ML20008G202
| ML20008G202 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 06/15/1981 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| REF-PT21-81-464-000 10CFR-050.55E, 10CFR-50.55E, PT21-81-464, PT21-81-464-000, NUDOCS 8107020440 | |
| Download: ML20008G202 (2) | |
Text
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['f' yf ph(3 0 400 Chestnut Street Tower II June 15, 1981 s
SQ ' 0-328/81-35 k
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s Mr. James O'Reilly, Director N
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[M Office of I tion and Enforcement U.S. Nuclear gulatory Commission i.{*.,JUL 011981 *h Region II - Sui e 3100 m
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1 101 Marietta S et Atlanta, Georgia 0303 O'
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Dear Mr. O'Reilly:
41[t' SEQUOYAH NUCLEAR PLANT UNIT 2 - POT.V OPERATING TIME - SQRD-5G-328/81-35
- FINAL REPORT The subject deficiency was initially mporten to NRC-0IE Inspector R. V. Crlenjak on April 24, 1981 in accordance with 10 CFR 50.55(e) as NCR SQN NEB 8122. An interim report was submitted on May 26, 1981.
Enclosed is our final mport. We consider 10 CFR 21 applicable to this deficiency.
If you havia any questions, please get in touch with D. L. Lambert at FTS 857-2581.
Very truly yours, TENNESSEE VALLEY AUTHORITY L. M. Mills, Manager Nuclear Eagulation and Safety Enclosure oo: Mr. Victor Stello, Director (Enclosure)
Office of Inspection and Enforceaant U.S. Nuclear Regulatory Cosmtission washington, De a555 f8I 8107020YYO 8
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ENCLOSURE SEQUOYAH NUCLEAR PLANT UNIT 2 PORV OPERATING TIME SQRD-50-328/81-35 10 CFR 50.55(e)
FINAL REPORT Description of Deficiency The operational time requirement for the pressurizer PORV l
(manufactured by Copes-Vulcan) is two seconds maximum. The PORV's are I
being used as the pressure relieving devices in the cold overpressurization system. The operating time of the PORV's at normal
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system pressure meets the design requipement of two seconds. As the system pressure decreases to 500 lb/in g, the operating time of the PORV's increases to between five and six seconds. This operating time for low pressures is unacceptable because the Westinghouse cold overpressurization setpoint analysis assumed an operating time of two seconds as stated in the FSAR (section 5.2.2.4.2).
The reason for t_he l
increased operating time is that, as system pressure decreases, less system force is being exerted on the valve plug which assists the operator to open the valve. Tte present air supply to the valve operator is insufficient to open the valve in the required time.
l The PORV's at Sequoyah unit 1 are Masoneilan valves and the PORV's at Watts Bar units 1 and 2 are Fisher valves. Therefore, this condition applies only to Sequoyah unit 2.
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Safety Implications l
Had this condition remained uncorrected, 'the cold overpressurization system l
would not operate es assumed in the Sequoyah FSAR. The cold overpressurization system could not have adequately mitigated the effects of all low temperature overpressure transients. Events could have occurred l
where 'the 10CFR50 Appendix G reactor vessel nil ductility transition temperature (NDT) limits could have been exceeded. Such events could have occurred aaly when the plant was in a water solid cold shutdown condition.
Corrective Action The air sup/ ply to the valve operator will be modified to provide sufficient i
air to the valve operator to achieve a 2-second stroke time. TVA will l
replace the present 3/8-inch air supply line from the air headers to the PORV's with a 1-inch air supply line.
If this change does not adequately correct the deficiency, the 1/4-inch NPT valve operator port will be changed to 1/2 inch. The above changes have been approved by Westinghouse.
The valve will be retested to verify the adequacy of the repairs. All modifications and tests will be completed before initial criticality
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of Sequoyah unit 2.
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