ML20046B230
| ML20046B230 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 07/13/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20046B229 | List: |
| References | |
| IEB-79-02, IEB-79-14, IEB-79-2, NUDOCS 9308030359 | |
| Download: ML20046B230 (2) | |
Text
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W A S H! N G T O N, D C. 2055%O01 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION PIPE-SUPPORT ANCHORAGES RESOLUTION OF IEB 79-02 l
GPU NUCLEAR CORPORATION 1
OYSTER CREEK NUCLEAR GENERATING STATION i
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DOCKET N0. 50-219 l
1.0 INTRODUCTIOJ l
l IE Bulletin (IEB) 79-02, " Pipe Support Baseplate Designs Using Concrete Expansion Anchor Bolts," required all the licensees of operatirig plants to j
conform to the criteria established in the Bulletin regarding the adequacy of 1
i the support plates and concrete expansion-anchor bolts for all safety related l
l piping supports.
At the Oyster Creek Nuclear Generating Station (OCNGS), GPU l
Nuclear Corporation (the licensee) had completed the evaluations and upgrades of the 90% of the support anchors in 1988 (Reference 1). At the time, the j
I licensee was in the process of developing the floor response spectra utilizing j
the latest available techniques.
Because of the expected significant l
reduction in the floor responses, the licensee wanted to utilize the newly generated spectra for the resolution of remaining supports (IEB 79-14),
i support anchorages (IEB 79-02) and for the future additions and modifications to the plant.
Later on the licensee decided to evalu&te and modify the supports and support anchorages using the original Final Safety Analysis Report (FSAR) commitment.
This evaluation addresses the adequacy of the pipe support anchorages with respect to the requirements of IEB 79-02.
2.0 EVALUATION In Reference 1, the licensee had provided a comprehensive summary of the status of the pipe supports and their anchorages qualified through evaluations i
and upgrades. Reference 1 indicated that 90% of the pipe-support anchorages were qualified to meet the IEB 79-02 acceptance criteria against the postulated loadings.
The remaining 10% of the anchorages were to be qualified in 1988 by using the new floor response spectra (FRS).
llowever, the ground response spectra to be used to generate the FRS were under discussion with the NRC staff.
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i The staff approved the use of the site specific spectra developed by the 4
licensee in March 1992 (Reference 2).
The licensee had an option to use either the licensing basis ground response spectrum or the newly developed site specific respont spectrum to generate the floor response spectra.
By j
letter dated June 4, _>93 (Reference 3), the licensee indicated that the i
remainina 67 pipe support anchorages (about 10%) have been qualified using the l
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.- original design basis Housner spectrum provided in the plant FSAR. The IEB 79-02 requires minimum factors of safety against the average strength of the individual anchors as 4 for the wedge-type anchors, and 5 for the shell-type anchors.
In Reference 3, the licensee indicates that the actual factors of safety varied between 4 and 20 for the wedge-type anchors, and between 5 and 20 for the shell-type anchors.
Though the staff recognizes that the Housner spectrum is not as conservative as the current requirements (i.e., Regulatory Guide RG 1.60) or the site specific spectrum, the absence of reduction due to deconvolution in the use of Housner spectrum would compensate for the unconservatism. Moreover, the Bulletin required the evaluation of pipe-support anchorages on the basis of FSAR commitments. Actual inspection results and upgrades were inspected by the NRC Region I staff (Reference 4) in November 1988.
Considering all these factors in the assessment, the staff finds the pipe-support anchorages to be in conformance with the requirements of IEB 79-02.
Relevant calculation packages should be kept in an auditable form and should be available for future staff audit.
3.0 CONCLUSION
Based on the review of i.ne previous efforts (before 1987) by the licensee to resolve this issue, the review of the inspection report prepared by the Region I staff related to the inspections and upgrades of the anchor bolts at the site, and the licensee's statements regarding the calculated factors of safety, the staff concludes that the pipe-support anchorages of the safety related piping at the (OCNGS) meet the criteria provided in IEB 79-02 and are acceptable.
It should be noted that for any future modification or upgrade activity, the use of the site specific spectra, or the spectra from the FSAR should be consistently applied to the entire design process; i.e., seismic input for one location using site specific spectra and for another location based on the FSAR criteria is not acceptable.
4.0 REFERENCES
1.
Letter from R. F. Wilson (GPUN) to NRC, " Seismic Floor Response Spectra,"
Dated September 19, 1988.
2.
Letter from A. Dromerick (NRC) to J. J. Barton (GPUN), " Review and Evaluation of Site Specific Spectra - OCGNS," Dated March 18, 1992.
3.
Letter from R. W. Keaton (GPUN) to NRC, " Completion of IEB 79-02 Requirements," Dated June 4, 1993.
4.
Letter from J. P. Durr (NRC-RI) to E. E. Fitzpatrick (GPUN), " Inspection Report No. 50-219/88-81," Dated Jan. 10, 1989.
Principal Contributor:
H. Ashar Dated: July 13,1993
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