Information Notice 1988-74, Potentially Inadequate Performance of ECCS in Pwrs During Recirculation Operation Following a LOCA

Potentially Inadequate Performance of ECCS in Pwrs During Recirculation Operation Following a LOCA

ML031150118
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, 05000000, Zimmer, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	09/14/1988
Revision:	0
From:	Rossi C E Office of Nuclear Reactor Regulation
To:
References
IN-88-074, NUDOCS 8809080339
Download: ML031150118 (8)

UNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF NUCLEAR REACTOR REGULATIONWASHINGTON, D.C. 20555September 14, 1988NRC INFORMATION NOTICE NO. 88-74: POTENTIALLY INADEQUATE PERFORMANCE OFECCS IN PWRs DURING RECIRCULATIONOPERATION FOLLOWING A LOCA

Addressees

All holders of operating licenses or construction permits for Westinghouse(W) and Babcock and Wilcox (B&W)-designed nuclear power reactors.

Purpose

This information notice is being provided to alert addressees to potentialproblems that could result in inadequate performance of the emergency corecooling system (ECCS) during the recirculation phase of operation followinga loss-of-coolant accident (LOCA). It is expected that recipients will reviewthe information for applicability to their facilities and consider actions, asappropriate, to avoid similar problems. However, suggestions contained inthis information notice do not constitute NRC requirements; therefore, nospecific action or written response is required.

