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Information Notice No. 89-21: Changes in Performance Characteristics of Molded-Case Circuit Breakers
UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF NUCLEAR REACTOR REGULATION WASHINGTON, D.C. 20555 February 27, 1989 Information Notice No. 89-21: CHANGES IN PERFORMANCE CHARACTERISTICS OF MOLDED-CASE CIRCUIT BREAKERS Addressees: All holders of operating licenses or construction permits for nuclear power reactors. Purpose: This information notice is being provided to alert addressees to an observed practice in which vendors make changes to the performance characteristics of molded-case circuit breakers without making any corresponding revisions to the breaker part number. It is expected that recipients will review the information for applicability to their facilities and consider actions, as appropriate, to avoid similar problems. However, suggestions contained in this information notice do not constitute NRC requirements; therefore, no specific action or written response is required. Description of Circumstances: During several inspections performed by the NRC, it was discovered that manu- facturers of molded case circuit breakers frequently altered the time-current characteristic curves pertaining to a particular style or type of breaker. These changes were made without changing the part number of the breaker and often without any specific notification to the customer. The changes identi- fied during the NRC inspections ranged from very minor alterations to the thermal portion of the curves to major alterations to the magnetic instanta- neous trip portion of the curves. One change for ITE-type 100-amp breakers involved the movement of the instantaneous band from 600-1000 amps to 1200-2000 amps. Although product literature usually contains the appropriate curves, the curves are not routinely provided with the breakers. Discussion: As a result of these changes, many licensees who procure replacement breakers by part number only are receiving breakers with performance characteristics that may be different from those assumed in the original plant design. If the breakers are not analyzed for performance characteris-tics, upon installation these breakers potentially could degrade the electrical protection system and/or cause premature tripping upon the energizing of vital safety-related systems. Additionally, many perceived failures of circuit breakers detected 8902210564 . IN 89-21 February 27, 1989 Page 2 of 2 during pre-installation or routine testing may actually be the result of un- known changes in time-current characteristic curves. One way to ensure that the breakers purchased conform to a particular curve would be to reference the specific curve (including the applicable revision) as part of the purchase requirements. If the breaker was no longer manufactured to meet the specifi- cations of that specific curve, the new curve would have to be analyzed for its effect on the overall system. No specific action or written response is required by this information notice. If you have any questions about this matter, please contact the technical contact listed below or the Regional Administrator of the appropriate regional office. Charles E. Rossi, Director Division of Operational Events Assessment Office of Nuclear Reactor Regulation Technical Contact: J. B. Jacobson, NRR (301) 492-0996 Attachment: List of Recently Issued NRC Information Notices .. Attachment IN 89-21 February 27, 1989 Page 1 of 1 LIST OF RECENTLY ISSUED NRC INFORMATION NOTICES ____________________________________________________________________________ Information Date of Notice No._____Subject_______________________Issuance_______Issued to________ 88-73, Direction-Dependent Leak 2/27/89 All holders of OLs Supplement 1 Characteristics of Contain- or CPs for nuclear ment Purge Valves power reactors. 89-20 Weld Failures in a Pump 2/24/89 All holders of OLs of Byron-Jackson Design or CPs for nuclear power reactors. 89-19 Health Physics Network 2/23/89 All holders of OLs or CPs for nuclear power reactors, and the following fuel facilities: Nuclear Fuel Services of Erwin, General Atomic, UNC Montville, B&W LRC Lynchburg, and B&W Lynchburg. 89-18 Criminal Prosecution of 2/22/89 All holders of OLs Wrongdoing Committed by or CPs for nuclear Suppliers of Nuclear power reactors. Products or Services 89-17 Contamination and Degra- 2/22/89 All holders of OLs dation of Safety-Related or CPs for nuclear Battery Cells power reactors. 89-16 Excessive Voltage Drop 2/16/89 All holders of OLs in dc Systems or CPs for nuclear power reactors. 89-15 Second Reactor Coolant Pump 2/16/89 All holders of OLs Shaft Failure at Crystal or CPs for nuclear River power reactors. 89-14 Inadequate Dedication 2/16/89 All holders of OLs Process for Commercial or CPs for nuclear Grade Components Which power reactors. Could Lead to Common Mode Failure of a Safety System __________________________________________________________________________________ OL = Operating License CP = Construction Permit ..
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