cost).
Dr. Okrent would like to better understand tha _ factors enterino into the_.
c_o s t_.
Would you please provide some specific information in this regard.
Please include in your response some estimate of the difference in cost, if any, if this trip had been included in the original design.
According to the transcript of the Midland portion of the June ACRS meeting (June 4,1982) the Staff reported that B&W plant steam generators should be protected from overfill from both main and auxiliary feedwater systems.
Dr. Mattson indicated that this equipment would be safety grade.
Dr. Mattson said that the staff is considering backfitting of the feedwater overfill protection to operating reactors.
He added that the Staff ought to gather some information on cost and benefit before it promulgates the requirement.
he indicated that the Staff had not yet looked at the cost side. According to Dr. Mattson the wheels are turning slowly in
'R in deciding how to promulgate new backfit requirements. He mention the role of the CRGR, the role of cost-benefit, etc. Dr. Mattson said that he did not expect to see a decision on this issue before the end of the year.
The above is my understanding of the situation as of June 4,1982.
Please e i the r con f i r_m_thi s un d n es tandi o3_o_t_p ravi de _ a_ statement _o f_l{RR_po s i ti o n_
OILthe_jnstall ati.on_of_ safety _srade _ steam _ generator _ overfill _ protect _ ion at currently licensed B&W plants.
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Attachment:
NRC Staff response to ACRS question on SG overfill protection on B&W 171 plants?
Excerpt from June 2,1982 ACRS Subcommittee on Midland Plant Unit 1 and 2 Meeting Transcript Excerpt from June 4,1982 266th ACRS Meeting Transcript bcc:
D. Okrent R. L. Tedesco R. F. Fral ey E. G. Adensam M. W. Libarkin J. C. McKinley G. Quittschr.iber 8209020126 820706 CF ADOCK 05000329 CF
9.
Will the staff require SG overfill protection on operating B&W 177 plants?
Answer i
As discussed in the work scope and schedule for Task II.E.5.1 of NUREG-0660, the staff will determine in the review of the modifications proposed for CP holders if the proposed modifications warrant backfit for operating plants.
The staff has not at this time imposed any requirement that operating plants install additional SG oyerfill protection.
It is also not known what hardware changes would be required, if any, to provide protection similar to that at Midland. Cost benefit studies in this area have not been performed to date.
This issue was discussed in Recommendation 2 of NUREG-0667, " Transient Response of B&W - Designed Reactors," May 1980. The conclusion was that provisions to throttle or trip the auxiliary feedwater system to avoid grossly overfilling the steam generators are subject to failures that could isolate the rea^ctor from its heat sink. The net effect of this type of overfill protection may increase risk.
Subsequent staff review (Mattson memo to Denton, 8/8/80) agreed with the NUREG -0667 recommendation.
Some operating plants (Rancho Seco, Crystal River 3, AND-1) have proposed g
installation of the SG 1evel protection in an effort to reduce plant sensitivity a
as part of the AFW upgrade and program required by Item II.E.1.1 of NUREG-0737.
The need for protection against steam generator overfill resulting from main feedwater control system failure is also being reviewed as part of Unresolved Safety Issue A-47 effort on safety implications of control system failures.
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% AMSCR IPT MR. DKBENT:
You have now, if I recall 20 21 correctly, a safety grade, high level trip of feedvater 22 for the steam generators.
MR. HAMMs That is correct.
23 I
24 MR. OKRENT:
When did that come about?
25 MR. HAMMs When did that partJcular evolution i
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come about?
2 MB. OKRENT:
Yes.
3 ER. HAMM:
It is within the last two years
'l 4
that we went in and upgraded -- not upgraded -- we put 5
in this high level protection.
The safety grade 6
overfill protection to the steam generators.
7 MR. OKRENT:
Is that at the initiative of the 8
staff?
9 ER. HAMM:
It was about the same time no, 10 it was not at the impetus of the staff.
It was about 11 t'e same time we were performing this particular 12 review.
There were things I guess we could have taken 13 credit for th a t we changed based on the integrated II 14 control system, but I didn't make the decisions to make 15 th e ch anges.
They had already been made.
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16 So one of the things that BCW reports looked 17 at, there were basically three ma jor things that could 18 go wrong with the integrated control system that can 19 affect you.
Cne is you end up over-feeding the steam 20 generators.
