ML20083Q035
| ML20083Q035 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point, Oyster Creek, 05000000 |
| Issue date: | 06/02/1972 |
| From: | Burt P NIAGARA MOHAWK POWER CORP. |
| To: | Skovholt D US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20083Q029 | List: |
| References | |
| NUDOCS 8302220582 | |
| Download: ML20083Q035 (3) | |
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NI AG ARA MO H Aw:t POwz R CO RPO RATION NIAGARA MOHAWX Nine Mile Point Nuclear Station Post Office Box 32 Lycoming, New York 13093 June 2, 1972 Mr. Donald J. Skovholt Assistant Director for Reactor Operations Division of Reactor Licensing United States Atomic Energy Commission Washington, D. C.
20545
Dear "r. Skovholt:
Re:
Provisional Operating License:
DPR-17 Dociet No.
50-220 During the annual inspection outage of Nine Mile Point Unit 2, which wiu serminate tonorron, June 3, 1972, a probler with the electromatic relief valves was iisclosed.
here are three 6" Consolidated Electromatic Relief salves, (ype 1523-n, installed on each of the two steam ines within the f.osso.1 rywe
- cr a tota. or six.
Three are required for depressuritation on f coolant accident and five are required to maintain pressure margin beween peax transient pressure and lowest safety valve setting on turbine trip witnout bypass.
w On one valve, the locking screw, Part #8 on enclosed drawing, had become unscrewed allowing lock retainer Plate #7 to fall free (both parts were recovered in the turbine stop valve strainer basket).
This permitted the disc retainer, Part 40, to coapletely back-out falling to the bottom of tc.e va.'ve body.
In this condition, it would be impossible to bleed enough steam f ron. Cnambe:
"C" to open the valve as it would be wide open to Ch..mbe:
"A" and would not have the benefit of the restricting orifice in ti.e reta.ner plate.
i One other valve was found with the locking screw, Part #8, backed out 1/16" but the lock retainer plate and disc retainer had not moved, therefore the valve was operable.
Tic-wires holding the locking screws were broken on all six valves.
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I" Was effected t0,, ] ! SiX Valves 'Oy removing,3g ;ggg ng 5cycg'
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3 73y oc acco..g14sneo-oy grinding out the stitch weld.
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uependa,alilty of valve operation is increased.
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CONSOLIDATED ELECTR0MATIC RELIEF VALVE 6" - TYPE 1525-VX Effected Parts
- 4 Valve Disc.
- 6 Disc Retainer
- 7 Lock Retainer Plate
- 8 Locking Screw When normally closed, steam pressure is equal in Chambers "A", "B" and "C".
Disc 4 is held to seat by greater force in "C" over "B" (difference in projected areas) and spring.
Valve operates when pressure in "C" is decreased by opening of pilot valve. Higher total force in "B" then pushes Disc 4 away from seat allowing steam to discharge.
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