NRC Generic Letter 1988-03

NRC Generic Letter 1988-003: Resolution of Generic Safety Issue 93, Steam Binding of Auxiliary Feedwater Pumps.

ML031200470
Person / Time
Site:	Beaver Valley, Millstone, Calvert Cliffs, Davis Besse, Salem, Oconee, Mcguire, Palisades, Palo Verde, Indian Point, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Watts Bar, Sequoyah, Byron, Arkansas Nuclear, Braidwood, Summer, Prairie Island, Seabrook, Surry, North Anna, Turkey Point, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Farley, Robinson, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, McGuire, 05000000, Washington Public Power Supply System, Trojan, Marble Hill, Crane
Issue date:	02/17/1988
From:	Miraglia F J Office of Nuclear Reactor Regulation
To:
References
GSI-093 GL-88-003, NUDOCS 8802180267
Download: ML031200470 (10)

I ..4 UNITED STATESNUCLEAR REGULATORY COMMISSIONe WASHINGTON, D. C. 2055TO ALL LICENSEES, APPLICANTS FOR OPERATING LICENSES, AND HOLDERS OFCONSTRUCTION PERMITS FOR PRESSURIZED WATER REACTORSGentlemen:

SUBJECT: RESOLUTION OF GENERIC SAFETY ISSUE 93, "STEAM BINDING OFAUXILIARY FEEDWATER PUMPS" (GENERIC LETTER 88-03)This generic letter is being issued:(1) to inform you of the staff's resolution of the subject generic safetyissue, and(2) to request that you continue to implement, as a minimum, themonitoring and corrective procedures previously identified forinterim resolution of this issue in IE Bulletin 85-01, "SteamBinding of Auxiliary Feedwater Pumps,' dated October 29, 1985.(A copy of this bulletin is attached.)The issue concerns the potential disabling of auxiliary feedwater (AFW) pumpsby steam binding that is caused by backleakage of main feedwater (MFW) pastthe isolation check valves between the AFW and MFW systems. The issue issignificant because most AFW systems are potentially vulnerable to commonmode failure of the redundant AFW pumps as a result of steam binding. Thisvulnerability is inherent to the piping configurations used, which allowredundant trains of AFW to be cross-connected via common headers on thesuction and discharge sides of the pumps.To reduce the probability of AFW pump failure as a consequence of steam bindingif backleakage does occur, IE Bulletin 85-01 requested that certain licenseesand construction permit holders implement procedures both for monitoring theAFW piping temperatures for indication of possible backleakage and forrestoring the pumps to operable status if steam binding were to occur. Thebulletin was not issued to all holders of operating licenses and constructionpermits for pressurized water reactors because the staff had determined thata number of them had already taken actions that would minimize the occurrenceof the AFW pump steam binding problem at their plants. The bulletin recommendeda monitoring frequency of once a shift, compared with the previously recommendedfrequency of once a month. This increased frequency reduced the likelihood ofpump unavailability because of steam binding by a factor of 90 (3 shifts/day x30 days/month).Cla FEB 1 7 8Multiple

Addressees

-2-As part of its efforts toward a final generic resolution of this issue, thestaff surveyed the backleakage experience in operating plants following theimplementation of monitoring procedures. Although the number of backleakageevents varied from an average of less than one per reactor year at i largemajority of plants to more than 100 per reactor year at others, none of thebackleakage events that occurred during the review period appeared to haveresulted in the steam binding of an AFW pump. This indicates that the variousmonitorina methods employed can be highly effective in preventing steam bindingif backleakage occurs. For the plants with a high backleakage event rate, theinstallation of continuous monitoring systems with control room alarms wasinstrumental in providing for early warning to the operator and timely correctiveaction.The results of the staff's regulatory analysis indicated that following therecommendations in Bulletin 85-01 would ensure that the contribution of AFNpump steam binding to core melt frequency and public risk was sufficientlylow and that there is no need for new recommendations beyond those in XEBulletin 85-01.The staff has concluded that the recommended monitoring actions of IE Bulletin85-01 should be continued. However, although the staff has concluded that thecurrently assessed risk associated with this issue is reasonably low, it isstill concerned about the generally unsatisfactory reliability of checik valvesin operating plants. Plant operators should continue to be alert to the possibledevelopment of malfunctioning check valves, especially as the plant ages. Theyshould be prepared to increase the monitoring frequency as needed and to implementappropriate recovery procedures to ensure that steam binding failure of the AFNpumps does not occur.IE Bulletin 85-01 recommended that procedural controls remain in effect (1)until the completion of hardware modifications to substantially reduce thelikelihood of steam binding, or (2) until it was superseded by actionImplemented as a result of resolution of Generic Issue 93. This genericletter resolves Generic Issue 93 by perpetuating the recommendations of IEBulletin 85-01. In particular, all addressees should:1. Maintain procedures to monitor fluid conditions within the AFW systemeach shift during times when the system is required to be operable.This monitoring should ensure that fluid temperature at the AFN pumpdischarge is maintained at about ambient levels.2. Maintain procedures for recognizing steam binding and for restoringthe AFW system to operable status, should steam binding occur.All addressees are requested to provide a letter of confirmation to the NRCwithin 90 days of receipt of this generic letter indicating that the proceduresdiscussed in this generic letter are in place and will be maintained. Confir-mation by addressees who did not previously receive IE Bulletin 85-01 is beingrequested because the staff believes that they would rely on these proceduresas part of the actions to minimize the occurrence of the AFW pump steam bindingproble Multiple

