ML021420459

VC Summer - Request for Use of ASME Code Case N-597 as Alternative Analytical Evaluation of Wall Thinning

ML021420459
Person / Time
Site:	Summer
Issue date:	05/22/2002
From:	John Nakoski NRC/NRR/DLPM/LPD2
To:	Byrne S South Carolina Electric & Gas Co
Cotton K, NRR/DLPM, 415-1438
References
TAC MB5056
Download: ML021420459 (7)

Text

May 22, 2002 Mr. Stephen A. Byrne Senior Vice President, Nuclear Operations South Carolina Electric & Gas Company Virgil C. Summer Nuclear Station Post Office Box 88 Jenkinsville, South Carolina 29065

SUBJECT:

VIRGIL C. SUMMER NUCLEAR STATION - REQUEST FOR THE USE OF ASME CODE CASE N-597 AS AN ALTERNATIVE ANALYTICAL EVALUATION OF WALL THINNING (TAC NO. MB5056)

By letter dated May 13, 2002, you submitted a request for Virgil C. Summer Nuclear Station (VCSNS) for relief from the American Society of Mechanical Engineers (ASME) Code Section XI (IWA-3100). IWA-3100 provides the process for the disposition of flaw examination evaluations that exceed the acceptance standards for materials and welds applicable to the construction of the component. As an alternative to IWA-3100, you proposed to use the provisions of ASME Boiler and Pressure Vessel Code Case N-597, Requirements for Analytical Evaluation of Pipe Wall Thinning,Section XI, Division I, for the analytical evaluation of Class 2 and 3 carbon and low-alloy steel piping components subjected to wall thinning as a result of flow-accelerated corrosion (FAC).

Code Case N-597 has not been endorsed by the NRC, but has been found conditionally acceptable. Since the Code case does not address inspection requirements and wall thinning rates, the staff determined that the Code case needs to be reviewed prior to use.

Although Code Case N-597 can be applied to other corrosion phenomena in addition to FAC, you provided information related only to the application of this Code case to FAC. The application of this Code case to corrosion phenomena other than FAC is not within the scope of the staffs evaluation.

Based on its review, the NRC staff has concluded that your alternative to use Code Case N-597 and industry standard NSAC-202L-R2, Recommendations for an Effective Flow-Accelerated Corrosion Program, with the clarification of the application of shall and should in this industry standard, provides an acceptable level of quality and safety. Therefore, the proposed alternative to use Code Case N-597 for the analytical evaluation of Class 2 and 3 carbon and low-alloy steel piping items subjected to wall thinning as a result of flow-accelerated corrosion is authorized pursuant to 10 CFR 50.55a(a)(3)(i).

In addition, components to which this Code case is applied must be repaired or replaced in accordance with the construction code of record and owners requirements, or a later approved edition of ASME Section III prior to reaching the allowable minimum wall thickness as specified in this Code case.

S. Byrne The NRC staff has completed its evaluation of this request; therefore, we are closing TAC No.

MB5056.

A copy of the staffs Safety Evaluation is enclosed.

Sincerely,

/RA/

John A. Nakoski, Chief, Section 1 Project Directorate II Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-395

Enclosure:

As stated

S. Byrne The NRC staff has completed its evaluation of this request; therefore, we are closing TAC No.

MB5056.

A copy of the staffs Safety Evaluation is enclosed.

Sincerely,

/RA/

John A. Nakoski, Chief, Section 1 Project Directorate II Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-395

Enclosure:

As stated DISTRIBUTION:

PUBLIC PDII-1 R/F H. Berkow J. Nakoski K. Cotton E. Dunnington OGC G. Hill (2)

ACRS S. Rosenberg, RII Accession Number: ML021420459 *See previous concurrence.

