Information Notice 2010-22, Fuel Assemblies Damaged During Refueling Operations due to Misalignment
| ML102200071 | |
| Person / Time | |
|---|---|
| Issue date: | 10/25/2010 |
| Revision: | 0 |
| From: | McGinty T J Office of Nuclear Reactor Regulation |
| To: | |
| References | |
| IN-10-022 | |
| Download: ML102200071 (3) | |
ML102200071 October 25, 2010 NRC INFORMATION NOTICE 2010-22: FUEL ASSEMBLIES DAMAGED DURING REFUELING OPERATIONS DUE TO MISALIGNMENT
ADDRESSEES
All holders of an operating license or construction permit for a pressurized-water nuclear power reactor issued under Title 10 of the Code of Federal Regulations, Part 50, "Domestic Licensing of Production and Utilization Facilities," except those who have permanently ceased operations and have certified that fuel has been permanently removed from the reactor vesse
PURPOSE
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to inform addressees of an event at a domestic pressurized-water reactor plant that resulted in damage to fuel assemblies during a refueling outage because of inadequate verification of core alignmen The NRC expects recipients to review the information for applicability to their facilities and consider actions, as appropriate, to avoid similar problem The suggestions that appear in this IN are not NRC requirements; therefore, no specific action or written response is require DESCRIPTION OF CIRCUMSTANCES On November 2, 2009, the Oconee Nuclear Station, Unit 1 (a Babcock & Wilcox Co. pressurized-water reactor), was unable to couple a control rod drive mechanism to its associated control rod assembly during reactor vessel reassembl The licensee subsequently disassembled the reactor vessel head and upper internals and discovered that multiple fuel assemblies were damaged during reactor vessel reassembly and that these damaged fuel assemblies were interfering with proper control rod couplin The damage to one fuel assembly resulted in bowed fuel pins and the detachment of pieces of multiple grid strap The licensee had to use a specially constructed tool to remove this fuel assembly from the reactor and place it in the spent fuel poo Other assemblies had minor damage mostly limited to the upper end fitting A post event examination of the fuel alignment video revealed that the gap between the inner wall of the baffle and an adjacent fuel assembly was larger than that allowed by the vendor specification The licensee's fuel alignment verification procedure was not in accordance with current vendor guidance; specifically, it did not include the maximum allowed gap valu The procedure called solely for a qualitative evaluation to determine the existence of gaps and provided a maximum number of gaps allowe In accordance with this procedure, the licensee determined that it met the acceptance criteria for fuel alignment and continued with vessel reassembl Because the licensee proceeded with a larger than allowed gap, the fuel assembly upper end fitting and reactor vessel plenum grid pads could not properly alig The weight of the plenum rested on the upper end fitting tabs and deformed the fuel assemblie Additional information is available in the NRC inspection report, "Oconee Nuclear Station-Integrated Inspection Report 05000269/2009005, 05000270/2009005, 05000287/2009005,"
dated January 28, 2010 (Agencywide Documents Access and Management System, Accession No. ML100280909).
DISCUSSION Deformations in fuel assembly geometry can undermine the integrity of the fuel cladding, which is one of the primary barriers to fission product releas Also, deformed fuel assemblies could affect reactivity control if they cause control rods to become stuck during reactor operation Furthermore, industry operating experience has shown that deformed fuel assemblies can become stuck within the reactor upper internals without the licensee's knowledg Unknowingly lifting fuel assemblies that have become stuck to upper internals or upper guide structures presents a risk of dropping the fuel assembly and the associated risk of fission product release should a fuel rod be breache The importance of verifying adequate core alignment and avoiding misalignments between fuel and reactor internals is evident and necessitates special preparation and consideration on behalf of licensee Before verifying core alignment, licensees should consider reviewing and applying related operating experience and verifying that their procedures and methods are in agreement with the latest fuel vendor guidanc
CONTACT
This IN requires no specific action or written respons Please direct any questions about this matter to the technical contacts listed below or to the appropriate Office of Nuclear Reactor Regulation (NRR) project manage /RA/ Timothy J. McGinty, Director Division of Policy and Rulemaking Office of Nuclear Reactor Regulation Technical Contacts: David Garmon-Candelaria, NRR Shih-Liang Wu, NRR 301-415-3512 301-415-3284 E-mail: E-mail: shih-liang.wu@nrc.gov david.garmon-candelaria@nrc.gov Note: NRC generic communications may be found on the NRC public Web site, http://www.nrc.gov, under Electronic Reading Room/Document Collection upper end fitting and reactor vessel plenum grid pads could not properly alig The weight of the plenum rested on the upper end fitting tabs and deformed the fuel assemblie Additional information is available in the NRC inspection report, "Oconee Nuclear Station-Integrated Inspection Report 05000269/2009005, 05000270/2009005, 05000287/2009005,"
dated January 28, 2010 (Agencywide Documents Access and Management System, Accession No. ML100280909).
DISCUSSION Deformations in fuel assembly geometry can undermine the integrity of the fuel cladding, which is one of the primary barriers to fission product releas Also, deformed fuel assemblies could affect reactivity control if they cause control rods to become stuck during reactor operation Furthermore, industry operating experience has shown that deformed fuel assemblies can become stuck within the reactor upper internals without the licensee's knowledg Unknowingly lifting fuel assemblies that have become stuck to upper internals or upper guide structures presents a risk of dropping the fuel assembly and the associated risk of fission product release should a fuel rod be breache The importance of verifying adequate core alignment and avoiding misalignments between fuel and reactor internals is evident and necessitates special preparation and consideration on behalf of licensee Before verifying core alignment, licensees should consider reviewing and applying related operating experience and verifying that their procedures and methods are in agreement with the latest fuel vendor guidanc
CONTACT
This IN requires no specific action or written respons Please direct any questions about this matter to the technical contacts listed below or to the appropriate Office of Nuclear Reactor Regulation (NRR) project manager. /RA/ Timothy J. McGinty, Director Division of Policy and Rulemaking Office of Nuclear Reactor Regulation Technical Contacts: David Garmon-Candelaria, NRR Shih-Liang Wu, NRR 301-415-3512 301-415-3284 E-mail: E-mail: shih-liang.wu@nrc.gov david.garmon-candelaria@nrc.gov Note: NRC generic communications may be found on the NRC public Web site, http://www.nrc.gov, under Electronic Reading Room/Document Collection ADAMS Accession Number: ML102200071 TAC ME4182 OFFICE NRR:DIRS:IOEB NRR:DSS:SNPB Tech Editor BC:NRR:DIRS:IOEB BC:NRR:SNPB NAME DGarmon SWu KAzariah-Kribbs JThorp AMendiola DATE 10/08/10 10/12/10 09/24/10 e-mail 10/20/10 10/20/10 OFFICE D: NRR:DSS NRR:PGCB NRR:PGCB BC:NRR:PGCB D: NRR:DPR NAME WRuland CHawes BPurnell SRosenberg TMcGinty DATE 10/22 /10 10/25/10 10/25/10 10/25/10 10/25/10 OFFICIAL RECORD COPY