United States Nuclear Regulatory Commission - Protecting People and the Environment

Potential Unreviewed Safety Question on Interaction Between Non-Safety Grade Systems and Safety Grade Systems (Generic Letter 79-42)



GL79042 

                               UNITED STATES 
                       NUCLEAR REGULATORY COMMISSION 
                          WASHINGTON. D. C, 20555 

                            September 17, 1979 

ALL OPERATING LIGHT WATER REACTORS 

SUBJECT:  POTENTIAL UNREVIEWED SAFETY QUESTION ON INTERACTION BETWEEN 
          NON-SAFETY GRADE SYSTEMS AND SAFETY GRADE SYSTEMS 

You were informed by IE Information Notice 79-22, issued September 14, 1979,
that certain non-safety grade equipment, if subjected to an adverse 
environment, could impact the safety analyses and the adequacy of the 
protective functions performed by safety grade equipment. Enclosed is a copy
of IE Information Notice 79-22, and reprinted copies of an August 30, 1979 
Westinghouse letter and a September 10, 1979 Public Service Electric and Gas
Company letter which address this matter. 

The NRC is concerned that a similar potential may exist at other operating 
light water reactor facilities, including yours, for an unreviewed safety 
matter related to the effects of the environment on control systems 
resulting from high energy line breaks inside or outside containment and the 
results of these effects on the required safety systems. 

In accordance with 10 CFR 50.54(f) you are requested to provide within 
twenty (20) days of the date of this letter, written statements, signed 
under oath or affirmation, which will enable the staff to determine, in 
light of the concerns discussed above, whether or not your NRC license(s) to 
operate your nuclear power generating facility(ies) should be modified, 
suspended, or revoked. 

                                   Sincerely, 


                                   Harold R. Denton, Director 
                                   Office of Nuclear Reactor Regulatory 

Enclosures:
1.   IE Information Notice 79-22
2.   Westingthouse's August 30, 1979 Letter
          (Reprint)
3.   Public Service Electric and Gas
          Company's September 10, 1979 Letter
          (Reprint)
Page Last Reviewed/Updated Wednesday, May 22, 2013