ML20215K740
| ML20215K740 | |
| Person / Time | |
|---|---|
| Site: | Braidwood  |
| Issue date: | 04/29/1987 |
| From: | Hunsader S COMMONWEALTH EDISON CO. |
| To: | Murley T Office of Nuclear Reactor Regulation |
| References | |
| 3019K, NUDOCS 8705110326 | |
| Download: ML20215K740 (4) | |
Text
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Commonwealth EcMoon
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, One First Nabonal Plaza. Chicago, Illinois
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/ Address Reply to: Post Omce Sox 767
\\d Chicago, Illinois 60690 0767 April 29, 1987 Mr. Thomas E. Murley, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555
Subject:
Braidwood Station Units 1 and 2 Containment Leak Chase Channels NRC Docket Nos. 50-456/50-457
Reference:
(a) NRC Inspection Report No. 50-456/86023 dated February 13, 1987
Dear Mr. Murley:
Reference (a) provided the results of the NRC Region III inspection of containment integrated leak rate testing (CILRT) for Braidwood Station Unit 1.
Open Item 456/86023-01 requires Commonwealth Edison Co. to submit to NRR the justification for performing Type A tests with the leak chase channel plugs installed.
The purpose of this letter is to provide you with that justification, which is included as Attachment A, for your review and acceptance.
Please address any questions concerning this matter to this office.
Very truly yours, 6 99b M-S.
C.
Hunsader Nuclear Licensing Administrator cc:
J. Stevens Resident Inspector - Braidwood NRC RIII Q
8705110326 870429 gDR ADOCK 05000456 PDR L_
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ATTACIG!ENT A COMMONWEALTH EDISON COMPANY BRAIDWOOD 1 NRC INSPECTION REPORT OPEN ITEM 86023-01 PLUGGED LEAK CHASE CHANNELS Leak chase channels are fillet welded over a number of liner seam welds for leak testing the seam welds during construction.
The area covered by the leak chase channels includes the basemat liner and the containment liner to a height 38' above the basemat.
The channel creates a volume which is pressurized to the design pressure during construction to demonstrate leak tightness of the liner seam welds.
After the tests, plugs may be installed in the test tap to seal this volume.
Plugging the leak chase channels is acceptable during the ILRT t'est and during operation of the pihnt based on the following:
1.
The channels and the 3/16" continuous fillet welds between the channel and the liner are designed to withstand accident pressure and accident temperature.
Stresses due to SSE on the channel and its weld are negligible compared to the magnitude of the accident pressure and temperature stresses.
The channel and the weld have a safety margin of 3.2 against allowables under the most severe loads.
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6 2.
As required by Sargent & Lundy Drawing S-1069, the leak chase channel assembly is a Category I structure.
3.
The liner seam weld was tested by partial radiography and 100% liquid penetrant or magnetic particle test. 'Furthermore, the leak test channels-and the liner weld underneath have been tested at 50 psig (containment design pressure) during construction and the leak tightness was established at that time.
- 4..
The welded steel plate liner, attached to the entire inside surface of the containment, serves as leaktight membrane but not as a structural load carrying element.
The liner seam weld is always in compression due to prestress in the containment wall even though the ILRT pressure will relieve this compression force to some extent.
Therefore, the liner seam weld can be considered non-structural.
5.
Venting the leak test channels during the ILRT will not provide information on the leak tightness of the liner weld, since the liner is backed by prestressed concrete and is an integral part of the containment wall which will act as a leak tight membrane.
The most effective procedure for performing the test on the liner weld is to test when it is not backed by concrete, and this has been dono during liner construction.
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l 4.
Based on the above discussion,'it is concluded that' installing leak' chase channel plugs'during ILRT or plant operation is not significant' to' the test or operation of the plant.
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