United States Nuclear Regulatory Commission - Protecting People and the Environment

Verification of Seismic Adequacy of Mechanical and Electrical Equipment in Operating Reactors, Unresolved Safety Issue (USI) A-46 (Generic Letter 87-02)



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

                              February 19,1987

TO:            All Holders of Operating Licenses Not Reviewed to Current 
               Licensing Criteria on Seismic Qualification of Equipment 

GENTLEMEN: 

SUBJECT:       VERIFICATION OF SEISMIC ADEQUACY OF MECHANICAL AND ELECTRICAL
               EQUIPMENT IN OPERATING REACTORS, UNRESOLVED SAFETY ISSUE 
               (USI) A-46 (Generic Letter 87-02) 

As a result of the technical resolution of USI A-46, "Seismic Qualification 
of Equipment in Operating Plants," the NRC has concluded that the seismic 
adequacy of certain equipment in operating nuclear power plants must be 
reviewed against seismic criteria not in use when these plants were 
licensed. The technical basis for this conclusion is set forth in References 
1 and 2. 

Direct application of current seismic criteria to older plants could require
extensive, and probably impracticable, modification of these facilities. An 
alternative resolution of this problem is set out in the enclosure to this 
letter. This approach makes use of earthquake experience data supplemented 
by test results to verify the seismic capability of equipment below 
specified earthquake motion bounds. In the staff's judgment, this approach 
is the most reasonable and cost-effective means of ensuring that the purpose 
of General Design Criterion 2 (10 CFR Part 50 Appendix A) is met for these 
plants. 

Because affected plants are being asked to carry out this evaluation against
criteria not used to establish the design basis of the facility, this 
resolution is a backfit under 10 CFR 50.109. The backfit analysis and 
findings may be found in the Regulatory Analysis (Reference 2) at pp. 31. 

Seismic verification may be accomplished generically, as described in the 
enclosure. Utilities participating in a generic program should so state in 
their reply to this letter, identifying the utility group and the schedule 
established for completion of the effort. The implementation schedule will 
be negotiated with utility groups or individual utilities in accordance with
the NRC policy on integrated schedules for plant modifications. See Generic 
Letter 83-20, May 9, 1983. Utilities not participating in a generic review 
may be allowed some additional time to complete the review. 



370200135 


We therefore request* that you provide within 60 days of receipt of this 
letter a schedule for implementation of the seismic verification program at 
your facility. 

                                   Sincerely, 


                                   Harold R. Denton, Director 
                                   Office of Nuclear Reactor Regulation 

Enclosure: 
Seismic Adequacy Verification 
Procedure 

References:    (1)  NUREG-1030, "Seismic Qualification of Equipment in 
                    Operating Nuclear Power Plants (USI A-46)," February 
                    1987 

               (2)  NUREG-1211, "Regulatory Analysis for Resolution of 
                    Unresolved Safety Issue A-46, Seismic Qualification of 
                    Equipment in Operating Plants," February 1987 



* This request is covered by Office of Management and Budget Clearance 
  Number 3150-0011 which expires September 30, 1989. Comments on burden and 
  duplication may be directed to the Office of Management and Budget, Room 
  3208, New Executive Office Building, Washington, DC 20503. 



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