ML25168A243
| ML25168A243 | |
| Person / Time | |
|---|---|
| Issue date: | 06/07/1982 |
| From: | Shewmon P Advisory Committee on Reactor Safeguards |
| To: | Palladino N NRC/Chairman |
| References | |
| Download: ML25168A243 (1) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION ADVISORY COMMITTEE ON REACTOR SAFEGUARDS WASHINGTON, D. C. 20555 Honorable Nunzio J. Palladino Chairman U. S. Nuclear Regulatory Commission Washington, D. C. 20555
Dear Dr. Palladino:
June 7, 1982
Subject:
ACRS REPORT ON PRESSURIZED THERMAL SHOCK During its 266th meeting, June 3-5, 1982, the Advisory Committee on Reactor Safeguards completed its review of the current status of the pressurized thermal shock problem (PTS).
The NRC Staff is developing a regulation based on a combination of deterministic and probabilistic analyses to establish regulatory requirements concerning pressurized thermal shock.
The ACRS has not been provided sufficient information to evaluate the adequacy of this approach.
The ACRS does not believe there is a need for any immediate plant modifi-cations to permit continued operation of the plants which have been identi-fied up to now as having potential PTS problems.
The most beneficial actions for these plants in the short term would be to:
- l. Make certain that the metallurgical properties of the vessel beltlines are established adequately with respect to fracture toughness.
- 2.
Determine which is the most effective in-service inspection capability for the beltline that current technology can provide.
For those welds of principal concern, inspection should be accomplished, if practical, at the next refueling shutdown using such techniques, if such inspec-tion has not previously been accomplished.
- 3.
Provide effective operator training to avoid pressurized thermal shock and provide capability to diagnose events that could cause it.
- 4.
Examine the depressurization capability for these plants and train operators when and how to use it.
- 5.
Provide a demonstration of pressure vessel annealing to recover fracture toughness.
There are many intricacies associated with evaluation of pressurized ther-mal shock consequences that deserve attention, but the above actions would be the most effective contributors to assuring that pressurized thermal shock does not create public safety problems.
2640
Honorable Nunzio June 7, 1982 The ACRS plans to continue its review of pressurized thermal shock and the related NRC Staff program.
The Committee will report further at an appro-priate time.
Sincerely,
~~
2641 P. Shewmon Chairman