ML13308B504
| ML13308B504 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 03/12/1975 |
| From: | Fogarty D SOUTHERN CALIFORNIA EDISON CO. |
| To: | Anthony Giambusso Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8103060653 | |
| Download: ML13308B504 (2) | |
Text
Southern California Edison Company P. O. BOX 800 2244 WALNUT GROVE AVENUE DAVID J. FOGARTY ROSEMEAD, CALIFORNIA 91770 TELEPHONE
.CA vc s) 213 -572-2796 March 12, 1975 Mr. Angelo Giambusso, Director Division of Reactor Licensing 77 Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission r
Mail Code: BETH 042 Washington, D..C. 20545 Docket Number 50-206 San Onofre Unit 1 No. 1 Diesel Generator
Dear Sir:
This report describes an in6ident experienced at the San Onofre Nuclear Generating Station concerning the No. 1 diesel generator.
In accordance with Station Order S-0-19 the two diesel generators are tested semi-annually. These tests are in addition to the weekly and refueling interval testing required by Technical Specifications 4.4 A and B. The semi-annual test requires that both diesel generators be operated at rated load (600 KW) for one hour. During this test, which was conducted on February 12, 1975, the No. I diesel generator tripped from loss of fuel after 45 minutes of operation.
The diesel fuel system consists of an underground fuel storage tank, a 50 gallon day tank at an elevation above the engine, an engine driven fuel transfer pump to lift fuel from the storage tank to maintain a constant level in the day tank and two engine driven injection pumps taking suction from the day tank and supplying the cylinders. A low day tank level alarm annunciates at a local panel along with other diesel generator alarms (overspeed, high temperature, etc.)
A common master alarm in the control room is initiated when any one of these conditions exist.
During the course of the investigation, it was determined that the transfer pump originally provided with the No. I diesel generator was of lower capacity than the one provided with the No. 2 diesel generator. The No. 1 diesel transfer pump apparently did not have sufficient capacity to keep the day tank 2866j
Mr.-Angelo Giambusso 2 -
March 12, 1975 full at rated load.
Since both diesels are identical, the transfer pumps should be the same capacity. The difference in capacities of the two transfer pumps had not been apparent previously because the exterior shape and dimensions of the two pumps are identical.
Despite a thorough investigation, it was not conclusively determined why the No. 1 diesel tripped on this occasion from loss of fuel after only 45 minutes of operation. Additionally, the No. 1 diesel generator had been operated at rated load for one hour on a number of previous occasions without loss of fuel.
It is felt, however, that (1) a series of other periodic tests which were performed prior to the full load test resulted in excessive fuel usage and lowered the fuel level in the day tank prior to the start of the semi-annual full load test (2) the capacity of the transfer pump was not sufficient to maintain level in the day tank with the diesel operating at full load (600 KW), and (3) alarms from previous testing prevented reinitiation of the master alarm in the control room when a low fuel level occurred in the day tank.
A transfer pump of the size used on No. 2 diesel generator was obtained and installed on the No. 1 diesel generator.
Testing at full load indicated that the new transfer pump has adequate capacity for extended full load operation.
In accordance with Technical Specification requirements, the No. 2 diesel generator remained operable during the period the No. 1 diesel generator was out of service. The fuel pump on No. 2 diesel generator was checked and found to be of the proper size and adequate capacity.
Sincerely, cc:
Director, Region V Regulatory Operations Office