05000280/LER-1976-002, Updated LER 76-02/01T:on 760313,determined Worst Break LOCA Core Thermal Transient Analysis Inaccurate Since Effects of Steam Generator Tube Plugging on LOCA Not Considered

Updated LER 76-02/01T:on 760313,determined Worst Break LOCA Core Thermal Transient Analysis Inaccurate Since Effects of Steam Generator Tube Plugging on LOCA Not Considered

ML20087A151
Person / Time
Site:	Surry
Issue date:	05/17/1976
From:	Stallings C, Sylvia B VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	Moseley N NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20087A154	List: 05000280/LER-1976-002, Updated LER 76-02/01T:on 760313,determined Worst Break LOCA Core Thermal Transient Analysis Inaccurate Since Effects of Steam Generator Tube Plugging on LOCA Not Considered
References
950-S, LER-76-02-01T-01, LER-76-2-1T-1, NUDOCS 8403070418
Download: ML20087A151 (3)

LER-2076-002, Updated LER 76-02/01T:on 760313,determined Worst Break LOCA Core Thermal Transient Analysis Inaccurate Since Effects of Steam Generator Tube Plugging on LOCA Not Considered

Event date:
Report date:
2802076002R00 - NRC Website

text

.

A0-S1-76-02

. UPDATE REPORT LICENSEE EVENT REP $

, CONTROL BLOCK:l gl l l l l l (PLEASE PRINT ALL EEGulREO INF%MATION) 1 6 NAME LCENSE NUM8ER YE TYPE b lVlAlSlPlSl1 l'14 l015l0 l-l 0l 0l 0l 0l0 l-l0 l 025l l4l1l1l1l0l 7 89 26 30 l0l1l 31 32 CATEGORY TYPE U DOCKET NUM8ER EVENT DATE REPORT DATE D 1 CONT [M l I l 7 8 57 58 W59 W60 l0 l5 l0 l-l 0 l 2 l 8l 0l l0 l3 l1 l 3 l 7 l 6l l0 l5 l1 l 7 l 7 l 6l 61 68 69 74 75 80 EVENT DESCRIPTION 96 l It was determined that the worst break LOCA core thermal transient analysis is inaccu-l 7 89 80

@E l rate since the effects of steam generator tube plugging on the LOCA were n6t con- l 7 89 80 SE lsidered therein. This was initially reported on March 26, 1976. (AO-S1-76-02 UPDATE) l 7 89 80 BE l l 7 89 80 DE I I 7 89 p,,g 80 CE CODE COMPONENT CODE ER M R VIOLATON h l Zl Zl [f_j lH l Tl El XlC lH l lNl blil2l0l47 d48 7 89 10 11 12 17 43 44 CAUSE DESCRIPTION h l Steam Renerator tube deterioration has resulted in the need to plug a number of tubes l 7 89 80 UE lin Surry steam eencrators. Surry Unit No. I has 6.31 percent of its steam generator l 7 89 80 BE I tubes pluaned, and surry Unit No. 2 is expected to have 5.55 percent of its (CONT'D) l FACRJTY METHOD OF STATUS  % POWER OTHER STATUS DrSCOVERY DISCOVERY DESCRIPTON 1

7 8 9 d l 0l 0l 0l l NA 10 12 13 l

44 d45 l NA 46 80 l

RELE SED AMOUNT OF ACTIVITY LOCATON OF RELEASE 1

7 8 9 lZ_j OF dREL ASE l NA 10 11 l

44 l NA 45 .

80 l

PERSONNEL EXPOSURES NUV8ER TYPE DESCRIPTON DE l ol 01 d L ZJ lNA l 7 80 11 12 13 80 PERSONNEL INJUR!ES NUM8ER DESCRIPTON H l 6l 010 l l NA l 7 89 11 12 80 OFFSITE CCNSEQUENCES EE l There are no offsite conscauences associated with this event. l 7 89 80 LOSS OR OAMAGE TO FACTUTY TYPE CESCR:PTON h lZ_)

7 89 l NA 10 l

80 PUBLICITY 8403070418 760517 36 l NA PDR ADOCK 05000200 l 7 89 s PDR so AOOITIONAL FACTORS 1 l The nuclear steam supply system vendor has performed LOCA analyses, using the March -l 7 89 80 D@ l1975 model, to examine the effects of various steam generator tube plugging '(CONT'D) l 7 89 80 NAME: B. R. Sylvia (804) 771-4442 PHONE:

GPO 808 667

o O CAUSE DESCRIPTION (CW T.'D) tubes plugged at the end of the current refueling outage. The nuclear steam supply system vendor continues to conduct research into the generic tube de-terioration phenomenon in PWR steam generators.

ADDITIONAL FACTORS (CONT'D) configurations on the Surry units. The results 'show that a total of 8.8 per-cent of a unit's steam generator tubes can be plugged before the ECCS criteria, peak clad temperature 2200 F, are exceeded.

Additional analyses, using the March 1975 model, are being conducted to examine the effects of non-uniform distribution of plugged tubes between loops. However, the current best estimate of the impact of non-uniform tube plugging is a 30 F increase in peak clad temperature. When this is applied to the results for uniform plugging, the maximum allowable plugging level is reduced to 7.5%. A special analysis run was made to determine if the worst non-uniform plugging currently present at Surry would result in exceeding the ECCS peak clad temperature limit. The results show that the ECCS peak clad tempera-turt limit is not exceeded due to the non-uniform plugging in either Surry -

unit. Further, this analysis contained sufficient margin to permit a signifi-

, cant number of additional tubes to be plugged in cach unit at Surry.

In conclusion, the ECCS peak clad tecperature limits are not exceeded in cither Surry unit as a result of plugged steam generator tubes nor are these-limits expected to be exceeded in the forseeable future.

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% p m c Mr. Norman C. Moseley, Director Serial No. 950 S Office of Inspection and Enforcement P0&M/ALH:jlf U. S. Nuclear Regulatory Cocunission Region II - Suite 818 Docket No. 50-280 230 Peachtree Street, Northwest License No. DPR-32 Atlanta, Georgia 30303

Dear Mr. Moseley:

Pursuant to Surry Power Station Technical Specification 6.6.2, the Virginia Electric and Power Company hereby submits a copy of the Supplemental .

Report to AO-S1-76-02

~

The substance of this report. has been reviewed by the Station Nuclear Safety and Operating Conrnittee and will be placed on the agenda for th'e next meeting of the System Nuclear Safety and Cperating Conraittee.

Very truly yours, f &

C. M. Stallings /M Vice President-Power Supply and Production Operations Enclosure i ec: Mr. Robert W. Reid, Chief (40) l Operating Reactors Branch 4 i

I s

5315.

COPY SENT REGION N_

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