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 87-03)



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

                              February 27, 1987

TO:            All Licensees, Applicants and Holders of Operating Licenses 
               Not Required to be Reviewed for Seismic Adequacy of Equipment
               Under the Provisions of USI A-46, "Seismic Qualification of 
               Equipment in Operating Plants" 

GENTLEMEN: 

SUBJECT:       VERIFICATION OF SEISMIC ADEQUACY OF MECHANICAL AND ELECTRICAL
               EQUIPMENT IN OPERATING REACTORS, UNRESOLVED SAFETY ISSUE 
               (USI) A-46 (Generic Letter 87-03) 

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 those operating nuclear power plants which 
have not previously been reviewed to current licensing requirements for 
seismic qualification must be reviewed to seismic criteria defined in the 
USI A-46 technical resolution. The USI A-46 developed procedures make use of
earthquake experience data supplemented by test data 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 USI A-46 Regulatory Analysis (NUREG 1211) at 
pp. 31. 

We have documented evidence in staff SERs that your plant either has been, 
or is required to be, reviewed to current licensing requirements for Seismic
Qualification of Equipment (i.e., SRP-3.10, IEEE-344/75 and Regulatory Guide
1.100) and therefore you are not required to respond to this letter or to 
perform the plant reviews described in the enclosures. 

The information developed in resolving USI A-46 is described in the 
enclosures to this letter and is being provided to you for information only.

We would also like to call to your attention several recent incidents 
reported in Licensee Event Reports (LERs) which involved inadequate or 
missing anchorage. Between late March 1986 and May 1986, three LERs were 
received that documented inadequate seismic anchorage of electrical 
equipment in operating nuclear power plants. The initial case was at the 
Davis-Besse 1 plant (LER 86-011) where cabinet doors on Cyberex Class 1E 
equipment for essential instrument 120 


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VAC power were found to lack the required door bolts. The second LER 
concerned emergency diesel generator switchgear cabinets at the Cooper plant
that were not fastened to embedded channels beneath the cabinets (LER 
86-009). The third deficiency was found at the Dresden 2 and 3 plants, where
it was determined that the control room control panels did not have positive
anchorage to the floor (LER 86-009). In each instance, the deficiency had 
existed since plant construction and was the result of installation errors, 
since the design drawings had specified seismic anchorage. As a consequence 
of these events, a review was initiated b the NRC Office for Analysis and 
Evaluation of Operational Data (AEOD). This review included an LER search 
which revealed four other instances of inadequate seismic anchorage or 
support of safety related electrical equipment plus other related seismic 
inadequacies. 

We are enclosing the regulator analysis (NUREG 1211) and the USI A-46 
technical findings (NUREG 1030) for your information. The generic letter, 
which was issued to each nuclear plant that is required to perform seismic 
adequacy reviews under the provisions of USI A-46, is included as Appendix A 
to NUREG-1211. 

                                   Sincerely, 


                                   Harold R. Denton, Director 
                                   Office of Nuclear Reactor Regulation 

Enclosures: 
1.   NUREG 1211
2.   NUREG 1030

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