ML20141M324

Special Rept:On 900817,discovered That TS Limit for Ultimate Heat Sink Established Nonconservatively.Caused by Design Calculation Error.Actions to Address Svc Water Sys Malfunction Incorporated Into Procedures

ML20141M324
Person / Time
Site:	Hope Creek
Issue date:	08/04/1992
From:	Labruna S Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NLR-N92065, NUDOCS 9208110315
Download: ML20141M324 (9)

Text

_

e 1

e r

Public Sofvice Electric and Gas

+

Ccmpany Stanley LaBruna Pubhc Service Electric and Gas Cornpany P.O. Box 236 Hancocks Bndge NJ 08038 609-33 % 1200 vu P<esseen so w orwawm AUG 0 41992 NLR-N92065 i

United States Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 Gentlemen:

ULTIMATE HEAT SItTK ISSUE CURRENT STATUS AND PROJECTED RESOLUTION DATE FACILITY OPERATING LICENSE NPF-57 1

HOPE CREEK GENERATING STATION DOCKET NO. 50 354 j

Public Service Electric and Gas Company (PSE&G) hereby submits the current status and projected resolution date pertaining to the ultimate heat sink issue at the Hope Creek Generating t

Station.

.In August, 1990, PSE&G identified that the Tecitnical-Specification limit for the ultimate heat sink (Delawars River) had been established nonconservatively-high (90.5*F)-due to a design calcu'aation error..PSE&G ne,tified the.NRC of this situation in a Licensee Event Report (LER) which also included our short term corrective actions.

Subsequently, in Ju)y, 1991, PSE&G provided an updated statun in the-form of a revision to the initial LER.

PSE&G feels that it is prudent at this time to agai'n document the current-status of this issue and-in addition, to provide ~a date l

at which time final resolution _of_this issue will occur.

This

.information is contained in httachment-1.

If you have any questions regarding this submittal or the subject issue, please do not hesitate to conte't us.

Sincerely, l

MOJ p

s208110315 920804 f'

I

/d t' DR ADOCK n5000334 S

pop I

~wvgg

i j

I Document Control Desk 2

AUG 0 41992 NLR-N92065 j

i C

Mr. T. T. Martin, Administrator - Region I U.

S.

Nuclear Regulatory Commission 475 Allendale Road King of Prussia, PA 19406 j

Mr. J.

Stone, Licensing Project Manager (Acting)

U.

S.

Nuclear Regulatory Commission one White Flint North 11555 Rockville Pike Rockville, MD 20852 1.s. A. Keller U.

S.

Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Rockville, MD 20852 Mr.

T. P. Johnson (S05)

USNRC Senior Resident Inspector Mr.

K. Tosch, Chief NJ Department of Environmental Protection Division of Environmental Quality Bureau of Nuclear Engineering CN 415 Trenton, NJ 08625 l

j 1

l

,,. -~. -. -...

~.

.. e.

+

4 s.

,y

.- 7.?

1..

.i i<

y r

o; x

Y f

if 4

4.

1; 1-

,-e

'. ATTACHMENT 1-1<

Y/

',.'(

ULTIMATE, HEAT-SINK; ISSUE 4 l

CURRENT =STNiUS AND? PROJECTED RESOLUTION.DATE--

1 FACILITY OPERATING : LICENSE NPF f' HOPE / CREEK, GENERATING =STATIONi.'

t; f.

, DOCKET;NO. 450-354' s

3 as

{

t' a.

I i

b-t'.

t s

a i

t Y

h, - _

h) S

~

-k"

(-

ra'

, e t

s

\\

n. '. ' '

a l

A op.

i y

- ~

4 s

0

_4^

.~'.6

\\

.'t

{

,p

.s

~

.+.

y

~

4 b

?

a

/

?

s

~ '.'-

5

,j

'f r

s I

4:

I.

)

~

i'i

.fi

<> +

7 v

ic

}.'

'a A-

> +

E Z-I_ '{

e 1 9 4

t 1

/

",.}.r[,.'._

}

.t,.

