ML023330366
| ML023330366 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 11/14/2002 |
| From: | Grecheck E Virginia Electric & Power Co (VEPCO) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 02-701 | |
| Download: ML023330366 (7) | |
Text
VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 November 14, 2002 United States Nuclear Regulatory Commission Serial No.02-701 Attention: Document Control Desk NLOS/ETS RO Washington, D.C. 20555 Docket No. 50-339 License No. NPF-7 Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNIT 2 ASME SECTION XI INSERVICE INSPECTION PROGRAM RELIEF REQUEST IWE9 CONTAINMENT TESTING During the current refueling outage for North Anna Unit 2, Virginia Electric and Power Company (Dominion) performed inspections of the reactor vessel head (RVH) and vessel head penetration (VHP) nozzles in response to NRC Bulletin 2002-02. Based on the results of those inspections and the expected dose and difficulty in reconstruction and repair of the VHP nozzles, Dominion has decided to replace the Unit 2 RVH during the current outage rather than waiting until the Spring 2004 refueling outage as previously planned. In order to replace the RVH, the containment concrete and metallic liner will be breached to facilitate moving the RVH into containment, since the existing equipment hatch is not large enough to accommodate the RVH. After the containment is repaired, leakage testing in accordance with ASME Section Xl is required to return the containment and metallic liner to operable status.
Pursuant to 10CFR50.55a(a)(3)(i), Dominion requests an alternative to the containment metallic liner test requirement of ASME Section Xl, paragraph IWE-5221 to reestablish the leak-tight integrity of the containment liner. Dominion proposes to perform an "as left" local leak rate test on the new pressure boundary weld of the containment metallic liner in lieu of the Type A test specified by ASME Section Xl, paragraph IWE-5221. This test will be performed subsequent to the containment pressure test, which will be performed at accident pressure (Pa) to verify concrete integrity.
The local leak rate test is considered a superior test for determining leakage at the repaired area as compared to the specified Type A test. A Type A test is a less sensitive test than a local leak rate test and unnecessary for the planned repair activity when considering the nondestructive examination and the alternate testing proposed.
The local leak rate test, in conjunction with the planned containment pressure test, will continue to provide for an acceptable level of quality and safety.
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This alternative to the ASME Code requirements has been approved by the Station Nuclear Safety and Operating Committee.
To support the ongoing RVH replacement project and the scheduled restart of North Anna Unit 2 in January of 2003, Dominion requests approval of the proposed alternative by December 31, 2002. Please contact Mr. Thomas Shaub at (804) 273-2763, if there are any questions about this submittal.
Very truly yours, Eugene S. Grecheck Vice President - Nuclear Support Services Attachment Commitments made in this letter: None cc: U. S. Nuclear Regulatory Commission Region 11 Sam Nunn Atlanta Federal Center 61 Forsyth St., SW, Suite 23T85 Atlanta, Georgia 30303 Mr. M. J. Morgan NRC Senior Resident Inspector North Anna Power Station Mr. M. M. Grace Authorized Nuclear Inspector North Anna Power Station Mr. J. E. Reasor, Jr.
Old Dominion Electric Cooperative Innsbrook Corporate Center 4201 Dominion Blvd.
Suite 300 Glen Allen, Virginia 23060
Attachment Alternative Test Requirements for Containment Repairs Virginia Electric and Power Company (Dominion)
North Anna Power Station Unit 2
Virginia Electric & Power Company North Anna Power Station Unit 2 First Containment Inspection Interval Relief Request RR-IWE9 SYSTEM/COMPONENT(S) FOR WHICH AN ALTERNATIVE IS REQUESTED:
Containment metallic liner CODE REQUIREMENT(S):
ASME Section Xl 1992 Edition with the 1992 Addenda, Subsections IWE and IWL CODE REQUIREMENT FROM WHICH AN ALTERNATIVE IS REQUESTED:
An alternative to the requirements of paragraphs IWL-5230 and IWE-5221 is requested.
Paragraph IWL-5230 requires testing as delineated in paragraph IWE-5221.
Paragraph IWE-5221 states in part:
"Except as noted in IWE-5222, repairs or modifications to the pressure retaining boundary or replacement of Class MC or Class CC components shall be subjected to a pneumatic leakage test in accordance with the provisions of Title 10, Part 50 of the Code of Federal Regulations, Appendix J, Paragraph IV.A, which states in part that "any major modification, replacement of a component which is part of the primary reactor containment boundary, or resealing a seal welded door, performed after the preoperational leakage rate test shall be followed by a either a Type A, Type B, or Type C test as applicable for the area affected by the modification."
BASIS FOR RELIEF:
To facilitate the North Anna Power Station Unit 2 reactor head replacement, the containment's concrete and metallic liner will be breached. This work must be performed because the existing equipment hatch is not large enough to accommodate the reactor heads. The purpose of this relief request is to propose that a local leak rate test be performed on the new pressure boundary welds of the metallic liner as an alternative to a Type A test, which is specified in the Code.
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Background===
During the current refueling outage for North Anna Unit 2, Virginia Electric and Power Company (Dominion) performed inspections of the reactor vessel head (RVH) and vessel head penetration (VHP) nozzles in response to NRC Bulletin 2002-02. Based on the results of those inspections and the expected dose and difficulty in reconstruction and repair of the VHP nozzles, Dominion has decided to replace the Unit 2 RVH during the current outage rather than waiting until the Spring 2004 refueling outage as previously planned. To accomplish the head replacement, a portion of the Unit 2 containment concrete, reinforcing steel, and metallic liner will be removed. After the reactor heads are moved through the containment access, the metallic liner section that was removed will be reattached by welding. Subsequent to reattaching the liner, the reinforcing steel and concrete will be replaced. In addition, attachment welds are planned on the metallic liner to create channels for local leak rate testing, and for construction aids during liner repair and concrete placement. Repair and testing of the metallic liner section, reinforcing steel, and associated concrete placement will be controlled under an ASME Section Xl repair program and Dominion's design control program. Program requirements will meet or exceed our original owner's requirements found in plant specifications, or will be reconciled in accordance with ASME Section XI.
