ML18029A540

Safety Evaluation Re Mark I Containment long-term Program Structural Review for Plant.Mods Follow NUREG-0661 Guidelines & Acceptable.Analyses Verified & Approved

ML18029A540
Person / Time
Site:	Browns Ferry
Issue date:	05/06/1985
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML18029A537	List: ML18029A536 ML18029A538 ML18029A539 ML18029A540
References
RTR-NUREG-0661, RTR-NUREG-661 NUDOCS 8505160247
Download: ML18029A540 (5)

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO MARK I CONTAINMENT LONG-TERM PROGRAM STRUCTURAL REVIEW TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT, UNITS 1, 2 AND 3 DOCKET NOS. 50-259, 50-260 and 50-296

1.0 INTRODUCTION

The capability of the boiling water reactor (BWR) Mark I containment structures and piping systems to withstand the effect of hydrodynamic loads resulting from a loss of coolant accident (LOCA) and/or a safety relief valve (SRV) discharge was not considered in the original design of the structures. The resolution of this issue was divided into a short-term program and a long-term program.

Based on the results of the short-term program, which verified that each Mark I containment would maintain its integrity and functional capability when subjected to the loads induced by a design-basis LOCA, the NRC staff granted an exemption relating to the structural safety requirements of 10 CFR 50.55(a). The study was reported in NUREG-0408, "Mark I Containment Short Term Program".

The objective of the long-term program was to maintain a margin of safety when the Mark I containment structures and piping system are subjected to additional hydrodynamic loads. The detailed guidance of the long-term pro-gram are contained in the NRC Safety Evaluation Report, NUREG-0661, "Mark I Containment Long-Term Program" and its supplement which describe the generic hydrodynamic load definition and structural acceptance criteria consistent with the requirements of the applicable codes and standards.

To fulfill the objective of the long-term program, Tennessee Valley Authority (TVA) has completed or is in the process of completing all modifications on the Browns Ferry Nuclear Plant containment and torus attached piping. The adequacy of these modifications was documented in a report prepared by TVA: CEB 83-24, titled, Browns Ferry Nuclear Plant, Torus Integrity Long Term Program, Plant Unique Analysis Report.

The Franklin Research Center (FRC) was contracted to review the structural adequacy issue for compliance with the staff's acceptance criteria.

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2.0 EVALUATION The Mark I long-term program of the Browns Ferry Nuclear Plant, Units 1, 2 and 3 was described in the plant-unique analysis report (PUAR) prepared by TVA. This report describes modifications performed on containment structures and torus attached piping at the Browns Ferry Nuclear Plant, Units 1, 2 and 3. Areas covered by the report include the torus shell, external support system, vent header system, internal structures, torus attached pipings, SRV lines and vent pipe penetrations. The materials, design and fabrication requirements of the modifications were in accordance with the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (BKPV) Code, Division 1,Section III with Addenda through Summer 1978 and Code Case N-197, "Service Limits for Containment Vessels".

Modifications were performed in accordance with the requirements of Section XI of the same code. To determine the appropriate code allowable service limits for the specified loading combinations, the TVA report followed guidelines of NUREG-0661 and the GE report, NED0-24583-1, "Mark I Containment Program Structural Acceptance Criteria Plant Unique Analysis Application Guide." The portion of the TVA report applicable to loadings and loading combinations was audited by BNL, and results of that audit are discussed in a separate Safety Evaluation.

Using the properly determined loadings and loading combinations, TVA employed the computer program STARDYNE as a major tool to perform the analyses. STARDYNE is a program which has been widely used in the industry for similar purposes and was approved by NRC. Results of the analyses were summarized to show that modifications are adequate under various loading combinations.

The adequacy of the modified containment structures and torus attached piping was audited by the FRC. FRC developed audit procedures for all Mark I long-term program users, which is described in detail in the FRC TER-C5506-308, "Audit Procedures for Mark I Containment Long-Term Program - Structural Analysis." The review performed by FRC followed this document closely.

Results and conclusions of this effort were reported in FRC TER-C5506-323.

"Audit for Mark I Containment Long-Term Program-Structural Analysis for Operating Reactors-Tennessee Valley Authority, Browns Ferry Nuclear Plant, Units 1, 2 and 3." The audit verified TVA analyses by examining mathematical models and loading combinations used, and summarized the results to see whether the modifications met the required criteria. A check list was compiled to ensure the completeness of the auditing. The staff has reviewed the FRC report and concurs with its conclusions that the modifications meet the Mark I Containment Long-Term Program objective. An augmented fatigue evaluation method for ASME Code Class 2/3 piping was developed by MPR for GE in MPR Report-751, titled, "Augmented Class 2/3 Fatigue Evaluation Method and Results for Typical Torus attached on SRV Piping System", dated November 1982. This report was reviewed by the staff and the conclusion that all torus piping systems have a fatigue usage of less than 0.5 during the plant life is acceptable for the Browns Ferry Nuclear Plant, Units 1, 2 and 3.

3.0 CONCLUSION

S The modifications performed at the Browns Ferry Nuclear Plant, Units 1, 2 and 3 followed the guidelines of NUREG-0661 and its supplement and met the respective requirements of Sections III and XI of the ASME Boiler and Pressure Vessel Code and are, therefore, acceptable. TVA's analyses have been verified by the FRC audit and approved by the staff under the LOCA and SRV discharge loads.

Principal Contributor: H. Shaw Date: May 6, 1985 Attached: TER prepared by Franklin Research Center, dated December 20, 1984

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