,4

,.o d

~

r i

r 4

t'

+

s d'

-^#55._'_

,,8 g r.-

I d e g

T' f

I j

Tk y

I M i

[

l" h

M

^ '

e d

wt-W M

PP e

IT M If k 7 f

TI* I T

NLR-N92065 1

BACKGROUND 4

On August 17, 1990, PSE&G discovered.that the Technical i

Specification limit for the ultimate heat sink (Delaware River) had bee estaolished nonconservatively high (90.5'F). due tx) a design calculation-error.

At that time, an administrative limit of 85'F, based upon the design temperature of the Station _ Service Water System (SSWS), was placed into effect and evaluations were initiated to establish the correct maximum allowable temperature.

4 It was determined that once this value had been established, a license change request (L(4) would be submitted to correct'the nonconservative value in Technical Specifications.

This was-communicated to the NRC via Licensee Uvent Report (LER) 90-014-00 dated September 12, 1990.

a When the issue was first' identified, it was expected that an evaluation of all applicable system design parameters and.

calculations could be completed in a time frame such that an LCR-could be submitted-in early 1991.

However, it-was subsequently realized that suc! a time frame could not be met.

Therefore, as an interim measure, a refined engineering analysis and 10 CFR 50.59 evaluation were conducted.

Results of the-evaluations indicated that the administrative limit could be increased to 87.5'F based upon the performance of operator actions to increase the heat removal capabilities of the STACS heat exchangers and' i

minimize the total heat duty.

i E

LER 90-014-01, dated July 12, 1991, was submitted to indicate 4

that an increased administrative limit of 87.5'F had been established, based upon a 10 CFR 50.59 evaluation, and that the 4

analysis to determine the ultimate. heat sink temperature upon which an LCR could be based was on going.

1 Subsegnant to submittal of the revised LER, the-administrative limit was further increased to 88.1*F.

The increase is based-upon results of detailed analysis of:the Safety-and Turtine Auxiliary Cooling System (STACS) heat exchangers.- This limit has been in effect since July 26, 1991, (reference-NRC inspection-report No. 354/91-14 dated August 16, 1991).and will. remain'in 5

effact until the final value SSWS design limit is established.

.PAGE 1 OF 6 ATTACHMENT 1 4

'NLR-N92065 II.

ACTIONS REOUIRED FOR RESOLUTION Throughout this effort,-various analytical techniques have been attempted; some proved beneficial toward approaching final resolution and were incorporated while others were unsuccessful.

and subsequently aborted.

one of the 's"hniques explored was to evaluate the conservatism l

associated with the system heat' loads.

The results indicated j

that the existing calculations are based on extreme operating conditions for each component that is being cooled and that additional margin could therefore be obtained by analyzing the system at the component level.

Consequently, PSE&G has determined that in order to proceed to final resolution, further engineering evaluations and analyses must be conducted for each component supplied by SSWS and STACS.

Up to this point, all calculations have been done by hand.

In order to proceed to the final stage at which the evaluations will-be done at the component level through an iterative process, the calculations must be computerized.-

To.this end, a-design specification entitled " Safety Related Computer Model_of the Hope Creek Generating Station Service Water / Safety.& Turbine Auxiliaries Systems" was developed and is presently proceeding.

The resulting computer model will be designed to provide an engineering tool for-a thermal / hydraulic evaluation of the combined SSWS and-STACS, As previously noted, the computer model will be required to-establish a new SSWS design temperature, thus providing the basis for the new ultimate heat sink temperature limit.

The development and utilization of the-computer:model will provide the required flexibility to evaluate the-numerous.

variables affecting the ultimate heat sink temperature such as pump and heat exchanger perforlaance.

The computer model will.

also be utilized to evaluate future proposed modifications and/or enhancements to the SSWS/STACS in order to assess their impact with respect to ultimate heat sink temperature.-

e III. COMPLETION DATE This project will be completed by r.ay, 1993.. At that_ time, a new SSWS design temperature-will be established and: incorporated into all applicable configuration documents and a amendment request will be submitted to incorporate the'new-value into Specification 3.7.1.3.

Until that time, the present administrative limit of 88.1*F will-remain in effect.

A discussion of the~ basis of this limit follows.

