NRC Generic Letter 1986-17
| ML031150302 | |
| Person / Time | |
|---|---|
| Issue date: | 10/17/1986 |
| From: | Bernero R M Office of Nuclear Reactor Regulation |
| To: | |
| References | |
| GL-86-017, NUDOCS 8610230062 | |
| Download: ML031150302 (5) | |
UNITED STATESNUCLEAR REGULATORY COMMISSIONWASHINGTON, D. C. 20555OCTi?18TO ALL LICENSEES OF BOILING WATER REACTORS AND APPLICANTSGentlemen:SUBJECT: AVAILABILITY OF NUREG-1169, "TECHNICAL FINDINGS RELATED TOGENERIC ISSUE C-8; BOILING WATER REACTOR MAIN STEAM ISOLATIONVALVE LEAKAGE AND LEAKAGE TREATMENT METHODS" (Generic Letter 86-17)This letter is to inform you that NUREG-1169, "Technical Findings Related toGeneric Issue C-8; Boiling Water Reactor Main Steam Isolation Valve Leakageand Leakage Treatment Methods", was published in June, 1986. This NUREGpresents the results of the NRC staff and contractor efforts to assess GenericIssue C-8, "MSIV Leakage and LCS Failures". This issue deals with thedifficulty of some main steam isolation valves (MSIVs) in Boiling WaterReactors (BWRs) to meet Technical Specification leakage rate limits (which aretypically 11.5 SCFH at a 25 psig test pressure) and with the need for leakagecontrol systems. The leakage rates are based on a large loss-of-coolantaccident (LOCA), a specified design basis source term from the core (TID 14844),the worst single active failure, and no credit for any non-seismic Category Iequipment, components, and structures. To ensure acceptable performanceguidelines for engineered safety features, leakage control systems (LCS) havebeen installed on most BWRs to direct any leakage past MSIVs during the designbasis LOCA to an area served by the Standby Gas Treatment System (SGTS). Ifthe leakage rate past an MSIV significantly exceeds the Technical Specificationvalue, the LCS may not be effective because of limitations in its design.As a result of these concerns, the staff prioritized the MSIV leakage and LCSfailures as a high priority Generic Issue in January 1983. Independently, theBWR Owners Group (BWROG) formed the MSIV Leakage Control Committee todetermine the cause of high leakage rates associated with many of the MSIVs,and to develop recommendations for reducing the leakage rates. The BWROG-: Committee completed its effort and provided recommendations and comments tothe staff in February, 1984 and April, 1986.In evaluating MSIV leakage with respect to offsite'doses following a LOCA, thetechnical evaluation of this Generic Issue has used realistic assumptionsconcerning the equipment, facilities and site characteristics available tomitigate the effects of a LOCA. The specific elements of the effort were:° To evaluate the BWROG recommendations associated with reducing leakagepast the MSIVs and assess the effectiveness of the recommendations asimplemented by licensees.o To evaluate the existing safety-related LCS comparing it's effectivenesswith that of other methods of handling the leakage likely to beavailable following a LOCA.A4, DOT 1 7 1986o To perform a probabilistic risk assessment (PRA) to evaluate thereliability and relative risks associated with the different methods ofmitigating the effects of a LOCA.° To evaluate the use of alternate equipment to mitigate the effects of aLOCA, and potential changes in allowable MSIV leakage rates.o To identify areas in current licensing guidance (the Regulations, the* Standard Review Plan, the Regulatory Guides, and the TechnicalSpecifications) that are related to MSIVs and LCSs that will beconsidered in the second, or regulatory assessment, phase of resolution.of the generic issue.A safety-related LCS was evaluated by comparing it's effectiveness with othermethods of handling leakage that could be available following a LOCA. Severalways to treat leakage which make.