ML20217N855
| ML20217N855 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 03/31/1998 |
| From: | Reid D VERMONT YANKEE NUCLEAR POWER CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| BVY-98-51, NUDOCS 9804090228 | |
| Download: ML20217N855 (3) | |
Text
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VERMONT YANKEE NUCLEAR POWER CORPORATION
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185 Old Ferry Road, Brattleboro, VT 05301-7002 (802) 257-5271 March 31,1998 BVY 98-51 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555
Subject:
Vermont Yankee Nuclear Power Station License No. DPR-28 (Docket No. 50-271)
Request For Alternative Testing Per 10CFR50.55a(a)(3)(1)
Containment Pressurization Test l
Pursuant to 10CFR55a(a)(3)(i), Vermont Yankee Nuclear Power Corporation (VY) hereby requests approval to perform attemative testing to that specified by American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code,Section XI, IWE-5221. Attachment 1 provides the justification for the attemative testing.
Approval for the use of the altemative testing is requested by April 22,1998 in order to support scheduled testing during our current refueling outage.
If you have any queysons on this transmittal, please contact Mr. Thomas B. Silko at (802) 258-4146.
Sincerely, VERMONT YANKEE NUCLEAR POWER CORPORATION Donald A. Reid ~'
Senior Vice President, Operations Attachrpent cc:
USNRC Region 1 Administrator i
USNRC Resident inspector-VYNPS USNRC Project Manager-VYNPS
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Vermont Department of Public Service o%
98o4090228 980331 ADOCK0500g21 DR
VERMONT YANKEE NUCLEAR POWER CORPORATION U.S. Nucle:r Regulatory Commhsion
' BVY 98-51/ Attachment 1/ Page 1 o
Vermont Yankee Nuclear Power Station 4
Request For Altemative Testing Per 10CFR50.55a(a)(3)(i)
Containment Pressurization Test BACKGROUND During the current refueling outage, VY will be replacing the Core Spray and Residual Heat Removal system suction strainers located within the Torus.- Because of the physical dimensions of the new strainers,. installation of the strainers can not be accomplished by use of the existing hatches in the Torus space. Consequently, VY has opted to cut a temporary hatch into the torus rather than constructing the strainers inside the torus. The location for this new hatch was selected based on freedom from obstructions, ease of access, and ability to facilitate traffic flow and rigging of the strainer sections. The temporary hatch will be made by cutting and removing a section of torus shell. The location of this entire hatch will be below the normal and post accident water line in the torus.
TESTING REQUIREMENTS Following the repairs to the Torus, the testing requirements are specified by ASME Section. XI " Rules for Inservice Inspection of Nuclear Power Plant. Components,"
IWE-5221 " Tests Following Repair, Modification, or Replacement - Leakage Test."
IWE-5221 states:
"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, Pad 50 of the Code of Federal Regulations, Appendix J..."
VY's containment structure is a Class MC component and thus the post repair testing requirements of IWE-5221 apply.
PROPOSED ALTERNATIVE TESTING Pursuant to.10CFR55a(a)(3)(i) VY is proposing to perform attemative testing to that
.specified by IWE-5221. The proposed attemative testing to verify structural integrity and water leak tightness would be to perform a pressurization test of the entire containment (Dryweil and Suppression Chamber) including the affected Torus area with the Torus water volume at that-specified by Technical Specifications.
This pressurization test will consist of pneumatically pressurizing the containment air volume to a minimum of 44 psig and holding for a minimum of 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />. During the performance of this test, a visualinspection of the torus shellin the area of the repair will be made to verify that there is no visible leakage and/or structural deformation.
VERMONT YANKEE' NUCLEAR POWER CORPORATION U.S. Nuclear Regulatory Commission BVY 98-51/ Attachment 1/ Page 2 -
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JUSTIFICATION FOR ALTERNATIVE TESTING Ths intent of 10CFR50, Appendix J'is to ensure that the escape of containment air to-the atmosphere following a design basis accident is maintained below established limits by the perfomiance of a pneumatic leakage test. This testing requires extensive pressure stabilization and temperature equalization for the test.
The _ actual
. performance of the test requires approximately 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of stabilization, temperature equalization, leakage testing' and verification. In addition, the Type A test requires
- extensive system line-up and extensive' supplemental instrumentation requirements.
None of these issues apply to the concem of structural integrity or water leak tightness of the repair area. Since the repair' being made.to the Torus is entirely located below the normal and post accident water level of the torus, the' repair area is completely water-sealed against any potential air leakage.
The proposed attemative test is to pressurize the containment air volume to a minimum of 44 psig and hold for a minimum of 1 -hour. This test exceeds the maximum j
Suppression Chamber pressure postulated during worst case accident conditions and j
will subject the repaired area of the. Torus shell to both the containment sir volume
-l pressure and the static pressure of the standing head of water.
This proposed-altemative testing is also justified due to the extensive non destructive j
testing that will be conducted. The shell repair will attempt to reuse the existing plate through the use of thin cutting tools and techniques. New plate material, curved to match the contour of the Torus, will be available if required. The shell repair will be accomplished under 1977 edition summer addenda of ASME Section lil, class MC, subsections NE. In conformance to ASME NE requirements, full radiographic test (RT) will be pelformed on the final weld joint. In addition to the requirements of ASME, VY will be performing the following; liquid penetrant inspection of the weld preps, visual inspection of the root pass of the weid, magnetic particle inspection and liquid penetrant inspection of the completed welds, and the use of charpy qualified weld materials and weld procedures. This will assure that the integrity of the repair meets or exceeds the I
quality _ requirements of the existing torus shell. Industry experience has proven that current state.of the art non-destructive testing techniques provide an accurate assessment of the acceptability of structural welds.
- Based upon the above, VY believes that the proposed attemative testing will provide an
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acceptable level of quality and safety to demonstrate the structural integrity of the i
repaired torus and is therefore justified.
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