ML13324A702
| ML13324A702 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 08/22/1985 |
| From: | Morgan H SOUTHERN CALIFORNIA EDISON CO. |
| To: | Martin J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737, TASK-2.B.3, TASK-TM TAC-44478, NUDOCS 8509030192 | |
| Download: ML13324A702 (4) | |
Text
Southern California Edison Company SAN ONOFRE NUCLEAR GENERATING STATION P.O.
BOX 128 SAN CLEMENTE, CALIFORNIA 92672 H. E. MORGAN TELEPHONE STATION MANAGER August 22, 1985 (714) 492-7700 U.S. Nuclear Regulatory Commission Office of Inspection and Enforcement Region V 1450 Maria Lane, Suite 210 Walnut Creek, California 94596-5368 Attention:
Mr. J. B. Martin, Regional Administrator
Dear Sir:
Subject:
Docket No. 50-206 PASS Grab Sample Facility Status Report San Onofre Nuclear Generating Station, Unit 1
Reference:
Telecon, W. G. Zintl (SCE) with G. P. Yuhas (NRC), August 16, 1985 As required by License Condition 3.K, Post-Accident Sampling System (PASS),
NUREG-0737, Item II.B.3, SCE will complete the installation of a post-accident sampling system at San Onofre Unit 1 by the end of the Cycle 9 refueling outage or July 1, 1986, whichever is earlier. Pursuant to the referenced telephone discussion, this letter is to provide you with a description of a recent event regarding the startup of the PASS at San Onofre Unit 1.
On August 12, 1985, it was discovered that the PASS equipment room had been flooded with primary plant makeup water, resulting in damage to PASS mechanical equipment (the PASS controls were not affected).
The undiluted grab sample capability was previously lost on June 21, 1985, when containment isolation valie SV-3302 to the RCS sample line was declared inoperable, as described in our June 28, 1985 letter. The condition of the PASS equipment has since been evaluated and it has been determined that the undiluted grab sample capability can be restored by August 28, 1985. In the interim period the remaining alternate PASS methods described in our August 14, 1984 letter will be maintained.
The damage to the PASS equipment is not expected to preclude the completion of startup of the PASS on a schedule consistent with License Condition 3.K with the exception that the impact on our schedule for training of PASS operators i-s still under evaluation. A more detailed description of the event is provided as an enclosure to this letter.
8509030192 850822 PDR ADOCK 05000206 S
Mr. J.
August 22, 1985 If you require any additional information, please so advise.
Sincerely, Enclosure cc:
F. R. Huey (USNRC Senior Resident Inspector, Units 1, 2 and 3)
J. B. Martin (Regional Administrator, USNRC Region V)
J. A. Zwolinski, Branch Chief, Office of Nuclear Reactor Regulation (NRR)
Institute of Nuclear Power Operations (INPO)
00 ENCLOSURE
- 1. DESCRIPTION OF OCCURRENCE AND GENERAL DESIGNATION OF APPARENT CAUSE
- a. Description of Occurrence:
On August 12, 1985, at 1100 hours0.0127 days <br />0.306 hours <br />0.00182 weeks <br />4.1855e-4 months <br />, the south Post-Accident Sampling System (PASS) pit was found to be filled with about eight feet of water. Further investigation found that the source of flooding was from the makeup water system. At 1130, the flow of makeup water was secured by closing valve MU-338. By 2025 hours0.0234 days <br />0.563 hours <br />0.00335 weeks <br />7.705125e-4 months <br />, the PASS pit was pumped dry by using a portable pump. An examination of the PASS indicated that the flow was coming from a backfiow preventer relief valve, PSV 4905. The flow was swirling around the catch drain system and spraying the PASS equipment in the general area. Also the relief valve flange gasket was ruptured and spraying the general area.
- b. Apparent Cause:
Material Failure of the relief valve flange gasket simulated a "backflow" pressure to the relief valve, causing it to open fully and vent the effluent into the Post Accident Sampling System (PASS) catch basin.
Therefore, the relief valve could not sense the "correct" condition and the makeup water continued to vent until action to manually isolate the line was taken.
Design The catch basin was not designed to collect the volume of effluent vented from the relief valve over the extended period. Observation showed a majority of the effluent avoiding the desired path by overflowing and spraying into the pit area before draining into the sump.
-2 ENCLOSURE (Continued)
- 2. OPERATING CONDITION AT TIME OF OCCURRENCE:
- a. Unit 1 was at 93% power, 393 MW.
- b.
The PASS system was de-energized with valves shut.
- 3.
IMMEDIATE EVALUATION, CORRECTIVE ACTION TAKEN AND RESULTS:
At 1120 hours0.013 days <br />0.311 hours <br />0.00185 weeks <br />4.2616e-4 months <br />, August 12, 1985, the effluent in the PASS pit was checked for contamination. The effluent was found to be primary makeup water and was removed from the pit with a portable pump. Pumping was completed at 2005 hours0.0232 days <br />0.557 hours <br />0.00332 weeks <br />7.629025e-4 months <br />.
- 4.
EVALUATION:
The flooding was caused by the failure of the relief valve flange gasket. SCE considers this gasket failure an isolated incident since another duplicate backflow preventer has been in use for several years on the Unit 2/3 PASS with no failure.
SCE will further evaluate the adequacy of the drain system.
6909u