ML18031A494

Requests TVA PRA & Critical Analysis of Strengths & Weaknesses of Pra,For Current Evaluation & as Condition for Restart

ML18031A494
Person / Time
Site:	Browns Ferry
Issue date:	06/17/1986
From:	Bernero R Office of Nuclear Reactor Regulation
To:	White S TENNESSEE VALLEY AUTHORITY
References
RTR-NUREG-CR-2802 TAC-63178, NUDOCS 8606240002
Download: ML18031A494 (6)

Text

Docket No. 50-259/260/296 Mr.

S.

A. White Manager of Nuclear Power Tennessee Valley Authority GN 38A Lookout Place 1101 Market Street Chattanooga, Tennessee 37401

Dear Mr. White:

, ~~~ y7 3986 Re:

Browns Ferry Nuclear Plant, Units 1, 2 8 3

Before I returned to reactor licensing work at the NRC, I was, for about five years, director of NRC's research in probabilistic risk analysis (PRA).

During that time, we at the

NRC, and some in the nuclear utility industry, sponsored many PRA studies of nuclear power plants to develop effective PRA methods and to understand plant reliability and other aspects as discovered by the studies.

One of the utilities which made substantial contributions in the PRA field was the Tennessee Valley Authority (TVA).

In a few instances it was possible for the same nuclear, power plant to be studied by different teams using different methods.

These crosschecks are especially valuable.

For

example, a study of the Oconee plant sponsored by NRC used the simplified methods of the Reactor Safety Study Methodology Applications Program (RSSMAP).

Later, Duke Power Company and the Nuclear Safety Analysis Center conducted a more comprehensive PRA of the same plant and discovered a great deal more important information, and thereby they demonstrated substantial shortcomings in the RSSMAP methods.

A cross comparison that has long held interest for me concerns the Browns Ferry plant.

Early in 1980 I reached an understanding with TVA that we would conduct independent PRAs of the Browns Ferry plant while taking care that the work of one team did not become available prematurely to the other team so that their independence might be compromised.

The NRC study of Browns Ferry was published as NUREG/CR-2802, "Interim Reliability Evaluation Program Analysis of the Browns Ferry, Unit 1, Nuclear Plant," in 1982.

I believe that substantial work on TVA's own PRA study continued until sometime in 1983-1984 but the results of the work have never been published.

The NRC and TVA are now engaged in extensive discussions of what actions TVA must complete prior to restart of each of the Browns Ferry reactors.

The availability of PRA analysis for the plants constitutes a valuable improvement in our ability to set the agenda and its priorities.

Of course, we have the NRC-sponsored study already available to all.

I believe it is necessary to have the TVA PRA study of Browns Ferry available as well.

Therefore, I request that you submit this study to us in the near future.

I consider its availability sufficiently important that it is a necessary part of the current evaluation and a condition for restart of any Browns Ferry plant.

8606240002 B60617

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• DOCK 05000259 P

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,ggg 17 1S86 I believe the Browns Ferry PRA by TVA is also a very important factor in completing the severe accident plant evaluations of the Browns Ferry units and the other reactors with Mark I containments, as called for in the NRC's Severe Accident Policy Statement.

Its importance here derives from the fact that Browns Ferry is the most studied Mark I plant after Peach Bottom, the IDCOR and NRC refer'ence Mark I plant.

I recognize that the Browns Ferry PRA work may not be complete, is by now a bit

dated, and may suffer from some other recognized deficiencies.

With the release of any PRA study there is a substantial risk of people making uncritical use of specific probabilities or consequences.

Since 1979 NRC has had an explicit policy against the uncritical use of PRA results. 'herefore, I

further request that you provide a competent analysis to accompany all copies of the PRA which will identify its strengths and weaknesses.

This critique should identify areas in which the TVA PRA of Browns Ferry may be incomplete and identify data or methodology used which may lead it to underestimate or overestimate probability or consequences.

Certainly if such critique is in part already incorporated in the PRA it should be noted.

Please advise me of the schedule on which you expect to respond.

Sincerely,

~krak Sigaol Rga

@0~.Qo SQRQoz Robert M. Bernero, Director Division of BWR Licensing Office of Nuclear Reactor Regulation cc:

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Mr. S.

A. '1!hite Tennessee Valley Authority Browns Ferry Nuclear Plant Units 1, 2, and 3

CC:

tl. S. Sanqer, Jr., Esauire General Counsel Tennessee Valley Authority 400 Commerce Avenue E

11B 330 Knoxville, Tennessee 37902 ter.

Ron Roaers Tennessee Valley Authority 5N 130B Lookout Place Chattanooga, Tennessee 37402-2801

Chairman, Limestone County Commission Post Office Box 188 Athens, 'Alabama 356'll E

Ira L. Meyers, M.D.

State Health Officer State Department of Public Health State Office Building Montqomery, Alabama 36130 Mr. K. t!. Mhitt E3AB 400 Hest Summit Hill Drive Tennessee Valley Authority Knoxville, Tennessee 37902 Reqional Administrator, Reqion II U. S. t(uclear Regulatory Commission 101 Marietta Street, Suite 3100 Atlanta, Georaia 30303 tlr. Steven Roessler U. S. Nuclear Regulatory Commission Reactor Training Cente~

Osborne Office Center, Suite 200 Chattanooga, Tennessee 37411 1!. C. Bibb Site Director, BFNP Tennessee Valley Authoritv Post Office Box 2000

Decatur, Alabama 35602 Resident Inspector U. S. Nuclear Reaulatory Commission Route "2, Box 311

Athens, Alabama 35611 Mr. Donald L. l!illiams, Jr.

Tennessee Valley Authority 400 1!est Summit flill Drive, l!10B85 Knoxville, Tennessee 37902 Robert L. Lewis, t1anaper, RFNP Tennessee Valley Authority Post Office Box 2000

Decatur, Alabama 35602.