TXX-4510, Forwards Safety Evaluations Performed by Westinghouse & Gibbs & Hill,Supporting 850517 Request to Change Tech Specs to Allow Use of Manual Operators on MSIV Bypass Valves. Analyses Indicate No Safety Impact as Result of Mod

Forwards Safety Evaluations Performed by Westinghouse & Gibbs & Hill,Supporting 850517 Request to Change Tech Specs to Allow Use of Manual Operators on MSIV Bypass Valves. Analyses Indicate No Safety Impact as Result of Mod

ML20128L032
Person / Time
Site:	Comanche Peak
Issue date:	07/10/1985
From:	Counsil W TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC)
To:	Noonan V NRC - COMANCHE PEAK PROJECT (TECHNICAL REVIEW TEAM)
References
TXX-4510, NUDOCS 8507240283
Download: ML20128L032 (10)

Text

G' l Log # TXX-4510 File # 10010 TEXAS UTILITIES GENERATING COMPANY MKYWAY YtlWEH

• 400 NDHTH OLIVE hTHEET, L.R. M1

• DALLAM, TEXAM 73201 July 10, 1985

?nM^5AMf05 Director of Nuclear Reactor Regulation Attention: Mr. Vincent S. Noonan, Director Comanche Peak Project Division of Licensing U. S. Nuclear Regulatory Commission Washington, D.C. 20555

SUBJECT:

COMANCHE PEAK STEAM ELECTRIC STATION DOCKET N05. 50-445 AND 50-446 REPLACEMENT OF MSIV BYPASS VALVE ACTUATORS

Dear Mr. Noonan:

Texas Utilities letter TXX-4642 dated May 17, 1985 requested a change to the CPSES Technical Specifications to allow the use of manual operators on the Main Steam Isolation Valve (MSIV) bypass valves. In support of this request the letter referenced an evaluation performed to determine the impact of the MSIV bypass valve actuator replacement on plant safety.

Enclosed are copies of analyses performed by Westinghouse and Gibbs & Hill.

The conclusions of these analyses indicate no safety impact as a result of this modification.

Should you have questions in this matter, please contact this office.

Sincerely, f 7. IfA, W. G. Counsil BSD/grr c - C. Trammell S. Burwell A. Vietti kA A

A DIYleilON 09' TEL4N l'TELETIEN ELECTRIC COME%NY 8ooI g

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bec: M. D. Spence J. B. George R. T. Jenkins J. D. Redding R. A. Jones J. W. Beck N. H. Williams J. Ellis Richard McCaskill - BEPC John Butts - TEX-LA Ed Wagoner -TMPA

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Q RECEIVED'

%7 WPr-778i4 APR 2 51985 Westinghouse Water Reacta'r 8" 355 TUGC0 Electric Corporation Division $ NUCCEAR ENGINEERING April 19,1985

. NS-0PLS-OPL-85-176 Mr. J. T. Merritt, Jr. S.O. 'IBX/TCX-4705 Assistant Project General Manager Texas Utilities Services, Inc. Ref.: WPT-7770 P.O. Box 1002 Glen Rose, Texas 76043 TEXAS UTILITIES GENERATING COMPANY COMANQiE PEAK STEAM ELECTRIC STATION SAFETY EVALUATION OF MSIV BYPASS VALVE ACTUNIDR REPL ACEMENT

Dear Mr. Merritt:

Attached please find the safety evaluation perfomed for the replacement of the Main Steam Isolation Valve '(MSIV) bypass valve autmatic hydraulic actuators with manual ones for the Cmanche Peak Units. The findings of this safety evaluation indicate that there is no impact on the steamline break core response analysis. The effect on the steamline break mass and energy release is also insignificant but a difference in the reverse flow blowdown resulting frm the proposed modified operating procedures should be evaluated by 'IUGC0 cnd Gibbs & Hill for any effect on the contaiment analyses.

Should you have any questions, please advise.

Very truly yours, WESTINGHOUSE ELECTRIC CORPORATION

'R. S. Howard, Manager

. fW HRD Cmanche Peak Projects A. M. Sicari/pj gw Attachment w

cc: J. T. Merritt, Jr. , IL, IA M -

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SAFETT EVALUATIDN FOR 1HE REPLACEENT OF 111E MAIN STEAM ISCLATION VALVE BYPASS VALVE ACTUA1DRS Each of the Main Stem Isolation Valves (MSIVs) at Cmanche Peak units 1 and 2 are equipped with a four-inch bypass valve. These bypass valves are used to wam up the steam piping and equalize the pressure across the MSIVs so that the MSIVs may be opened. The bypass valve hydraulic actuators have required extensive maintenance and repair work and are being replaced with manual actuators.