'f PAGE 2 OF 6 ATTACHMENT 1

NLR-N92065 IV.

TEQHNICAL BASIS OF ADMINISTRATIVE LIMIT

}

A.

River Temperature Variance Each day, river temperature, which is monitored at the-intakes of-the Station Service Water System (SSWS) pumps,' varies _directly with cyclic tidal surges.

During the hottest days of late July j

and August, the incoming tide causes. warm surface water from shallow estuarine marshes and the discharge from the Salem Generating Station to be transported upstream to the Hope Creek i

SSWS intake structure.

Historically, this has been_the time when indicated river temperature has exceeded 85'F.

However, since the high temperature conditions only exist at the maximum-i incoming tidal surges, they have not been-sustained.over long periods of time.

l B.

Design Basis The Hope Creek SSWS was designed in compliance with 10 CFR'50, o

Appendix A-Criterion 44, which in part, requ4 res a system to transfer heat from structures, systems and components important to safety-to an ultimate heat sink to be provided.

The system safety function shall be to transfer the total heat load of these components under both normal operating and-emergency conditions.

Further, suitable redundancy in components and features shall be provided to assure the system safety function can be:

accomplished, assuming a single failure.

To meet this objective, the SSWS and Safety and Turbine Auxiliaries Cooling System (STACS) are composed.of.two redundant loops, or subsystems, designated'A and B.

_UFSAR Sections.9.2.1 and 9.2.2 state that only one SSWS and'STACS loop.is required for normal operation, shutdow; and emergency shutdown. 'The system.

design therefore, provides protection against complete loss of-the cooling function, assuming.the occurrence of.a single active or passive failure.

In summary, the-SSWS and STNCS must.be capable of providing sufficient cooling to safety related loads with only a single i

SSWS/STACS loop available.

All'SSWS and STACS operating modes are bounded by this requirement.

3 PAGE'3 OF 6 ATTACHMENT 1 i

t i

.c --

Pubhc Service Electdc and Gas Company

-Ct nley LaBruna Put>he Service Eectrc and Gas Company PA Box 236, Hancocks Bridge. NJ 08033 609-339 1200 Vu Pedect Naev Om.es AUG 0 41992 NLR-N92065 United States Nuclear Regulatory Commission Document Control DeLK Washington, DC 20555 Ger.tlemen:

ULTIMATE HEAT SINK ISSUE CURRENT STATUS AND PROJE(.*. FED RESOLUTION DATE FACILITY OPERATING LICENSE NPF-57 HOPE CREEK GENERATING STATION DOCKET NO. 50-354 Public Service Electric and Gas Company (PSE&C) hereby submits the current status and projected resolution date pertaining to the Ultimate neat sink issue at the Hope-Creek Generating Station..In August, 1990,.PSE&G identified that the-Technical Specification' limit for the ultimate heat sink (Delaware River) had been established nonconservatively high (90.5'F) due to a design calculation error.

PLE&G notified the NRC of'this situation in a Licensee Event Report-(LER) which also included our short term corrective actions., Subsequently, in July, 1991, PSE&G provided an updated status in the form of a revision to the initial LER.

PSE&G feels that it is prudent at this time to again document tne current status of this issue and in addition, to provide a date at which time. final resolution or this issue will occur.

This information is contained in Attachr.ent l'.

If you-have any questions regarding this submittal or the subject issue, p3 ease do not hesitate to contact us..

Sincerely, Vud L

9208110315 920304 fI PDR ADOCK 05000354 S

)

. ppp I

Document Control Desk 2

AUG O 41992 NLR-N92065

.C-Mr. T. T. Martin, Administrator - Region I U.

S.

Nuclear Regulatory Commission 475 Allendale Road King of-Prussia, PA 19406 Mr. J.

Stone, Licensing Project Manager (Acting)

U.

S.

Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Rockville, MD 20852 Ms. A.

Keller U.

S.

Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Rockville,_MD 20852 Mr. T. P. Johnson (SOS)

USNRC Senior Resident Inspector Mr. K. Tosch, Chief NJ Department of Environmental Protection Division of Environmental Quality Bureau of Nuclear Engineering CN 415 Trenton, NJ 08625

_ _ _ _ _ _ _ - _ = _ _ _ _ _ _ - _

i -

x J_.

