Information Notice 1991-74, Changes in Pressurizer Safety Valve Setpoints Before Installation
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IUNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF NUCLEAR REACTOR REGULATIONWASHINGTON, D.C. 20555August 6, 1991NRC INFORMATION NOTICE NO. 91-47: FAILURE OF THERMO-LAG FIRE BARRIER MATERIALTO PASS FIRE ENDURANCE TEST
Addressees
- All holders of operating licenses or construction permits for nuclear powerreactors.
Purpose
- This information notice is intended to alert addressees to problems that couldresult from the use of or improper installation of THERMO-LAG material tosatisfy the electrical raceway fire protection requirements for safe shutdowncomponents specified in Section III.G.2 of Appendix R to Part 50 of Title 10of the Code of Federal Regulations (10 CFR Part 50). It is expected thatrecipients will review the information for applicability to their facilitiesand consider actions, as appropriate, to avoid similar problems. However,suggestions contained in this information notice do not constitute any newNuclear Regulatory Commission (NRC) requirements; therefore, no specificaction or written response is required.
Description of Circumstances
- The Gulf States Utilities Company, the licensee for the River Bend Station(RBS), submitted Licensee Event Reports (LERs)87-005, 89-009,90-003, and anInformational Report to the NRC concerning deficiencies identified in firebarriers. The NRC staff reviewed test report information and associateddocuments regarding the RBS electrical raceway fire barriers to determine ifthe problems identified in the LERs and Informational Report could affectother NRC licensees. The electrical raceway fire barrier material used at RBSis THERMO-LAG, a product manufactured and supplied by Thermal Science,Incorporated, (TSI), of St. Louis, Missouri. TSI provides THERMO-LAG for1-hour and 3-hour rated fire barriers.A 3-hour fire endurance test of a 30-inch aluminum electrical cable tray wasperformed in October 1989 at the Southwest Research Institute (SwRI) for GulfStates Utilities Company. In this test, a THERMO-LAG envelope system failedresulting in high temperatures inside the cable tray envelope and loss ofcircuit integrity within approximately 60 minutes. Catastrophic failure andcollapse of the tray occurred within 1 1/2 hours. The failure of this testraised concerns regarding the adequacy of THERMO-LAG cable tray enclosuresprotecting 30-inch wide cable trays.9108020180 -PY- Xat r q 9 &je Go 4oi IN 91-47August 6, 1991 Discussion:NRC requirements and guidelines for fire barriers are contained in variousdocuments, including Appendix R to 10 CFR 50, Generic Letter 86-10,"Implementation of Fire Protection Requirements", and NUREG-0800, "StandardReview Plan." The extent to which these requirements or guidelines are applic-able to a specific plant depends on plant age, commitments established by thelicensee in developing the fire protection plan, the staff safety evaluationreports (SERs) and supplements, and the license conditions pertaining to fireprotection. Fire barrier wrap material is designed to provide reasonableassurance that the effects of a fire are limited to one division of a safeshutdown related system while another division will remain free of fire damage.The Gulf States Utilities Company uses THERMO-LAG to protect raceways andcomponents throughout RBS that are related to safe shutdown. In addition, atleast 40 NRC licensed facilities use THERMO-LAG to construct fire barrierassemblies with 3-hour and 1-hour ratings to enclose electrical raceway andother safe shutdown components.During routine walkdown inspections in early 1987, RBS fire protection personnelidentified degradation of the THERMO-LAG 1-hour and 3-hour rated barriers.During repairs to correct the deficiencies discovered during the walkdowns, thelicensee found that the fire barriers had not been installed in accordance withthe manufacturer's specifications. The large number of observed deficienciesprompted the licensee to expand these walkdown inspections to include allTHERMO-LAG fire barriers. Hourly fire watches were posted in all affectedsafety-related areas pending completion of all inspections and correction ofany deficiencies found. The licensee attributed the deficiencies to failure ofthe subcontractor installation and quality control inspection program.During maintenance activities in early 1989, the licensee found-additionaldeficiencies indicating an apparent deficiency in the installation and qualitycontrol inspection program. The subcontractor who installed the THERMO-LAGfire barriers at RBS was approved by TSI as a qualified installer. However,during the installation at RBS, the subcontractor removed the factory-installedcomponents of the THERMO-LAG called "stress skin" and structural ribbing. Thestress skin component, a wire mesh, is critical to the structural integrity ofthe fire product during fire exposure. The RBS fire protection personnelconsidered that all barriers were degraded because of the many sections of theinside Layer