ML20235H032
| ML20235H032 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 07/09/1987 |
| From: | Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| 87-421, NUDOCS 8707140462 | |
| Download: ML20235H032 (6) | |
Text
_ _ _ _ _
VInorwzA ELECTRIC AND Pownn COMPANY Rxcnuann,V1uaisir souas w,L.srewAur Vaca Passisswr '
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July 9, 1987 l
United-States Nuclear Regulatory Commission Serial No.87-421 Attention: Document Control Desk NAPS /MLB:vlh.
Washington,-D. C.
20555 Docket No.
50-338
)
License No. NPF-4 Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNIT 1 JUSTIFICATION FOR CONTINUED OPERATION UNDER TECHNICAL SPECIFICATION 3.7.1.7 Confirming our conference call on July 8, 1987, attached is our basis for requesting continued operation under Technical Specification 3.7.1.7 with the "B"
Reheat Stop Valve inoperable and the "B" Intercept Valve isolated. This request is based on our conclusion that no safety problem exists with operating the unit with the "B" Reheat Stop Valve inoperable.
Further, we are experiencing record demands for electrical power at this time due to weather conditions, and the power being generated by the ur.it is an important factor in our ability to meet these demands.
It is our understanding that this mode
.of. operation is acceptable to the NRC through July 10, 1987.
In summary, continued operation is based on isolating steam flow from the "B" Moisture Separator Reheater (MSR) to the Low Pressure Turbine by closing and hydraulically isolating the "B" Intercept Valve. This action precludes the "B" MSR Train from causing or contributing to a postulated turbine overspeed condition.
Operation with the "B"
MSR isolated has been evaluated by the turbine manufacturer (see attached memo) and found to be acceptable.
Operation, in this condition, will not exceed approximately 47% power and will not continue past 2400 hours0.0278 days <br />0.667 hours <br />0.00397 weeks <br />9.132e-4 months <br /> on July 10, 1987.
By this time, the turbine-generator will be off-line and main stet.m to the turbine will be completely isolated.
The basis for continued operation with the "B" Reheat Stop Valve inoperable has been reviewed and approved by the Station Nucicar Safety and Operating Committee.. It has been found not to involve an unreviewed safety question as defined in 10 CFR 50.59.
Very truly yours, W. L. Stewart Attachments k
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cc:
U. S. Nuclear Regulatory Commission 101 Marietta Street,-N. W.
Suite.2900 Atlanta, GA 30323 Mr. J. L. Caldwell NRC Senior Resident Inspector North Anna Power Station i
1 1
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l
l Attachment On July 6,
- 1987, at 1824 hours0.0211 days <br />0.507 hours <br />0.00302 weeks <br />6.94032e-4 months <br />, it was observed that "A" MSR cycle steam exhaust temperature decreased significantly during a power ramp up from approximately 50% to 83% power.
Efforts to stop the temperature reduction were not successful.
Power incrctse was terminated on July 7, 1987, at 0153 hours0.00177 days <br />0.0425 hours <br />2.529762e-4 weeks <br />5.82165e-5 months <br /> at 83%, and a unit ramp down to 50% was commenced at 0240 hours0.00278 days <br />0.0667 hours <br />3.968254e-4 weeks <br />9.132e-5 months <br />. After investigation of the MSR problem, it was determined that the "B"
MSR Reheat Valve may not be full open.
At approximately 1200 hours0.0139 days <br />0.333 hours <br />0.00198 weeks <br />4.566e-4 months <br /> on July 7, 1987, a Special Test was written and approved by SNSOC to determine the position and condition of the "B" MSR Reheat Valve.
The procedure was written to cycle both the "B" MSR Intercept and Reheat Valves at alternate times to collect data for evaluation.
During the performance of the test, with the Intercept Valve already closed, the EHC fluid supply was isolated from the actuator of the Reheat Valve to allow the valve to close by spring action.
Four independent parameters were observed that indicated that the Reheat Valve closed.
First, actuator piston motion was observed as EHC fluid was drained, accompanied by noise reduction in the crossover piping similar to that encountered in routine Reheat Valve closure.
- Secondly, "B"
MSR cycle steam outlet temperature and flow dropped indicating that steam flow was isolated. Thirdly, at the same time, a drop in "A"
MSR cycle steam outlet temperature occurred indicating increased steam flow through the "A" MSR.
