ML20245D571

Safety Evaluation Re Rust in Lower Containment Spray Header Due to Leaking Isolation Valves

ML20245D571
Person / Time
Site:	Browns Ferry
Issue date:	04/19/1989
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20245D567	List: ML20245D563 ML20245D571
References
TAC-00454, TAC-454, NUDOCS 8905010055
Download: ML20245D571 (4)

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ENCLOSURE 1 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION CONCERNING RUST IN LOWER CONTAINMENT SPRAY HEADER DUE TO LEAKING ISOLATION VALVES TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT, UNIT 2 DOCKET NO. 50-260

1.0 INTRODUCTION

The Tennessee Valley Authority (TVA or the licensee) submitted Licensee Event Report (LER) 88-003-000 concerning the presence of rust in the lower containment spray header (LCSH) at Browns Ferry Nuclear Plant, Unit 2. The staff issued a safety evaluation dated December 20, 1988 which concluded that performance of the committed work was satisfactory for short-term measures. However, long-tenn measures to prevent or mitigate the possible occurrence of excessive rust in both headers (and those of Units 1 and 3) in the future needed to be established should the isolation valves develop leaks.

In a letter dated March 17, 1989, TVA reported it had completed its commitment to clean (hydrolazing) the rust from the header, measure wall thickness of the lower header to assure structural integrity, and rework the inboard and the outboard isolation valves. Rework involved machining the valve discs and l installing new seat rings in the inboard valve. Both valves passed their leak rate tests.

As a long-term measure. TVA comitted to perform a visual inspection of the Unit 2 LCSH during the next outage, and if no problems are found, the LCSH will be inspected every five years at the appropriate outage. TVA will also inspect the LCSH for Units 1 and 3 before restart of the respective unit. If no rust problems are found, the LCSHs will be inspected approximately every five years at the appropriate outage.

2.0 EVALUATION TVA has restored the LCSH and its nozzles to full operational efficiencf,'

provided adequate assurance of the lower header's structural integrity and the leak tightness of the isolations valves for the near term. The staff finds TVA's planned actions of in-service inspections of the LCSH for each unit provide adequate long-term measures to detect damage caused by leaking isolation valves.

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3.0 CONCLUSION

Based on TVA's commitment to perform the above described inspections, the staff considers the open item concerning the long-term measures for preventing or I mitigating rust in the lower containment spray headers to be closed.

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l SALP INPUT FROM THE ENGINEERING BRANCH l FOR BROWNS FERRY NUCLEAR PLANT, UNITS 1, 2 AND 3 Functional Area:

Title / TAC Nos. TAC 00454 A. Licensing Activities

1. Assurance of Quality, Including Management Involvement and Control Assessment: There is evidence of prior planning and assignment of priorities; procedures for control of activities are stated and defined.

Rating: 2

2. Approach top Resolution of Technical Issues from a Safety Standpoint Assessment: Approaches are viable and generally sound and thorough.

Rating: 2

3. Responsiveness to NRC Initiatives Assessment: Responses are viable and generally sound and thorough.

Rating: 2

4. Reporting and Analysis of Operational Events Assessment: Events are properly identified, but some analyses are marginal.

Rating: 2

5. Staffing (IncludingManagement) .-

Assessment: N/A Rating:

6. Training and Qualification Program Effectiveness Assessment: N/A Rating:

7. Overall Rating for Licensing Activity in Functional Area Assessment: The licensee has responded quickly to us and has demonstrated an adequate knowledge of the. technical decisions. Higher ratings were not reconsnended because the last step of integrating the actions of this item (inserting the subject inspections into the appropriate in-service inspection instructions) was not addressed.

Rating: 2 l

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