Information Notice 1999-14, Unanticipated Reactor Water Draindown at Quad Cities Unit 2, Arkansas Nuclear One Unit 2, & FitzPatrick

Unanticipated Reactor Water Draindown at Quad Cities Unit 2, Arkansas Nuclear One Unit 2, & FitzPatrick

ML031040444
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:	05/05/1999
From:	Marsh L B Division of Regulatory Improvement Programs
To:
References
IN-99-014, NUDOCS 9905070080
Download: ML031040444 (8)

May 5, 1999

NRC INFORMATION NOTICE 99-14: UNANTICIPATED REACTOR WATER DRAINDOWNAT QUAD CITIES UNIT 2, ARKANSAS NUCLEAR ONEUNIT 2, AND FITZPATRICK

Addressees

All holders of licenses for nuclear power, test, and research reactors.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to alertaddressees to the potential for personnel errors during infrequently performed evolutions thatresult in, or contribute to, events such as the inadvertent draining of water from the reactorvessel during shutdown operations. It is expected that recipients will review the information forapplicability to their facilities and consider actions, as appropriate, to prevent a similaroccurrence. However, suggestions contained in this information notice are not NRCrequirements; therefore, no specific action or written response to this notice is required.DescriDtion of CircumstancesQuad Cities Unit 2On February 24, 1999, Quad Cities Unit 2 was in cold shutdown with reactor water temperatureat 131 'F and reactor water level at 80 inches indicated level (normal level during operations is30 inches indicated or 173 inches above the top of active fuel [TAF]). Core cooling was beingmaintained in a band of 120 'F to 170 OF by the OA" loop of the shutdown cooling mode of theresidual heat removal (RHR) system after being switched from the nB" loop at 12:32 a.m.During the switch over the licensee inadvertently failed to close the OA RHR minimum flowvalve as required by the procedure. Sometime later operators noted a decreasing reactor waterlevel and at about 1:02 a.m. secured the *2A RHR pump and isolated shutdown cooling. At1:55 a.m. operators restored the *2A' loop of shutdown cooling to the proper lineup and startedthe *2A RHR pump. Water level had decreased to a minimum of about 45 inches indicated,and reactor water temperature had risen to a maximum of about 163 OF. Forced circulation ofreactor vessel water using a reactor recirculation pump remained in effect throughout the event.On the basis of post event reviews, It appears that the minimum flow valve in the OA loop wasleft open because the nuclear station operator failed to ensure that the tasks were performed inthe sequence specified in the operating procedures. The nuclear station operator who was(7008 PD(L H ort<<4qj-Oiif qqos(J5C7FfcjANW\\b IN 99-14May 5, 1999 directing the evolution from the control room gave the non-licensed operator permission to de-energize the breaker for the WA RHR minimum flow valve operator before the valve was takento the required closed position. De-energizing the breaker also removed power to the valveposition indicator lights in the control room. Thus, when the nuclear station operator tried toverify that the valve was closed, there was no position indication in the control room to makethat verification. The nuclear station operator made the incorrect assumption that the valve wasalready closed and moved to the next step in the procedure. This failure to close the WAX RHRminimum flow valve opened a drain path from the reactor to the suppression pool. To furthercomplicate the event, the operating crew did not recognize that there was any problem untilapproximately 10 minutes had passed and the water level had decreased about 13 inchesbecause of a misinterpretation of causes of the level decrease. After detecting the decrease,the operating crew was slow to react, which allowed the level to decrease another 20 inchesbefore the operators isolated shutdown cooling which terminated the draindown. The licenseeestimated that a total of 6000 to 7000 gallons was drained from the reactor to the suppressionpool.Operations staff practices including poor communications, poor activity briefings for high-riskactivities, lack of effective pre-shift briefings, inadequate supervision of important control roomactivities, inadequate monitoring of control room panels, and slow event response may havecontributed to the event. Although the unintended loss of inventory to the suppression poolhighlighted significant weaknesses in plant operations, the safety significance was minimized bytwo