- Finally, turbine power dropped slightly.
These independent parameters indicate that the "B" MSR Reheat Valve did close and isolate steam wher EHC fluid supply was isolated frcm the actuator. Also, when the Intercept Valve was reopened, exhaust cycle steam temperature and turbine power did not change.
(There was a slight increase in temperature which was indicative of a small amount of Icak by.)
)
The performance of the special test (1-ST-74) indicated that both the "B" MSR Intercept and Reheat Valves will close and isolate steam when EHC fluid is j
isolated from the actuators. Thus, the "B" MSR intercept and reheat valves are capable of performing their turbine overspeed protection function as described in the LCO of T.S. 3.7.1.7.
l l
At approximately 1600 bcurs on July 7, 1987, a conference call was held with Westinghouse to discuss the technical impact of operating at approximately 50%
1 power with the "B" Reheat Valve throttled open. Westinghouse concluded that no adverse impact on the LP or HP turbine existed for continued operation through July 8, 1987.
On July 8,
- 1987, further discussions were held with Westinghouse that concluded:
- 1) operation in this condition could continue at least through July 10, 1987, and 2) the steam flow from the "B" MSR could be isolated.
1 Based on observation and inspection of the replacement Reheat Stop Valve, which is currently being staged in the Turbine Building, a concern on the part of station management developed as to whether the inservice Reheat Stop Valve would continue to position correctly on demand. At 1300 hours0.015 days <br />0.361 hours <br />0.00215 weeks <br />4.9465e-4 months <br /> on July 8, 1987, the "B" Reheat Stop Valve was declared inoperable, and the Action Statement of T.S. 3.7.1.7 was entered.
The NRC Resident Inspector was also notified.
Subsequently, at 1415 hours0.0164 days <br />0.393 hours <br />0.00234 weeks <br />5.384075e-4 months <br />, the EHC high pressure fluid to both the "B" Reheat Stop Valve and the "B" Intercept Valve was isolated. Both valves cycled when EHC fluid was isolated and steam flow was isolated from the "B" MSR.
- However, the "B" Reheat Valve actuator piston cycle length was greatly in excess of the cycle length observed during July 7, 1987, Special Test. Therefore, the exact position of this valve is currently in question.
The "B"
Intercept Valve cycled closed.
I In summary, the plant can continue to operate because the steam flow to the l
l turbine through the inoperable valve has been isolated, and turbine operation in this condition has been analyzed to be acceptable. Although the "B" Reheat
]
l Stop Valve is part of the Turbine Overspeed Protection System and may be i
partially open, the "B" Intercept Valve is closed and hydraulically isolated from opening, thereby eliminating the B "MSR Trafn" from causing or contributing to a postulated turbine overspeed condition. Also, a Turbine i
Overspeed Test performed in accordance with T.S.
4,7.1.7.2c was completed satisfactorily on July 2, 1987.
i V
i MEMO
- WESTINGHOUSE -
ENERGY SYSTEMS SERVICE DIVISIONS TO: Wayne Harrell - Station Manager CC: Bob Enfinger - Superintendent Operations i
FROM: Clive Callaway - Westinghouse Site Service Manager DATE: JULY 8,1987 i
SUBJECT:
Operating at <50%
power with "B"
Moi sture Separator Reheater isolated Westinghouse concurs that it is acceptable to operate Unit 1 1
Turbine with the "B" Moisture Separator Reheater isolated through Friday of this week.
We understand that Virginia Power will l
initially decrease power to approximately 47%
and then isolate l
"B" MSR by securing the EHC fluid to both the "B"
Reheat Stop Valve and the "B"
Intercept Valve and allowing the valves to drift shut. The valves will then remain shut while the Unit is on line.
Westinghouse's acceptance of this temporary mode of operation is based on our belief that there will be no detrimental affects on both the both LP and HP sections of Unit 1 Turbine.
We feel that there will not be a problem with vour concern of missile generation due to blade degradation on #1 LP.
I would like to al so address your additional concern pertaining to the "80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br /> limitation" mentioned in the Technical Manual. This limitation is applicable only at 100%
power operation and does not apply at this reduced power level.
Regards.
/
/
/ST
'li ve Call aGay l
l
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