The second is you under-feed the steam 21 generators, and the third is you depressurize the steam 22 generators.
23 Now we hsve safety systems that back all of I
24 those up.
So that for the overfeed, we have the overfill protection, for the underfeed ye have safety 25 I
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grade auxiliary feedwater independent of the ICS, and we
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have main steam isolation for the depres'urization of s
3 that.
So it was at about the same timef ra me because 4
when I was looking at those pa rticular events, I was 5
making sure we had a rafety system to back them all up.
6 At the same time, we were also taking about putting in 7
the overfill protection.
8 MR. OKRENT4 What was the cost, roughly, of, 9
for example, the safety grade high level trip on 10 feedwater flow?
11 MR. HAMMs I am afraid I can't answer that one 12 directly.
I can look and see if there is anyone who can.
13 MR. OKRENT:
I an interested.
Does anyone II 14 know a pproximately?
15 MR. BALLWEO:
Tom Ballweg with Bechtel.
I 16 would guess that the cost would be somewhere on the 17 range of a quarter to a half of a million dollars per 18 unit total installed cost.
19 MR. OKRENTs Where does that go, primarily?
20 Is it f or hardware per se or installation per se?
I 21 must conf ess it is more than I was going to guess.
22 MR. BALLWEG:
The direct hardware cost of the 23 parts cost is a small percentage of the total cost.
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24 lot of the cost goes into evaluating the effects, a lot 25 of it into modifying related systems that interface with I
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it.
2 It is not apparent when you first get into 3
these things how they interact with other systems,
' I so 4
there is a tremendous amount of other systems type 5
in ter a ctions, and the biggest cost is really in the 6
construction labor.
7 ER. OKRENT:
Okay.
9 i
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E.xctRPr froA4 guntq,ggg 16G"JM ACES MELMOJG NM SCd!P T M Ps HERN A 23 The design incorporates feedvater overfill 24 protection both on the main f eedvater systems and on the 25 main feedveter systems.
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1 "P.
MATISCN That was one of the questions 2
the subcommittee had.
icold this be a good point to 3
address tha t, Dr. Okrent?
4 MR. OKEENT:
As you wish.
5
%P. EEEPSOLE:
Before you do, vculd you 6
include an observation as to whether you expact it to 7
work in a blowdown case?
The systems are notoriously 8
nonresponsive.
9 ME. MATTSON:
I will defer this to the Staff 10 to answer that question.
11 You may remember from the T3I Action Plan that 12 there were a number of items dealing with the BCW design 13 sensitivity, one of which was to issue to plants under
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14 construction with the BEW design of a requirement of a 15 wey te reduce design sensitivity.* That is a requirement 16 that generated some of these changes in Midland by the 17 time it was finished at Midland and some othE-BEW 18 plants under construction.*
19 There wa s a subsequent item in the TMI Action 20 Plan that said thst once you look to those things you 21 could do to plants under construction, the Staff ought 22 to consider back fitting them to operatin. plants. I do 23 not remember the exact number, II.E.51 or II 2.52 of the
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24 TMI Action Plan.
25 At about the same time, there was a task
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1 force, I believe that maybe Mr. Tedesco headed, that 2
looked at Crystal River; snd again from the Crystal 3
River blowdown, there were some recommendations made.
I 4
believe, feedwater overfill protection may have been one 5
of them.
6 Bob reminds me tha t Karl Michelsen fror AEOD 7
in those same days, 1980, early 1980, was making 8
recommendations regarding feedvater overfill 9
protection.
10 I believe you were told in answer to a 11 question you raised tha t we had not decided to look at 12 operating reactors on this feedwater overfill protection 13 matter even though we had decided for the safety grade 14 trip on the Midland plant that we were not going to do 15 it to operating plants.
16 If you carefully examine the written response, 17 it says we were not going to do it for aux feedwater 18 system overfill.
Somehow, that response did not get 19 very well coordinated in the Staff.
20 On Februar) 6, 1982, I wrote a memorandum to 21 the director of safety, Steve Hanauer, in execution of 22 this THI Action Plan II.E.52.
We looked at the things 23
!idland did.
Of those, we think there are three that 24 ought to be backfit to operating reactors.
We ought to 25 ga ther some infomation on cost and benefit before we
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1 promul;ete the requirement because we had not Icoked at 2
costs.