of the stress skin that had been removed during initial installa-tion at RBS.The discrepancies identified between the manufacturer's installation manual,actual site installation manual and qualification fire tests resulted in thelicensee conducting additional fire endurance testing. In October 1989, SwRItested a U-shaped 30-inch wide aluminum ladder back cable tray enclosed in a3-hour fire-rated barrier constructed of THERMO-LAG material. RBS personnelconstructed the cable tray protective envelope in accordance with themanufacturer's published installation instruction IN 91-47August 6, 1991 During the 3-hour fire endurance test, all thermocouples inside the THERMO-LAGprotected tray reached failure temperatures (>3251F) in times ranging fromapproximately 45 minutes to 80 minutes. Conductor-to-ground failure occurredin the power cable at 60 minutes. The THERMO-LAG enclosure disintegrated at77 minutes, and the cable tray collapsed at 82 minutes. The SwRI test resultson the as-designed THERMO-LAG configuration prompted RBS to institute a firewatch patrol in all areas that depend on THERMO-LAG barriers for protection ofsafe shutdown capability.Additional deficiencies, such as small holes, cracks and unfilled seams, werefound in the THERMO-LAG material during walkdowns conducted in early 1990.The licensee conducted additional testing of as-installed barriers in Novemberand December 1990. Certain 1-hour and 3-hour cable tray and conduit envelopetests failed. The envelopes were upgraded and tests of the upgraded barrierspassed with the exception of the 3-hour cable tray envelope. Final resolutionof the 3-hour envelope may include replacing existing fire wrap materials withfully qualified fire wrap, repairing and then qualifying in-plant fire wrapassemblies by supplemental fire tests, or rerouting the cables into acceptableenclosures.Additionally, other fire barrier wrap design and installation concerns havebeen reported by RBS that indicate the possibility that NRC requirements forfire protection were not being met in all aspects. The type of concernsidentified to date include the following:1. Lack of documentation of qualification tests which demonstrate thataluminum conduits penetrating the THERMO-LAG protective envelope havebeen tested.2. Lack of documentation of qualification tests for different jointinstallations that demonstrate that varying fitup methods (i.e., dryfitting) are qualified.3. Lack of documentation of qualification tests of THERMO-LAG installationsapplicable to large cable trays. The licensee questioned the validity ofextrapolating results from small cable tray tests to its 30-inch widetrays.The NRC is particularly interested in obtaining information on fire barriersthat have been found with deficiencies similar to those described in thisnotice. Documentation, in as much detail as practicable, of any suchdeficiencies discovered, especially in cases where a fire barrier may havebeen improperly installed or tested is important. Licensees may communicatethe availability of information of this type by telephone to the NRC technicalcontact listed below. Information Notice No. 88-04, "Inadequate Qualificationand Documentation of Fire Barrier Penetration Seals," provides additionaldiscussion and considerations regarding qualification of installed firebarrier IN 91-47August 6, 1991 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactthe technical contact listed below or the appropriate Office of NuclearReactor Regulation (NRR) project manager.Charles E. o S, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor Regulation
Technical Contact:
Ralph Architzel, NRR301-492-0804
Attachment:
List of Recently Issued NRC Information Notices
.IAttachmentIN 91-47August 6, 1991 LIST OF RECENTLY ISSUEDNRC INFORMATION NOTICESInformation Date ofNotice No. Subject Issuance Issued to89-56,Supp. 291-4691-4591-4491-4391-4291-4188-63,Supp. 2Questionable Certificationof Material Supplied tothe Defense Department byNuclear SuppliersDegradation of EmergencyDiesel Generator Fuel OilDelivery SystemsPossible Malfunction ofWestinghouse ARD, BFD, andNBFD Relays, and A200 DCand DPC 250 Magnetic Con-tactorsImproper Control ofChemicals in Nuclear FuelFabricationRecent Incidents InvolvingRapid Increases in Primary-to-Secondary Leak RatePlant Outage EventsInvolving Poor Coordina-tion Between Operationsand Maintenance PersonnelDuring Valve Testing andManipulationsPotential Problems withThe Use of Freeze SealsHigh Radiation Hazardsfrom Irradiated IncoreDetectors and Cables07/19/91 All holders of OLs or CPsfor nuclear power reactors.07/18/91 All holders of OLs or CPsfor nuclear power reactors.07/05/91 All holders of OLs or CPsfor nuclear power reactors.07/08/91 All nuclear fuel facilities.07/05/91 All holders of OLs or CPsfor pressurized-waterreactors (PWRs).06/27/91 All holders of OLs or CPsfor nuclear power reactors.06/27/91 All holders of OLs or CPsfor nuclear power reactors.06/25/91 All holders of OLs or CPsfor nuclear power reactors,research reactors, andtest reactors.OL = Operating LicenseCP = Construction Permit