ML13330B507
| ML13330B507 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 03/24/1989 |
| From: | Medford M SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 8903300089 | |
| Download: ML13330B507 (2) | |
Text
Southern California Edison Company P. 0 BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD, CALIFORNIA 91770 M.O.MEDFORD TELEPHONE MANAGER OF (818) 302-1749 NUCLEAR REGULATORY AFFAIRS March 24, 1989 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555 Gentlemen:
Subject:
Docket No. 50-206 Standby Diesel Generators Turbocharger Reliability San Onofre Nuclear Generating Station Unit 1
References:
(A) Letter dated March 14, 1989, from F. R. Nandy (SCE) to the NRC, Standby Diesel Generators (B) Letter dated February 14, 1989, from F. R. Nandy (SCE) to the NRC, Standby Diesel Generators By Reference A Southern California Edison (SCE) provided responses to NRC staff requests for additional information regarding the San Onofre Unit I standby diesel generators. A brief discussion of the reliability of the turbochargers was included in that reference. As requested by the NRC, the following additional information regarding turbocharger reliability is provided.
During the period from 1977 to 1984, the only significant problem associated with the San Onofre Unit 1 diesel turbochargers was excessive turbine and thrust bearing wear. With the completion of modifications to improve the turbocharger drip lubrication system during Cycle 10 refueling, this problem has been corrected.
4ool 8903300089 890324 PDR ADOCK 05000206 P
Document Control Desk
-2 A review of plant specific reliability data and maintenance records for the period from the completion of Design Review and Quality Revalidation (DRQR) inspections in 1985-86 until the present indicates that all installed turbochargers have continued to demonstrate highly reliable performance, with the single exception of the casing failure or crack which was briefly discussed in Reference A. This crack, which was in the intermediate casing of one of the turbochargers of diesel generator No. 2, resulted in a slow water leak, which was discovered while the engine was shut down. The defective turbocharger was replaced prior to re-starting the engine. As stated in Reference A, the cause of the water leak was determined to be a casting defect in the casing. Based on the absence of another similar casing failure in the entire turbocharger maintenance history at San Onofre Unit 1, this particular failure is considered to be an isolated incident.
During Cycle 10 refueling, the required inspections of two turbochargers (one per engine) were performed in accordance with the Owners Group recommendations and NUREG-1216. No adverse findings resulted from these inspections.
In accordance with SCE's comments in Table B of Reference B, all the turbochargers are scheduled for a re-inspection at the next major engine overhaul.
Until then, the selected refueling interval inspections recommended by the Owners Group will be continued.
Based on the history of reliable performance, the results of DRQR inspections, and the implementation of a comprehensive maintenance and surveillance program, it is expected that the turbochargers will continue to provide reliable service in the future.
If you have any questions, please call me.
Very truly yours, cc: J. B. Martin, Regional Administrator, NRC Region V F. R. Huey, NRC Senior Resident Inspector, San Onofre Units 1, 2 and 3