3
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We vent on to recommend that we ask the 4
operating pinLts what it vould cost before va put the 5
issue on the street.
One of the thr?e was ste 3 6
generators should be protected from overfill from main 7
or auxiliary feedvater flow.
To limit overcoolino, this 8
equipment should be safety grade if flooding of the 9
steam lines is an unanalyzed event.
10 So I think we gave you partial inforretion, 11 and it was partially wrong at the subcommittee level.
12 But I think this corrects it today.
We are recommending 13 backfit of the feedvater overfill protection to
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14 operating reactors.
I understand some may have already 15 installed it on their own volition.
16 But the wheels are turning slowly in NER today 17 in deciding how to promulgate new backfit requirements, 18 the role of the CRGR, the role of cost-benefit, what 19 have you, tends to slov these decisions down somewhat.
20 I would not expect to see a decision on that before the 21 end of this year.
22 ER. OKRENT:
Well, what yea have said is 23 certainly not identical to what is in the written answer i
24 dated 5/2/B2 from the Staff.
It is still not clear to 25 se quite what it is that is being considered, whether it
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1 is control-grade or safety-grade overfill protection.
2 ER. EATTSON:
Safety-grade.
3 MR. OKRFET:
Considering that answer, cf 4
course, it is not clear where the Staff vill come down 5
and when, as you have indicated, and why.
The Staff 6
thinks, for example, that it is okay for this problem to 7
take some considerable pe ri od of time while it makes up 8
its mind, whereas on other matters I have seen where it 9
does not allow a plant to run at ell.
10 Ts there some knowledge that the Staff has 11 that this is an acceptable situation?
In wha t I read in 12 the BCU decument, I must say that it is suggested that 13 they thought this was really an important guestion.
It
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14 was very high on the list of what the operator needed to 15 know.
They said, in fact, overfill was a nonexamined 16 safety issue, or maybe something stronger, I cannot 17 remember the exact words.
18 Does the Staff know that the operating plants, 19 each and every one of them, can accept it or that the 20 frequency of this event was sufficiently s' ell that you 21 do not care?
Cr just what var the basis by which you 22 are precea ding at what I will call the usual pace?
23 MR. MATTSON:
Bob Tedesco, who made the I
24 recommendation to do this 2 years ago, probably feels ve 25 should have done this faster than we have.
If it is
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1 your sense that t he priori ty is too reall, that it is 2
nore important than what I had indicated, it vould 3
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ce rt ai nly change somewhat the outlock on that priority 4
if you were to say so to the Staf f, if the committee 5
were to say so.
6 The ba sis f or moving slowly is tha t compared 7
to some other things beino worked on, the unresolved 8
safety issues, the other developmental items in the TEI 9
Action Plan, that this one does not particularly rise to 10 the surf ace.
11 If you think tha t is a mistake in priority, 12 then the people who prioritize these things in the 13 Division of Safety Technology would certainly react from
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14 advice from this committee.
15 ER. OKPENT:
Well, the vendor apparently -- I 16 do not have the document here -- but considers it to be 17 a very important issue and rentions that 2 minutes for 16 the ope ra tor at a time like this to know that this is 19 occurring and to correct it.
Furthermore, he says, the 20 event is an unanalyzed event, or something stronger, 21 vith regard to what would transpire should this occur 22 now.
23 If the Staf f knows this is okay and it occurs k-24 and so forth and they can tell us,, I do not want to urge 25 you to rush out and do something, but given the
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1 information I have read, personally I do not know what 2
the basis for delay on Mr. Tedesco's recommendation or 3
vhatever is.
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4 MR. MATTSON:
We vill take your opinion and go 5
back and see that that changes the priority or not.
I 6
do not know what to tell you, unmless Walt has some 7
particular information about the operating plant.
8 ER. MARK.
This particular item is on 9
Midland.
10 MR. OKRENT:
Midland has, in f act, 11 sa f ety-gra de protection which now Mr. Ebersole has a 12 question on.
That is a separate question.
I would just 13 asssume myself that we could ha ve the Staf f give us a
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14 vritten answer within the next month.
15 MR. MATTSON:
Fine.
