ML030560640

Emergency Core Cooling System Evaluation Model Changes - 30 Day Report

ML030560640
Person / Time
Site:	Watts Bar
Issue date:	02/21/2003
From:	Pace P Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML030560640 (7)

Text

Tennessee Valley Authority, Post Office Box 2000, Spring City, Tennessee 37381-2000 FEB 2 12003 10 CFR 50.46 U.S. Nuclear Regulatory Commission ATTN:

Document Control Desk Washington, D.

C.

20555 Gentlemen:

Docket No.

In the Matter of Tennessee Valley Authority 50-390 WATTS BAR NUCLEAR PLANT (WBN)

UNIT 1 -

EMERGENCY CORE COOLING SYSTEM (ECCS)

EVALUATION MODEL CHANGES -

30 DAY REPORT

References:

(1)

TVA letter to NRC, April 3,

2002, "WBN Unit 1 -

ECCS Evaluation Model Changes -

Annual Notification and Reporting for 2001" (2)

TVA letter to NRC, September 7,

2001, "WBN Unit 1 -

ECCS Evaluation Model Changes -

30 Day Report and Revised Annual Notification and Reporting for 2000" (3)

Westinghouse letter to TVA (WAT-D-11100),

January 15,

2003, "Watts Bar Nuclear Plant Unit 1, ECCS Relief Valve Leakage of 30 GPM -

Effect on the Current Analyses" The purpose of this letter is notify the NRC of change or errors discovered in the WBN ECCS evaluation models for peak cladding temperature (PCT) in accordance with 10 CFR 50.46, and actions TVA has taken to address a temporary change of more than 501F in calculated PCT.

This report includes model changes or errors since TVA's last report (Reference 1), and is intended to satisfy the 30 day reporting requirements of 10 CFR 50.46.

As reported by Westinghouse in Reference 3, this temporary change to WBN's ECCS evaluation model affects the small break LOCA (SBLOCA) analysis, and is described in. The PCT margin allocations resulting from this change are summarized in.

There were no additional PCT impacts reported in Reference 3 for SBLOCA from those previously reported in Reference 1.

P\\

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U. S. Nuclear Regulatory Commission Page 2 FEB 2 1 2003 As discussed in Enclosure 1, TVA has experienced a repeat condition (Reference 2) involving apparent leakage when running the Watts Bar Unit 1 Safety Injection (SI) pumps which could result in diverting some SI flow to the pressurizer relief tank (PRT).

TVA had previously taken measures to identify and correct this situation, including evaluation and replacement/refurbishment of SIS piping relief valves during the last refueling outage.

Following this valve replacement, no leakage was identified until a single repeat occurrence this January.

TVA has decided to conservatively treat this event as a recurrence of the condition and is performing additional cause determinations.

TVA requested Westinghouse to evaluate the impact of this condition.

Their evaluation results, Reference 3, were received by TVA on January 22,

2003, and concluded that there will be sufficient flow to meet the requirements of the safety analyses.

Westinghouse evaluated the SI flow reduction for its impact on SBLOCA and BELOCA.

As a result, a temporary PCT penalty of 120°F has been assessed on SBLOCA for the reduction in SI flow.

This penalty has been added to the PCT Summary Sheet in Enclosure 2 and is expected to remain in place for the duration of the current operating cycle (Cycle 5).

As shown in the summary sheet, the inclusion of this penalty results in a PCT of 1270'F which is considerably less than the 2200°F regulatory limit.

There was no impact associated with the limiting PCT for BELOCA.

The temporary PCT assessment of 120°F for SBLOCA exceeds the threshold defined in 10 CFR 50.46(a) (3) (i) for a change of more than 50*F in calculated PCT.

Therefore, TVA is reporting this change within the 30-day time limit specified in 10 CFR 50.46.

In accordance with 10 CFR 50.46(a) (3) (ii), TVA is required to provide a proposed schedule for providing a reanalysis or taking other actions needed to show compliance with 50.46 requirements for the changes or errors discussed above.