features. First, a reactor recirculation pump remained in service throughout the eventwhich served to distribute decay heat. Second, an automatic isolation of shutdown coolingwould have occurred at 8 inches indicated level which would have stopped the draining event.An indicated water level of 8 inches corresponds to approximately 151 inches of water levelabove the TAF in the reactor core.Arkansas Nuclear One Unit 2On February 2, 1999, at Arkansas Nuclear One Unit 2, the operators were draining therefueling canal in preparation for installing the reactor vessel head. Refueling was completeand steam generator nozzle dams were installed. The operators were using the two lowpressure safety injection (LPSI) pumps to drain the canal to the refueling water storage tank;one pump also served as the shutdown cooling pump. The rate of draindown wasapproximately 3.3 Inches per minute. When the water level reached 105 inches, the reactoroperator noted that level started to lower rapidly. Operators stopped one of the LPSI pumpsand instructed a local operator to close the isolation valve to the refueling water tank. Thismanually operated valve required 55 turns of the handwheel to fully close. Withinapproximately 1.5 minutes, the reactor vessel level had dropped below the 65 inch level (wherereduced inventory begins) and continued down to 56 inches before the valve could be fullyclosed. (Reference zero on these level instruments is the bottom of the hot leg, with mid-loopbeing defined at approximately 24 inches.) The average rate of level decrease between 105 IN 99-14May 5, 1999 inches and 56 inches was approximately 33 inches per minute. At its lowest level, 56 inchesindicated, there were still 93 inches of water above the TAF. Using the high pressure safetyinjection (HPSI) pump the operators brought the level back up to 90 inches. The plant was inreduced inventory operations (below 65 inches) for approximately 7 minutes. During the eventthe level remained well above the point where LPSI pump cavitation would be expected. Thelicensee concluded that the safety significance of the event was minimal because multiplesources of makeup water were available, redundant mitigation equipment was available, andthe operators were quick to recognize and respond to the event.On the basis of post event reviews, it was determined that the procedure used for drainingdown the refueling canal was inadequate in that it incorrectly stated that the draindown shouldbe secured at the 90-inch level. The procedure should have directed that the rate of drainingbe secured at the 106-inch level so that appropriate precautions could be taken beforeresuming the draindown. These precautions should have Included reminders to the operatingcrew that below the 106-inch level the level will drop much more quickly due to the transition ofpumping from a large volume in the refueling canal to a small volume In the reactor vessel.Therefore, in order to maintain control of the water level, the draindown rate should bedecreased and an operator should be stationed to directly monitor the level.Additional factors that contributed to this event include: the operators received little specifictraining on this evolution; the crew was inexperienced in performing this task; the task shouldhave been classified as an infrequent task requiring a more thorough briefing; and, operatorsfailed to station an operator in a position where he could directly monitor the water level in therefueling canal. Instead they monitored it remotely using a video camera that did not provide aclear picture of the water level.FitzPatrickOn December 2, 1998, at the James A. FitzPatrick Nuclear Power Plant, the operators were inthe process of reassembling the reactor following refueling. Operators were controlling thereactor vessel water level at 357 inches above TAF by adjusting the water discharge rate tocompensate for the constant input from the control rod drive cooling water system. While in thiscondition, the licensees risk analysis requires that reactor vessel water level be monitored usingtwo independent level indicators. To meet this requirement, the licensee designated a widerange indicator which provided Indication up to the top of the reactor vessel and an RHRinterlock level indicator which provided indication in the range from -150 inches to +200 Inchesas the instruments to be used during this evaluation.In order for the wide-range level Indicator to remain available with the reactor head removed, atemporary standpipe and fill funnel were used to replace