16 MR. EBERSOLE:
Would you include in your 17 answer just a simple statement of what the consequences 18 are if you just continue t o bl ast cold main f eedvater 19 into -he plant?*
20 Whether this works or not may be conditioned 21 upon the degree of the transient that it is f acino.
If 22 ve have it to occur or if we have to extricate
- a main 23 steam water flow in the presence of a main steam vatr
's 24 failure, do we have a system that vill really work, or 25 do we face the possibility of an extremely severe k
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1 secondary transient leading to the pressurized thermal 2
shock problem in this vessel?'
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MR. MATTSONs That was the question you raised 4
before.
5 Walt, do you want to try that on e?
6 ER. JENS05:
My name is Walter Jenson, NRC 7
Staff.
8 About all I can add to that is that the 9
Applit.snt did not take any credit in the analysis of 10 Chapter 15 steam generator blowdown either in the 11 feedwater line break or the steam line break for the 12 operation of the system.
The steam generator was 13 assumed to be isolated by the low secondary system
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14 pressure signal.
15 ER. EBERSOLE:
If you have a secondary line 16 failure, you lose steam pressure, which loses the 17 driving pressure to the turbine-driven pump.
- However, 18 it also drops the impedance to flow.
How these go down 19 in a relative context, I do not know.
But it would seem 20 that there is still quite e potential f or maintaining 21 continued and f ull flow into the steam generator from 22 the booster pumps which are fairly high-head pumps efter 23 it gets down.
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24 And therefore, what you have is a blown steam 25 generator with a superheated section now f ull of water
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1 producing an extrefte chillin,1 transient on the primary 2
loop, especially if the pumps continue'to run.
So you 3
heve the ultinate of ther:tal transients on the primary
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4 loop for this case.
5 This is a copper-containing vessel, and 6
certainly there are a few years to sort this out while 7
ve look at the vessel.
8 9
10 11 12 13
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14 15 16 17 18 19 20 21 22 23
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1 I think it ought to be looked at nov.
2 ER. MATTSON:
let me see if I understand 3
Jesse's question.
Your question is:
Eecause of the 4
peculiaritic of the design of this plant 5
Ef. IBEESOLE:
Yes.
6 MR.
nTTSON:
-- and flowing from the Dov 7
connection --
8 ER. EBERSOLE:
Yes.
9 ER. EATTSOHa
-- have we looked at whether the 10 steam line break challenge to pressurized thermal shock 11 is unique?
Is that your question?
12 ER. EBERSOLE:
Yes.
Uniquely bad, and coupled 13 with the potential f or continued runon of the main feed
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14 pumps.
15 ME. MATTSON:
That is not how I understood 16 your question before.
Now that I do understand your 17 question, I do not know the answer.
Walt, do you kno<
18 the answer?
19 ER. JENSON:
The analyses that vere done by 20 the appl 2 cant for n sten: line break were a large number 21 of sensitivity studies looking at the effect of barriers 22 in the process stenm, barriers of steam lines inside and 23 outside containment.
k 24 MB. EBERSOLE:
I will venture a guess that all 25 of them vere based on the premise that all water was cut k
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1 off to the failed steam generator virtually 2
instantaneously.
3 ER. JENSON:
Not instantaneously by a low 4
reactor system, low steam generator pressure.
5 ER. EATTSON:
That was a mistake ve picked up 6
generically several y ears ago.
That problem has been 7
fixed on all PWRs.
8 ER. EBERSOLE:
In other words, you assume 9
there is an overfill on a secondary failure?
10 ER. EATTSON:
You continue to get feedvater 11 af ter the main steam --
12 ER. EBERSOLE:
For the transient analysis?
13 Are you sure?
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14 MR. EATTSON:
From the broken steam line -- I 15 believe so.
16 MR. EBERSOLE:
For the pressurized thermal 17 shock analysis?
18 ER. SHEWMON:
They will check it and be sure 19 when they wri te you back, Jess.
Can we gci on and leave 20 it with that?
21 MR. EATTSON:
Bob says if you are talking 22 overfill, no.
23 MR. EBERSOLE:
Right.
I am talking overfill.
k 24 MR. 52.TTSON:
The continued running of the 25 pump, that we account for.
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1 ER. SEEWMOFs Gentlemen, I would like to r.ove 2
on to the item scheduled f er 9:15 now if we could.
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( La u g h t. e r. )
4 5R.
!' ATT50H z We vill try to cover it in our 5
vritten answer to you.
.