ML25195A152
| ML25195A152 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 04/07/1979 |
| From: | Carbon M Advisory Committee on Reactor Safeguards |
| To: | Hendrie J NRC/Chairman |
| References | |
| Download: ML25195A152 (1) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION ADVISORY COMMITTEE ON REACTOR SAFEGUARDS WASHINGTON, D. C. 20555 Honorable Joseph M. Hendrie Chairman U.S. Nuclear Regulatory Coounission Washington, DC 20555 April 7, 1979
SUBJECT:
INTERIM REPORT ON RECENT ACCIDENT AT THE THREE MILE ISLAND NUCLEAR STATION UNIT 2 Dear Dr. Hendrie During its 228th meeting, April 5-7, 1979, the Advisory Committee on Reactor Safeguards reviewed the circumstances relating to the recent accident at the Three Mile Island Nuclear Station Unit 2. During this review, the Committee had the benefit of discussions with the NRC Staff.
our study of the accident at Three Mile Island has shown that it is very difficult for a PWR plant operator to understand and properly control the course of an accident involving a small break in the reactor coolant system accompanied by other abnormal conditions.
The Committee recommends that further analyses be made, as soon as pos-sible, of transients and accidents in PWRs that involve initially, or at some time during their course, a small break in the primary system.
The computer codes used for these analyses should be capable of predict-ing the conditions observed during the accident at Three Mile Island, including thermal-hydraulic effects and clad and fuel temperatures.
The range of break sizes considered should include the smallest that could be deemed significant, and should consider a range of break loca-tions.
The Cornrnittee believes that the analyses recommended above will demon-strate, as has the accident at Three Mile Island, that additional information regarding the status of the system will be needed in order for the plant operator to follow the course of an accident and thus be able to respond in an appropriate manner.
As a minimum, and in the interim, it would be prudent to consider expeditiously the provision 1653
Honorable Joseph M. Hendrie 2 -
April 7, 1979 of instrumentation that will provide an unambiguous indication of the level of fluid in the reactor vessel. Early consideration should be given also to providing rem::>tely controlled means for venting high points in the reactor system, as practical.
The foregoing recommendations apply to all pressurized water reactors.
The reconmendations in IE Bulletin 79-0SA, dated April 5, 1979, are be-lieved to be generally suitable for Babcock and Wilcox facilities, on an interim basis. However, the Committee believes that the actions listed in Item 4b. under the heading, "Actions To Be Taken by Licen-sees," may prove to be unduly prescriptive in view of the uncertainties in predicting the course of anomalous transients or accidents involving small breaks in the primary system.
With regard to Three Mile Island Unit 2, the Committee believes that decisions should be made expeditiously with regard to contingency meas-ures which may be prudent concerning containment and reactor cooldown as a backup to the currently planned cooldown procedure.
The Committee is continuing its review of these and other concerns arising from this accident and will provide further advice as it is developed.
1654 Max w. Carbon Chairman