As a result of the temporary nature of the PCT assessment due to a hardware condition, and based on the acceptable evaluation results described herein, the WBN SBLOCA ECCS Model for the current cycle satisfies and complies with the 10 CFR 50.46 acceptance criteria.

Accordingly, TVA has completed the analysis required of 10 CFR 50.46 for changes or errors in an ECCS model and no further action is currently required.

Because the SBLOCA change is a

temporary condition which will be moot after the correction of the safety injection flow deficiency, TVA does not consider it will be necessary to make a 30-day report regarding the negative 120°F PCT change (increasing margin) that will occur when WBN reverts back to the previous SBLOCA model.

U.

S.

Nuclear Regulatory Commission Page 3 FEB 2 1 2003 If you have any questions about this change, please contact me at (423) 365-1824.

Sincerely, P. L. Pace Manager, Site Licensing and Industry Affairs Enclosures cc (Enclosures):

NRC Resident Inspector Watts Bar Nuclear Plant 1260 Nuclear Plant Road Spring City, Tennessee 37381 Mr.

K.

N.

Jabbour, Senior Project Manager U.S. Nuclear Regulatory Commission MS 08G9 One White Flint North 11555 Rockville Pike Rockville, Maryland 20852-2738 U.S. Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth St.,

SW, Suite 23T85 Atlanta, Georgia 30303 cc:

See page 4

ENCLOSURE 1 DESCRIPTION OF CHANGES WHICH AFFECT WBN'S EMERGENCY CORE COOLING SYSTEM EVALUATION MODEL(S)

AND ITS CALCULATION OF PEAK CLADDING TEMPERATURE

1.

Evaluation of Temporary Safety In3ection Leakage to Pressurizer Relief Tank (PRT)

Background

Westinghouse was informed by TVA of an apparent leak when running the Safety Injection (SI) pumps in Watts Bar Unit 1 which could result in a loss of up to 30 gpm SI flow to the pressurizer relief tank (PRT).

TVA requested Westinghouse to evaluate the impact of this condition.

Based on the following evaluations, Westinghouse concluded that the SI shortfall can be accommodated by the amount of margin available and/or the lack of sensitivity to the SI flow volume in the various design basis analyses, and the pump performance will not be degraded and there will be sufficient flow to meet the requirements of the safety analyses.

This conclusion is valid for the duration of the current operating cycle (Cycle 5) and is not intended to support a permanent reduction in SI flow.

In particular, the evaluations do not account for the insertion of Tritium Producing Burnable Absorber Rods in future cycles.

Affected Evaluation Models 1985 Westinghouse Small Break LOCA Evaluation Model with NOTRUMP 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model Estimated Effect SBLOCA The 30 gpm SI flow reduction was evaluated for its impact on small break LOCA (SBLOCA).

The impact was evaluated based on the SBLOCA analysis of record (References 1 and 2).

The most recent small break LOCA PCT summary sheet was transmitted via Reference 3.

A PCT penalty of 120'F has been assessed for the reduction in SI flow.

This penalty, which has been added to the PCT Summary Sheet provided in,

is expected to remain in place for the duration of the current operating cycle (Cycle 5).

As shown in the summary sheet, the inclusion of this penalty results in a PCT of 1270°F which is considerably less than the 2200°F regulatory limit.

Best Estimate LBLOCA (BELOCA)

The BELOCA analysis for Watts Bar was evaluated for the impact of the reduction in SI flow.

It was determined that the 30 gpm reduction results in a total integrated SI flow reduction of 3.36%.

Based on a calculation documented in Reference 4, which reduced overall SI flow by 10%,

it is concluded that the 30 gpm SI EI-I

flow reduction has no effect on the limiting PCT for the BELOCA.

References

1. WAT-D-10337, "Tennessee Valley Authority, Watts Bar Nuclear Plant, Final Safety Evaluation to Support Technical Specification Changes", March 5, 1997.

