Information Notice 1992-35, Higher than Predicted Erosion/Corrosion in Unisolable Reactor Coolant Pressure Boundary Piping inside Containment at a Boiling Water Reactor

Higher than Predicted Erosion/Corrosion in Unisolable Reactor Coolant Pressure Boundary Piping inside Containment at a Boiling Water Reactor

ML031200365
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:	05/06/1992
Revision:	0
From:	Rossi C E Office of Nuclear Reactor Regulation
To:
References
IN-92-035, NUDOCS 9205010009
Download: ML031200365 (5)

UNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF NUCLEAR REACTOR REGULATIONWASHINGTON, D.C. 20555May 6, 1992NRC INFORMATION NOTICE 92-35: HIGHER THAN PREDICTED EROSION/CORROSION INUNISOLABLE REACTOR COOLANT PRESSURE BOUNDARYPIPING INSIDE CONTAINMENT AT A BOILINGWATER REACTOR

Addressees

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

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information noticeto alert addressees to erosion/corrosion rates that could be higher thanpredicted in certain unisolable reactor coolant pressure boundary piping insidethe containment drywell at boiling water reactors. It is expected that recip-ients will review the information for applicability to their facilities andconsider actions, as appropriate, to avoid similar problems. However, sugges-tions contained in this information notice are not NRC requirements; therefore,no specific action or written response is required.

Description of Circumstances

The Pennsylvania Power and Light Company (the licensee) recently performederosion/corrosion inspections at the Susquehanna Steam Electric Station, Unit1, and may have identified an unexpectedly high rate of erosion/corrosion incertain main feedwater (FW) piping inside containment (Attachment 1). Erosionof this portion of FW piping is of particular concern since this portioncannot be isolated from the reactor vessel, and erosion/corrosion inspectionstrategies may not direct attention to that part of the FW system.When the licensee began operating the unit commercially in June 1982, thenominal wall thickness for the pipe was about 0.688 inch. During the currentrefueling outage, wall thinning was found in one of the 20 inch by 12 inchreducing tee risers approximately 10 inches downstream from the tee in the 12inch pipe section, immediately above a circumferential pipe weld. During theprevious refueling outage (18 months ago) the licensee had measured the pipewall as 0.619 inch thick at that location. During the current refuelingoutage, the licensee measured a thickness of 0.521 inch at the same location.The licensee measured a thickness of 0.482 inch within about 2 inches of thatlocation. The licensee calculated a minimum allowable wall thickness of 0.440inch for that portion of FW pipe. Previous experience and models had indicatedan erosion wear rate of no more than 0.085 inch each cycle. However, the most9205010009 r& / A EC /i'-'- 9 /JA J20'o IN 92-35May 6, 1992 recent measurement indicates a higher wear rate that may be greater than 0.100inch each cycle.The licensee evaluated the data for the FW system and determined that continuedoperation could not be justified for another fuel cycle. Therefore, thelicensee repaired, rather than replaced, the FW pipe in accordance with SectionXI of the American Society of Mechanical Engineers (ASME) Boiler and PressureVessel Code.DiscussionThe licensee determined that although it had expected to find erosion/corrosionat this location, the magnitude of wall thinning exceeded expectations. Thelicensee is continuing its investigation to determine the root cause of theunexpected erosion/corrosion rate.Related Generic CommunicationsFollowing a pipe rupture at the Surry Power Station in 1986, the NRC issuedBulletin 87-01, "Thinning of Pipe Walls in Nuclear Power Plants," July 9, 1987.In this bulletin, the staff requested licensees and applicants to inform theNRC about their programs for monitoring the wall thickness of carbon steelpiping in both safety-related and nonsafety-related high energy fluidsystems.In 1989, following an audit of the erosion/corrosion programs at 10 plants,the NRC issued Generic Letter (GL) 89-08, "Erosion/Corrosion-Induced Pipe WallThinning," May 2, 1989. In this generic letter, the staff requested licenseesand applicants to implement long term erosion/corrosion monitoring programs.The staff made this request to obtain assurances that the addressees had imple-mented procedures or administrative controls to maintain the structural integrityof all carbon steel systems carrying high energy fluids.The NRC also issued several information notices on the subject of erosion/corrosio IN 92-35May 6, 1992 This information notice requiresyou have any questions about theof the technical contacts listedReactor Regulation (NRR) projectno specific action or written response. Ifinformation in this notice, please contact onebelow or the appropriate Office of Nuclearmanager.Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical contacts:K. I. Parczewski, NRR(301) 504-2705S. Barber, Region I(717) 542-2134David(301)Gamberoni, NRR504-1171John White, Region I(215) 337-5114

Attachments:

1. Feedwater System2. List of RecentlyErosion/Corrosion LocationIssued NRC Information Notices II*REACTORVESSELl12- 20- X 12'REDUCERREACTORVESSEL20 X 12'-REDUCING1, I I--OREACTORVESSEL24' X 12-REDUCINGTEEo- IFLOWIl l7r--, A -20-24 X 20-REDUCER24-"BPFEEDWATERLINEEROSION/CORROSI ONZONE1I FLOW20" X 12"REDUCINGTEEFLOWFEEDWATER SYSTEM EROSION/CORROSION LOCATION(D 'OObco rr'0 r-%."-I" Attachment 2IN 92-35May 6, 1992 LIST OF RECENTLY ISSUEDNRC INFORMATION NOTICESInformation Date ofNotice No. Subject Issuance Issued to92-3492-3392-32New Exposure Limits forAirborne Uranium andThoriumIncreased InstrumentResponse Time WhenPressure DampeningDevices are InstalledProblems Identified withEmergency VentilationSystems for Near-Site(Within 10 Miles) Emer-gency Operations Facili-ties and Technical SupportCentersElectrical ConnectionProblem in JohnsonYokogawa CorporationYS-80 Programmable Indi-cating ControllersFalsification of PlantRecordsSpent Fuel Pool Re-activity CalculationsPotential Breaker Mis-coordination Caused byInstantaneous TripCircuitry05/06/9204/30/9204/29/9204/27/9204/23/9204/22/9204/17/92All licensees whose opera-tions can cause airborneconcentrations of uraniumand thorium.All 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.92-3192-3092-21,Supp. 192-29Allforandandholders of OLs or CPsnuclear power reactorsall licensed operatorssenior operators.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.OL = Operating LicenseCP = Construction Permit