ML20149E560
| ML20149E560 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood, 05000000 |
| Issue date: | 02/02/1988 |
| From: | Hunsader S COMMONWEALTH EDISON CO. |
| To: | Murley T Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8802110142 | |
| Download: ML20149E560 (4) | |
Text
nr P
'N Commonwealth Edison j,
[
X ) One First National Plaza. Chicago, Illinois s
Address Reply to: Post Omcc Box 767 (j
Chicago, Illinois 60690 0767 Fotruary 2, 1988 Mr. Thomas B. Murley, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555 ATTN: Document Control Desk
Subject:
Byron Station Units 1 and 2 Braidwood Station Units 1 and 2 containment Leak Chase Channels NRC Docket Nos. 50-454/455 a.id 50-456/457 References (a): NRC Inspection Report Nos. 50-454/86035; 50-455/86022 dated October 2, 1986 (Byron Station)
(b): NRC Inspection Report No. 50-456/86023 dated February 13, 1986 (Braidwood Station)
(c): April 29, 1987 letter from S.C. Hunsader to T.E. Murley
Dear Sir:
Reference (a) provided the results of the NRC Region III inspection of containment integrated leak rate testing (CILRT) performed at Byron Station Units 1 and 2.
Reference (b) provided the results of the same kind of inspection at Braidwood Unit 1.
Open Items 50-454/86035-02; 50-455/86022-03 and 456/86023-01 required Commonwealth Edison Company to submit to NRii the justification for performing Type A tests with the leak chase channel plugs installed. Reference (c) provided that justification for Braidwood Units 1 and 2.
The purpose of this letter in ta update Reference (c) and apply that justification (which is inclus'ed as Attachment A) to Byron Station Units 1 and 2.
I60I 8902110142 08020'ADOCK 05000 M
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U.S. NRC February 2, 1988 This is being provided for your review and acceptance. Please address any questions you may have concerning this matter to this office.
Very truly yours,
{.fp.
- -lL, S. C. Hunsader Nuclear Licensing Administrator 1m Attachment cc:
L. N. Olshan - NRR S. Sands - NRR NRC Resident Inspector - Braidwood NRC Resident Inspector - Byron Regional Administrator - RIII 4173K i
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ATTACHMENT A COMMONWEALTH EDISON COMPANY BYRON STATION BRAIDWOOD STATION NRC INSPECTION REPORT NRC INSPECTION REPORT OPEN ITEMS 50-454/86035-02; 50-455/86022-03 OPEN ITEM 50-456/86023-01 PLUGGED LEAK CHASE CHANNELS Leak chase channels are fillet welded c,ver 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 for 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 test and during operation of the plant 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.
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 particule test.
Furthermore, the leak test channels and the liner 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 structure load carrying element. The liner seam weld is always in comparison 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.
7y-
-. 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 test on the liner weld is to test when it is not backed by concrete, and this has been done during liner construction.
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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