ML17059B157
| ML17059B157 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 06/10/1996 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML17059B156 | List: |
| References | |
| NUDOCS 9606180567 | |
| Download: ML17059B157 (6) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.
72 TO FACILITY OPERATING LICENSE NO.
NPF-69 IAGARA MOHAWK POWER CORPORATION NINE MILE POINT NUCLEAR STATION UNIT 2 DOCKET NO. 50-410
- 1. 0 INTRODUCTION By letter dated January 25,
- 1996, Niagara Mohawk Power Corporation (the licensee) submitted a request for an operating license amendment to change the Technical Specifications (TSs) for Nine Mile Point Nuclear Station, Unit 2.
The requested changes would revise footnotes in two tables referenced by TS 3/4.3.3, Emergency Core Cooling System Actuation Instrumentation, to more clearly define when, during cold shutdown and refueling, the Loss of Voltage and Degraded Voltage relays associated with the Loss of Power actuation trip functions are required to be operable.
Specifically, the footnotes to Tables 3.3.3-1 and 4.3.3. 1-1 currently state:
"Required when ESF
[Engineered Safety Features]
equipment is required to be OPERABLE."
These would be changed to state:
"Required when the associated diesel generator is required to be OPERABLE."
2.0 BACKGROUND
Successful operation of the required safety functions of the Emergency Core Cooling Systems (ECCS)
- depends, in large measure, upon the availability of adequate power sources to energize the various components such as pump motors, motor-operated
- valves, and the associated control components.
Loss of power (LOP) instrumentation monitors the 4. 16 kV emergency buses.
Offsite power is the preferred source for the 4. 16 kV emergency buses.
If the monitors sense that insufficient power is available, the buses are automatically disconnected from the offsite power sources and connected to the onsite diesel generator (DG) power sources.
Each 4. 16 kV emergency bus has its own independent LOP instrumentation and associated trip logic circuits.
The voltage for each bus is monitored at two
- levels, which can be considered as two different undervoltage functions:
- 4. 16 kV Emergency Bus Undervoltage Loss of Voltage, and 4. 16 kV Emergency Bus Undervoltage - Degraded Voltage.
Each function causes various bus transfers and disconnect operations.
Each function is monitored by three undervoltage relays for each emergency
- bus, whose outputs are arranged in a two-out-of-three logic configuration.
The channels include electronic equipment (e.g., trip units) that compares measured input signals with pre-established setpoints.
When the setpoint is reached or exceeded, the 9606180567 9606i0 PDR ADOCK 050004i0 P
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channel output relay actuates, which then sends a
LOP trip signal to the associated trip logic circuits.
- 3. 0 EVALUATION Loss of voltage on a 4. 16 kV emergency bus indicates that offsite power may be completely lost to the respective emergency bus.
Therefore, the power supply to the bus is transferred from offsite power to DG power when the voltage on the bus drops below the loss of voltage function setpoint (loss of voltage with a short time delay).
This ensures that adequate power will be available to the required equipment.
Since the function of LOP instrumentation is to start and load the DGs, the 4. 16 kV Emergency Bus Undervoltage - Loss of Voltage function associated with each emergency bus is only required to be operable when the associated DG is required to be operable.
The proposed changes to the footnotes are consistent with this requirement.
A reduced voltage condition on a 4. 16 kV emergency bus indicates that, while offsite power may not be completely lost to the respective emergency
- bus, available power may be insufficient for starting large ECCS motors without risking damage to the motors that could disable the ECCS function.
Therefore, the power supply to the bus is transferred from offsite power to onsite DG power when the voltage on the bus drops below the degraded voltage function setpoint (degraded voltage with a time delay).
This ensures that adequate power will be available to the required equipment.
Since the function of LOP instrumentation is to start and load the DGs, the 4. 16 kV Emergency Bus Undervoltage Degraded Voltage function associated with each emergency bus is only required to be operable when the associated DG is required to be operable.
The proposed changes to the footnotes are consistent with this requirement.
Accordingly, since the function of LOP instrumentation is to start and load the
- DGs, and LOP instrumentation associated with each emergency bus is only required to be operable when the associated DG is required to be operable, the NRC staff finds that the licensee's proposed changes to the footnotes of TS Tables 3.3.3-1 and 4.3.3. 1-1 comply with applicable regulatory requirements and are acceptable.
4.0 ST T CO S
TATION In accordance with the Commission's regulations, the New York State official was notified of the proposed issuance of the amendment.
The State official had no comments.
- 5. 0 ENVIRONHENTA CONSIDERATION The amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20.
The NRC staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure.
The Commission has previously issued a proposed finding that the
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amendment involves no significant hazards consideration, and there has been no public comment on such finding (61 FR 20851).
Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
- 6. 0 CONCLUSION The Commission has concluded, based on the considerations discussed
- above, that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed
- manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributors:
V. Beaston D.
Hood Date:
June 10, 1996
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