ML20040C113
| ML20040C113 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 10/29/1976 |
| From: | Goller K Office of Nuclear Reactor Regulation |
| To: | Johari Moore SOUTHERN CALIFORNIA EDISON CO. |
| Shared Package | |
| ML13319A635 | List:
|
| References | |
| FOIA-81-313 NUDOCS 8201270280 | |
| Download: ML20040C113 (3) | |
Text
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UNITED STATES i.
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. f.I NUCLEAR REGUI.ATORY COMMisslOL j
O WASHINGTON, D. C. 2055E
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Docket No. 50-206 October 29, 1976 C
'S Southern California Edison Company ATTN: Mr. Jack B. Moore Vice president F ".'
2244 Walnut Grove Avenue Post Office Box 800 Rosemead, California 91770 Gentlemen:
.g Your letter dated October 26, 1976 provided specific connitments concerning i
a steam generator inspection program for the San Onofre Nuclear Generating i=
Station, Unit No.1 (San Onofre, Unit No.1).
This program will be carried 2=
out as a result of the failure of a steam generator tube at Surry Unit No.
F 2.
The failure at Surry Unit No. 2 appears to be due to a combination of intergranular stress corrosion and high stress in the inner row of U-bends resulting from tube support plate material movement at the center of the tube support plate which causes flow slot "hourglassing".
This tube
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support plate material movement appears to be a result of stresses in the tube support plate as a result of tube " denting" which in turn appears to be the result of the expansion of precipitate and corrosion products deposited in the' tube. support plate annuli where the tubes pass through the
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tube support plate.
. ;...g Your letter of October 26, 1976, stated that the specific steam generator
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tube inspections and any remedial action dulgned to limit the possibility for U-bend leakage as determined by the inspection findings will be
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accomplished to the satisfaction of the NRC and yourselves prior to the resumption of power operation at San Onofre, Unit No.1. The facility was shutdown on September 30, 1976 for refueling and other planned major activities, and will not return to power operation before February,1977.
We find your proposed actions acceptable as follows:
(a)
During the present facility shutdown, inspections will be conducted as necessary to ascertain the potential for excessive stress in the steam generator tube U-bends or other conditions that may be F+
conducive to intergranular stress corrosion of steam generator tubes.
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' Southern California Edison Company October 29, 1976 (b)
Based on the conditions observed, SCEC will propose a program of '
repai r.
San Onofre, Unit No.1 shall not resume operation until:
(1) the proposed repair for Unit Nc. 'l has been approved in writing by the NRC, (2) all tubes required to be plugged by such criteria have been properly plugged, and (3) the unit is otherwise properly prepared to resume power operation.
The foregoing are deemed by the NRC staff to be minimum requirements to ensure that your facility does not operate with reduced integrity of the reactor cooling system pressure boundary.
Sincerely, WY b
Karl R. Goller, Assistant Director l
for Operating Reactors Division of Operating Reactors cc:
See next page O
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Southern California Edison Company 3-
. October 29, 1976 cc:
Rollin E. Woodbury, Vice President and General Counsel Southern California Edison Company Post Office Box 800 zu Rosemead, California 91770 J~~
Chickering & Gregory, General Counsel ATTN:
C. Hayden Ames
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Esquire San Diego Gas and Electric Company 111 Sutter Street San Francisco, California 94104 San Clemente Public Library
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233 Granada Street San Clemente, California 92672 n
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