ML20128B333
| ML20128B333 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 06/14/1985 |
| From: | Phyllis Clark GENERAL PUBLIC UTILITIES CORP. |
| To: | Murley T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| IE-79-02, IE-79-2, IEB-79-14, NUDOCS 8507030198 | |
| Download: ML20128B333 (3) | |
Text
T GPU Nuclear Corporation I
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ME 100 Interpace Parkway Parsippany, New Jersey 07054-1149 (201)263-6500 TELEX 136-482 Wnter's Direct Dial Number:
201-299-6797 June 14,1985 Dr. Thomas E. Murley, Administrator Region 1 U.S. Nuclear Regulatory Comission 631 Park Avenue King of Prussia, PA 19406
Dear Dr. Murley:
Subject:
Oyster Creek Nuclear Generating Station Docket No. 50-219 Preliminary Response to IE Inspection 85-14 During IE Inspection 85-14, several discrepancies between drawings which were updated as a result of IE Bulletin 79-14, and the inspector's field observations were identified. At a meeting with members of your staff on May 20,1985, we committed to reinspect those systems accessible during operation to ascertain the extent that drawings reflect actual field conditions and determine if seismic analyses, which were based on these drawings, were still valid. On June 13, 1985, we presented our preliminary results of that reinspection. This letter complies with your request that we provide a written response outlining the bases for continued operation of the Oyster Creek Nuclear Generating station until the reinspection is completed.
We have concluded that the major technical requirements of IE Bulletin 79-14 have been addressed and satisfied through a review of documentation relating to the 1979/1980 inspection. This documentation review has determined that seismic concerns were addressed and corrected during the 1979/1980 effort.
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Dr. Thomas E. Murley June 14,1985 Page Two With regard to IE Bulletin 79-02, our review of the existing documentation has concluded that the technical requirements of the Bulletin such as base plate flexibility, factor of safety, cyclic loads and load testing have been addressed and show evidence of being satisfied. The existing test results will be summarized and statistics developed to document confidence levels.
The 1979/1980 inspection contained all the attributes required by IE Bulletin 79-14. The 1985 inspection included all the required 79-14 attributes plus additional attributes which surpass the requirements of the bulletin.
Based on our 1985 inspection results, as of June 13, 1985, we have seen numerous minor deviations from the engineering drawings, primarily with regard to hangers.
Many of these nonconformances are being corrected as they are found and the remainder are being evaluated by engineering for impact on system seismic capability. An engineering assessment is being performed in two steps. Each Material Nonconformance Rcport (MNCR) is first individually evaluated for conditional release. A system reevaluation is then conducted in order to assess the aggregate effect of all the MNCR's issued against that system. No variances have resulted in any safety related system being declared inoperable. The 1985 inspection effort, as of June 13, 1985, confirms Bulletin 79-14 conclusions reached in 1979/1980, and it does not change our conclusions about the overall seismic acceptability of the affected piping systems.
Because of the plant trip on June 12th, we are now in the process of performing inspections in the drywell. As of today we would expect to complete the 79-14 inspections of the accessible portions of one Main Steam Line, one equivalent Recirculation Piping Loop, one Main Feedwater Line, and one Core Spray Line. We will continue to inspect until the plant is ready for restart. Very preliminary inspection results from within the drywell, current as of June 14th, show a much reduced number of deviations between inspection attributes and drawings. No significant or major defects have been found to date. The reinspection effort will be completed during our next scheduled outage of October,1985.
If system reanalysis is required, the results will be reported to you as they become available.
1 In 1978 and 1979, a probabilistic risk analysis of the Oyster Creek Nuclear Generating Station was performed.
This analysis, entitled the "0yster l
Creek Probabilistic Safety Analysis" (OPSA) estimated earthqyakes of 0.22g or greater to have a mean frequency of approximately 1.15 x 10-4/yr.
The OPSA
Dr. Thomas E. Murley, Administrator June 14,1985 Page Three study calculated a core melt frequency of approximately 1.5 x 10-4/yr for all seismic related events and approximately 2.8 x 10-o/yr due to seismic-induced LOCAs (seismic pipe breaks which is the 79-14 issee). This equates to approximately 2% of the seismic core melt frequency, and is about 1% of the total core melt frequency.
This results from the relatively high seismic capacities of the piping systems.
In summary, our bases for concluding there is reasonable justification for continuing Oyster Creek operation pending final completion of the inspections are as follows:
- 1. Inspection to date as previously noted does not change the prior 1979-1980 effort on Bulletin 79-14. Hence we conclude the seismic piping design capability is valid.
- 2. Very preliminary inspection results from within the drywell, current as of June 14th, show a much reduced number of deviations between inspection attributes and drawings.
No major defect has been found.
- 3. The probability of a design bases or more severe earthquake prior to the completion of 79-14 inspection activities, is extremely remote.
- 4. The PRA studies show seismic induced LOCA's to be a very small contribution to core melt frequency and inspection results do not change this assessment.
It is our conclusion from all of the above that there is no perceptible change in any seismic induced LOCA risk which would affect public health and safety due to the continued operation of Oyster Creek.
Very truly yours, P. R. Clark President PRC:kh 05340 cc: Mr. John A. Zwolinski, Chief Operating Reactors Branch No. 5 U. S. Nuclear Regulatory Comission Washington, DC 20555 NRC Resident Inspector Oyster Creek Nuclear Generating Station Forked River, N. J. 08731 0534U