ML20029E797
| ML20029E797 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 05/11/1994 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20029E798 | List: |
| References | |
| NUDOCS 9405200176 | |
| Download: ML20029E797 (1) | |
Text
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4.
In addition to the crossover steam dump system, the turbine is provided with three different turbine overspeed protection systems which control steam supply to the high pressure turbine.
The mechanical overspeed trip mechanism and the Independent Overspeed Protection System (IOPS) prevent an overspeed condition by rapidly closing the turbine stop and governor valves using independent trip mechanisms when an overspeed condition is sensed. The auxiliary governor uses solenoid operated hydraulic dump valves to rapidly close the turbine governor valves when an overspeed condition or a mismatch 1
between MSR pressure and generator output is sensed.
Each turbine governor valve must be operable or closed in order for the auxiliary governor overspeed 4
i protection function to be operable.
Each of the systems described above reduce the probability of generation of a turbine missile with sufficient energy to damage safety-related structures, systems, o'r components.
1 l
The licensee proposes adding the following specification for the crossover i
steam dump system as TS 15.3.4.E:
i The crossover steam dump system shall be operable.
If the crossover steam dump system is determined to be inoperable, reduce 3
power to less than 480 MWe (gross) within three hours.
l The crossover steam dump system is required to be operable since there is no redundant system which performs its function. The licensee has determined that the turbine will not exceed 132 percent of rated speed following a unit 1
trip when initially operating at less than 480 MWe (gross) regardless of the status of the crossover steam dump system.
Therefore, the proposed action is acceptable because it places the plant in a condition where the function of the crossover steam dump is not required. The required time to complete the action is acceptable based on the low probability of a unit trip requiring operation of the crossover steam dump system during that time.
The licensee proposes adding the following specification for the turbine overspeed protection systems as TS 15.3.4.F:
i j
During power operation, at least one of the turbine overspeed protection systems that trips the turbine stop valves or shuts the turbine governor valves shall be operable.
If all three systems are determined to be inoperable, isolate the turbine from the steam supply within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.
The licensee also proposed. adding the following specification for the turbine stop and governor valves as TS 15.3.4.G.
Should one of the turbine stop valves or governor valves be declared inoperable, restore the inoperable valve to an operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
If operability cannot be restored, perform one of the following actions:
1.
Shut the affected valve within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.
2.
Isolate the turbine from the steam supply within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.
4 9405200176 940511 PDR ADOCK 05000266 P
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