ML13333B768
| ML13333B768 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 08/12/1982 |
| From: | Michelson C NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| To: | Ray H SOUTHERN CALIFORNIA EDISON CO. |
| Shared Package | |
| ML13333A766 | List: |
| References | |
| NUDOCS 8208270695 | |
| Download: ML13333B768 (2) | |
Text
AUG 1 2 1982 Mr. Harold B. Ray, Station Manager San Onofre Nuclear Generating Station P.O. Box 128 San Clemente, CA 92672
Dear Mr. Ray:
SUBJECT:
CASE STUDY REPORT ON SAN ONOFRE UNIT 1 LOSS OF SALT WATER COOLING EVENT OF MARCH 10, 1980 On March 10, 1980, while operating at 100% power, San Onofre Unit 1 experienced a complete loss of the salt water cooling system. The event involved an unlikely triple failure which resulted in operations exceeding the plant's limiting conditions for operations.
The event was later determined to be an abnormal occurrence. Enclosed for your information and consideration is the AEOD case study of the event.
The report contains a detailed description of what occurred, along with our findings, conclusions, and recommendations.
The most important recommendations concern:
a) single failure vulnerability of the salt water cooling system; b) contamination of plant air systems; c) in-service testing programs; and d) plant technical specifications In addition to presenting the aforementioned recommendations, the case study has findings and conclusions regarding shortcomings in the plant maintenance at San Onofre Unit 1. We note that on May 13, 1982, while the plant was in cold shutdown, maintenance activities were performed which caused two more complete losses of the salt water cooling system. These occurred as follows:
While the plant staff was removing the internals of one salt water cooling pump for preventive maintenance operations, the Pacific Ocean flooded the pump bay. The flooding took place because an error was made in calculating the tide elevation. Subsequently, the operating salt water cooling pump was secured to prevent it from being damaged.
The auxiliary salt water cooling pump was inoperable due to the on going maintenance activities.
8208270695 820812 PDR ADOCK 05000206 P
PDR OFFICEP........................
SURNAME DATE NRC FORM 318 (10-80) NRCM 0240 OFFICIAL RECORD COPY USGPO: 1981-335-960
Central File AEOD Reading File AEOD Chron. File NRC PDR Harold B. Ray 2 -
HOrnstein, AEOD KSeyfrit, AEOD CJHeltemes, AEOD CMichelson, AEOD About an hour after resuming salt water cooling pump operations, the discharge valve on the north salt water cooling pump failed closed causing another interruption of the salt water cooling system. The flooding is suspected as the cause of this failure (residual moisture in the pressure switch and melted insulation in an associated time delay relay).
During both of these interruptions of cooling the screen wash pumps (which are of a lower capacity and are not "safety-related")
were used to supply salt water cooling. Since the unit had been in cold shutdown at the time, there were no adverse effects to the plant or the public.
As shown in Section 3.1 of the case study report, a complete loss of the salt water cooling system during the early stages of RHR operation could lead to damage to safety-related equipment within a few minutes.
Fortunately, the March 10, 1980 and May 13, 1982 events did not occur while the plant was in the early stages of RHR operation.
If you have any questions regarding this matter, please contact either myself or Harold Ornstein of my staff.
Sincerely, Original Signed by carlyle Michelson Carlyle Michelson, Director Office for Analysis and Evaluation of Operational Data
Enclosure:
As Stated A D AE(D AEOD AEOD SURNAME.
.......Stein t
Seyfrit Heltemes CMichelson 8/
/82 8/9/82 8/u /82 8
DATE
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10-0 * **..........
. R..
NRC FORM 318 (10-80) NROM 0240 OFFI CIA L RECORD COP Y USGPO: 1981-335960