Safety Evaluation for Operation of Browns Ferry, Units 1 and 2, Following the March 22, 1975 Fire (NUREG-0061, Initial Report)
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Date Published: March 1976
Division of Operating Reactors
Office of Nuclear Reactor Regulation
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001
On March 22, 1975, a fire at the Browns Ferry Nuclear Plant caused a shutdown of Units 1 and 2. The facility subsequent to the shutdown was found to have incurred substantial damage to power, control, and instrumentation wiring. All three units are presently in the shutdown condition with the fuel removed from the vessels for Units 1 and 2; the Unit 3 reactor is still under construction with operation for that unit scheduled for early 1976. An overall program has been developed by the licensee delineating the necessary activities required to restore damaged portions of the facility to a safe level so that operation of Units I and 2 can be resumed. This program has been described in "Plan for Evaluation, Repair and Return to Service of Browns Ferry Units 1 and 2 (March 22, 1975 Fire)" dated April 13, 1975, and revisions thereto up to and including Revision 37 (the Plan).
As a result of the fire an NRC review program was developed consisting of three major and parallel elements. The first element was the investigation conducted by the Office of Inspection and Enforcement (OI&E) of events leading to the fire, fire fighting efforts, sequence of operational events and problems experienced with the nuclear steam supply system, interaction between units, and the response of TVA, and State and Local authorities. This phase of the NRC program has been completed and the results are given in the OI&E Investigation Report of the March 22, 1975 Fire at the Browns Ferry Nuclear Station, dated July 25, 1975.
The second element of the program, being performed by the Office of Nuclear Reactor Regulation has as its objectives (1) to assure that a safe plant configuration was attained and is being maintained subsequent to the fire, (2) to assure safety during removal of fuel from Units 1 and 2, (3) to assure plant safety during fire damage removal and restoration, and (4) to determine that the design changes that are required for restoration of these plants to operational status are acceptable. (See Attachment 1 for Chronology)
The third element of the NRC program consists of the review being performed by the Special Browns Ferry Review Group established on March 26, 1975. Efforts of this review group will be to prepare for NRC, recommendations to change, as required, NRC policies, procedures, and technical requirements in regard to fire protection at nuclear 'power plants. The Review Group's report is anticipated about March 1, 1976.
The NRR reviewers of Browns Ferry Plant restoration and modifications have had the benefit of informal discussions with members of the Special Review Group (SRG). In this way, the NRR reviewers have been aware of the recommendations to be made by the SRG. These recommendations were considered and appropriately implemented in Browns Ferry. In some cases, the SRG recommended that further generic consideration be given to certain aspects of fire protection or recommended that consideration be given to changing NRC requirements or guidelines. In the areas that require additional future consideration, the Browns Ferry modifications will be reevaluated when any new position has been developed.
The SRG also had the benefit of the ongoing TVA and NRC evaluations of the Browns Ferry fire and the proposed restoration and corrective modifications. Copies of the Plan and all revisions thereto were supplied to the SRG, as well as NRR correspondence, meeting summaries, and safety evaluations for NRR licensing actions during the course of restoration.
A comparison of the Special Review Group's recommendations with the modified Browns Ferry Plant will be presented in a supplement to this report.
Thus far there have been three significant licensing actions taken to meet the objectives of the review performed by the Office of Nuclear Reactor Regulation. First, the plant Technical Specifications were changed to Temporary Technical Specifications designed to assure that a safe configuration was maintained following the fire, while further corrective action plans were under development. These Temporary Technical Specifications and the associated safety evaluation were issued with Amendment 9 to License DPR-33 (Unit 1) and Amendment No. 6 to License DPR-52 (Unit 2) on May 9, 1975.
The Technical Specifications were again changed to provide for the removal of fuel from both Unit 1 and 2 reactor vessels and placement into the respective storage pools. These changes and their associated safety evaluation were issued with Amendment 10 to License DPR-33 and Amendment 7 to License DPR-52 on June 13, 1975. These changes also assure that the necessary protective equipment to assure protection of- the fuel in the storage pools from damage would be available with adequate redundancy and would be protected against adverse interaction with the fire affected wiring and cables, while such fire damage was removed and when the damaged wiring and cabling was replaced.
On September 2, 1975, NRC issued Amendment 14 to License DPR-33 and Amendment 11 to License DPR-52 that authorized restoration and modification activities described in the Plan up to and including Revision 20. The safety evaluation accompanying those amendments describes the work that was authorized and presents our conclusions as to its acceptability. Part of our conclusion at that time was that additional measures would be required to enable us to find that the plant was acceptable for return to operation. By letter dated August 29, 1975, TVA agreed to provide further improvements in fire protection. The revisions to the Plan from Revisions 22 to 37 included provisions of the implementation of the commitments made in the August 29, 1975 letter.
This Safety Evaluation Report presents the results of our evaluation regarding the acceptability of the restoration and modifications at the Browns Ferry Nuclear Plant Units 1 and 2 to establish that the facility may be operated in the restored and modified condition without endangering the health and safety of the public. Although some of these activities were the subject of the September 2, 1975 evaluation, a complete evaluation will be presented herein. This will present a total picture of the substantial enhancement of the capability of the facility that is now provided to prevent and withstand a fire. In our evaluation, we made use of our own consultants and those of the licensee. (See Attachment 2)
The TVA modification program related to fire detection and extinguishment is being conducted in two stages. The first stage covers those changes to be accomplished prior to restart, which is currently scheduled by TVA for the end of March 1976. Section 7.5 of this report discusses these changes and provides the staff evaluation for approval. Section 7.6 discusses the second stage modifications which are intended to be completed at the first refueling outage of either unit. It provides the staff evaluation for approval of the design criteria.
A letter from the Office of Inspection and Enforcement will provide confirmation that all of the work described in the Plan as being required prior to restart has been completed before the authorization for return to operation will be issued.