NRC Generic Letter 87-03, Verification of Seismic Adequacy of Mechanical and Electrical Equipment in Operating Reactors (USI A-46)
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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
8703060307VAC 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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