ML20084T733
| ML20084T733 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 06/01/1995 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20084T721 | List: |
| References | |
| NUDOCS 9506120510 | |
| Download: ML20084T733 (3) | |
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3 UNITED STATES 7
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.163 TO FACILITY OPERATING LICENSE NO. DPR-35 BOSTON EDISON COMPANY
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PILGRIM NUCLEAR POWER STATION QQGET NO. 50-293
1.0 INTRODUCTION
By letter dated November 22, 1994, the Boston Edison Company (the licensee or BECo) submitted a request for changes to the Pilgrim Nuclear Power Station Tw hnical Specifications (TSs). The requested changes would revise the suppression chamber water level operating range, increasing it 2 inches, and revises the water level recorder range in response to a commitment from an inspection.
2.0 VALUATION The proposed change revises the suppression chamber water level operating range, increasing it 2 inches, and revises the water level recorder range in response to a commitment from Inspection 91-201 (BECo Letter dated March 10, 1992).
In the March 10, 1992, response to the Systems Based Instrumentation and Control Inspection No. 50-293/91-201, BECo committed to evaluate the feasibility of increasing the water level operating range.
The basis for the TS limit on maximum suppression pool water level relates to the fact that the water level affects the line clearing loads from safety / relief valves discharges and the vent clearing and pool swell loads associated with a design-basis accident loss-of-coolant accident (LOCA).
Other considerations involve the need for margin to the evaluation of torus vent connections and instrument line connections, and the need for a minimum free air volume to accommodate the blowdown of non-condensible gases during a LOCA. All necessary calculations have been completed and BECo has determined the torus water level operating range can be increased by 2 inches.
BECo did not repeat the hydrodynamic and structural analyses performed as part of the Mark I Long Term Program but by scaling the loads calculated in the previous analyses, and applying an uncertainty factor, they found that the hydrodynamic load increases due to the increased water level could be accommodated by the existing excess margins. This change reflects the inspection commitment.
Increasing the operating range for the suppression chamber water level will allow plant operators greater maneuvering flexibility while maintaining a sufficient margin of safety.
The current 3-inch range for the torus water level requires frequent operator manipulations, (filling or draining),
especially during testing of emergency core cooling systems.
Increasing the 9506120510 950601 PDR ADOCK 05000293 P
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. range to 5 inches will reduce the manipulations plant operators are required to make to maintain the appropriate water level. The level transmitters were replaced with a smaller span (14 inches) for better accuracy since accuracy is related to span. The recorder scale was replaced due to this change.
- An increase in water level enhances the suppression pool's ability to mitigate an accident by providing more water for use by emergency cooling systems. The higher water level increases the heat sink capabilities resulting in lower torus water temperatures from steam blowdowns. There is a minor reduction in the free air volume of the torus which has a negligible effect on containment post-accident pressures. The change in the water level recording range is due to replacing the transmitter with a smaller span. The change from 0 to 32 inches to -7 to +7 inches enhances resolution and accuracy of the water level instrument loop. The change in water level recorder range does not involve an increase in the probability or consequences of an accident because the new recording range accounts for instrument loop uncertainties and is thus more conservative than the previous range.
This proposed change is a result of a response to a commitment from an inspection. The increase in water level enhances the suppression pool's ability to mitigate an accident by providing more water for use by emergency cooling systems.
The new recordings range is more conservative than the previous range. Therefore, the NRC staff finds this change acceptable.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Massachusetts State official was notified of the proposed issuance of the amendment. The State official had no comments.
4.0 ENVIRONMENTAL 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 and changes surveillance requirements. 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 amendment involves no significant hazards consideration, and there has been no public comment on such finding (60 FR 3672). Accordiagly, 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.
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5.0 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 Contributor:
K. R. Cotton Date: June 1, 1995
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