a portion of the reference leg. At thetime of the event, the licensee was in the process of removing this temporary standpipe andreinstalling the original reference leg components. As the water drained from the standpipe, itcaused the wide-range level indicator to erroneously show an increasing water level. For aperiod of approximately one hour the operators in the control room, unaware that the ongoingmaintenance would cause an error in the indicated water level, compensated for the apparentincreasing level by increasing the discharge rate. This action had the effect of reducing the IN 99-14May 5, 1999 actual water level from 357 inches to 255 inches. During the same time period, the operatorswere also in the process of filling and venting the reactor feedwater piping, which could haveaffected the reactor water level. Once the normal reference leg piping had been reinstalled andthe reference leg began to refill, the indicated level decreased from 357 inches to the actuallevel of 255 inches. The second level instrument, which does not come on-scale until the levelgoes below 200 inches, remained off-scale high.When operators discovered the level discrepancy, they used a temporary pressure gaugeconnected to the reactor vessel low-point tap to confirm the actual water level. After confirmingthe accuracy of the wide-range indicator, they restored the reactor vessel water level to 357inches. The 100-inch error represented approximately 14,000 gallons of water. The licenseedetermined that the safety significance of this event was low since the reactor was in coldshutdown with low decay heat and the reactor water level remained well above the TAF. Inaddition, the drain-down would have been limited by an automatic Isolation of the draindownpath, which would have occurred prior to vessel level reaching 177 Inches above the TAF.The licensee's post event review identified: weaknesses in the operator's knowledge of thereactor assembly process; lack of explicit detail in the reactor assembly procedure; and,weaknesses in the plant risk assessment process. Contrary to the assumption that twodesignated reactor water level indicators were available, only one indicator, the wide-rangeinstrument, was available in the range above 200 inches. When the reference leg on the wide-range instrument was disassembled and drained, the one usable indicator was renderedunavailable. The second instrument was pegged off-scale high and remained that waythroughout the event because the level never dropped below 200 inches. A post event review bythe licensee indicated that other reactor water level instruments, remained operable during theevent but, apparently the operators did not rely on these other instruments or notice thediscrepancy between them and the wide range Indicator. Proposed corrective actions includedprocedural enhancements to ensure that reactor level instrumentation credited by the outagerisk assessment remains available during reactor disassembly and reassembly.DiscussionPersonnel errors appear to have caused, or contributed to, these three inadvertent reactorvessel draindown events. The likelihood of personnel errors is dependent upon the operatorsknowledge of the task gained through previous experience and training. It is also dependentupon the quality of the procedures used to perform the task, the level of supervision, theadequacy of pre-job briefings, fatigue, and distractions resulting from multiple tasks. In each ofthe events, the plant staff made errors during a seldom-performed evolution. Because it was aseldom-performed evolution, more training, better pre-job briefings, closer supervision, andprocedures that contain more details than those for frequently performed activities might haveprevented these event IN 99-14May 5, 1999 This information notice requires no specific action or written response. If you have anyquestions about the information in this notice, please contact the technical contact listed below,the appropriate regional office, or the appropriate Office of Nuclear Reactor Regulation (NRR)project manager.Ledyard B. Marsh, ChiefEvents Assessment, Generic CommunicationsAnd Non-Power Reactors BranchDivision of Regulatory Improvement ProgramsOffice of Nuclear Reactor RegulationTechnical contact: Chuck Petrone, NRR301-415-1027E-mail: cdDRenrc.aovREFERENCES:NRC Integrated Inspection Report No. 50-333/98-08, issued February 10, 1999 (Accession No.9902170348) for the James A. FitzPatrick Nuclear Power Plant for the period November 22,1998, through January 10, 1999.

