ML19284A422
| ML19284A422 | |
| Person / Time | |
|---|---|
| Issue date: | 10/31/1978 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19284A421 | List: |
| References | |
| NUDOCS 7903060387 | |
| Download: ML19284A422 (4) | |
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ENCLOSURE g
Safety Evaluation Report on Licensing Topical Reports by Westinghouse Electric Co.
" Safety Analysis of the Fuel Assembly for Combined Seismic and Loss-of-Coolant Accident" WCAP-7950, July 1972 WCAP-8236, December 1973 WCAP-8236, Addendum 1, March 1974 hp Co b
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Core Performance Branch October 1978 UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON. D. C. 20655 t
-2, Evaluation Two Westinghouse topical reports (Refs.1, 2) on fuel assembly mechanical response to seismic and LOCA loads have been reviewed; they both use a cominon analytical method.
The first report discusses the 15x15 fuel assembly design (Ref. 1), and the second report discusses 'the 17x17 fuel assembly design (Ref. 2).
Since the issuance of these two reports, Westinghouse has changed the design of the 17x17 fuel assembly from 7 to 8 grids to reduce the mag-i nitude of rod bowing. An addendum to WCAP-8236 was issued to account for the change (Ref. 3).
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NRC initially reviewed the 17x17 fuel assembly for both 7 and 8 grid i
designs, and a preliminary safety evaluation was issued (Ref. 4). The r
staff evaluation noted that there was an adequately simulated vertical test to verify the calculated response of the vertical components from the seismic and LOCA loads. However, a simulated test for the horizontal response of the fuel assembly was not performed because the predominant load came from the vertical LOCA shock locd. At that time we concluded that the reports were acceptable for plant licensing purposes, and that i
further review of the analytical method was not essential. No separate review was performed for the 15x15 fuel assenbly because the analytical method used for the 15x15 fuel assembly duplicated that used for the 17x17 fuel assembly.
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. Since the preliminary safety evaluation of the subject reports was issued, a new horizontal load on the fuel assembly was recognized in connection with a postulated inlet pipe break at the reactor nozzle safe ends (as first reported by VEPC0 during the North Anna plant review). The previous NRC conclusion has therefore been reexamined because (1) the horizontal load h'as increased substantially, and (2) no satisfactory horizontal confirmatory test was available'.
Because of the lack of complete experimental verification, NRC's consul-tants at the Idaho National Engineering Laboratory performed an independent calculation of horizontal loads for comparison with the Westinghouse calculation. On the basis of this comparison (Ref. 5), we conclude that the Westinghouse analytical method is still acceptable provided a conser-vative factor (sometimes also called a safety factor) is applied to cover 7
analytical uncertainties. Conservative margin is needed because (1) the system is non-linear and (2) a full set of verification studies would be very difficult and was not performed. The magnitude of the conservative safety factor and other acceptance criteria have not been included in this review and will be considered for each plant.
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4-References 1.
L.T. Gesinski, " Fuel Assembly Safety Analysis for Combined Siesmic and Loss-of Coolant Accident," Westinghouse Report WCAP-7950, July 1972.
2.
L. T. Gesinski and D. Chiang, " Safety Analysis of the 17x17 Fuel Assembly for Combined Seismic and Loss-of-Coolant Accident," Westinghouse Report WCAP-8236 (non-proprietary version WCAP-8288), December 1973.
3.
L. T. Gesinski and G. LeBastard, " Safety Analysis of the 8-Grid 17x17 Fuel Assembly for Combined Seismic and Loss of Coolant Accident,"
Addendum #1 to WCAP-8236, March 1974.
4.
Letter from D. B. Vassallo of USNRC to R. Salvatori of Westinghouse, June 12, 1974.
5.
R.L. Grubb, "PWR Fuel Assembly Mechanical Response Analysis," Idaho National Engineering Laboratory, INEL Report RE-E-77-140 and Amendment No. 1 RE-E-77-140, March 22, 1977.
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