ML13308B481
| ML13308B481 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 12/01/1976 |
| From: | Head J SOUTHERN CALIFORNIA EDISON CO. |
| To: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| References | |
| NUDOCS 8103060491 | |
| Download: ML13308B481 (2) | |
Text
Southern California.;Tdison Company 2244 WAI LNujr GHQVE AVENUE J.
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ROSEME1AD.ALI OR I91770 Reulatory Docket File ce NOOCKEEQ 19,;6 U. S. Nuclear Rgulatory issiof U.S. NUCLE GU Reio1n V COMMISSIONro Office of Inspection and Enforcement Suite 202 WValnut Creek Plaza 1990 North California Boulebard Walnut Creek, California 94596 Docket No. 50-206 Attention:. R. H. Engelken, Director
Dear Sir:
References:
(1) Letter from SCE (H. L. Ottoson) to USNRC Regioh V dated November 16, 1976; Antivibration Bar Indications (2) Letter from SCE (A. Arenal) to USNRC Region V dated November 15, 1976; Steam Generator Tube Examination This letter provides the required follow-up information for reference (1) letter which discussed the preliminary results of a visual inspection conducted in the "C" steam generator. Indications were that abnormal degradation of some tubes and antivibration bars had occurred in the U bend area.
Two antivibration bars have now been removed from the "C" steam generator for detailed examination. Each bar exhibits several locations where the steam generator tubes have worn into the bar. In some cases, only 25% of the bar diameter remains. Other bars, examined in place, exhibit similar wear patterns.
Metallurgical analysis on the bars removed from the steam generator is continuing but the wear appears to be the result of mnecrianical fretting between the bar and tubes.
It is our intention to correct this prolblem by the desigri and installation of additional antivibration bars with rectangular cross section. The design would be incorporated in all three steam generators. This design work is presently underway and will be reviewed by our Safety Committee. Following
-2 this review, we will forward pertinent details of the new design and the findings made by the Safety Committee.
As indicated in reference (2), some 50 tubes will be plugged as a result of tube thinning in the antivibration bar area.
If you should require additional information on this matter, please let The know.
Sincerely,
/&