ML19345G130
| ML19345G130 | |
| Person / Time | |
|---|---|
| Site: | Humboldt Bay |
| Issue date: | 10/05/1972 |
| From: | Searls F PACIFIC GAS & ELECTRIC CO. |
| To: | Skovholt D US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| 5510, NUDOCS 8103020697 | |
| Download: ML19345G130 (2) | |
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PACIFIC GRAS AND ELECTR,IC C O M PANY b b'M3 l
77 B E ALE S T R E E T. SAN F R AN CISCO, C A Oyj (415) 781 4211 e
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October 5, 1972
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U. S. Atomic Energy Commission Washington D. C.
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Donald J.
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Assistant Director for Operating Reactors f j st 9
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[#geolgQ Directorate of Licensing
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Re:
Docket No. 50-133 License No. DPR-7 Humboldt Bay Power Plant g
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O 6f Gentlemen:
As requested in your letter of August 3, 1972, a review of the Humboldt Bay Power Plant Unit No. 3 has been conducted in light of the recent flooding incident which occurred at Quad-Cities Unit 1.
The probability and the possible consequences of massive flooding of the site by a 20 foot tsunami (8 feet above plant grade) at the Humboldt Bay Power Plant have been extensively investigated with the conclusion that Unit No. 3 is adequately protected against such an occurrence.
The results of this investigation are discussed in a letter from R. H. Peterson to the Director, Division of Reactor Licensing, dated June 8, 1966, and in a report entitled " Report on Protection of Reactor Caisson Access Shaf t Against Tsunami Flooding," dated July 15, 1969.
Modifications indicated by this study were accomplished, and the completion of the tsunami protection system was reported in the report on the operation of Humboldt Bay Power Plant Unit No. 3 covering the period July 1, 1971, through December 31, 1971, submitted February 25, 1972.
The Unit No. 3 circulating water system is the only plant water system with sufficient capacity to cause flooding of the P00R ORIGINAL f/)$b80b1 5510 a
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..t Page two proportions necessary to affect the performance of engineered safety systems.
However, any flooding from this system would be of significantly smaller magnitude than that which would result from the design basis tsunami.
The area flooded by such an occurrence would be the turbine building pipe tunnel, generator seal oil room, and the main condenser area (See Figures 5, 6 and 7 on pages 10, 11 and 12 of the Final Safety Analysis Report).
Once flooding reached grade (plus 12 feet),
water would flow from these areas into the yards through the various doorways leaving these areas.
There would be no flow of water into the reactor feedwater pump area since a watertight door is provided between this area and the pipe tunnel.
The only engineered safety system equipment located in the areas subject to flooding are the main steam isolation valves and the emergency condensate retrrn valve.
One of the two main steam isolation valves has itr, motor operator located on the opera-ting floor of the refueling building thereby protecting it from such flooding.
.This detail is shown in Figure 17 on page 32 of the FSAR.)
As a part of the tsunami modifications, the emergency condenser condensate return valve was equipped with a motor operator designed for submerged operation.
As in the case of a tsunami, a small flow of water from the flooded pipe tunnel could enter the two radwaste tanks located in the refueling building through floor drains.
Protection against this eventuality is afforded by high level annuncia-tion on these tanks and by the remotely operable valves pro-vided as part of the tsunami protection system.
It is our plan to modify the existing emergency operating pro-cedure for use of the tsunami protection system explicitly to cover flooding of the turbine building areas due to a malfunction in the circulating water system.
This procedure will be reviewed, approved and issued for use by November 1, 1972.
Sincerely,
/
d2 F. T. S EARLS
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