ML20070H421
| ML20070H421 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 07/12/1994 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20070H418 | List: |
| References | |
| NUDOCS 9407210280 | |
| Download: ML20070H421 (3) | |
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UNITED STATES
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NUCLEAR REGULATORY COMMISSION
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WASHINGTON. D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NOS. 67 AND 51 TO FACILITY OPERATING LICENSE NOS. NPF-76 AND NPF-80 HOUSTON LIGHTING & POWER COMPANY CITY PUBLIC SERVICE BOARD OF SAN ANTONIO CENTRAL POWER AND LIGHT COMPAN1 CITY OF AUSTIN. TEXAS DOCKET NOS. 50-498 AND 50-499 SOUTH TEXAS PROJECT. UNITS 1 AND 2
1.0 INTRODUCTION
By application dated March 21, 1994, Houston Lighting & Power Company, et.al.,
(the licensee) requested changes to the Technical Specifications (Appendix-A to Facility Operating License Nos. NPF-76 and NPF-80) for the South Texas Project, Units 1 and 2 (STP).
The proposed changes would modify Technical Specifications 3.1.2.1 and 3.1.2.3 to permit energizing of an inoperable centrifugal charging pump (CCP) in preparation for switching of the CCPs, provided pump discharge is isolated from the reactor coolant system.
2.0 BACKGROUND
The centrifugal charging pumps provide inventory control and normal boration to the reactor coolant system (RCS) and flow to the reactor coolant pump 4
seals.
During shutdown conditions, it is necessary to render a CCP inoperable to maintain the cold overpressure mitigating system design bases assumptions.
This ensures that the flow will not exceed the relieving capacity of one power operated relief valve.
Cold overpressure protection at the South Texas Pr oject is provided by two pressurizer power operated relief valves.
Current technical specifications (TS) require that a boration flow path be maintained-during Modes 4, 5, and 6, and, because it is not acceptable to have both i
charging pumps running simultaneously and aligned to the RCS due to the potential pressure transients, technical specifications also require that only one CCP be operable in Modes 4, 5, and 6.
During shutdown conditions, i
switching from one CCP to the other is sometimes desirable for pump testing purposes.
Therefore, the licensee proposes to modify TS 3.1.2.3 to allow both CCPs to be energized simultaneously for pump switching.
Technical i
Specification 3.1.2.1 would also be modified to allow the pumps to be briefly isolated from the RCS during pump switching.
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2 3.0 EVALUATION The licensee proposes to modify the note of Surveillance Requirement 4.1.2.3.2 (which permits an inoperable CCP to be energized for pump testing purposes) by extending the note to also include pump switching. The note requires that the discharge of the pump be isolated from the RCS during the switching, but allows reactor coolant pump seal injection flow to be maintained during the isolation. A note would also be added to TS 3.1.2.1 stating that the boron injection flow path requirements are not applicable during CCP testing or switching.
The requirements of Technical Specifications 3.1.2.1 and 3.1.2.3 as they currently exist, do not allow for both CCPs to be simultaneously running for switching purposes during pump testing. The proposed changes would allow two CCPs to be energized during switching and would protect the RCS from
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overpressurization by briefly isolating it from the CCPs while allowing continued reactor coolant pump seal injection flow.
The proposed changes could potentially impact two events:
(1) cold overpressurization of the reactor coolant system, and (2) boron dilution resulting in a return to criticality.
The revised note of TS 3.1.2.1 requires i
that the RCS be isolated during testing or pump switching. Therefore, charging pump flow is not increased and current cold overpressurization analyses would remain valid.
The revised technical specification provides for continued flow through the reactor coolant pump seals. Whether one or both CCPs are lined up to the reactor coolant pump seal flow path, the credible flow through the seals can only be 20 gpm with letdown isolated. This is less than the maximum analyzed CCP flow of 100 gpm with failure of one power operated relief valve to open.
Therefore, cold overpressurization is not a safety concern for this change.
Boron dilution is a potential concern because the boron injection flow paths are isolated during pump switching. The licensee has evaluated the effect of temporary loss of the flow paths and has determined that the brief period in which pump switching occurs would not have a significant effect on the margin of safety for this event. The pump energization and accompanying RCS isolation is a momentary action under direct j
administrative control.
Because the time in which the flow paths would be 1
isolated is limited and because isolation would occur during modes in which the reactor is relatively stable, this action is acceptable.
If one of the boron injection flow paths could not be restored following pump switching, the j
action statement of TS 3.1.2.1 would be entered which requires that all operations involving core alterations or positive reactivity changes be suspended.
Therefore, boron dilution is not a safety concern for this change.
4.0 STATE CONSULTATION
in accordance with the Commission's regulations, the Texas State official was notified of the proposed issuance of the amendments. The State official had no comments.
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5.0 ENVIRONMENTAL CONSIDERATION
The amendments change 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 amendments involve 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 amendments involve no significant hazards consideration, and there has been no public comment on such finding (59 FR 17602). 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 amendments.
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 amendments will not be inimical to-the common defense and security or to the health and safety of the public.
Principal Contributor:
D. Skay Date:
July 12, 1994 i
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