ATTACHMENT 1-ULTIMATE! HEAT SINK ISSUE-CURRENT-STATUS AND' PROJECTED' RESOLUTION DATE FACILITY: OPERATING LICENSE NPF-57 HOP 2. CREEK GENERATING STATION-

- DOCKET NO.!50-354 -

u

+

1

?

f 1

. =.

NLR-N92065 I.

BACKGROUND On August 17, 1990, PSE&G discovered that the Technical Specification limit for the ultimate. heat sink (Delaware River) had been established nonconservatively high (90.5'F) due'to a-design calculation error.

At-that time, an administrative limit' of 85*F, based upon the design temperature of the Station Service Water System (SSWS), was placed into effect and evaluations were initiated to establish the correct maximum allowable temperature.

It was determined that once this value:had been established, a license change request (LCR) would-be submitted to correct the nonconservative value in Technical Specifications.

This was communicated to the NRC via Licensee Event Report (LER) 90-014-00' dated September 12, 1990.

When the issue was first identified, it was expected tnat.an evaluation of all applicable system design parameters and calculations could be completed in a time frame such that an LCR could be submitted in early 1991.. However, it was_ subsequently realized that such a time frame could not be met.

Therefore,-as an interim measure, a refined engineering analysis and 10 CFR 50.5 evaluation were conducted.

Results of the evaluations indicated that the administrative limit could be increased to 87.5'F based upon the performance of operator actions to increase the heat removal-capabilities of the STACS heat exchangers and minimize'the total' heat duty.

LER 90-014-01, dated July 12, 1991, was submitted to indicate that-an increased adminiatrative limit of 87.5*F_had been established, based upon a 10 CFR 50.59 ovaluation, and that the analysis to determine the-ultimate heat sink temperature upon

~

which an LCR could be based was on going.

Subsequent to submittal.of the revised LER, the administrative limit was further increased to 88.1*F.

The increase-is based-upon results of detailed analysis of theJSafety and Turbine Auxiliary Cooling System (STACS)Jheat.exchangers.- This limit has l-beenlin effect since~ July 26, 1991,-(reference NRC inspection-report No. 354/91-14 dated August 16, 1991) and will remain in effect until the final value SSWS design: limit is established.

l l

PAGE 1 OF.6 i

ATTACHMENT 1 l

l NLR-N92065 II.

ACTIONS RELUIRED FOR RESOLUTION Throughout this effort, various analytical techniques have been attempted; some proved beneficial toward approaching final resolution and were incorporated while othera were unsuccessful and subsequently aborted.

One of the techniques explored was to evaluate the conservatism associated with the system heat loads.

The results indicated that the existing calculations are based on extreme operating conditions for each component that is being cooled and that additional margin could therefore be obtained by analyzing the system at the component level.

Consequently, PSE&G has determined that in order to proceed to final resolution, further engineering evaluations and analyses must be conducted for each component supplied by SSWS and STACS.

Up to this point, all calculations have been done by hand.

In order to proceed to the final stage at which the evaluations will be done at the component level through an iterative process, the calculations must be computerized.

To this end, a design specification entitled " Safety Related Computer Model of the Hope Creek Generating Station Service Water / Safety-& Turbine Auxiliaries Systems" was developed and is presently proceeding.

The resulting computer model will be designed to provide an engineering tool for a thermal / hydraulic evaluation of the combined SSWS and STACS.

As previously noted, the computer model will be required to establish a new SSWS design temperature, thus providing the basis for the new ultimate haat sink temperature limit.

The development and utilization.of the computer model will-provide the required flexibility to evaluate the numerous variables:affecting the ultimate heat sink temperature such as pump and heat exchanger performance.

The computer model will also be utilized to evaluate future proposed modifications and/or enhancements to the SSWS/STACS in order to assess their. impact with respect to ultimate heat sink temperature.

