Information Notice No. 85-45: Potential Seismic Interaction Involving the Movable In-core Flux Mapping System Used in Westinghouse Designed Plants
SSINS No.: 6835 IN 85-45 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C. 20555 June 6, 1995 Information Notice No. 85-45: POTENTIAL SEISMIC INTERACTION INVOLVING THE MOVABLE IN-CORE FLUX MAPPING SYSTEM USED IN WESTINGHOUSE DESIGNED PLANTS Addressees: All power reactor facilities holding an operating license (OL) or a construction permit (CP). Purpose: This information notice is provided as notification of a potentially generic problem involving seismic interactions within the movable flux mapping system at Westinghouse designed plants. It is expected that recipients will review the information for applicability to their facilities and consider actions, if appropriate, to preclude a similar problem from occurring at their facilities. However, suggestions contained in this information notice do not constitute requirements and, therefore, no specific action or written response is required. Description of Circumstances: On June 22, 1984, Carolina Power and Light (CP&L) Company informed the Nuclear Regulatory Commission (NRC) of a potentially reportable item per the provisions of 10 CFR 50.55(e) and 10 CFR 21 at their Shearon Harris Nuclear Power Plant (SHNPP) Unit 1. The NRC was informed that interactions between the nonsafety related portions of the flux mapping system and the tubing/seal table during a seismic event had not been adequately considered by Westinghouse. At that time CP&L was waiting for Westinghouse to perform a structural integrity analysis for the portion of the in-core flux mapping system that is located above the in-core instrumentation tubing/seal table. In a letter dated February 12, 1985, CP&L informed the NRC that the potential seismic interactions were indeed reportable. The potential interactions exist because portions of the flux mapping system that have not been seismically analyzed are located directly above the in-core instrumentation tubing/seal table. Failure during a seismic event could possibly cause multiple failures in the flux mapping tubing or fittings that would produce a small break loss of coolant accident. Recent discussions with Westinghouse have revealed that the potential seismic interactions could exist at other Westinghouse plants including operating plants. Furthermore, multiple failures of flux mapping tubing and/or fittings constitute an unanalyzed small break loss of coolant accident because the break flow would effectively be from 8506060677 . IN 85-45 June 6, 1985 Page 2 of 2 the bottom of the reactor vessel. Thus, the consequences could be beyond the licensing design basis for loss of coolant accidents. It should be noted that any loss of reactor coolant system pressure boundary integrity caused by seismically induced failures in the flux mapping system would be outside the design basis of a plant and, therefore, unacceptable, regardless of whether the consequences were within those for loss of coolant accidents analyzed in safety analysis reports. The NRC staff has discussed this issue with the Westinghouse Regulatory Response Group. Based on discussions with the Regulatory Response Group and Westinghouse, it is our understanding that Westinghouse will notify their customers of this problem by letter in the near future. No specific action or written response is required by this information notice; however, contingent upon the results of further staff evaluations, a bulletin or a generic letter requesting specific licensee actions may be issued. If you have any questions regarding this matter, please contact the Regional Administrator of the appropriate NRC regional office or this office. Edward L. Jordan, Director Division of Emergency Preparedness and Engineering Response Office of Inspection and Enforcement Technical Contact: David Powell (301) 492-7155 Attachment: List of Recently Issued IE Information Notices
Page Last Reviewed/Updated Tuesday, March 09, 2021
Page Last Reviewed/Updated Tuesday, March 09, 2021