The only impact this change has on the safety analysis is on the main steamline break analyses assmptions. Should a main steamline break occur when more than one of the bypass valves are open, the possibility exists that two or more steam generators would have an tricontrolled blowdown. In order to eliminate the potential for the tricontrolled blowdown of two or more stem generators, TUGC0 will apply operating procedures to use only one bypass valve during startup. This one bypass valve will be used to equalize the pressure across the corresponding MSIV. The corresponding MSIV will then be opened and the single bypass valve will be closed prior to the opening of the reaining MSIVs.

The Cmanche Peak (units 1 and 2) stealine break core response analyses are triaffected by the replacement of the hydraulic actuators with manual ones.

The existing analyses asstne that only one steam generator entirely depressurizes and the remaining three intact steam generators isolate from the break uhen steamline isolation occurs by closure of the MSIVs. If one bypass valve and/or the corresponding MSIV are open (with the remaining bypass valves and MSIVs closed), only the faulter ';eam generator can depressurize. With only one steam generator depressuru.ing through the break, the primary.

temperature reduction is less severe than the current FSAR analyses.

Therefore, the existing core response analyses remain bounding.

The steamline break mass and energy release analysis has been evaluated to detemine the impact of the steamline bypass valve manual actuators. The assumption made in the existing analysis is that all MSIVs are open at the time the postulated break occurs. As for the core analysis, the MSIVs of the intact

. loops are assmed to close within the technical specification response time requirments.

For the cases where the faulted loop MSIV is assmed to fail, the main steamline header and unisolated steamlines completely blow down through the break in addition to the reverse blowdown (prior to steamline isolation) from the intact stem generators. Since the new operating procedures require that all of the MSIVs and bypass valves be closed when the one bypass valve is open (this assmes the loop with the break has the bypass and/or MSIV open) the intact steam generators cannot blewdown. The reverse flow out of the break would then be made up of the mass contained only in the misolated steamlines and the main steamline header. Should a break occur in a loop where the bypass

' and MSIVs are closed, the mass and energy release would be limited to the one stem generator and the small amount of mass contained between the steam generator and MSIV piping. The proposed operating restrictions would have an insignificant impact on the forward flow mass and energy release from the faulted stem generator. In either case, the existing analysis which assmed a failure of the MSIV remains bounding.

For the cases where all of the MSIVs are assmed to operate properly, the reverse blowdown out of the break location is made up of mass frm the unisolated stealine and the intact steam generators. With the new operating procedures, the steamline isolation signal will cause the only open MSIV to automatically close, but the bypass valve will remain open allowing a continous blmdown of the misolated steamlines and the main stemline header. However, no blowdown will occur frm the intact steam generators. The effect on the forward fim mass and energy release out of the break is again insignificant.

To evaluate the impact of this modified reverse flow mass and energy release, 1UGC0 and Gibbs & Hill should evaluate the contaiment analyses based on a l

total reverse flow mass and energy release limited by the mount of mass contained in the misolated stealines and main stealine header (no blmdown of the intact sten generators).

l In conclusion, the replacement of the hydraulic actuators with manual devices on the steamline bypass valves around the MSIVs has no impact on the

! steamline break core response analysis and a small effect on the steamline break mass and energy analysis. The consequences of the mass and energy release should be evaluated by 1UGC0 and Gibbs & Hill.

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-Gibbe B HM,kno. Interoffice Memorandum

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"' 8' *""*" -- April 22, 1985 T0: DATE:

S. C. Mairal 00-2323-050 '

FROM: -

JOB NO: -

Replacement of MSIV Bypass '

SUBJECT:

-- = REF. NO: ,

Valve Actuators Please find attached the safety evaluation report for the proposed replacement of the Main Steam Line Valve (MSIV) bypass valve actuators.

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COMANCHE PEAK STEAM ELECTRIC STATION i REPLACEMENT OF THE MSIV BYPASS VALVE ACTUATORS er-

. SAFETY EVALUATION I

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APRIL 22, 1985 PREPARED BY: S. C. MAIRAL

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1.0 OBJECTIVE To per form a safety evaluation of the proposed replacements of g- Main Steam Line Valve actuators, following the guidelines of ss f 10 CPR 50.59. ,

2.0 SCOPE OF PROPOSED CHANGE t

The Main steam Isolation valves (MSIVs) at Comanche Peak are equipped with four-inch bypass valves and their corresponding  ;

actuators. The bypass valves are used to warmup the steam  :)

piping and equalize the pressure across the MSIVs during startup. They remain closed during normal power operation.

