NRC Generic Letter 81-20, Safety Concerns Associated with Pipe Breaks in the BWR Scram System

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WASHINGTON, D. C. 20555

APR 10 1981

TO ALL BWR LICENSEES

SUBJECT: SAFETY CONCERNS ASSOCIATED WITH PIPE BREAKS IN THE BWR SCRAM SYSTEM (81-20)

Yesterday, we discussed With Your representatives the NRC's Office of Analysis and Evaluation of Operational Data report entitled, "Safety Concerns Associated with Pipe Break in the BWR Scram System." The Report describes a potential sequence of events which could result from a break in the BWR scram discharge piping during a scram condition concurrent with an inability to reclose the scram outlet valves. Concerns identified include the quality of the scram discharge volume piping, the ability to detect and isolate such a break, and potential water and steam degradation of available ECCS equipment as a result of the break. A number of recommendations were made in the report to remedy the potential concerns.

We are presently studying these issues and recommendations to determine whether BWR design basis accidents should be modified and as a consequence whether appropriate actions should be taken for operating BWR plants. The purpose of this letter is to provide to you the AEOD report so that you can evaluate its applicability to your plant and determine appropriate remedial measures, and to request information from you concerning your evaluation in order to assist in determining an appropriate course of action for the NRC.

Therefore, pursuant to 10 CFR 50.54(f) please provide us in writing, under oath or affirmation, within 45 days of your receipt of this letter, the following information:

1. A generic evaluation of the applicability of the indicated sequences of events in the report to the BWR plant design, your estimate of the probability of occurrence of such sequences, and the bases for these conclusions,

2. A generic evaluation of the applicability of the indicated safety concerns and findings in the report relative to BWR plant construction, design, and operation and the bases for these conclusions, and

.

BWR Licensees3. A generic evaluation of the recommendations listed in the report discussing the degree to which the recommendations are being or have been implemented with bases why the recommendations should or should not be completely implemented on BWRs.

In addition, pursuant to 50.54(f) provide the following information in writing within 120 days of your receipt of this letter:

1. Provide an evaluation of the applicability of the 45 day generic evaluation to your plant. This evaluation should contain plant specific considerations related to system design, instru-

mentation, construction, operation, operator training, and emergency procedures for your plant.

2. In light of the AEOD report and the 45 day generic evaluation, provide a plant specific evaluation of your facility's Scram Discharge Volume System conformance to GDC 14, GDC 35 GDC 55, SS50.2(v), 50.55a (including footnote 2): and SS50.46 of the Commission's regulations. This evaluation should address which portions of the Scram Discharge Volume System are considered to be part of the reactor coolant pressure boundary, the quality group and safety class of the Scram Discharge Volume System, the codes and standards used for the design, fabrication ,and inservice inspection of this system and your bases for the above classifications or groupings.

3. Provide by analysis or reference a demonstration that a break located anywhere in the Scram Discharge Volume System could meet the requirements of 650.46 of the Commission's regulations, taking into account the environmental and flooding aspects of such a break.

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BWR Licensees -3-

This request for information was approved by GAO under a blanket clearance number R0072 which expires November 30, 1983. comments on burden and duplication may be directed to the U.S. General Accounting Office, Regulatory Reports Review, Room 5106, 441 G Street, N.W., Washington, D.C. 20548.

Sincerely,

Darrell G. Eisenhut, Director Division of Licensing Office of Nuclear Reactor Regulation

Enclosure:

As stated

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