The details of the concrete, reinforcing steel, and liner repair and testing are provided below.
Concrete The concrete will be replaced with concrete that meets the design strength requirements of the original owner's requirements and will be tested in accordance with ASME Section Xl, paragraph IWL-5500, as applicable. Prior to the placement of the concrete, the outside of the metallic liner, the reinforcing steel and the surfaces of the existing concrete will be visually examined to assure proper surface preparation. After placement of the concrete, the containment will be pressure tested at accident pressure (Pa) to reestablish structural integrity of the containment structure in accordance with paragraphs IWL-5220 and 5250, and the required concrete visual examinations (VT-1C) will be performed prior to testing, at test pressure, and following depressurization. Qualified individuals will perform these tests and examinations.
Reinforcing Steel Consistent with ASME Section Xl requirements, the reinforcing steel exposed when the concrete is removed will receive a VT-1 visual examination by qualified personnel, and the Responsible Engineer will determine if the original reinforcing steel is acceptable for re-use. Reinforcing steel will be repaired or replaced to meet the original owner's requirements or ASME Section III, Division 2. The exposed reinforcing steel will be 100% VT-1 visual inspected. Qualified individuals will perform these inspections and examinations.
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Compliance with the original owner's requirements or ASME,Section III, Division 2, and the associated inspections and tests of the concrete and reinforcing steel are adequate to ensure that the structural integrity of the containment is restored.
Metallic Liner The section of the metallic liner that was removed will be rewelded in place by qualified personnel in accordance with the original owner's requirements. Consistent with the owner's requirements, examinations will be performed on the metallic liner repair welds. As a minimum, 100% surface (liquid penetrant or magnetic particle) and spot volumetric (radiography at 50-foot intervals at locations specified by the examiner) will be performed on the pressure boundary containment metallic liner repair welds. In addition, ASME Section XI requires both a General Visual and a VT-3 visual examination of the new metallic liner pressure boundary welds. The metallic liner repair weld will be tested by a local leakage/pressure test using a channel over the new welds after completion of the required containment pressure test. Qualified personnel will conduct all examinations.
The attachment welds for both leak testing and construction aids will be performed and inspected in accordance with the Section XI repair program. In accordance with paragraph IWE-5222(a), leakage testing for repairs and modifications of these types may be deferred to the next scheduled leakage test. This guidance is also provided in NEI 94-01, Industry Guideline for Implementing Performance-Based Option of 10 CFR 50, Appendix J.
Justification for Alternative ASME Section Xl, paragraph IWE-5221, by reference to paragraph IWE-5000 in paragraph IWL-5230, requires that an appropriate 10 CFR 50 Appendix J test be performed following a repair or modification of the pressure retaining boundary.
Specifically, the Code requires a Type A, Type B, or Type C test, as appropriate, for the repaired or modified pressure boundary component.
Appendix J, Option B provides guidelines for meeting the safety objectives of the Appendix J requirements. Section 9.2.4 of NEI 94-01, states that "repairs and modifications that affect the containment leakage rate require leak rate testing (Type A testing or local leak rate testing) prior to returning the containment to operation."
A local leak rate test provides the most accurate and direct method of assuring the leak tight integrity of the repair weld. The local leak rate test is considered a superior test for determining leakage at the repaired area as compared to the specified Type A test. The local leak rate test will directly measure the leakage at the repair area, while a Type A test measures total containment leakage. This test is being performed to reestablish the leak-tight integrity of the containment liner due to the repair weld. No other work has been performed to warrant a test of the entire containment. Also, Dominion's Page 3 of 4
acceptance criterion for leakage of the repair weld will be zero leakage. This acceptance criterion is a more stringent criterion than that of a Type A test. Therefore, if there is any leakage of the liner at the repair weld, it would be identified by the local leak rate test, and corrected.
Additionally, the containment pressure test, performed at Pa, to establish the structural integrity of the reinforced concrete, will structurally test the metallic liner repair weld.
This pressure test and the subsequent local leak rate test will establish the "as-left" leak tightness of the metallic liner repair weld. Therefore, the required concrete pressure test at Pa and the local leak rate test of the liner repair weld satisfy or exceed the intent of a Type A test to establish containment integrity after a repair activity.
Dominion has determined that a local leak rate test is the most appropriate test to perform on the metallic liner to meet the testing requirements of the Code. A Type A test is a less sensitive test than a local leak rate test and unnecessary for the planned repair activity when considering the nondestructive examination and the alternate testing proposed. Dominion considers that the local leak rate test, in conjunction with the planned containment pressure test, will continue to provide for an acceptable level of quality and safety.
ALTERNATIVE REQUIREMENTS:
In accordance with 10 CFR 50.55a(a)(3)(i), Dominion requests an alternative to the containment metallic liner test requirement of ASME Section Xl, paragraph IWE-5221 to reestablish the leak-tight integrity of the containment metallic liner. Dominion proposes to perform an "as-left" local leak rate test on the containment metallic liner pressure boundary repair weld in lieu of the Type A test specified by ASME Section Xl, paragraph IWE-5221 for this type of repair activity. The local leak rate test will be performed after the containment pressure test has been completed.
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