ML19220C061
| ML19220C061 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 07/30/1976 |
| From: | Arnold R Metropolitan Edison Co |
| To: | Volgenau E NRC/IE |
| References | |
| GQL-1090, NUDOCS 7904280154 | |
| Download: ML19220C061 (2) | |
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METROPOLITAN EDISON COMPANY 8CSr CF*ltE 3CX 542 RE ACING. PENN3YLV ANI A ?$600 TELE 3 HONE 2?5 - 323 ;IC July 30, 1976 GQ1 1090
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Director of Nuclear Reactor Regulation Office of Inspection & Enforcement U. S. Nuclear Regulatory Cor:nission
'a'ashington, D. C. 20555 Attention:
Dr. Ernst Volgenau, Director Subj ect :
Three Mile Island Nuclear Station Unit 2, Docket No. 50 '20
Dear Dr. Volgenau:
On June 18, 1976, Mr. L. Narrow of your office was verbally notified of a situation which Metropolitan Edison Conpany considered to be reportable in accordance with the requirements of 10 CFR 50.55 (e). This letter constitutes a thirty-day follow-up letter.
Description As part of the construction of the shield walls and slabs around the fuel transfer tubes, holes were drilled into the north exterior wall of the Fuel Transfer Canal for reinforcing dowels.
During the process of drilling these holet and exposing the rebar, a void was opened within the concrete over both fuel transfer tubes.
Each void extended about 3 to 4 feet into the concrete, was approxi-nately 18" high and 6' to 8' wide.
3e voids were located in a section of the wall that had initially been blockouts for the subsequent installation of the fuel transfer tubes. Apparently, when the blockouts were poured, the interior pertion of the pour did not fill the keyways on top of the blockouts leaving the recently detected voids.
A similar condition was discovered at the blockouts for the fuel transfer tubes on the south exterior wall of the Fuel Handling Building and was reported to Mr. Narrov on October 17, 1975 and February 20, 1976.
c on a vas,2 99 hew 86 208 a m u ua s u r W, g
m Dr. Ernst Volgenau Analvsis of Safetv I=plications The fuel transfer canal is located within the Containment Structure and was designed and constructed as a Seismic Class I structure. Had the voids remained undetected, it is possible that during a seismic event, cracks might occur at the high stress concentration corner areas of the void; these cracks could then propagate throughout the structure. This would not have a significant effect en the structural integrity of the building nor would it co= promise the health and safety of the public or the plant staff.
Corrective Action The above condition was reported on a site deviation report. The Engineer has prepared a procedure for filling in the void.
It is estimated that the repairs should be completed by Septenber 30, 1976.
An investigation of all scjor blockouts in Class I buildings was con-ducted. It was found that the Fuel Transfer Tube Blockouts both in the Fuel Building and in the Reactor Building were unique in that they were the only blockouts which contained large embednents and the only blockouts which contain a keyway in the top horizontal construction joint. The remainder of the construction blockouts were made with the top horizontal construction joint sloped from inside to outside approximately one foot thereby eliminating the trapping of air as placement la topped off. The results of this investi-gation are availaole at the job site.
Three blockouts remain to be placed, one in the Service Building, one in the Control Building and one in the Secondary Shield k'all.
None of tbese blockouts have a configuration which would present problems in placing concrete.
No further problens are anticipsted in the construction blockouts.
Very truly yours,
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R. C. A. old Vice President 86 209
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