Addressees

-3- FEB 17 WC3Pursuant to 10 CFR 50.54(f), you are requested to submit under oath or affirma-tion the letter of confirmation to the U.S. Nuclear Regulatory Commission, DocumentControl Desk, Washington, D.C. 20555, for reproduction and distribution. Thisrequest for information is covered by the Office of Management and Budget underblanket clearance number 3150-0011, which expires December 31, 1989. Comment onburden and duplication should be directed to the Office of Management and Budget,Reports Management, Room 3208, New Executive Office Building, Washington, D.C. 20503.Although no specific request or requirement is intended, the following informa-tion would be helpful to the NRC in evaluating the cost of this generic letter:1. Staff time to perform the requested confirmation and any neededfollowup actions.2. Staff time to prepare requested documentation.If there are any questions regarding this matter, please contact the RegionalAdministrator of the appropriate NRC regional office or your project manager inthis office.

Sincerely,Frank J. ra Associate Directorfor ProjectsOffice of Nuclear Reactor Regulation

Enclosure:

IEB 85-01a- Attachment.OMB No.: 3150-0011Expiration Date: 9/30/861EB 85-01UNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF INSPECTION AND ENFORCEMENTWASHINGTON, D.C. 20555October 29, 1985IE BULLETIN 85-01: STEAM BINDING OF AUXILIARY FEEDWATER. PUMPS

Addressees

For Action -Those nuclear power reactor facility licensees and constructionpermit MCP) holders listed in Attachment 1.For Information -All other nuclear power reactor facilities.

Purpose

The purpose of this bulletin is to inform licensees and CP holders of a poten-tially serious safety problem that has occurred at certain operating facilitiesinvolving the inoperability of auxiliary feedwater (AFW) pumps as a result ofsteam binding. Certain PWR licensees and all PWR CP holders are requested totake further action to prevent similar events from occurring at their facili-ties and to document those actions taken or planned.

Description of Circumstances

Numerous events have been reported where hot water has leaked into AFW systemsand flashed to steam, disabling the AFW pumps. Events at Robinson 2 in 1981through 1983, Crystal River 3 in 1982 and 1983, and D. C. Cook 2 in 1981 weresummarized in IE Information Notice (IN) 84-06, issued in January 1984. Alsoin January 1984, the Institute of Nuclear Power Operations (INPO) issuedSignificant Event Report (SER) 5-84 detailing'events at Robinson 2 and Farley.In April 1984, INPO issued Significant Operating Experience Report (SOER) 84-3that discussed another event at Surry 2 In 1983.The NRC's Office for Analysis and Evaluation of Operational Data (AEOD) issueda case study report entitled "Steam Binding of Auxiliary Feedwater Pumps" inJuly 1984. This study identified 22 events since 1981; 13 of these occurringin 1983. Based on operating experience, it appears that backleakage into AFWcould occur in any PWR. In a number of plants, the two motor-driven pumps feedinto a single pipe which feeds into the steam generator; therefore, a leakingvalve in that pipe increases the probability of steam binding in both trains ofAFW. Also, multiple AFW pumps often take suction from a common manifold;therefore, if one pump becomes steam bound because of leaking check valves, thesteam can heat the common suction and cause other pumps to become steam bound.~~ l g .