Attachment:

List of Recently Issued NRC Information Notices

~~ Attachment 1IN 99-14May 5, 1999Page 1 of ILIST OF RECENTLY ISSUEDNRC INFORMATION NOTICESInformation Date ofNotice No. Subject Issuance Issued to99-13 Insiahts from NRR Inspections 4129199 All holders of operatina licensesof Low-and Medium-VoltageCircuit Breaker MaintenanceProgramsfor nuclear power reactors99-12Year 2000 Computer SystemsReadiness AuditsIncidents Involving the Use ofRadioactive Iodine-1314/28/994/23/99All holders of operating licensesor construction permits for nuclearpower plantsAll medical use licensees99-1197-15, Sup 1Reporting of Errors and 4/16/99Changes in Large-Break/Small-Break Loss-of-Coolant EvaluationModels of Fuel Vendors andCompliance with 10 CFR 50.46(a)(3)All holders of operating licensesfor nuclear power reactors, exceptthose who have permanentlycease operations and havecertified that fuel has beenpermanently removed from thereactor99-1099-09Degradation of Prestressing 4/13/99Tendon Systems in PrestressedConcrete ContainmentsProblems Encountered When 3/24/99Manually Editing Treatment Dataon The Nucletron Microselectron-HDR(New) Model 105.999Urine Specimen Adulteration 4/1/99All holders of operating licensesfor nuclear power reactorsAll medical licensees authorizedto conduct high-dose-rate (HDR)remote after loadingbrachytherapy treatmentsAll holders of operating licenseesfor nuclear power reactors andlicensees authorized to possessor use formula quantities ofstrategic special nuclear material99-08OL = Operating LicenseCP = Construction Permit IN 99-xxApril xx, 1999Page 5of 5This information notice requires no specific action or written response. If you have anyquestions about the information in this notice, please contact the technical contact listed below,the appropriate regional office, or the appropriate office of Nuclear Reactor Regulation (NRR)Project Manager.Ledyard B. Marsh, ChiefEvents Assessment, Generic CommunicationsAnd Non-Power Reactors BranchDivision of Regulatory Improvement ProgramsOffice of Nuclear Reactor RegulationTechnical contact:Chuck Petrone, NRR301-415-1027E-mail: cdRDanrc.aovREFERENCES:NRC Integrated Inspection Report No. 50-333198-08, issued February 10, 1999 (Accession No.9902170348) for the James A. FitzPatrick Nuclear Power Plant for the period November 22,1998, through January 10, 1999.

Attachments:

1. List of Recently Issued NMSS Information Notices2. List of Recently Issued NRC Information NoticesDOCUMENT NAME: G:ICDPDRAININ\DRAIN.0B.WPDTo receive a copy of this document, Indicate In the box C=Copy w/o attachmentlenclosure E=Copy with attachment/enclosure N = No copyOFFICE PECB:DRIP I Tech Editor l DRCH I PDIV-1 INAME CPetrone I_ RGallo 1 MNolangfarP.DATE V /0199 [3 /1/99 4 /4I9 1' /0g99F .V. ...OFFICEPDI-1 IA .IPDIII-2IC:PECB:DRIPINAME 2Jiiam RPulsjier LMarshDATE lf/499 I1'/t 99 I /99OFFICIAL RECORD COPY IN 99-14May 5, 1999 This information notice requires no specific action or written response. If you have anyquestions about the information in this notice, please contact the technical contact listed below,the appropriate regional office, or the appropriate Office of Nuclear Reactor Regulation (NRR)project manager.[arig sjid by]Ledyard B. Marsh, ChiefEvents Assessment, Generic CommunicationsAnd Non-Power Reactors BranchDivision of Regulatory Improvement ProgramsOffice of Nuclear Reactor RegulationTechnical contact:Chuck Petrone, NRR301-415-1027E-mail: cdr)ODnrc.govREFERENCES:NRC Integrated Inspection Report No. 50-333/98-08, issued February 10, 1999 (Accession No.9902170348) for the James A. FitzPatrick Nuclear Power Plant for the period November 22,1998, through January 10, 1999.

Attachment:

List of Recently Issued NRC Information NoticesDOCUMENT NAME: S:XDRPMSEC\99-14.IN*See previous concurrenceTo receive a copy of this document. indicate in the box C=CoDv w/o attachment/enclosure E=CoDv with attachment/enclosure N = No coovOFFICE PECB:DRlIP I Tech Editor l DRCH l-ii PDIV-1 lINAME CPetrone* BCalure* RGallo* MNolan*DATE 04/27/99 .3/15/99 _________04128199 = 04/27/991 ...OFFICEPDI-1IPD111-2C:PECB:DJRIPINAME JWilliams* RPulsifer' I-Marsh _ _ __ _DATE 04/27/9 .04/27/99 k,-u99OFFICIAL RECORD COPY