ML19345G125
| ML19345G125 | |
| Person / Time | |
|---|---|
| Site: | Humboldt Bay |
| Issue date: | 10/16/1973 |
| From: | Searls F PACIFIC GAS & ELECTRIC CO. |
| To: | US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| 7704, NUDOCS 8103020656 | |
| Download: ML19345G125 (2) | |
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PACIFIC G-A S AND ELECTR,IC C O M PANY 1POUIr l
77 BEALE STREET. SAN F R AN CISCO, C A LIFO R NI A 94106 *(415) 781 4211 IIi C '. s'..".S.21.E ^.".II October 16, 1973
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Docket No. 50-133 License No. DPR-7
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Gentlemen:
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During the period from August 31, 1973 through October 2, 1973 Humboldt Bay Power Plant Unit No. 3 was shut down for the an-nual refueling and maintenance outage.
As a part of the outage operational tests were performed in accordance with the requirements of Table IX-1 of the Technical Specifications.
Portions of two of the operational tests showed settings that were out of tolerance in the conservative direction and are thus reportable under Section IX.H.2.b(2) of the Technical Specifications.
On September 17, 1973 during the check of the trip setting of the four Main Steam Isolation Valve Closure Reactor Trip switches associated with MO-6101 (second off main steam isolation valve), it was discovered that the settings varied from 34.7 to 37.0% closed in-stead of 40 1 3% as stated in Table VI-1 of the Technical Specifica-tions.
These settings were conservative in that they would have caused the reactor to trip earlier than normal from main steam isolation valve closure.
Observation disclosed that the mounting bracket used to trans-mit the valve stem motion to the trip switches was loose.
The bracket was tightened with lock nuts at the proper position to bring the trip settings within specifications.
The switch mounting on the other main steam isolation valve was found to be in satisfactory condition.
During each future regularly scheduled refueling outage, the brackets will be inspected as a part of the operational test.
On September 19, 1973 during the check of the settings of the two drywell vacuum breakers, the upper breaker was observed to operate at 4.0" H 0.
Section III.B.5(c) of the Technical Specifications re-2 quires the vacuum breakers to begin to open at a pressure differential of 0.5 1 0.2 psi (approximately 13.5 i 5 inches of H O).
Had the vacuum 2
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Director, Directorate of Licensing October 16, 1973 U. S. Atomic Energy Commission Page 2-breakers been required to operate, the upper vacuum breaker would have lifted at a more conservative setting than required by the Technical Specifications.
The lower vacuum breaker sutting was found to be 15.4" H 0, which is within the specifications.
2 Both vacuum breakers were dissassembled and inspected.
It appears that excessive lubricant had been used on the guide rods.
Both vacuum breakers were cleaned and the guide rods were lightly lubricated.
A retest on September 25, 1973 showed that the vacuum breaker operated smoothly and lifted at 14.7" H O during two separate tests.
Maintenance 2
personnel have been cautioned not to use an excessive amount of lubricant on the guide rods during vacuum breaker maintenance.
Very truly yours, e
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Director Directorate of Regulatory Operations Region V U. S. Atomic Energy Commission P. O. Box 1515 Berkeley, California 94701 I
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