I..tachmerotIEB 85-01October 29, 1985 AFW capability is needed for normal shutdown and transient conditions as wellas for accident mitigation. The AEOD case study examined the effects.of steambinding on a sequence in which there was a loss of the power conversion (steamgeneration) system after a transient other than loss-of-offsite power. Aprobabilistic risk analysis had previously shown this sequence to be a dominantcontributor to the core-melt risk for a sample plant (Sequoyah). The casestudy indicated that unavailability of the AFW system as a result of steambinding contributes significantly to the risk of core melt in PWRs. MonitoringAFW to detect backlealkage and to promptly correct the situation if backleakageoccurs would reduce the probability of steam binding.Since the AEOD study was issued, a series of events involving backflow of hotwater into the AFW system occurred at McGuire 2 over a period of 7 days inAugust 1984, before effective corrective action was taken. One of these eventsinvolved overpressurization of the suction line and damage to instruments. InNovember 1984, Catawba 1 experienced backflow of hot water into AFW resultingin fumes from Insulation and blistering of paint. In December 1984, the NRC'sOffice of Nuclear Reactor Regulation (NRR) determined that steam binding of AFWwas a generic issue and assigned it a high priority (Generic Issue 93, SteamBinding of Auxiliary Feedwater Pumps").To determine the extent of the safety issue and the need for short-term correc-tive actions, the NRC's regional offices conducted a survey in April and May of1985. Of the 58 operating reactors surveyed, 39 had temperature monitoring ofAFW piping at least once per shift. Of the remaining 19, 17 had normallyclosed gate or globe valves in the pump discharge path in addition to checkvalves, or some unique feature such as complete separation of trains that madeserious safety problems unlikely. The remaining 2 licensees have subsequentlydecided to monitor AFW piping temperature.Although some degree of action has been taken at all units, many have notincorporated these actions into procedures to detect or correct steam binding.Without these provisions, there is little assurance that effective actions willcontinue. For this reason, the addressees are requested to take the followingactions:Action for

Addressees

Listed in Attachment 11. Develop procedures for monitoring fluid conditions within the AFW systemon a regular basis during times when the system is required to beoperable. This monitoring should ensure that fluid temperature at the AFRpump discharge is maintained at about ambient temperature. Monitoring offluid conditions, if used as the primary basis for precluding steambinding, is recommended each shift.This item is not intended to require elaborate instrumentation. A simplemeans of monitoring temperature, such as touching the pipe, is a satisfac-tory approach. a2. Develop procedures for recognizing steam binding and for restoring the AFWsystem to operable status, should steam binding occu .ttachmentIEB 85-01October 29. 1985 . Procedural controls should remain in effect until completion of hardwaremodification to substantially reduce the likelihood of steam binding oruntil superseded by action implemented as a result of resolution ofGeneric Issue 93.Schedule: For operating plants, develop and implement procedures within 90-days of the date of this bulletin. For plants under construction, develop andimplement procedures within 90 days after receiving an operating license orprovide an appropriate response and commitment within 1 year of the date ofthis bulletin, whichever comes first.Re orting Requirements: Prepare and submit a report describing the methodsused to accomplish these actions. Include the date(s) that procedures andtraining were implemented or scheduled to be implemented. State the frequencyof monitoring of the temperature. For operating plants, submit this reportwithin 120 days of the date of this bulletin. For plants under construction,submit the report within 120 days after receiving an operating license orwithin 1 year of the date of this bulletin, whichever comes first. It is notnetessary to submit the procedures for review.The written report, requested above, shall be submitted to the appropriateRegional Administrator under oath or affirmation under provisions of Section182a, Atomic Energy Act of 1954, as amended. In addition, the original copy ofthe cover letter and a copy of the attached report should be transmitted to theU. S. Nuclear Regulatory Commiss0on, Document Control Desk, Washington, DC20555 for reproduction and distribution.This request for information was approved by the Office of Management andBudget under blanket clearance number 3150-0011. Comment on burden and dupli-cation should be directed to the Office of Management and Budget, ReportsManagement, Room 3208, New Executive Office Bullding, Washington, DC 20503.Although no specific request or requirement is intended, the following informa-tion would be helpful to the NRC in evaluating the cost of this bulletin:1. staff time to perform requested review and testing2. staff time to prepare requested documentation IAttachmentIEB 85-01October 29, 1985 If there are any questions regarding this matter, please contact the RegionalAdministrator of the appropriate NRC regional office or this office.es 14. Taylor, S'rectorice of Inspection and EnforcementTechnical Contacts:Mary S. Wegner% IE(301) 492-4511C. Vernon Hodge, IE(301) 492-7275

Attachments:

• 1.

