ML20058P198
| ML20058P198 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 12/16/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20058P187 | List: |
| References | |
| REF-GTECI-A-46, REF-GTECI-SC, TASK-A-46, TASK-OR NUDOCS 9312230139 | |
| Download: ML20058P198 (4) | |
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S UNITED STATES
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NUCLEAR REGULATORY COMMISSION-k....,/
WASHINGTON, D.C. 20555-4001 a
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION FOR RESOLUTION OF USI A-46 CRYSTAL RIVER. UNIT 3 INTRODUCTION In the 120-days response to Generic Letter 87-02, Supplement 1 (Reference 1),
dated September 4, 1992, Florida Power Corporation (the licensee) provided its plans for resolution of Unresolved Safety Issue (USI) A-46.
In the submittal l
dated April 16,1993 (Reference 2), the licensee provided some information related to the development of floor response spectra to be used for the
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resolution of USI A-46.
In the responses, the licensee indicated that.it would review a number of issues related to the safety enhancement of the plant's equipment and cost of implementing the final program before deciding on the final plans. After reviewing the last submittal, the staff requested additional information (RAI, Reference 3) for completing its review. The licensee provided responses to the RAI in submittals dated September 7 and October 6, 1993 (Reference 4).
This evaluation addresses the extent of adequacy of floor response spectra (FRS) and reasonableness of the methods utilized in their development for resolution of USI A-46.
EVALUATION Ground Response Spectra The licensing basis design ground response spectra (DRS) were developed for the peak ground acceleration of 0.19 corresponding to safe shutdown earthquake (SSE). The spectral shape was determined by utilizing Housner spectral shape up to a period of about 0.4 sec.; and utilizing a method developed by Estere and Rosenbleuth, Weston Geophysics determined the spectral values (Reference
- 5) for periods above 0.4 sec., which resulted in larger spectral ordinates (compared to Housner's spectra) for the frequencies lower than 2.5 hz. Since the DRS is the current licensing basis, the staff finds its use acceptable and adequate for developing FRS.
Structural modellino Parameters All skismic Category I structures are modelled as lumped mass stick models with a fixed base. The responses of the containment structure were compared usirg the fixed base model and the flexible base model (with appropriate soil spr8ag.t) to demonstrate the conservatism of the fixed base modelling. Though t
9312230139 931216 PDR ADDCK 05000302-P PDR
O the design was performed using 2% damping for the containment' structure and 5%
damping for all other concrete structures, the licensee plans to use 5%
structural damping for all concrete structures for the resolution of USI A-46.
The staff finds the structural modelling parameters acceptable.
Floor Response Soectra The licensee has used the response spectrum method of developing FRS from the ground response spectra as developed by Biggs and Rosset (Reference 6).
In Rev.14 of the Final Safety Analysis Report, the licensee has documented the conservatism associated with the use of the response spectrum method as compared to the time-history method by comparing the FRS for two structures.
The available FRS are for equipment damping values of %% and 2%. The Generic Implementation Procedure (GIP-Reference 7), as approved by the staff (Reference 8), allows the use of 3% and 5% equipment damping values depending upon the type of equipment. The licensee plans to extrapolate the available FRS to 3% and 5% equipment damping values using ' power method' derived by the licensee. The power method requires responses at two damping values for derivir.g responses at a third damping value. The staff reviewed the derivation and found the method to be reasonable for broadened smooth FRS.
l The staff also spot checked some of the spectral acceleration values using the l
procedure recommended in Section 4.4.3 of Reference 7 and found that, in general, the power method gives conservative values. As the plant structures are founded on rock, the FRS peaks are broadened by 110%, and the peaks are found to exhibit adequate amplifications at various elevations. Overall, the I
staff finds the approach used in generating FRS for verifying the seismic adequacy of equipment to be reasonable and acceptable.
It should be noted, however, that the staff's acceptance of the relaxation from the licensing commitment (for the use of higher equipment damping values) is based on the assumption that the subsequent seismic verification of the equipment and anchorages will be in accordance with Supplement I to Generic Letter 87-02 (Reference 8).
Treatment of Earthauake Components The licensee plans to combine the responses due to one horizontal direction and vertical direction by the absolute sum method.
In response to the staff question (Reference 3) regarding the incorporation of vertical seismic responses, the licensee plans to verify the seismic adequacy of equipment and anchorages by considering vertical FRS as two-thirds of the horizontal FRS.
i Overall, the approach indicated by the licensee for treatment of earthquake components in the resolution of USI A-46 is found to be adequate and acceptable.
I CONCLUSION Based on the review of the information submitted by the licensee in the original submittal, and as responses to the request for additional information, the staff concludes that the ground response spectra utilized and I
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l t r the approaches used in the development of floor response spectra are in accordance with the licensing commitment, and are acceptable for the resolution of USI A-46. This conclusion is based on the assumption that the subsequent verification of the equipment and anchorages will be in accordance with Supplement I to Generic Letter 87-02.
i Date: December 16, 1993 i
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References 1.
Letter from P. Beard (FPC) to NRC on Generic Letter 87-02, SupplementL1, Dated Sept. 4,J1992.
2.
Letter (with attachments) from P. Beard-(FPC) to NRC, on Generic Letter, Supplement 1.-Dated April 16, 1993.
3.
Memorandum from G. Bagchi to H. Berkow, " Request for Additional-
'Information. (RAI) Lon Develcpment of Floor Response' Spectra," Dated June 11, 1993-(Faxed to FPC).
L 4.
Letters from P. Beard (FPC) to NRC, " Responses to RAI on Development of Floor Response Spectra," Dated Sept. 7,~1993 and Oct. 6, 1993.-
5.
Weston Geophysical Research, Inc., " Seismic Analysis and Response Spectra for Crystal River Nuclear Power Plant," June 1967.
6.
- Biggs, J., Rosset, J.,
" Seismic Analysis of Equipment Mounted on.
Massive Structure," MIT, March 1969.
-7.
Generic Implementation Procedure (GIP) for Seismic Verification of Nuclear Plant Equipment, Rev. 2, Seismic Qualification Utility Group,:
Feb. 1992.
8.
Generic Letter 87-02, Supplement 1, " Supplemental Safety Evaluation No.
2 on-SQUG Generic Implementation Procedure (Reference 7 above)," Dated' May 22, 1993.
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