ML20086E322
| ML20086E322 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 06/29/1995 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20086E321 | List: |
| References | |
| NUDOCS 9507110325 | |
| Download: ML20086E322 (3) | |
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4 UNITED STATES j
NUCLEAR REGULATORY COMMISSION WASHINGTON. D.C. 20$65@01
,o SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 200 TO FACILITY OPERATING LICENSE NO. DPR-32 AND AMENDMENT NO. 200TO FACILITY OPERATING LICENSE NO. DPR-37 VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION. UNIT NOS. I AND 2 DOCKET NOS. 50-280 AND 50-281
1.0 INTRODUCTION
By letter dated January 24, 1995, the Virginia Electric and Power Company propoced changes to the Surry, Units 1 and 2 Technical Specifications (TS) to increase the "as-found" test acceptance criterion for the pressurizer safety valves (PSVs) from fl% to 13%. The "as-left" acceptance criterion of fl%
remains unchanged.
2.0 EVALUATION Surry, Units 1 and 2, each has one pressurizer.
Each pressurizer has three PSVs with lift settings at 2485 psig. The licensee is proposing to relax the "as-found" setpoint tolerances for the PSVs from 11% to i3%. This relaxation is applicable to the PSV setpoint drift which may occur during an operating cycle. The licensee's submittal included an evaluation of the overall effect of changing the PSVs setpoint criterion on those transients which experience the most limiting pressure increases. These transients are the Complete Loss of External Electrical Load, the Locked Reactor Coolant Pump Rotor, and the Rod Withdrawal events at low power. Departure from nucleate boiling and operational margins considerations were also evaluated.
These analyses were performed assuming an uprated core power level of 2546 MWt; the currently licensed core power level is 2441 MWt.
2.1 Loss of External Electrical Load The Loss of Load event causes a rapid reduction in steam flow from the steam generators and a rapid increase in the secondary system pressures. This transient is terminated either by a direct reactor trip or by the high pressurizer pressure reactor trip. The maximum primary and secondary pressures resulting from this transient are 2680 psia and 1187 psia, respectively.
The overpressure limits for the primary and secondary system are 2750 psia and 1210 psia, respectively.
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' 2.2 Reactor Coolant Pump Locked Rotor Event The peak primary and secondary system pressures developed during this transient are 2677 psia and 1164 psia, respectively, which are below the respective safety limits of 2750 psia and 1210 psia.
2.3 Rod Withdrawal Events The licensee's analysis evaluated the Rod Withdrawal at Power (RWAP) and Rod Withdrawal from Subcritical (RWSC) events. The limiting case was initiated from 12% power and assumed a bounding reactivity insertion rate, a 3% PSV lift setpoint tolerance, a drained loop seal, and a least negative Doppler temperature coefficient. This case resulted in a maximum primary system pressure of 2697 psia. A similar analysis of the RWSC case yielded a maximum primary system pressure of 2643 psia.
Both of these results are below the design pressure of 2750 psia.
2.4 Departure from Nucleate Boiling Considerations Because the increased low-end tolerance (i.e. -3%) potentially reduces the system pressure experienced at the point of minimum departure from nucleate boiling ratio (DNBR), the effects of both the low-end (-3%) and high-end (+3%)
tolerance acceptance criterion on the DNBR results of the affected transients were evaluated. Of the affected transients, only the DNBR results of the Locked Rotor event are potentially adversely influenced by the increased low-end tolerance. The licensee's analysis of this case revealed that the minimum 4
DNBR statepoint pressure is below the proposed low-end PSV lift setpoint of 2425 psia.
2.5 Operational Margin Considerations The licensee states that the proposed "as-found" lift setpoint acceptance criterion was selected to minimize the potential for an inadvertent opening of 4
the PSVs during normal operation. The nominal high primary system pressure reactor trip setpoint is 2400 psia with a maximum uncertainty of 16 psi.
4 Thus, the nominal reactor trip setpoint is 2416 psia.
Since the nominal PSV lift setpoint (2500 psia) minus the 3% tolerance (75 psia) corresponds to a trip setpoint of 2425 psia, a reactor trip would occur before an inadvertent opening of the PSVs would occur.
3.0
SUMMARY
CONCLUSION Based on the above evaluation, the NRC staff agrees that the analysis which the licensee has performed demonstrates the acceptability of the proposed TS changes. The proposed increase in the "as-found" setpoint tolerances of the PSVs has been shown to be acceptable for meeting the plant design basis. The "as left" tolerance of il% remains unchanged. Therefore, the proposed TS changes have no significant safety impact to the operation of Surry, Units 1 and 2, and are acceptable.
4.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Virginia State official was notified of the proposed issuance of the amendments. The State official had no comment.
5.0 ENVIRONMENTAL CONSIDERATION
These 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 cccupational radiation exposure. The Commission has previously issued a proposed finding that these amendments involve no significant hazards consideration and there has been no public comment on such finding (60 FR 18631). Accordingly, these amendments meet 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 these 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 these amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
B. Buckley Date: June 29, 1995 I
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