United States Nuclear Regulatory Commission - Protecting People and the Environment

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  


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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 

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