Information Notice 1993-45, Degradation of Shutdown Cooling System Performance

Degradation of Shutdown Cooling System Performance

ML031070480
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, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	06/16/1993
From:	Grimes B K Office of Nuclear Reactor Regulation
To:
References
IN-93-045, NUDOCS 9306090036
Download: ML031070480 (9)

UNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF NUCLEAR REACTOR REGULATIONWASHINGTON, D.C. 20555June 16, 1993NRC INFORMATION NOTICE 93-45: DEGRADATION OF SHUTDOWN COOLINGSYSTEM PERFORMANCE

Addressees

All holders of operating licenses or construction permits for nuclear powerreactors.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this informationnotice to alert addressees to degradation of shutdown cooling systemperformance at the Oyster Creek Nuclear Generating Station resulting frominadequate operating procedures. 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 are not NRC requirements; therefore, no specificaction or written response is required.

Description of Circumstances

On January 23, 1993, the Oyster Creek Nuclear Generating Station was in day 57of the 14R refueling outage. The plant was in a normal cold-shutdowncondition with the primary containment open and the reactor coolant system atabout 43' C [110* F]. One reactor recirculation loop was in service, onerecirculation loop was open, and the remaining three recirculation loops wereeither idled or isolated. Two shutdown cooling loops were operating with acombined flow rate of 11,735 liters per minute 13,100 gpm].In order to support the planned activities, the licensee elected to secureoperation of all recirculation pumps and lower reactor water level. Thisconfiguration would allow completion, in parallel, of recirculation pumpmaintenance activities and main steam isolation valve local leak rate testing.When the operators lowered the reactor water level to approximately 419 cm(165 inches] above the top of active fuel and secured the running.recirculation pump, the shutdown cooling water took the least resistance paththrough the open recirculation loop, and the majority of flow bypassed thecore (see Attachment 1). During the time that the planned activities were inprogress, plant personnel did not realize that shutdown cooling systemperformance was degraded, allowing unmonitored heatup of the reactor core.On January 25, 1993, after completing the main steam isolation valve localleak rate testing, an operations engineer discovered that the reactor vesselmetal temperature was about 109C 1228F] at the mid-vessel point. Several9306090036 PDI I.E No*[ct 3-. oj58P ..'v1\

IN 93-45June 16, 1993 Technical Specifications prerequisites for exceeding 100. C [212 F] were notmet, including the requirement to establish primary containment integrity.After discovery, operators took immediate measures to reduce reactor coolantsystem water temperature by first maximizing flow in the two operatingshutdown cooling loops and then placing a third shutdown cooling loop inservice. Additionally, the reactor water level was raised to approximately508 cm [200 inches] above the top of active fuel and a recirculation pump wasstarted.The immediate cause of the event was determined to be plant conditionsestablished by a temporary procedure change to the shutdown cooling operatingprocedure that failed to provide sufficient forced flow through the reactorcore to prevent thermal stratification. The temporary procedure change hadbeen implemented to allow shutdown operations with all recirculation pumpssecured and the nominal reactor water level less than the level at whichspillover from the core region to the annulus is assured (approximately 470 cm[185 inches] above the top of active fuel). The change had been developedfrom a draft engineering evaluation, but did not include a requirement (statedin the body of the evaluation) to maintain a specified shutdown cooling flowof 22,712 liters per minute [6,000 gpm]. Instead, the usual shutdown coolingflow of about 11,735 liters per minute [3,100 gpm] was maintained which, dueto the specified configuration, allowed the inadvertent reactor heatup.Further details can be found in Licensee Event Report 50-219/93-002 and NRCAugmented Inspection Team Inspection Report No. 50-219/93-80.DiscussionThis event at Oyster Creek indicated that the temporary procedure changerepresented a significant procedure revision and that the review process didnot identify deficiencies in the procedure before it was implemented. Thetemporary procedure change had been developed from a draft engineeringevaluation which concluded that two shutdown cooling loops in operation wouldadequately cool the core. An additional assumption in the body of theevaluation was that each loop of shutdown cooling would be operating at itsdesign flow rate of 11,356 liters per minute [3,000 gpm], for a total flowrate of 22,712 liters per minute [6,000 gpm]. This flow rate would beadequate to induce spillover from the core region to the annulus at thereduced nominal water level. The temporary procedure change that implementedthe engineering evaluation did not require a minimum flow rate of 22,712liters per minute [6,000 gpm]. As a result, the operators following thedeficient temporary procedure change placed two shutdown cooling loops inoperation, but did not provide sufficient shutdown cooling water to thereactor core to maintain reactor vessel temperatures. In addition, thetemporary procedure change contained no provision or guidance for monitoringavailable instruments to ensure that decay heat was being adequately removedfrom the reactor core.As part of the licensee corrective actions, the licensee reviewed theeffectiveness of its safety review process concerning temporary changes andprovided training on the subject of this event to all site personnel whoperform technical and safety review IN 93-45June 16, 1993 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Offic ofNuclear Reactor Regulation (NRR) project manager.Brian K. Grimes, DirectorDivision of Operating ReactorSupportOffice of Nuclear Reactor RegulationTechnical contacts: James S. Stewart, RI(215) 337-5240Peter C. Wen, NRR(301) 504-2832