-use of the holdup volume and surfaces of themain steam lines (MSL) and condenser and fission product attenuation elsewhere,were considered. A PRA considering the reliability and relative risks associatedwith the different-methods of mitigating the effects of a LOCA was performed.The overall risks from the accident sequences in which MSYV leakage could be asignificant factor were found to be low without an LCS, and alternate fissionproduct handling techniques were shown to produce significant potential dosereductions.NUREG-1169 represents technical findings associated with Generic Issue C-8 andthe staff expects it tlobe used in the regulatory resolution of the issue. Thelatter is anticipated to be complete in another year in coordination withongoing generic activities relating to accident source terms, to overallcontainment leak rate and leak rate testing considerations.Neither this letter nor NUREG-1169 constitute a change in the existing genericstaff positions or allowable MSIV leakage rates, nor the specifications forMSIV leakage control systems. Therefore, no action is being requested ofapplicants or licensees. The information contained in NUREG-1169, however,including the recommendations of the BWROG, may be useful guidance for somelicensees contemplating plant specific change requests related to this issuepending final generic resolution.NUREG-1169 may be purchased by calling (202) 275-2060 or (202) 275-2171 or bywriting to the Superintendent of Documents, U.S. Government Printing Office,Post Office Box Number 37082, Washington, D. C. 20013, or the NationalTechnical Information Service, Department of Commerce, 5258 Port Royal Road,Springfield, Virginia 22161.I
GOT 17 a-3 -This letter is provided for information only. It does not contain any newrequirements or guidance for licensees of boiling water reactors. Actionsbased on the contents provided herein are voluntary and no reply to the NRC isrequired.Sincerely,Acb~ertXb rRobert M. Bernero, DirectorDivision of BWR LicensingOffice of Nuclear Reactor RegulationOFC : PSB:DBL PSB:DBL AW A:R .BWRye .b--------:------------ --- N f --:- ----- -----NAME :JRidgely:ye : iman :G nas : TSpeis : RBerero ::E ------------ ------/ ------------8------------ ---------DATE :IV/lv/86 :10 3 /86 :{V/ L/6 :f//6 :fr 8OFFICIAL RECORD COPY
LIST L. RECENTLY ISSUED GENERIC LTERSGenericLetter No.SubjectDate ofIssuanceGL 86-16 WESTINGHOUSE ECCS EVALUATIONMODELS10/22/86Issued ToALLPRESSURIZEDWATER REACTORAPPLICANTS ANDLICENSEES6L 86-156L 86-14INFORMATION RELATING TOCOMPLIANCE WITH 10 CFR 50.49,"EQ OF ELECTRICAL EQUIPMENTIMPORTANT TO SAFETY"OPERATOR LICENSINGEXAMINATIONS09/22/8608/20/86ALL LICENSEESAND HOLDERS OFAN APPLICATIONFOR ANOPERATINGLICENSEALL POWERREACTORLICENSEES ANDAPPLICANTSGL 66-13 POTENTIAL INCONSISTENCYBETWEEN PLANT SAFETY ANALYSESAND TECHNICAL SPECIFICATIONSOL 86-12 CRITERIA FOR UNIQUE
PURPOSE
EXEMPTION FROM CONVERSION FROMTHE USE OF HEU FUEL07/23/8607/03/66ALL POWERREACTORLICENSEES WITHCE AND B&WPRESSURIZEDWATER REACTORSALL NON-POWERREACTORLICENSEESAUTHORIZED TOUSE HEU FUELGL 66-116L 66-10DISTRIBUTION OF PRODUCTSIRRADIATED IN RESEARCHREACTORSIMPLEMENTATION OF FIREPROTECTION REQUIREMENTS06/25/8604/28/86ALL NON- POWERREACTORLICENSEESALL POWERREACTORLICENSEE ANDAPPLICANTS6L 86-09 TECHNICAL RESOLUTION OFGENERIC ISSUE NO. B-59(N-1) LOOP OPERATION IN BWRSAND PWRSGL 86-08 AVAILABILITY OF SUPPLEMENT 4TO NUREG-0933, "APRIORITIZATION OF GENERICSAFETY ISSUES"GL B6-07 TRANSMITTAL OF NUREG-1190REGARDING THE SAN ONOFRE UNIT1 LOSS OF POWER AND WATERHAMMER EVENT03/31/8603/25/8603/20/86ALL BWR ANDPWR LICENSEESAND APPLICANTSALL LICENSEES,APPLICANTS ANDCONSTRUCTIONPERMIT HOLDERSALL LICENSEESAND APPLICANTS
iCT I7 c-3 -This letter is provided for information only. It does not contain any newrequirements or guidance for licensees of boiling water reactors. Actionsbased on the contents provided herein are voluntary and no reply to the NRC isrequired.Sincerely,Robert M. Bernero, DirectorDivision of BWR LicensingOffice of Nuclear Reactor RegulationOFC : PSB:DBL PSB:DBL :KA WR D:SRO Ae D:BWR--- --- -- -- --- --X----- :- -- -- -- -: -- ----:NAME :JRidgely:ye : iman :G nas : TSpeis : RBer ero :DATE :01S1t/86 :1IG3 /86 :10/ /86 :10/ /86 :19/rI /86OFFICIAL RECORD COPY