III. COMP 1ETIOT DATE This project will be-completed by May,:1993.

At that-time, a new SSWS design temperature will be established and incorporated into all applicable configuration documents-and a amendment request will be submitted to incorporate the new value into-Specification 3.7.1.3.

Until that time, the-present administrative limit of 88.l*F will remain in effect.

A discussion of the basis of this' limit follows.

PAGE 2 OF 6 ATTACHMENT 1 i

1

N LR-N92065 lEz_ TECHNICAL BASIS OF ADMINISTRATIVE LIMII A.

River Temperature Variance Each day, river temperature, which is monitored at the intakes of the Station Service Water System (SSWS) pumps, varies directly with cyclic tidal surges.

During the hottest f.ays of late July and August, the incoming tide causes warm surface water from shallow estuarine marshes and the discharge from the Salem Generating Station to be transported upstream to the Hope Creek SSWS intake structure.

Historically, this has been the time when indicated river temperature has exceeded 85*F.

However, since the high temperature conditions only exist at the maximum incoming tidal surges, they have not been sustained over long periods of time.

B.

Design Basis The Hope Creek SSWS was cesigned in compliance with 10 CFR 50, Appendix A-Criterion 44, which in part, requires a system to transfer heat from structures, systems and components important to safety to an ultimate heat sink to be provided.

The system safety function shall be to transfer the total heat load of these components under both normal opc'::ating and emergency conditions.

Further, suitable redundancy in components and features shall be provided to assure the system safety function can be accomplished, assuming a single failure.

To meet this objective, the SSWS and Safety and Turbine Auxiliaries Cooling System (STACS) are composed of two redundant loops, or subsystems, designated A and B.

UFSAR Sections 9.2.1 and 9.2.2 state that only one SSWS and STACS loop is required for normal operation, shutdown, and emergency shutdown.

The system design therefore, provides protection against complete loss of the cooling function, assuming the occurrence of a single active or passive failure.

In summary, the SSWS and STACS must be capable of providing sufficient cooling to safety related loads with only a single SSWS/STACS loop available.

All SSWS and STACS operating modes are bounded by this requirement.

PAGE 3 OF 6 ATTACHMENT 1

NLR-N92065 i

C.

Maximum River Temperature During the design phase of the SSWS, the Architectural Engineer (AE) for Hope Creek originally identified the following four bounding modes of system operation: 1) power generation, 2) normal shutdown, 3) loss of offsite power.(LOP), and 4) operation greater than ten minutes after a. loss of coolant accident (LOCA >

10 minutes).

For each operational mode, the AE calculated the resulting STACS heat exchanger loads for both single and two-loop SSWS configuration and subseque.7tly determined that, in each mode, single loop operation resulted in the highest heat exchanger heat duty.

l Based on the calculated SSWS performance under each-of-the four modes of. operation that were evaluated, PSE&G has concluded that.

the ultimate heat sink will remain operable with river temperatures exceeding the current docur9nted design limit of 4

85'F up to and including a value of 88 i" F.

The basis of-this temperature limit assumes:

1.

Operator actions are taken to increase the heat removal capabilities of the STACS heat m' changers and minimize the total heat duties of the tva em, _

2.

All four SSWS pumps are degraded by 15%, and 3.

50 tubes in each STACS heat exchanger are blocked.

D.

Required Operator Actions - Description Operational tests have been conducted to determine-and mark the throttle positions of the SACS. heat Exchanger SSWS outlet valves which would provide the required - flow during LOCAL or LOCA/ LOP -

conditions.

If river temperature' exceeds 85'F_the valves are throttled to these predetermined postions.

In the_ event of a LOP with only one SSWS/STACS-loop available-and:

river-water temperature is between 85' and 88.1'F,-the1following actions must be'taken:=

1.

_The operating STACS loop flow'is11solated to the-Fuel

-Pool-Heat Exchangers.

2._

SSWS flow is isolated to one RACS7 Heat Exchanger.

3.

SSWS flow is throttled to'the-remaining RACS Heat exchanger-to obtain'2,550 gpm; 4.

SSWS flow is increased to the heatLExchangers in the-in-service STACS loop to obtain at least 12,200-gpm through each heat exchanger.

