ML20076F863

Requests Relief from ASME Code Requirement for Performing Hydrostatic Pressure Tests After Repairs by Welding or Installation of Replacement Items by Welding on Pressure Retaining Boundary of Class 1,2 & 3 Components

ML20076F863
Person / Time
Site:	Sequoyah
Issue date:	10/11/1994
From:	Zeringue O TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9410180204
Download: ML20076F863 (6)

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Tenne $sce Va% Aumny. Pod One &a POOO SMSDag Tennessee 37379 October 11, 1994 s

U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555 Gentlemen:

In the Matter of

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Docket Nos. 50-327 i

Tennessee Valley Authority

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50-328 SEQUOYAH NUCLEAR PLANT (SON)- AUTHORIZATION TO USE AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME) BOILER AND PRESSURE VESSEL (B&PV) CODE CASE N-416-1 Pursuant to 10 CFR 50.55a(g)(5),TVA has determined that conformance with a 1

pressure test requirement from Section XI of the ASME Code (1980 Edition, Winter

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1981 Addenda) is impractical for SON Units 1 and 2.

TVA requests relief from the ASME code requirement for performing hydrostatic pressure tests after repairs by welding, or the installation of replacement items by welding, on the pressure retaining boundary of Class 1,2, and 3 components. TVA proposes to utilize the alternative requirements of Code Case N-416-1, " Alternative Pressure Test Requirement for Welded Repairs or Installation of Replacement items by Welding," for repair and replacement activities on specified systems with Class 1, 2, and 3 components. In addition to the alternative requirements from Code Case N-416-1, TVA willincorporate into SON's Repair and Replacement Program, additional nondestructive examinations (NDE) requirements on Class 3 butt welds.

The alternative testing and NDE requirements in Code Case N-416-1 are supported by the recent approval by the Board of Nuclear Codes and Standards on May 18,1994.

The additional NDE requirement for Class 3 butt welds is based on the NRC staff's position for performing additional surface examination on the root (pass) layer for Class 3 butt welds. TVA considers the alternative requirements in ASME Code Case -

N-416-1, and the additional NDE for Class 3 butt welds to provide an acceptable level of quality and safety in lieu of a hydrostatic pressure test.

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U.S. Nuclear Regulatory Commission Page 2 October 11, 1994 TVA's request for relief is similar to a letter of request from Commonwealth Edison for its Dresden Nuclear Power Station that was approved by NRC in a safety evaluation report dated May 25,1994. contains TVA's Request for Relief (RR-1). Enc losure 2 contains TVA's commitment for incorporating additional requirements into SQN's Repair and Replacement Program. NRC review and approval is requested before October 1,1995, in order to support completion of SON's first 10-year inservice inspection interval for both units. The first 10-year intervalis scheduled to end in December 1995 for both units.

For further information concerning this issue, please contact D. V. Goodin at (615)843-7734.

Sincerely, v

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.-2'eringue Acting Site Vice President Enclosures cc (Enclosures):

Mr. D. E. LaBarge, Project Manager Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852-2739 NRC Resident inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy-Daisy, Tennessee 37379-3624 Regional Administrator U.S. Nuclear Regulatory Commission Region il 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323-2711

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ENCLOSURE 1 RELIEF REQUEST-1 (RR-1) i Units:

1&2 Components:

All Class 1,2, and 3 pressure retaining components subject to hydrostatic testing in accordance with IWA-4700.

Systems:

Main steam, feedwater, auxiliary feedwater, chemical volume and j

control, residual heat removal, safety injection, containment spray, reactor coolant, primary water, waste disposal, fire protectior',

essential raw cooling water, fuel pool cooling, demineralized water, component cooling, sodium hypochlorite, air conditioning chilled water, and sampling.

.i Classes:

1, 2, and 3 Code

References:

IWA-4400(a) and IWA-4600 i

Code i

Requirements: IWA-4400(a) states: "After repairs by welding on the pressure

.l retaining boundary, a system pressure test shall be performed in accordance with IWA-5000."

i IWA-4600(a) states: "The rules and requirements of this Article shall apply to the attaching of replacements (as defined in IWA-7110) to the i

system where such attachment is by welding."

l Proposed Alternative:

As an alternate to the existing Section XI requirements, SON will adopt the provisions of Code Case N-416-1, as approved by the Board of.