OFFICE PDII-1/PM PDII-1/LA OGC* PDII-1/SC NAME KCotton EDunnington AHodgdon JNakoski DATE 05/22/02 05/22/02 05/21/02 05/22/02 OFFICIAL RECORD COPY

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO THE USE OF CODE CASE N-597 AS AN ALTERNATIVE TO IWA-3100 VIRGIL C. SUMMER NUCLEAR STATION DOCKET NUMBER 50-395

1.0 INTRODUCTION

The inservice inspection of the American Society of Mechanical Engineers (ASME) Code Class 1, 2, and 3 components must be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel (B&PV) Code and applicable edition and addenda as required by 10 CFR 50.55a(g), except where specific written relief has been granted by the Commission pursuant to 10 CFR 50.55a(a)(3). 10CFR 50.55a(a)(3) states, in part, that alternatives to the requirements may be used provided the licensee demonstrates that (i) the proposed alternatives would provide an acceptable level of quality and safety, or (ii) compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

Pursuant to 10 CFR 50.55a(g)(4), ASME Code Class 1, 2, and 3 components (including supports) must meet the requirements, except the design and access provisions and the preservice examination requirements, set forth in the ASME Code,Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components, to the extent practical within the limitations of design, geometry, and materials of construction of the components. The regulations require that inservice examination of components and system pressure tests conducted during the first 10-year interval and subsequent intervals comply with the requirements in the latest edition and addenda of Section XI of the ASME Code incorporated by reference in 10 CFR 50.55a(b) 12 months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein and subject to Commission approval. The applicable ASME Code for Virgil C. Summer Nuclear Station (VCSNS) is the 1989 Edition, no Addenda.

By letter dated May 13, 2002, South Carolina Electric & Gas Company (SCE&G, the licensee) submitted a request for relief from the ASME Code Section XI (IWA-3100) for VCSNS that provides the process for the disposition of flaw examination evaluations that exceed the acceptance standards for materials and welds specified in the Section III Edition applicable to the construction of the component. The request provides for an analytical evaluation of Class 2 and 3 carbon and low-alloy steel piping items subjected to wall thinning as a result of flow-accelerated corrosion (FAC).

2.0 BACKGROUND

2.1 ASME Section XI Code Requirement ASME B&PV Code Section XI (IWA-3100) provides the process for the disposition of flaw examination evaluations that exceed the acceptance standards for materials and welds specified in the Code applicable to the construction of the component. This provision stipulates that the disposition shall be subject to review by the regulatory and enforcement authorities having jurisdiction at the plant site.

2.2 Proposed Alternative As an alternative to the requirements of IWA-3100, Evaluation, the licensee proposes to use the provisions of ASME B&PV Code Case N-597, Requirements for Analytical Evaluation of Pipe Wall Thinning,Section XI, Division 1, for the analytical evaluation of Class 2 and 3 carbon and low-alloy steel piping items subjected to wall thinning as a result of FAC rather than to repair the component if the construction code minimum wall thickness has been reached. This Code case stipulates that the methods of predicting the rate of wall thickness loss and the predicted remaining wall thickness shall be the responsibility of the owner. The licensee has procedural controls in its FAC program that provide direction for calculating wear rates, forecasting remaining life, and conducting inspections of piping components susceptible to FAC. The methodology is consistent with industry standard NSAC-202L-R2, Recommendations for an Effective Flow-Accelerated Corrosion Program, for calculating wear rates, forecasting remaining life, and conducting inspections as programmatic requirements.

3.0 EVALUATION The Code requires that the component whose flaws exceed the acceptance standards must be evaluated to determine disposition that shall be subjected to review by the regulatory and enforcement authorities having jurisdiction at the plant site. As an alternative to the Code requirements, the licensee has proposed to use Code Case N-597 for Class 2 and 3 carbon and low-alloy steel piping items for VCSNS. The staff has reviewed this Code case previously in preparing its position for incorporation into 10 CFR Part 50 and determined that it is conditionally acceptable. Since the Code case does not address inspection requirements and wall thinning rates, the staff determined that the Code case needs to be reviewed and approved prior to use.

