ML20028D518
| ML20028D518 | |
| Person / Time | |
|---|---|
| Issue date: | 12/18/1979 |
| From: | Rosztoczy Z NRC - TMI-2 BULLETINS & ORDERS TASK FORCE |
| To: | Ross D NRC - TMI-2 BULLETINS & ORDERS TASK FORCE |
| Shared Package | |
| ML20027A678 | List:
|
| References | |
| FOIA-82-543, RTR-NUREG-0611, RTR-NUREG-611 NUDOCS 8301190219 | |
| Download: ML20028D518 (2) | |
Text
as' Z, Moy#')y p Itic UNITED STATES uq[g NUCLEAR REGULATORY COMM!sslON 4
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DEC' 81979 MEMORANDUM FOR:
D.F. Ross, Jr., Director, Bulletins & Orders Task Force FROM:
Z.R. Rosztoczy, Chief, Bulletins & Orders Task Force
SUBJECT:
GENERIC EVALUATION OF SMALL BREAK LOSS-0F-COOLANT ACCIDENT BEHAVIOR FOR WESTINGHOUSE OPERATING PLANTS The Analysis Group has completed the review and evaluation of information
~ received from Westinghouse and the Westinghouse Owners Group on small break loss-of-coolant accidents.
Our evaluation, conclusions and -recommendations are presented in the attached draft report. This report has been prepared as Appendix VIII of NUREG-0611.
The most important findings are:
The small break evaluation presented by Westinghouse is appropriate for use in operator training, however improvements are required before it could be used to show compliance with 10CFR50.46.
iWe' reactor protection system and the engineered safety features do not provide automatic protection in case of a small break LOCA.
Prompt operator action is required to protect public health and safety.
The Westinghouse plants are protected for small breaks if only a single failure is postulated and if the operators perform as required.
l Approximately 50% of the Westinghouse plants are probably not. protected for either of the following two events: (1) loss of main feedwater and auxiliary feedwater at the same time; and (2) loss of natural circulation.
The Westinghouse evaluation relied on equipment which is not considered i
part of the safety systems and is not qualified for operation in the post LOCA environment.
The Westinghouse evaluation also relied on two-phase' natural circulation in the reactor coolant system, a mode of heat removal that has not yet been demonstrated experimentally.
l The challenge rate of relief valves per reactor year of operation could be rather large for Westinghouse plants, comparable to the challenge rate of relief valves on B&W plants prior. to 4-25-79, and an order of magnitude higher than the challenge rate of B&W plants in their present mode of operation.
8301190219 821122 PDR FOIA SHOLLY82-543 PDR 6
D.F. Ross, Jr. DEC1819IS Appropriate corrections have been recommended in the report for the existing shortcomings.
The recommendations, if implemented, will provide reasonable assurance that continued operation of the Westinghouse plants'does not endanger public health and safety.
The Analysis Group performed its work during the past seven months in parallel with the work of other task forces.
I am certain that some of our recommendations are similar to recommendations coming from other groups.
Nevertheless, the reasons for the recommendations, and the urgency and importance of the rec-ommendations might be different in the various evaluations.
I would like to urge you to include Appendix VIII in NUREG -0611 in its entirety.
If NRC is not ready yet to implement some of the recommendations or if some of the recommendations need to be considered on a broader basis than the small break LOCA alone, these considerations should be mentioned in the main part of the report, rather than eliminating the recommendations in question from the appendix.
Z k
Z.R. Rosztoczy, Chief f
Bulletins & Orders Task Force Distt$bution w/o
Enclosure:
T. Novak W. Kane P. Norian R. Audette J. Guttmann W. Jensen B. Sheron E. Throm R. Frahm W
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