United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 82-11: Potential Inaccuracies in Wide Range Pressure Instruments Used in Westinghouse Designed Plants

                                                           SSINS No.:  6835 
                                                           IN 82-11 

                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                    OFFICE OF INSPECTION AND ENFORCEMENT
                           WASHINGTON, D.C.  20555

                                April 9, 1982

Information Notice No. 82-11:  POTENTIAL INACCURACIES IN WIDE RANGE 
                                  PRESSURE INSTRUMENTS USED IN WESTINGHOUSE 
                                  DESIGNED PLANTS 

Addressees: 

All nuclear power reactor facilities holding an operating license or a 
construction permit.  (This information was transmitted by facsimile on 
April 9, 1982 to Westinghouse designed nuclear power plants holding an 
operating license.) 

Purpose: 

This Information Notice is provided as an early notification of a 
potentially significant problem pertaining to wide range pressure 
instruments used in Westinghouse nuclear power plans.  It is expected that 
recipients will review the information for applicability to their 
facilities.  No specific action or response is required at this time. 

Description of Circumstances: 

By telephone calls on April 7 and 8, 1982, Westinghouse notified the NRC of 
information it had conveyed to its customers regarding the results of recent
qualification tests in post-accident high energy line break environment on 
the wide range pressure instruments supplied by Westinghouse.  Westinghouse 
stated that when combining transmitter, signal conditioning and indicator 
allowances for errors due to calibration uncertainty, drift and 
environmental effects that the qualification tests indicated that the RCS 
wide range pressure channels exhibited ambiguities in their accuracy which 
could potentially result in inappropriate operator actions. 

Westinghouse stated that post-accident accuracy ambiguities for RCS wide 
range pressure instruments under certain plant accident conditions have the 
potential for maximum accumulated inaccuracies of +/- 363 psig actuation and 
+/- 390 psig indication.  Accordingly, the inaccuracy of RCS wide range 
pressure measurements could lead to pressurizer power operated relief valves 
being lifted prior to the termination of safety injection (SI) and to a 
greater number of valve challenges, thereby increasing the probability of a 
small break loss-of-coolant accident due to a valve failing to close.  
Likewise, the inaccuracy of the wide range pressure instruments could lead 
to the termination of SI without adequate reactor coolant subcooling.  In 
addition, the inaccuracies could lead to premature or late tripping of the 
RCS pumps during the course of a small break loss-of-coolant accident. 
.

                                                            IN 82-11
                                                            Page 2 of 2

Westinghouse further stated that it is reviewing the design and operational 
bases for the wide range pressure instrumentation, that it will advise its 
customers of appropriate actions, and that continued safe plant operation 
has been demonstrated by prior analyses. 

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 Engineering and 
                                  Quality Assurance 
                                Office of Inspection and Enforcement 

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