ML20003G150
| ML20003G150 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 04/20/1981 |
| From: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Stolz J Office of Nuclear Reactor Regulation |
| References | |
| TASK-2.K.3.30, TASK-TM TAC-45859, NUDOCS 8104280382 | |
| Download: ML20003G150 (2) | |
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$ SACRAMENTO MUNICIPAL UTILITY DISTRICT C SMUD 95813; (916) 452-3211 April 20,1981
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DIRECTOR OF NUCLEAR REACTOR REGULATION
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ATTENTION JOHN F STOLZ CHIEF OPERATING REACTORS BRANCH 4
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RANCHO SEC0 NUCLEAR GENERATING STATION, UNIT NO. 1 SMALL BREAK LOCA MODEL Your letter of February 24, 1981 requested further post-test analyses of the S-07-100 and L3-1 tests.
The B&W prediction of the L3-1 test cocpared very favorably with the other Vendor predictions. All of the predictions showed the clearing of liquid from the pump loop seal. Hcwever, the test did not produce this result due to a bypass flow path which existed between the vessel upper head and the downcomer annulus, as well as another bypass between the hot-and cold-leg pipes due to leakage through the reflood assist valves. EG&G calculations indicate that this leakage path in LOFT is approximately 3 percent of the core flow, or comparable to prototype valves. However, the actual leakage path cannot be measured directly, but only indirectly, inferred by assuming a value which leads to the prediction agreement with the test. Therefore, the leakage ficw frem L3-1 must be further evaluated before additional analytical work could be justified.
In addition, on page 40 of EGG-CAAP-5255 (LOFT L3-1 Preliminary Comparison Report) it is stated that B&W was the only Vendor who accurately cal-culated tne behavior of the secondary side of the steam generator.
For these reasons, we are of the opinion that only a marginal benefit at best could be realized from further evaluation of the L3-1 test.
Regarding the S-07-100 test, the situation is a little different. None of the Vendor predictions characterized the test very well. However, we feel this is due in large measure to insufficient infomation to model the steam side of the steam generator, as well as insufficient data on the valve and associated piping.
There is also insufficient information to adequately model the steam separator.
Based on these reasons, we are of the opinion that our current results are not unreasonable considering the conservative features of the model B&W used to predict the experiment.
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John F. Stolz April 20, 1981 Notwithstanding the above. arguments, we are evaluating a program being proposed by the Babcock & Wilcox Company to the B&W Owners Group to provide a qualitative opinion of the impact of identified test uncertainties and model conservatisms on the results previously provided on the blind predictions of L3-1 and S-07-100.
This effort would not result in a response to your letter before June 1,1981.
We will provide you with the results of our decision by May 1,1981.
L WW ohn. Mattimoe Assistant General Manager and Chief Engineer
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