PAGE 4 OF 6 ATTACHMENT 1 i

l

+.+

l NLR-N92065 Evaluations based upon the amount of_ spent fuel that is presently stored in the spent fuel pool indicate that the Fuel Pool Conling Heat Exchangers say be out of service for up-to eight days before pool boiling would occur.

This provides sufficient time to establish cold shutdcwn conditions.

Thus it may be concluded that fuel pool cooling can be restored prior to the onset of boiling conditions.

E.

Required Operator Actions-- Procedure The preceding actions have been incorporated into station operating procedure HC.OP-AB.ZZ-0122(Q), " Service Water System Malfunction", and subsequently included in the operator training programs.

In order to key operators into entering this procedure, " Service Water Temperature > 85'F" has been added to the list of " Symptoms" which are located in Section 1.0 of the procedure.

F.

Required Operator Actions - Probabilistic Assessment u

The subject operator actions are required only if all of the following conditions exist simultaneously:

River' temperature is above 85'F, and A LOCA and/or LOP occurs, and A loop of SSWS and/or SACS malfunctions.

Insofar as the amount of time that_ river temperature has exceeded 85'F over the course of any one-year is very-low (an annual total average of 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br /> / year over a three year period), it is highly unl'"ely that these actions will be required during this. summer.

To q.ontify this value, a probabilistic risk assessment was completed and indicates that there is 1.12E-8Lto 5.6E-lO event / year probability (ranging from a large LOCA to a LOCA/ LOP combination) of these conditions occurring simultaneously.

G.

Inservice Testing Program Considerations Evaluation of the Inservice Testing (IST) Program for the SSWS Pumps indicated that the current minimum SSWS pump performance specified in the IST program is_ acceptable for an 88.1'F river temperature limit.

i PAGE 5 OF 6 ATTACHMENT 1

- NLR-N92065 H.

Stress Calculation Considerations i.

Since the Line Index for Hope Cre" piping systems indicates that the maximum operating temperatur< for the SSWS supply piping to the STACS and RACS heat exchangers is 05'F, a review of the applicable stress calculations was performed.

SSWS supply piping from the river to the STACS and RACS heat exchangers has been i

analyzed to operate between 31*F r.nd 85'F thermal rangt.

A review of stress calculations for piping in the SSWS Intake Structure and Reactor Building shows significant design margin l

for a small increase in the thermal stresses due to a 5'F elevated river temperature.

]

A minimum of 20% margin has been found to exist against allowances for thermal expansion per ASME Section III, Paragraph NC/ND 3652.3 Equation (10), whereas a maximum of about a 10%

i increase in expansion stresses can be expected from a thermal range between 31'F and 90*F.

Higher allowances for combined effects of pressure, weight, other sustained loads, and thermal expansion urder equation (11) provide further assurance for code compliance for this low pressure and temperature piping system.

This review also shows that the loading combination-for equipment nozzles and pipe support design is governed by higher loads due to the operating mode at 31*F during the winter, rather than loads at 85'F or even 90*F during the summer.

Hence the piping system is capable of meeting its intended design functions under tbase additional loads.

i The piping system on the SSKS outlet of the heat exchangers'is analyzed for 110*F.

It is assumed in the vendor data sheets for the STACS and RACS heat exchangers that with a supply-temperature i

of 90'F to these components the discharge temperature will rise to a maximum of 111*F.

Additional stresses and loads due to this change are considered to be within the design of'this piping.

I.

Option i

An alternative to establishing 88.1*F as the interim maximum river temperature limit and taking credit for operator actions is to incorporate the current documented design limit of-85*F with no credit-for operator actions.

This alternate course of action could potentiallyLforce a plant shutdown during-the hottest time of the year thereby threatening the integrity of;the electrical 1

distribution grid during the period of maximum electrical demand.

Insofar as here is a high. degree of confidence that the design-

,J limit can be increased with refined analysis and that PSE&G is reby commit.ing to complete that analysis and submit an nendment request to incorporate the final value by May,'1993, we feel that the potential consequences of pursuing this alternate course of action are not-warranted.

PAGE 6 OF 6 ATTACHMENT 1

--