ML19257B926
| ML19257B926 | |
| Person / Time | |
|---|---|
| Site: | Lynchburg Research Center |
| Issue date: | 01/16/1980 |
| From: | Olsen A BABCOCK & WILCOX CO. |
| To: | Reid R Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8001210251 | |
| Download: ML19257B926 (2) | |
Text
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Babcock &Wilcox nes.<cn ano oeveicoment oivision P.O. Box 1260, Lynchburg, Va. 24505 Telephone: (804) 384-5111 January 16, 1980 Mr. Robert W. Reid, Chief Operating Reactors Branch #4 Division of Operating Reactors U. S. Nuclear Regulatory Commission Washington, D. C.
20555 License: CX-10, docket 50-13
Reference:
Letter to Mr. Robert W. Reid from A. F. Olsen dated October 18, 1979.
Dear Mr. Reid:
My request for an amendment to the license was forwarded by the reference.
The Lynchburg Research Center has performed an additional accident analysis.
The study does not effect the previously arrived at conclusions regarding the safety of the proposed experiments but I feel that the information should be entered in the record.
Attached are twenty-three copies of a new page for insertion in our report entitled " Hazards Evaluation Report for Tightly-Packed Fuel Storage Critical Experiment Program", dated October 23, 1979. This page 18a should be entered in the report between pages 18 and 19.
The experiments are required to fulfill the terms of a contract with the Department of Energy and our schedule requires that these experiments begin in late February, 1980.
I therefore request your continued consideration.
Yours very truly, BABCOCK & WILCOX COMPANY LYNCHBURG RESEARCH CENTER 3 CA~
Arne F. Olsen 1 7 7 4 1 1 5'.-
License Administrator AFO:ccf 8001210 25/
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The Babcock & Wilcox Company / Established 1867 y-
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The accident analysis assumes that a scram eventually occurs as a result of continuous reactivity addition, although not until the initial power surge i.as nearly passed. This scram occurs even if partial failure of the safety system (period ' channels) is assumed.
Complete failure of the scram system is considered incredible because:
1.
The safety system is comprised of four independent channels; 2 log N (period) and 2 linear.
2.
The four chambers use 2 separate DC power supplies.
3.
The safety system is designed so that loss of power to any of the safety channels, the safety amplifier, the rod drives or the dump valve will automatically result in reactor shutdown.
4.
The proper operatior. of each safety channel is verified with a radiation source each day that the reactor is operated.
At no time in the history of the CX-10 facility has any failure occurred that permitted continued operation with an inoperative safety systed.
In fact, no partial failure of the safety system has ever occurred that would retard reactor shutdown as assumed in the hazard's evaluation.
In the proposed program, eventual operation of the safety system is most important to core 3 of the triangular pitch loadings (p.12).
Since the water gap separating the fuel assemblies in this case is greater than the optimal (i.e., most reactive) spacing, a prolonged excursion with-out external shutdown (long enough to conduct substantial heat from fuel into moderator) might result in a secondary power surge. Howeste, the acci-dent evaluation demonstrates that even a greatly retarded shutdown following a continuous reactivity addition occurs within 0.2 seconds after the initial power peak, well before a significant quantity of heat can be conducted into the moderator. This precludes the possibility of any secondary power surge.
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