ML20004F579
| ML20004F579 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 05/28/1981 |
| From: | Papay L SOUTHERN CALIFORNIA EDISON CO. |
| To: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, NUDOCS 8106190122 | |
| Download: ML20004F579 (3) | |
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Southern California Edison Company
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May 28, 1981 Mr. R. H. Engelken, Director Office of Inspection and Enforcement
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Dear Mr. Engelken:
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Subject:
Docket Nos. 50-361 and 50-362 San Onofre Nuclear Generating Station, Units 2 and 3 In a letter to your office dated April 30, 1981 we identified a condition which we considered potentially report-able in accordance with 10CFR50.55(e).
The condition concerns the use of Y-pattern, unidirectional valves in the nitrogen pressurizer lines to the safety injection' tanks.
Enclosed are twenty-five (25) copies of a final report entitled, " FINAL REPORT ON THE USE OF TARGET ROCK Y-PAITERN GLOBE VALVES IN THE SAFET'l INJECTION TANK FILL LINES, San Onofre Nuclear Generating Station, Units 2 end 3."
If you have any questions regarding this report w2 would be pleased to discuss them with you at your convenicace.
Very truly yours, Enclosures
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Victor Stello (NRC, Director I&E)
R. J. Pate (NRC, San Onofre Units 2 and 3)
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o FINAL REPORT ON THE USE OF TARGET ROCK Y-PATTERN GLOBE VALVES IN THE SAFETY INJECTION TANK FILL LINES San Onofre Nuclear Generating Station, Units 2 and 3 INTRODUCTION This report is submitted pursuant to 10CFR50.55(e)(3).
It describes a condition in which the nitrogen pressurization of the safety injection tanks (SIT) could be vented during a seismic or high energy line break event.
This report includes a descrip-tion of the deficiency, analysis of the safety implications and a summary of the corrective actions taken.
By letter dated April 30, 1981, Edison confirmed notification to the NRC of this potentially reportable condition.
BACKGROUND i
During the review of high energy piping for potential pipe breaks and system responses, it was determined that it would be beneficial to depressurize the seismic Category II portion of the nitrogen supply header inside containment during opera-tion in order to minimize the potential for high energy pipe breaks.
A review of the SIT isolation valves showed that they are unidirectional and would not be effective with a reverse.
pressure differential (vented fill line).
Further review indicated that the valves and their associated supports were 4
class boundaries between seismic category I and II systems.
Consequently, if the nitrogen supply header (seis nic category II) failed during a seismic event, the safety injection ta:*a uculd have depressurized.
l DISCUSSION 1
The following discussion is responsive to 10CFR50.55(e)(3).
Description of the Deficiency l
The nitrogen fill valve (HV-9344, -9354, -9364, -9374) to the safety, injection tanks are solenoid operated unidirectional Y-pattern globe valves manufactured by Target Rock.
A pressure i
differential in the direction opposite to the normal direction l
of flow will unseat these valves, resulting in the simultaneous loss of nitrogen overp:cessure to all safety injection tanks.
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I FINAL REPORT ON THE USE OF TARGET ROCK Y-PATTERN Page 2 GLOBE VALVES 1N THE SAFETY INJECTION TANK FILL LINES San Onofre Nuclear Generating Station, Units 2 and 3 Analysis of Safety Implications If the seismic category I nitrogen supply header failed during a seismic event, the safety injection tanks would depressurize and not serve their safety function.
CORRECTIVE ACTION A review of the use of all solenoid operated Target Rock Y-pattern globe valves was performed to determine whether this deficiency was present in any other system.
The results of that investigation indicated that this was a unique situation.
Seismic Category I check valves will be installed upstream of the Target Rock valves to prevent depressurization through the valves.
Schedule for completion is August 1, 1981.
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