Description of Circumstances

The NRC has received two licensee event reports on potential deficiencies inperformance of the ECCS during the recirculation phase of operation following.a small-break LOCA. These events were reported by the licensees of the Oconeeand Turkey Point facilities after engineering analysis for each facility hadidentified the potential problems.Oconee Nuclear StationDuring a technical review of nuclear safety-related mechanical calculations,the licensee discovered that the design analysis had not been adequately per-formed for the recirculation phase of operation following a small-break LOCA.Subsequent engineering analysis indicated the following design deficiencies:(1) Under certain small-break LOCA scenarios, when the borated water storagetank (BWST) is depleted and the reactor coolant system (RCS) pressureremains high (greater than the low-pressure injection (LPI) pump shut-off head), a piggyback-type operation is required to ensure core cooling.This operation entails taking suction from the reactor building sump,through the LPI pumps, through the high-pressure injection (HPI) pumps,880900339c IN 88-74September 14, 1988 and then to the RCS. However, because of (1) the high flow resistancein the cross-connect piping between the HPI and LPI pumps, (2) thepotential for partially closed LPI discharge throttle valves, and (3)the high flow rate downstream of the LPI pumps, there may not have beenadequate net positive suction head (NPSH) at the suction inlets of theHPI pumps. Inadequate NPSH would render the HPI system inoperable. Thehigh flow rate would have occurred when the reactor building spray pumpsand HPI pumps take suction simultaneously from the LPI pump discharge.The licensee has corrected the problem by revising the operating pro-cedures to provide guidance for maintaining adequate NPSH to the HPIpumps operating in the piggyback mode. The revised procedures providefor (1) HPI flow limitations when the HPI and reactor building spraypumps are piggybacked off the LPI pumps, (2) precautions on the use ofreactor building spray, and (3) precautions on the throttling of theLPI discharge valves LP-12 and LP-14. (A simplified Oconee ECCS andreactor building spray system are shown in Attachment 1.)(2) A single failure of the "TD" ECCS switchgear during loss of offsite powerwould have prevented the remote alignment of the LPI system to the HPIsystem in the piggyback mode because (1) valves LP-9, LP-15, and LPIpump B are powered by ECCS switchgear bus "TDV but their backup powersupplies are classified as load shed power supplies,'and (2) valvesLP-9.and LP-15 were in the normally closed position.The licensee has corrected the problem by (1) changing valve LP-9 to anormally open position so that it will not be required to operate whenthe LPI system is being aligned with the HPI system in the piggyback modeof operation, and (2) revising the emergency operating procedure to ensuretime is available for operators to locally, manually open valves LP-15 andLP-16 (if the valves cannot be opened remotely) before LPI suction must beswapped from the BWST to the reactor building sump.Turkey Point Nuclear StationAs part of its ongoing design-basis reconstitution program, the licensee dis-covered a condition of potentially inadequate NPSH for the containment sprayand safety injection (SI) pumps during the recirculation mode of operationfollowing a LOCA. Under these conditions, the low head residual heat removal(RHR) pumps are providing flow to the containment spray pumps and the SI pumps.A throttle valve in each RHR discharge line is normally throttled to 30 percent.However, an analysis to support this valve throttling position had not beenperformed. To resolve this discrepancy, the subject valves were locked in thefully open, position until an engineering evaluation showed that the originalconfiguration (30 percent open) was acceptabl IN 88-74September 14, 1988 Discussion:Following a small-break LOCA, the piggyback mode of operation may be required(depending on the size and location of the break) to sustain injection flowwhen the BWST (B&W plant) or refueling water storage tank (Westinghouse plant)has been depleted and RCS pressure remains above the shutoff head of the lowhead pumps. As previously described, two mechanisms could prevent this in-tendeo piggyback mode from operating: (1) insufficient MPSH at HPI (or SI)pump suction inlets, or (2) inadequate operating procedures combined withsystem design deficiencies for a loss-of-offsite-power condition. Althoughthe low head pumps provide relatively high discharge pressure, the interveningcross-connect piping between the high head and low head systems and/or partiallyclosed low head pump discharge valves could result in excessive hydraulicresistance and cause insufficient NPSH at the HPI (or SI) pump suction inlets.Insufficient NPSH could also be caused by running multiple pumps off the dis-charge of a single pump that may increase the flow above the design flow rateand consequently reduce the available pressure at the low head pump discharge.These are safety concerns because of the reliance on HPI (or SI) for mitigatingsmall-break LOCAs, and in some cases, the piggyback-type operation is used forhot leg recirculation even for large-break LOCAs.There are no redundant systems to perform the function of the HPI (or SI) systemin the piggyback mode. Although the reactor vessel high-point vents and thepower-operated relief valve(s) could be used to depressurize the RCS to lowhead pump operating pressures, the related safety analysis had never beenperformed -- thus, their effectiveness was not ensured.No specific action or written response is required by this information notice.If you have any questions about this matter, please contact one of the technicalcontacts listed below or the Regional Administrator of the appropriate regionaloffice.ar esI E. ossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical Contacts: S. Israel, AEOD(301) 492-4437J. Thompson, NRR(301) 492-1175P. Wen, NRR(301) 492-1172

Attachments:

1. Figure 1, Simplified Oconee Emergency Core Coolingand Reactor Building Spray Systems2. List of Recently Issued NRC Information Notices Figure 1 Simplified Oconee Emergency Core Coolingand Reactor Building Spray Systems.a > i a a al zrLI LI LI LI LI.EI 4RID SPRAY "UPSec -7 o- _DECAY HEAT lANYMPS CODEtRSCF I CF 2_ 1,r CtDEG 2AI 2 .R.iCAt IE _ M_; ^,L v fW GNfCl :Hp 41 liD lIGAJF4--tEip 100X~ HP al? Frin r (.D_T. r__ _ c -1$fill L 2lp 'SI, .-I Attachment 2IN 88-74September 14, 1988 LIST OF RECENTLY ISSUEDNRC INFORMATION NOTICESInformation Date ofNotice No. Subject Issuance Issued to88-7388-7288-71Direction-Dependent LeakCharacteristics ofContainment Purge ValvesInadequacies in the Designof dc Motor-Operated ValvesPossible EnvironmentalEffect of the Reentryof COSMOS 1900 andRequest for Collectionof Licensee RadioactivityMeasurements Attributedto That EventCheck Vdlve InserviceTesting ProgramDeficienciesMovable Contact FingerBinding in HFA RelaysManufactured by GeneralElectric (GE)9/8/889/2/889/1/888/29/888/19/88All holders of OLsor CPs for nuclearpower reactors.All holders of OLsor CPs for nuclearpower reactors.All holders of OLsor CPs for nuclearpower reactors, fuelcycle licensees,and Priority 1material licensees.All holders of OLsor CPs for nuclearpower reactors.All holders of OLsor CPs for nuclearpower reactors.88-7088-6988-48,Supplement 1Licensee Report of DefectiveRefurbished Valves8/24/88All holders of OLsor CPs for nuclearpower reactors.88-6888-6788-66Setpoint Testing of Pres-surizer Safety Valves withFilled Loop Seals UsingHydraulic Assist DevicesPWR Auxiliary Feedwater PumpTurbine Overspeed TripFailureIndustrial RadiographyInspection and Enforcement8/22/888/22/888/22/88All holders of OLsor CPs for nuclearpower reactors.All holders of OLsor CPs for nuclearpower reactors.All NRC industrialradiography licensees.OL = Operating LicenseCP = Construction Permit IN 88-74September 14, 1988 Discussion:Following a small-break LOCA, the piggyback mode of operation may be required(depending on the size and location of the break) to sustain injection flowwhen the BWST (B&W plant) or refueling water storage tank (Westinghouse plant)has been depleted and RCS pressure remains above the shutoff head of the lowhead pumps. As previously described, two mechanisms could prevent this in-tended piggyback mode from operating: (1) insufficient NPSH at HPI (or SI)pump suction inlets, or (2) inadequate operating procedures combined withsystem design deficiencies for a loss-of-offsite-power condition. Althoughthe low head pumps provide relatively high discharge pressure, the interveningcross-connect piping between the high head and low head systems and/or partiallyclosed low head pump discharge valves could result in excessive hydraulicresistance and cause insufficient NPSH at the HPI (or SI) pump suction inlets.Insufficient NPSH could also be caused by running multiple pumps off the dis-charge of a single pump that may increase the flow above the design flow rateand consequently reduce the available pressure at the low head pump discharge.These are safety concerns because of the reliance on HPI (or SI) for mitigatingsmall-break LOCAs, and in some cases, the piggyback-type operation is used forhot leg recirculation even for large-break LOCAs.There are no redundant systems to perform the function of the HPI (or SI) systemin the piggyback mode. Although the reactor vessel high-point vents and thepower-operated relief valve(s) could be used to depressurize the RCS to lowhead pump operating pressures, the related safety analysis had never beenperformed -- thus, their effectiveness was not ensured.No specific action or written response is required by this information notice.If you have any questions about this matter, please contact one of the technicalcontacts listed below or the Regional Administrator of the appropriate regionaloffice.Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical Contacts: S. Israel, AEOD(301) 492-4437J. Thompson, NRR(301) 492-1175P. Wen, NRR(301) 492-1172

Attachments:

1. Figure 1, Simplified Oconee Emergency Core Coolingand Reactor Building Spray Systems2. List of Recently Issued NRC Information Notices*SEE PREVIOUS PAGE FOR CONCURRENCE*AEOD *OEAB:DOEA *OGCB:DOEA *TECH ED *SRXB:DEST *D:DESTSIsrael JThompson PWen WHodges LShao8/30/88 8/30/88 8/30/88 8/30/88 8/30/88 8/31/88,:OGCB:DOEAHBerlinger 48/31/88 9/ V/88 IN 88-xxAugust xx, 1988 been depleted and RCS pressure remains above the shutoff head of the low headpumps. As previously described, two mechanisms could prevent this intendedpiggyback mode from operating: (1) insufficient NPSH at HPI (or SI) pumpsuction inlets, or (2) inadequate operating procedures combined with inadequatesystem design during a loss-of-offsite-power condition. Although the low headpump provides relatively high discharge pressure, the intervening cross-connectpiping between the high head and low head systems and/or partially closed lowhead pump discharge valves could result in excessive hydraulic resistance andcause insufficient NPSH at the HPI (or SI) pump suction inlets. InsufficientNPSH could also be caused by running multiple pumps off the discharge of a singlepump that may increase the flow above the design flow rate and consequentlyreduce the available pressure at the low head pump discharge. These are safetyconcerns because of the reliance on HPI (or SI) for mitigating small-break LOCAs,and in some cases, the piggyback-type operation is used for hot leg recirculationeven for large-break LOCAs.There are no redundant systems to perform the function of the HPI (or SI)system in the piggyback mode. Although the reactor vessel high-point ventsand the power-operated relief valve (PORV) could be used to depressurize theRCS to low head pump operating pressures, the related safety analysis hadnever been performed -- thus, their effectiveness was not ensured.No specific action or written response is required by this information notice.If you have any questions about this matter, please contact one of thetechnical contacts listed below or the Regional Administrator of theappropriate regional office.Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical Contacts:S. Israel, AEOD(301) 492-4437J. Thompson, NRR(301) 492-1175P. Wen, NRR(301) 492-1172

Attachments:

1. Figure 1, Simplified Oconee Emergency Core Coolingand Reactor Building Spray Systems2. List of Recently Issued NRC Information Notices*SEE PREVIOUS PAGE FOR CONCURRENCE*AEOD *OEAB:DOEA *OGCB:DOEA *TECH ED *SRXB:DESTSIsrael JThompson PWen WHodges8/3 /88 8/30/88 8/30/88 8/30/88 8/30/88C: CB:DOEA D:DOEACHBerlinger CERossif/ 31/88 9/ /88*D: DESTLShao8/31/88 IN 88-xxAugust xx, 1988 been depleted and RCS pressure remains above the shutoff head of the low headpumps. As previously described, two mechanisms could prevent this intendedpiggyback mode from oeprating: (1) insufficient NPSH at HPI (or SI) pumpsuction inlets, or (2) inadequate operating procedures combined with inadequatesystem design during a loss-of-offsite-power condition. Although the low headpump provides relatively high discharge pressure, the intervening cross-connectpiping between the high head and low head systems and/or partially closed lowhead pump discharge valves could result in excessive hydraulic resistance andcause insufficient NPSH at the HPI (or SI) pump suction inlets. InsufficientNPSH could also be caused by running multiple pumps off the discharge of a singlepump that may increase the flow above the design flow rate and consequentlyreduce the available pressure at the low head pump discharge. These are safetyconcerns because of the reliance on HPI (or SI) for mitigating small-break LOCAs,and in some cases, the piggyback-type operation is used for hot leg recirculationeven for large-break LOCAs.There are no redundant systems to perform the function of the HPI (or SI)system in the piggyback mode. Although the reactor vessel high-point ventsand the power-operated relief valve (PORV) could be used to depressurize theRCS to low head pump operating pressures, the related safety analysis hadnever been performed -- thus, their effectiveness was not ensured.No specific action or written response is required by this information notice.If you have any questions about this matter, please contact one of thetechnical contacts listed below or the Regional Administrator of theappropriate regional office.Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical Contacts: S. Israel, AEOD(301) 492-4437J. Thompson, NRR(301) 492-1175P. Wen, NRR(301) 492-1172

Attachments:

1. Figure 12. List of Recently Issued NRC Information NoticesAEOEa11A OEAB: OGCB:DOEA T CH ED SRX :DEST C:OGCB:DOEAP Israel JTh idon PWen ( f5 WHodges CHBerlingerV8/3c88 8/ -jr 8/30 /88 /3i /88 8/3 0 /88 8/ /88D:DOEA D4_0CERossi LShao8/ /88 8/)//88