ML17195A953

Safety Evaluation Approving Util Mods to Containments & Torus Attached Piping as Documented in COM-02-041-1 Through 7 Entitled, Technical Evaluation of Dresden Nuclear Power Station Units 2 & 3,Plant-Unique Analysis Rept.

ML17195A953
Person / Time
Site:	Dresden
Issue date:	09/18/1985
From:	Office of Nuclear Reactor Regulation
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ML17195A951	List: ML17195A950 ML17195A952 ML17195A953 ML20204G817 ML20205B027
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NUDOCS 8509230625
Download: ML17195A953 (3)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION*

WASHINGTON, D. C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION*

RELATED TO MARK I CONTAINMENT LONri-TERM PROGRAM STRUCTURAL REVIE~

COMMONWEALTH EDISON COMPANY DOCKET NOS. 50-237/249

1.0 INTRODUCTION

ThP. capability of the boiling water reactor (BWR) Mark I containment structures and pipin9 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.SSa. 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 program 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, Commonwealth Edison

. Company (CECo) has completed all modifications on the Dresden Nuclear Power Station, Unit ffos. 2 and 3 containments and torus attached piping.

The adequacy of these modifications was documented in a report prepared by the Nutech Engineers, Inc. (Nutech)~and Sargent and Lundy Engineers (S&L) COM-02-041-1 through 7 titled "Dresden Nuclear Power Station, Units 2 and 3, ... Plant Unique Analysis Report "(PUA 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 Dresden llnits 2 and 3 was described jn the plant-unique analysis report (PUAR) prepared by Nutech and S&L. This report describes modifications performed on containment structures and torus attached piping at Dresden Units 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. Thamaterials, desiq" and fabrication requirements of the modifications were in accordance with the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (B&PV) Code, Division 1,Section III with Addenda through Summer 1977 and Code Case N-197, 11 Service Limits for Containment Vessels 11

• Modifications were performed in accordance with the requirements of Section XI of the same codP. To determine the appropriate code allowable service limits for the specified loading combinations, the repnrt followed guidelines of NUREG-0661 and the GE report, NED0-24583-1, 11 Mark I Containment Program Structural Acceptance Criteria Plant Unique Analysis Application Guide. 11 The portion of the 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, Nutech and S&L employed the computer programs STARDYNE, PISTAR and PIPSYS as major tools to perform the analyses. Results of the analyses were sununarized to show that modifications are adequate under various loading combinations.

The adequacy of the modified containment structures and torus attached pipi~g was audited hy the FRC. FRC developed audit procedures for all Mark I long-tenn 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-C5506-324, "Audit for Mark I Containment Long-Term Program - Structural Analysis for Operating Reactors - Commonwealth Edison Company - Dresden Nuclear Power Station, Units 2 and 3. 11 The audit verified 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, 11 Augmented Class ~/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 Dresden Units 2 and 3.

3.0 CONCLUSION

S The modifications perfonned at Dresden Units 2 and 3 followed the ouidelines rif N11Prn-Ofi61 and its supplement and met the respective requirements *of Sections III and XI of thP. ASME Boiler and Pressure Vessel Code r.nd are, therefor~, acceptable. CECo analyses have been verified by the FRC audit and approved by the staff*under the LOCA and SRV discharge loads.

4.0 ACKNOWLEDGEMENT Principal Contributor: H. Shaw Date: Septembe~ 18~ 1985.

Attached: TER prepared by Franklin Research Center, dated June ?l, 1985