2. WAT-D-10356, "Tennessee Valley Authority, Watts Bar Nuclear Plant Units 1 & 2, Final Report and Safety Evaluation for 10%

SGTP Program",

June 2 1997.

3.

TVA letter to NRC, April 3,

2002, "WBN Unit 1 -

ECCS Evaluation Model Changes -

Annual Notification and Reporting for 2001"

4.

WCAP-14839, "Best Estimate Analysis of the Large Break Loss of Coolant Accident for the Watts Bar Nuclear Plant," July 1997.

E1-2

ENCLOSURE 2

SUMMARY

OF PEAK CLADDING TEMPERATURE MARGIN ALLOCATIONS RESULTING FROM CHANGES TO THE EMERGENCY CORE COOLING SYSTEM EVALUATION MODEL

I Wtai~nghau LOCA Peak Clad TemperatuP. Summery for Simal 1reak flintName:

Watts Bar Unit I Vtility Nun.:

Twmgeasa Valley Authlority Revision Data:

1115103 Anal'vSl l t'rwaion Em; NOTRUMP Aualysis Date:

1112/96 LicnititzBrek Stu: 4 inch FQZ 2.S Fan:

1.65 Fe:

Vantage +

SGTP(%):

10 Not=

mixed Cwc - Vintage + I Pa~formace +

Cliad Temp (OF)

Ret.

Notes LICENSING BASIS Analysis-Of.Record PCT II~

1.1 MARGIN ALLOCATIONS (Delta PCT)

A. PRIOR PERMANENT ECCSNMODE.L ASSESSMENTS I1. VOTRtflMP Matuw Level Trackmg/ Ropm Depletion EITOT 13 4

B. PLANNED PLANT CHANGE EVALUATIONS I.Annu~~DaW]kdk=

10 3

C.. 2002 PERMANENT ECCS MODEL ASSESSMENTS I1.

u 0

D. TEMPORARY ECCS MODEL ISSUES*

I1.

?4wic 0

E. OTHER I1. TavgUrie ny of 6 I 2.

TcmpcoruySI Leaka~ tioPRT 120 S(2)

LICENSING BASIS FCT + MARGIN ALLOCATIONS

?CT =

1270 It is rocomcnwded that these tempomzy PCT allocatios which address current LOCA model isaues not be consircmd, vMth cespect tolD CFRS. 5.rcportinrxqmtmu

References:

1. WAT-D-1 0337. 7munesset Vaflcy Authority. Wits i DNuclear Plant. Final Safety Byalutioc to Support TotmwAcl SpecillcstiocDn gee.c" Much S. 1997.

2.

WAT-D-1 035 6. -r-1,64SB Valley Authority. WLs B4ar uar Plant Vaui I A 2. Final Repom %ad Sam& Ev~atusm for the 10% SO'!? Progrm." one 2,1997.

3. WAT*D-1061 S. Tcuoesuc Valley Authouity, Watu Bat Noeleur Plant Ulnit 1. 10 CPR 5OA6 Annual Nodcanon and Repotng for 199.", murch S, 1999.

4. WAT-fl-10810, "TeaneuaetV2fey Anthorny. Wall BUN OC)CU PlRan Unit 1. 10 CFR SO.46 Appendix IC (BART/BASH/NOTRUMP Evaguatio Model MKd.YeU NotifiCation 2nd Reporting for 2M." Jbat 30, 2000.

5.

WAT-D-11 100, -Tenanmxo Valley Amducitf, Wintu SuNucleu Phat Unit 1. Evnimaatc of Tempory 3t Lcakqz to flTV Januazq 15. 2003.

Notes (a) r~~mmn o tue tfo u oS ~aei R t3p~al ni the end of Cycle S.

Weduesday. lzrnaary 15. 2003 sIrn xCl~4~wfli Srf-[

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