NRC Generic Letter 1991-07

NRC Generic Letter 1991-007: GI-23, Reactor Coolant Pump Seal Failures and Its Possible Effect on Station Blackout

ML031140509
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, Fort Saint Vrain, Washington Public Power Supply System, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant, Clinch River
Issue date:	05/02/1991
From:	Partlow J G Office of Nuclear Reactor Regulation
To:
References
GL-91-007, NUDOCS 9104290113
Download: ML031140509 (3)

63 'A*o UNITED STATESNUCLEAR REGULATORY COMMISSIONWASHINGTON. D.C. 20555May 2, 1991TO: ALL POWER REACTOR LICENSEES AND HOLDERS OF CONSTRUCTION PERMITS

SUBJECT: GI-23, "REACTOR COOLANT PUMP SEAL FAILURES" AND ITS POSSIBLE EFFECTON STATION BLACKOUT (GENERIC LETTER 91-07)The staff published a notice in the Federal Register (56 FR 16130) on April 19,1991, soliciting public comments on Generic Issue (GI)-23, "Reactor CoolantPump Seal Failures." This letter informs licensees of the possible effectof GI-23 on their responses to the station blackout (SBO) rule (Section 50.63of Title 10 of the Code of Federal Regulations [10 CFR 50.63]).Reactor coolant pump (RCP) seals and their supporting systems have experienceddegradations and failures, some of which have been of sufficient severity to beclassified as small break loss of coolant accidents (SBLOCAs). Preliminaryanalyses by the NRC indicated that the RCP seal failures could dominate theoverall probability of a core melt caused by SBLOCA. As a result, the staffestablished GI-23 to provide for the evaluation of the adequacy of currentlicensing requirements relating to RCP seal integrity and to determine if theU. S. Nuclear Regulatory Commission (NRC) should take any further action.In resolving the SBO issue (USI A-44), the NRC staff considered the relationshipof this issue with other NRC generic issues, including GI--23. In determiningestimates of core damage frequency for SBO events in NUREG/CR-3226, "StationBlackout Accident Analyses," the staff assumed that the RCP seals would leak ata rate of 20 gallons per minute (gpm) per pump. During the final resolution ofthe station blackout issue and the development of the Nuclear Management andResources Council (NUMARC) Report 87-00, "Guidelines and Technical Bases forNUMARC Initiatives Addressing Station Blackout at Light Water Reactors," NUMARCand the staff agreed to assume that RCP seal leakage during an SBO would be nogreater than 25 gpm per pump. Further, NUMARC and the staff agreed that if thefinal resolution of GI-23 results in higher RCP leakage rates, then the SBOanalyses would have to be reevaluated.The SBO rule became effective on July 21, 1988, and the NRC received responsesfrom all licensees addressing the SBO rule by April 21, 1989. Licensees mayhave analyzed their reactor coolant inventories for the SBO conditions usingthe specific guidance provided in NUMARC Report 87-00 of 25 gpm for RCP sealleakage for pressurized water reactors (PWRs) and 18 gpm for boiling waterreactors (BWRs). These leak rates could be greater if the seals failedduring the SBO event.The preliminary results of the staff's studies for GI-23 indicate that thepump seal leak rates could be substantially higher than those assumed for theresolution of the SBO issue. The staff determined that RCP seal leakage couldexceed 25 gpm and lead to core uncovery during an SBO in any of the PWRs and inany of the four BWRs (Millstone Unit 1, Oyster Creek, Nine Mile Point Unit 1,9104290113 sPD POcK OSOObOOZ P ¶OSO 2GA Generic Letter 91-07-2 -May 2, 1991and Big Rock Point) that do not have an AC-independent makeup capability.Having made these findings, the staff is soliciting public comments on itscurrent understanding of GI-23. One possible outcome may be that sealcooling be provided by an independz.it cooling system during off-normal plantconditions involving the loss of all seal cooling, such as could occur duringan SBO. This recommendation, if adopted, would apply to all PWRs and mightapply to the above-mentioned BWRs, which do not have AC-independent makeupLapabilities for their reactor coolant systems. Therefore, utilities shouldrecoanize that such a recommendation could affect their analyses and actionsaddressing conformance to the SBO rule.Thiis generic letter consists of information only and does not require specificaction or written response. Therefore, an Office of Management and Budget(0MB) clearance number is not necessary. If you have any questions about thismatter, please :3ntact one of the technical contacts listed below or theRegional Administrator of the appropriate regional office.

Sincerely,Ja es G. PartlowAs ociate Director for ProjectsOffice of Nuclear Reactor RegulationTechnical Contacts: Chu-Yu Liang, NRR(301) 492-0878Paul Gill. NRR(30t) 492-3265 Generic Letter 91-07-2 -May 2, 1991and Big Rock Point) that do not have an AC-independent makeup capability.HaVins radL thLSte firdinrs, the staff is sClicitil.9 public conmnents on itscurry.,t ui.eur t4Laedo., a. -L'-L.. Bla. Loeitle outccme may be that sealC.LLi i.y LL pYUviddc! by an independent cocliiiq SYS L. (Iting off-nUrnial pialmtcourciticrs involving the loss of all seal cooling, such as could occur duringan SBO. This recommendation, if adopted, would apply to all PWRs and mightapply to the above-mentioned BWRs, which do not have AC-independent makeupcapabilities for their reactor coolant systems. Therefore, utilities shouldrecognize that such a recommendatiun could affect their analyses and actiounsaddressing conforaLrcE to the SEC, rule.This ger.eric letur corsists of infonnation only and does not require specificaction or written response. Therefore, an Office of Management and Budget(ONE) clearance number is not necessary. If you have any questions about 'Ihismatter, please contact one of the technical contacts listed below: or theRegional Administrator of the appropriate regional office.

Sincerely,original signed by James G. PartlowJames G. PartlowAssociate Director for ProjectsOffice of Nuclear Reactor RegulationTechnical Contacts: Chu-Yu Liang, NRR(301) 492-0878Paul Gill, NRR(301) 492-3265DISTRIBUTIONCentral Files NRC PDR PD5 Reading LKokajko DFosterJDyer MVirgilio BBoger AThadani WlinnersJPartlow CBerlinger*See previcus concurrenceReviewed by J. Main*, Technical Editor, on January 29, 1991. _.0 "3 A ri- Ok as revisedC :LA/PD5/DRPW :P1M/P 5/DRPW :D/PD5/DRPW* :AD/DRPW* :D/DP.P l' :t'PP/DSTME :DFoster* M 'okajko:sg :JDyer :MVirgilio :BBoger :AThadani*-: .I- 7 -I t:i ,"*s., , /L I t J J /pT3 1/0 / CI-^ k-Tr^Ty:NRIT0FRCL X7H -:T-,S e :-- ------- -- -- ------- ----- ---- -------- ----------------- :-E:r :V.T irnere*41 :CPerlir~e :,- rt i 1 :---------------- 2/-/-9--------- ---------- --- --------- ---------- -- ..---TE :2/5/91 4/a9 C,See memo Minners to Jordon (CRGR) Dated 2/5/91.OFFICIAL RECORD COPY Document Name: GL LTR