Addressees

for Action'2. List of Recently Issued1E BulletinsIa- Attachment 1IEB 85-01October 29. 1985

ADDRESSEES

FOR ACTION:The following PWRs having an OL:BYRON 1CRYSTAL RIVER 3DAVIS-BESSEDIABLO CANYON 1GINNAINDIAN POINT 3KEWAUNEEMAINE YANKEEMILLSTONE 2NORTH ANNA 1NORTH ANNA 2PALISADESPOINT BEACH 1POINT BEACH 2PRAIRIE ISLAND 1PRAIRIE ISLAND 2RANCHO SECOSAN ONOFRE 1ST. LUCIE 1ST. LUCIE 2SUMMERTMI ITROJANTURKEY POINT 3TURKEY POINT 4WATERFORD 3WOLF CREEK 1YANKEE-ROWEAll PWRs holding a CP ta Attachment 2IEB 85-01October 29, 1985LIST OF RECENTLY ISSUED IE BULLETINShued to*Bulletin Date ofNo. Subject Issue Isl84-03 Refueling Cavity Water Seal 8/24/84 All0 fananCovsued to,_ oe eco84-0284-01Failures Of General ElectricType HFA Relays In Use InClass 1E Safety SystemCracks In Boiling WaterReactor Mark I ContainmentVent Headers3/12/842/3/84vlAlfaanAlWiamifa'V.ii1 power

• eactor:1ilities holdingOL or CP exceptrt St. Vrain1 power reactorcilities holdingOL or CP1 BWR facilitiesith Mark I contain-ent and currentlyi cold shutdownith an OL for Actionad All other BWRsIth an OL or CP fornformation83-0883-07Sup. 283-07Sup. 183-07Electrical Circuit BreakersWith An Undervoltage TripFeature In Use In Safety-Related Applications OtherThan The Reactor Trip SystemApparently FraudulentProducts Sold By Ray Miller,Inc.Apparently FraudulentProducts Sold By Ray Miller,Inc.Apparently FraudulentProducts Sold by Ray Miller,Inc.12/28/8312/09/8310/26/837/22/83All power reactorfacilities holdingan OL or CPSame as IEB 83-07Same as IEB 83-07All power reactorfacilities holdingan 0L or CP; Otherfuel cycle facilitiesand Category B,Priority I (processorsand distributors)material licenseesA*DL = Operating LicenseCP

• Construction Permit 1 5ST OF , ENTLY ISSUED ENEFIC LETTDate ofSub ect. I sSuanceSb em 1r i c'Letter No.I ssuIE~d ToGL 8R-02GL 69-01GL 87-1 6"INTEGRATED SEFETY ASSESSMENTPROGRiAM II (ISAP-8F II)""NRC POSITION1l O;J IGSCC IN BWlR(-t Ic~i.r II( STAINLESS STEEL.P P1NbF,"NlJREG--1262. "ANSWERS TOQUESTIONS AT PUBLIC MEETINGSRE IMPLEMENTATION OF 1o CFR55ON OFERAT ORSLICENSESt- 1. /20tO/a9A1 /25/8811 / 12/87ALL POWERREACTORLICENSEESALL LICENSEESOF OPERATINGBOILING WATERREACl ORS ANI,HOLDERS OFCONSTRUCT I ONPERMITS FOR14FRSALL. POWER ANDNONP OWERREACTORLICENSEES ANDAPPLICANTS FORLICENSESGL 87-15 POLICY STATEMENT ON DEFERREDPLANTS11/04/87ALL HOLDERS OFCONSTRUCT I ONPERMITS FOR ANUCLEAR POWERPLANTGL 87-14UL 87-13REQUEST FOR OPERATOR LICENSESCHEDUiJLESINTEGRITY OF REQUALIFICATIONEXAMINATIONS AT NON-POWERREACTORS08 / 04 / 8707/ 10/87ALL. POWERREACTORLICENSEESALL NON-POWERREACTORLICENSEESGL 87-12 50.54(f) LETTER RE. LOSS OFRESIDUAL HEAT REMOVAL (RHR)DUFING MID-LOOP OPERATION07 / 09/87ALL LICENSEESOF OPERATINGPWRS ANDHOLDERS OFCONSTRUCT I ONPERM ITS FORFPWR' SGL 87-11GL 87-10RELAXATION IN ARBITRARYINTERMEDI ATE PIPE RUFTUREREQU I REMENTSIMPLEMENTATION OF 10 CFR73.57, REQUIREMENTS FOR FBICRIMINAL HISTORY CHECk:S06/23/8706/12/87* ALL OFPERATINGLICENSEES,CONSTRUCTIONPERMITHOLDERS, ANDAPPLI CANTS FORCONSTRUCTIONPERMITSAL.L POWERREACT ORLI CENSEES