ML13333A491
| ML13333A491 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 08/10/1979 |
| From: | Head J SOUTHERN CALIFORNIA EDISON CO. |
| To: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| References | |
| NUDOCS 8002140258 | |
| Download: ML13333A491 (3) | |
Text
-,--7 Sout/mrn Ciffornia Edison Company P.
.BOX 800 224-1 WALNUT GRZOVE AVENUE J. T. H EAD, JR.
ROSEMEAD,CALIFORNIA 1770 TFLEPHONE
.iC~
.'cc~n.~r213-5 72 -1472 August 10, 1979 U. S. Nuclear Regulatory Ccmnission Office of Inspection and En forcement Pagion V Suite 202, Walnut Creek Plaza 11)90 Nor:th California Boulevard Wialnut Cree k, California 94596 Attention:
Mc. R. H. Engelken, Director Docket No. 50-206 San Onofre Unit 1
Dear Sir:
References:
- 1.
Letter dated August 1, 1979 frcn SCE (J. T. Head, Jr.) to NRC (R.
H. Engelken)
- 2.
Letter dated June 15, 1979 from SCE (J.
B. Moore) to NRC (R. H. Engelken)
Transmitted herewith are ten (10) copies of Westinghcuse report WCAP-9544 entitled "Metallurgical Investigations of Cracks in the Stera Generator Feed water Lines of San Onofre Unit I".
This report contains the results of 'he complete metallurgical evaluaticn of specimens reraoved fron the San Onofre Unit 1 "B" scea generator feedwater nozzle and reducer during the June 1979 outage.
S&onittal of this report is in accordance with References 1 and 2 above.
As stated in Section 4, Conclusions, of WCAP-9544, and consistent with our Interim Report dated June 13, 1979 previously sUaitted to your office by Reference 2, it has been concluded that the cracking observEd in the San Onofro Unit I feedwater nozzle and reducer is attributable to stress assisted corro-sicn acccompanied by iritervals of corrosion fatigue.
The evidence gathered from the metallurgical investigations further suggests that the cracking occurred early in plant life and has not progressed during the intervening years of plant operation.
Cur program of corrective -actions, including the status of those described in the June 13, 1979 Interim.Report, is sunmarized below:
If4
U.S. Nuclear Regulatory Comnission Page 2 A.
Reducer Replacement Reducer replacement was accomplished as described in Section V. A.
of the Interim Report except as follows:
- 1.
In addition to post weld heat treatment of the feedwater nozzle to reducer welds, post vield heat treatment was performed on all three feedwater piping to reducer welds.
- 2.
Weld build ups for fit up of all three reducers were satis factorily exanined using MT, Pr, RT and UT.
- 3. The root passes of each reducer to nozzle and reducer to pipe weld were satisfactorily examined using MT.
- 4.
The completed reducer to nozzle and reducer to pipe welds were satisfactorily examined using MT and RT. Due to the geometric configuration of these welds, UT was performed of the reducer to nozzle weld from the reducer side only for each reducer.
These UT examinations were completed satisfactorily.
B.
Leak Test The leak test as described in the Interim Report was satisfactorily completed.
C.
Future Non-Destructive Examinations During the next refueling outage, presently scheduled for April, 1980, each of the nozzle to reducer and reducer to pipe welds will be examined using RT.
The remainder of the welds in the feedwater lines will be inspected as required by Item 2 of IE Bulletin 79-13.
D.
Continuing Investigations SCE, in association with other utility corrpanies, and Westinghouse, is sponsoring additional studies and analyses in an effort to better define the underlying causes of the different types and instances of cracking in feedwater lines which have recently been observed.
The details of these investigations are presently being formulated.
Based upon the results of the completed metallurgical examinations and other considerations as set forth in our June 13, 1979 Interim Report, it is
U. S. Ibclear Regulatory Commission Page 3 concluded that operation of San Onofre Unit 1 can continue without undue risk to public health and safety.
Should you have any questions on the above or require additional informa tion, please let ne k-now.
Sincerely,
Enclosure:
VCAP-9544 (10 copies)