ML20247N881
| ML20247N881 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 07/31/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20247N878 | List: |
| References | |
| NUDOCS 8908030208 | |
| Download: ML20247N881 (3) | |
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UNITED STATES g
NUCLEAR REGULATORY COMMISSION j-W4 SHINGTON, D. C. 20555
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT N05. 123 AND 126 TO FACIETTY OPERAT.~NG LICENSE N05. DPR-24 AND DPR-27 WISCONSIN ELECTRIC POWER COMPANY POINT BEACH UUCLEAR PLANT, UNIT N05. 1 AND 2 DOCKET N05. 50-266 AND 50-301
1.0 INTRODUCTION
By letter dated March 17, 1989, Wisconsin Electric Power Company (the licensee) requested amendments to the Point Beach Nuclear Plant, Unit Nos.
I and 2, operating licenses. The amendments would revise the Technical Specification (TS) 15.2.3.1.B.(5) to eliminate the f-delta-I function from the Overpower Delta-T (OPDT) setpoint to increase the flexibility of operation at full power by allowing use of the full flux difference operating envelope. The request would also change the associated TS bases for this specification.
2.0 EVALUATION i
The licensee has requested that the f-delta-I function found in TS 15.2.3.1.B.(5) be removed from the OPDT setpoint calculation to increase the flexibility of plant operation at full power.
Further, the licensee requested the specification bases be nodified to reflect that the OPDT trip setpoint does not include corrections for axial power distribution. This latter request is necessary since the setpoint would no longer require that correction.
In TS change request 127 (dated August 26,1988), the licensee proposed a flux difference operating envelope that allows a flux difference at full power of +9 percent. The TS-required delta flux penalty for the OPDT trip setpoint is +9.5 percent at full power. Currently, the setpoints of approximately +6.5 percent delta flux for turbine runback and approximately
+7.5 percent delta flux for reactor trip are used to ensure the TS setpoint limit is not violated. These actual setpoints account for instrument calibration drift. With these conservative setpoints and the revised flux difference operating envelope, the plant cannot be operated normally with 1
all rods out and at full power during the beginning of each fuel cycle without causing a runback or trip. The elimination of the f-delta-I function was chosen by the licensee as the preferred method of resolving this issue.
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l The elimination of the f-delta-1 function will allow normal operation at full power with all control rods out at any time during core life, and it will allow the flux difference operating envelope to be fully utilized. The alternative is to operate the core with control rods partially inserted to decrease the power at the top of the core. This alternative is not desirable in a pressurized water reactor (PWR) because it increases control rod exposure (causing a decrease in service life) and creates uneconomical fuel burnup patterns. Additionally, operational maneuverability during power swings and transient recoveries is limited.
The design bases of the OPDT and the Overtemperature Delta-T (0 TDT) setpoints are presented in WCAP-8745-P-A, " Design Bases for the Thermal Overpower Delta-T and Thermal Overtemperature Delta-T Trip Functions,"
September 1986. The NRC accepted this document for referencing in a Safety Evaluation Report dated April 17, 1986.
Though the OPDT setpoint is intended to protect against fuel centerline melting in Condition 11 transients, the WCAP report concluded that no f-delta-1 function is required to preclude fuel centerline melting during overpower events in 16x16 and 17x17 fuel plants. Moreover, the WCAP re concluded that the OPDT trip setpoints (including f-delta-I adjustment) port for 14x14 and 15x15 fuel plants were established in a more conservative manner than required to prevent fuel centerline melting. Therefore, 14x14 and 15x15 fuel plants could be evaluated in accordance with the WCAP methodology to justify removal of the f-delta-I function on a plant-specific basis.
Point Beach Unit Nos. 1 and 2 are 14x14 fuel plants.
Analyses on the proposed flux difference operating envelope were performed for Point Beach.
Condf tion 11 events were analyzed for control bank and boration/ dilution system malfunctions, which are potentially limiting during overpower events. An overpower limit of 114 percent, based on a nominal TS value of 108.9 percent, was used for all values of delta-1 (i.e., no f-delta-1 penalty was applied). The analyses confirmed that the resulting overpower conditions did not yield a linear power density that would cause fuel centerline melting. Therefore, the f-delta-1 function could be removed from the OPDT setpoint calculation with no adverse impacts to safety.
Based upon the information above, the staff concludes that the requests to remove the f-delta-I function from the 0PDT setpoint calculation and to modify the related specification bases, as stated in the March 17, 1989 letter, are acceptable.
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3.0 ENVIRONMENTAL CONSIDERATION
These amendments involve a change in the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 or change an inspection or surveillance requirement. The 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 occupa-tional radiation exposure. The Commission has previously-published a proposed finding that these amendments involve no significant-hazards consideration and there has been no public comment on such finding. Accordingly, these amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 951.22(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.
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4.0 CONCLUSION
The staff 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, and (2) such activities will be conducted in compliance with the Commission's regulations, and 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: Lawrence E. Kokajko Dated: July 31, 1989
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