The installed Unit 1 and Unit 2 MSIV bypass yhlve actuators require excessive maintenance and repair for reliable oper-ation. The r efo r e , it is proposed to replace the existing hydraulic actuators for these bypass valves with manual .]

actuators. This operating restriction would involve the following steps:

a. Open only one MSlV bypass valve ar.d use it to equalize the pressure across the corresponding MSIV.

b. Open the MSIV associated with the open bypass valve to heat the piping in the remaining lines.

c. Close the bypass valve which will be kept locked closed during normal plant operation.

d. Open remaining MSIVs.

3.0 SCOPE OF THE SAFETY EVALUATION The purpose of this Safety Evaluation is to review the effect of the proposed bypass valve actuator replacement upon the accident analyses per formed by Gibbs & Hill.

Specifically, the review assessed whether the scenario resulting from a main steam line break accident during startup when one of .the MSIV bypass valves is opened has any adverse safety impact.

Based on 10 CPR 50.59' guidelines, the review evaluated (a) if the probability of occur rence or the consequences of an acci-dent or malfunction of equipment important to safety previ-ously evaluated in the safety analysis report may be in-creased; or ( b) if a possibility for an accident or malfunc-tion of a different type than any evaluated previously in the safety report may be createdt or (c) if the margin of safety T

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r~s u (C) as defined in the basis for any technical specification is reduced. H The scope of the review was the FSAR and all the accident analysis calculations that are potentially affected by the L

! prposed change and have an impact on (a) containment F l

integrity; and (b) raiological evaluation of environmental consequences. The following calculations were reviewed for possible changes on the assumptions used and the conclusions ,

I reached:

a. Calculation No. NC-AA Stoam Line Br eak Accident ,

b. Calculation No. NC-AA Steam Generator Tube Rupture q Accident b

c. Calculation No. NC-AA Loss of Coolant Accident

d. Calculation No. NC-AA-ld - Emergency planning Dose Calculation j l

e. Calculation No. NC-CT-3 - Steam Line Break Analysis for TUSI.

CPSES FSAR i .

f. Calculation No. NC-CT-F - MSLB Reanalysis Due to BlT Removal

^ j) CPSES/FSAR j i

4.0 DISCUSSION '

4.1 CONTAIN4ENT INTEGRITY The analysis and the FSAR description assumed the four MSIVs, or their corresponding valves, would be open at the time of 4 the break thus resulting in a fast decrease of secondary side  ;

steam inventory coming from all steam generators until steam line isolation occur s. However, should the main steam line break occur during startup under the operating restriction described in Section 2.0 the potential for the uncontrolled blowdown of two or more steam generators would be eliminated. .

Also, should the accident occur during startup, the operating restriction would decrease the rate at which the secondary fluid is lost through the break. This would load to a lower containment temperature and pressure buildup rate.

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• 86

() 4.2 RADIOLOGICAL CONSEQUENCES l

The changes introduced by the operating restriction do not af fect the analyses as per formed. In case of a main steam line break, the only possibility of having a radioactive release to the environment is that the break occurs outside containment between the containment penetration and the MSIV.

Doses resulting from this accident were analyzed and found to be below the regulatory limits established in 10 CFR 100.

'9. 0 CONCLUSION 1.

There is no change in the probability of occur rence of any of the accidents already analyzed by Gibbs & Hill.

2 The operating restriction introduced due to the replacement of bypass valve hydraulic operators with manual operators does not bring the possibility for an l l.

accident of different type than any evaluated previously. ,

In fact it is not necessary to revise the accident analysis up by theto incorporate the new accident scenario brought replacement.

. The original main stoam line break analysis assumptions are more stringent.since in this type of energy accident is released. the controlling factor is the rate at which l

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3 There is no reduction in safety margins since the assumptions used in previous accident safety analysis are more stringent and therefore the results more conservative.

6.0 REFERtNCES

1. TUGCo' letter dated Match 5, Steam Isolation Valve (MSIV) 1985 on " Valyc Bypass Replacement Actuatots" of Main 2.

10 CFR 50.59 " Changes Tests and Experiments" 3.

CPSES FSAR Section 6.2.1.4 " Mass and Energy Releaso Analysis for Postulated Secondary System Pipe Rupture" 4.

CPSES FSAR Section 15.5.5 " Steam System Piping Failure"

5. CPSES Technical Consequences of Design Base Accidents" Specifications Section 15.4 " Radiological

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