The staff finds that the licensees use of Code Case N-597 provides an acceptable approach for determining wall thinning as a result of the FAC phenomena; however, the approach makes note of the owners responsibility in developing the methods of predicting the rate of wall thickness loss and the value of the predicted remaining wall thickness. Although Code Case N-597 can be applied to other corrosion phenomena in addition to FAC, the licensee provided information related only to the application of this Code case to FAC. Therefore, the application of this Code case to corrosion phenomena other than FAC is not within the scope of this evaluation.

The licensee provided information on the plant inspection and evaluation procedures for calculating wear rates, remaining life, and predicting remaining wall thickness. These

procedures are based on industry standard NSAC-202L-R2. Despite the ambiguities in this industry document, the staff finds the methods summarized for controlling FAC acceptable.

The licensee, in its implementation procedures, has resolved the ambiguities in NSAC-202L-R2; in particular, the licensee clarified the following definitions used in the plant procedures governing its FAC program:

Shall is a mandatory requirement.

Should is non-mandatory, but is considered the preferred method to comply with a specific requirement, unless otherwise determined by engineering support personnel or management.

Components to which this Code case is applied must be repaired or replaced in accordance with the construction code of record and owners requirements or a later approved edition of ASME Section III prior to reaching the allowable minimum wall thickness as specified in Code Case N-597.

Therefore, the NRC staff finds that the licensees alternative to use Code Case N-597 as applied through industry standard NSAC-202L-R2, with clarifications of the application of shall and should in this standard, provides an acceptable level of quality and safety for use in connection with Class 2 and 3 carbon and low-alloy steel piping subject to FAC.

4.0 CONCLUSION

The NRC staff concludes that the use of Code Case N-597 and industry standard NSAC-202L-R2, with clarification of the terms shall and should in this standard, as an alternative evaluation for Class 2 and 3 carbon and low-alloy steel piping items subject to FAC is authorized pursuant to 10 CFR 50.55a(a)(3)(i). The application of this Code case to corrosion phenomena other than FAC is not within the scope of this evaluation. In addition, components to which this Code case is applied must be repaired or replaced in accordance with the construction code of record and owners requirements prior to reaching the allowable minimum wall thickness as specified in this Code case. At such time as Code Case N-597 is incorporated into 10 CFR Part 50, and the licensee intends to continue to implement Code Case N-597, the licensee should follow all the provisions in Code Case N-597 with limitations issued in the rule, if any.

Principal Contributor: C. Lauron Date: May 22, 2002

Mr. Stephen A. Byrne VIRGIL C. SUMMER NUCLEAR STATION South Carolina Electric & Gas Company cc:

Mr. R. J. White Ms. Kathryn M. Sutton, Esquire Nuclear Coordinator Winston & Strawn Law Firm S.C. Public Service Authority 1400 L Street, NW c/o Virgil C. Summer Nuclear Station Washington, DC 20005-3502 Post Office Box 88, Mail Code 802 Jenkinsville, South Carolina 29065 Resident Inspector/Summer NPS c/o U.S. Nuclear Regulatory Commission 576 Stairway Road Jenkinsville, South Carolina 29065 Chairman, Fairfield County Council Drawer 60 Winnsboro, South Carolina 29180 Mr. Henry Porter, Assistant Director Division of Waste Management Bureau of Land & Waste Management Department of Health & Environmental Control 2600 Bull Street Columbia, South Carolina 29201 Mr. Gregory H. Halnon, General Manager Nuclear Plant Operations South Carolina Electric & Gas Company Virgil C. Summer Nuclear Station, Mail Code 303 Post Office Box 88 Jenkinsville, South Carolina 29065 Mr. Melvin N. Browne, Manager Nuclear Licensing & Operating Experience South Carolina Electric & Gas Company Virgil C. Summer Nuclear Station, Mail Code 830 Post Office Box 88 Jenkinsville, South Carolina 29065