Nuclear Codes and Standards (BNCS), along with the following additional nondestructive examinations (NDE) requirements.

i When performing repairs by welding, or the installation of replacement items by welding, on the pressure retaining boundary of Class 3 components, NDE shall be performed in accordance with the methods and acceptance criteria of Subsection ND cf the 1992 Edition of Section Ill. In addition, when the surface examination method is used.

in accordance with ND-5222 for a butt weld, an additional surface examination shall be performed on the root (pass) layer, 1

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2-Basis for the Proposed Alternative:

Elevated pressure hydrostatic tests are difficult to perform and often represent a true hardship. Some of the difficulties associated with elevated pressure testing include the following:

- Hydrostatic testing often requires complicated or abnormal valve line-ups in order to properly vent, fill, and isolate the components requiring testing.

- Relief valves with setpoints lower than the hydrostatic test pressure must be gagged or removed and blind flanged. This process requires the draining and refil;ing of the system.

- Valves that are not normally used for isolation (e.g., normally open pump discharge valves) are often required to provide pressure isolation for an elevated pressure hydrostatic test. These valves frequently require time consuming seal maintenance in order to allow for pressurization.

- The radiation exposure required to perform a hydrostatic pressure test is high in comparison to a system leakage test. The amount of time required to prepare the volume for hydrostatic pressure testing (i.e., installing relief valve gags, performing appropriate valve line-ups, etc.) is significantly large.

The difficulties encountered in performing a hydrostatic pressure test are prohibitive when weighed against the benefits. Industry experience, which is supported by SON's experience, shows that most wall leakage is detected during system operation as opposed to during elevated pressure tests.

Little benefit is gained from the added challenge to the piping system provided by an elevated pressure hydrostatic test (when compared to a system leakage test), especially when one considers that the piping stress experienced during a hydrostatic test does not include the stresses affiliated with the thermal growth and dynamic loading for design basis events.

The acceptability of performing nominal operating pressure tests, in lieu of hydrostatic tests,is supported by the recent approval by the BNCS of Code Case N-416-1," Alternative Pressure Test Requirements for Welded Repairs or Installation of Replacement items by Welding."

This code case allows a system leakage test at nominal operating pressure and temperature (in accordance with IWA-5000 of the 1992 Edition of Section XI) to be used in lieu of a hydrostatic test, provided that NDE of the weld (s)is performed in accordance with the methods and acceptance criteria of the applicable Subsection of the 1992 Edition of Section Ill.

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Based on the above, TVA requests relief from the Arnerican Society of Mechanical EngineersSection XI requirements for performing elevated I

pressure hydrostatic tests after repairs by welding, or the installation b.

of replacement items by welding, on the pressure retaining boundary of Class 1,2, and 3 components.

Applicable Time Period:

Relief is requested for the first 10-year interval of the In-Service Inspection Program for SON Units 1 and 2, which is scheduled to end in December 1995.

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• a ENCLOSURE 2 TVA COMMITMENTS

1. TVA will revise SON's Repair and Replacement Program (Site Standard Practice [ SSP] 6.9, " Repair / Replacement of ASME Section XI Components") to allow the use of ASME Code Case N-416-1 for repairs and replacements by welding within three months of NRC approval of Relief Request RR-1.

2. TVA will revise SON's Site Welding Program (SSP-7.50, " Welding, Brazing, and Soldering") to' address the nondestructive examination (NDE) requirements of American Society of Mechanical Engineers (ASME) Code Case N-416-1 and the additional NDE for Class 3 butt welds within three months of NRC approval of l

Relief Request RR-1.

3. TVA will revise SON's Site ASME,Section XI, Pressure Test Program (SSP-8,5, "ASME Section XI Pressure Test Program") to address the alternative pressure test requirements allowed by ASME Code Case N-416-1 within three months of NRC approval of Relief Request RR-1.

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