Attachments:

1. Figure 1, *Oyster Creek Shutdown Cooling SystemFlow With Open Recirculation Loop"2. List of Recently Issued NRC Information Notices K. /I'l ISteam Flow *-4-TO Recirculation# ~LoopShutdown CoolingSystem(3 Cooling Loops)Figure 1Attachment 11iK 93-45June 16, 1993 Open RecirculationLoopOyster Creek Shutdown Cooling System Flow With Open Recirculation Loop IAttachment 2IN 93-45June 16, 1993 LIST OF RECENTLY ISSUEDNRC INFORMATION NOTICESInformation Date ofNotice No. Subject Issuance Issued to93-4493-4393-42Operational ChallengesDuring A Dual-UnitTransientUse of InappropriateLubrication Oils inSafety-Related ApplicationsFailure of Anti-RotationKeys in Motor-OperatedValves Manufactured byVelan06/15/9306/10/9306/09/93All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.93-41One Hour Fire EnduranceTest Results for ThermalCeramics Kaowool, 3MCompany FS-195 and3M Company Interam E-50Barrier Systems05/28/93All holdersfor nuclearof OLs or CPspower reactors.93-40,93-3993-38Fire Endurance TestResults for ThermalCeramics FP-60 FireBarrier MaterialRadiation Beams fromPower Reactor Biolog-ical ShieldsInadequate Testing ofEngineered SafetyFeatures ActuationSystem05/26/9305/25/9305/24/93All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.All holdersfor nuclearof OLs or CPspower reactors.93-37Eyebolts with Indeter-minate Properties In-stalled in LimitorqueValve Operator HousingCovers05/19/93All holders of OLs or CPsfor nuclear power reactors.0L -Operating LicenseCP -Construction Permit IN 93-45June 16, 1993 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation (NRR) project manager.Original !1gnd byBrian K. GdmegBrian K. Grimes, DirectorDivision of Operating Reactor SupportOffice of Nuclear Reactor RegulationTechnical contacts:James S. Stewart, RI(215) 337-5240Peter C. Wen, NRR(301) 504-283],

Attachments:

61. Figure 1, "Oyster Creek Shutdown Cooling SystemFlow With Open Recirculation Loop'2. List of Recently Issued NRC Information Notices*rFF pRmVrnus CONCURRFNCFOFFICE *OGCB:DORS *DRS:RI **SC:DRS:RI **BC:DRS:RI **D:DRS:RINAME PCWen/vsb JSStewart PKEapen JPDurr MWHodgesDATE 04/29/93 05/03/93 03/19/93 03/19/A3 .03/19/93_______- _ .*Tech Ed. I *C:OGCB:DORS--*D:DSSA:NRRRSanders I GHMarcus ACThadani04/29/93 05/10 05/24/93.=DOCUMENT NAME: 93-45.IN**SEE MEMO FROM M.. HODGES TO B.K. GRIMESDATED 3/19/93PM (A. Dromerick), EAB (J. Carter) and AITTeam Leader (J. Beall) were consulted duringthe development of this I IN 93-XXMay xx, 1993 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation (NRR) project manager.Brian K. Grimes, DirectorDivision of Operating Reactor SupportOffice of Nuclear Reactor RegulationTechnical contacts:James S. Stewart, Region I(215) 337-5240Peter C. Wen, NRR(301) 504-2832

Attachments:

1. Oyster Creek Shutdown Cooling System Flow With Open Recirculation Loop2. List of Recently Issued NRC Information Notices*SEE PREVIOUS CONCURRENCEOFFICE *OGCB:DORS *DRS:RI **SC:DRS:RI **BC:DRS:RI **D:DRS:RINAME PCWen/vsb JSStewart PKEapen JPDurr MWHodgesDATE l04/29/93 l05/03/93 I 03/19/93 l 03/19/93 l03/19/93*Tech Ed.*C:OGCB:DORSD:DORS:NRRI RSanders GHMarcus04/29/93 _ 05/10/93 ;onf~~~l ----1F o I~tsPImBKGrimesUULUIMNI NAMI: UIIrMUN .PW)05/ /93 4xk)**SEE MEMO FROM M.W. HODGES TO B.K. GRIMESDATED 3/19/93PM (A. Dromerick), EAB (J. Carter) and AITTeam Leader (J. Beall) were consulted duringthe development of this IN.530ACiwAt #f A);mli v-AV'I/tllos IN 93-XXMay xx, 1993 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation (NRR) project manager.Brian K. Grimes, DirectorDivision of Operating Reactor SupportOffice of Nuclear Reactor RegulationTechnical contacts:James S. Stewart, Region I(215) 337-5240Peter C. Wen, NRR(301) 504-2832

Attachments:

1.2.Oyster Creek Shutdown Cooling System Flow With Open Recirculation LoopList of Recently Issued NRC Information Notices*SEE PREVIOUS CONCURRENCE .OFFICE *OGCB:DORS DRS:RI SC:DRS:RI BC:DRS:RI D:DRS:RINAME PCWen/vsb 4SStewart PKEapen JPDurr MWHodgesDATE 04/29/93 05/3,0 Cal P/1/93 0/ l/93I__ 1_/93_J*Tech Ed.C:OGCB:DORSD:DORS:NRR4xx %E memoFizz MYS 144RSanders GHMarcus Ci~l BKGrimes04/29/93 05/ 1q993 1 05/ /9344 1/1 A/ 3DOUUMENT NAME: OCTPCIN.PWPA (A 'rolnerlk&) , 1 (. Covte). tAlT Team Leader (J. &3eA.A) LxQe cuAJX4AAlxrzrl t. 4JeLt"e'4 .tk& z4 BJ IN 93-XXMay xx, 1993Page 2 ofThis information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation (NRR) project manager.Brian K. Grimes, DirectorDivision of Operating Reactor SupportOffice of Nuclear Reactor RegulationTechnical contacts:James S. Stewart, Region I(215) 337-5240Peter(301)C. Wen, NRR504-2832

Attachments:

1.2.Oyster Creek Shutdown Cooling System Flow With Open Recirculation LoopList of Recently Issued NRC Information NoticesOFFICE OBORS DRS:RI SC:DRS:RI BC:DRS:RI D:DRS:RINAME PCWen/vsb JSStewart PKEapen JPDurr MWHodgesDATE _/aq/93_ 05/ /93 05/ /93 05/ /93 105/ /93Tech Ed.C:OGCB:DORSD: DORS:NR RIflU"AJA& GHMarcus BKGrimesON/.11/93 05/ /93 05/ /93%^rrlT scur -rnT -abUUUMt Ii NAMt: ULIrMLIN.fW