ML20077Q280
| ML20077Q280 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 01/09/1995 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20077Q260 | List: |
| References | |
| NUDOCS 9501190184 | |
| Download: ML20077Q280 (2) | |
Text
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UNITED STATES g
j NUCLEAR REGULATORY COMMISSION 4
2 WASKINGTON, D.C. 20086 4001
+9 * * * * *,o SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 83 TO FACILITY OPERATING LICENSE NO. NPF-42 WOLF CREEK NUCLEAR OPERATING CORPORATION WOLF CREEK GENERATING STATION DOCKET NO. 50-482
1.0 INTRODUCTION
By application dated October 27, 1993, Wolf Creek Nuclear Operating Corporation (the licensee) requested a change to the Technical Specifications (Appendix A to Facility Operating License No. NPF-42) (TS) for the Wolf Creek Generating Station. The proposed change would revise Note 5 of TS Table 4.3-1, "Reettor Trip Instrumentation Surveillance Requirements." The change reflects the use of integral bias curves, rather than detector plateau curves, to calibrate the source range instrumentation.
Both calibration methods measure the boron trifluoride (BF ) gas multiplication in the nuclear 3
instrument detectors.
2.0 EVALUATION The implementation of the boron mitigation system at Wolf Creek added a low-noise preamplifier to the source range detector channel of the nuclear instrumentation system (NIS) as originally designed. The Westinghouse NIS manual recommends the integral bias curve as the required calibration method for source range instrumentation calibration in NISs that have low-noise preamplifiers. The integral bias curve is considered to be a more inclusive calibration providing the same information as the detector plateau curve (i.e., high-voltage setpoint).
According to Westinghouse, the source range high-voltage setting cannot be obtained by using the detector high-voltage plateau curves in systems that have low-noise preamplifiers installed in the source range NIS channels. The detector plateau curves have a charge-sensitive design that integrates the pulses in the area under the curve and could result in erroneous settings if 1
gamma pulses and noise are present. Since the low-noise preamplifier is a voltage-sensitive design, the high-voltage plateau curve will not retain the typical " knee" of the curve and the characteristic few-100-volt plateau length.
The integral bias curves set up the high voltage as well as the gains and the discriminator bias. The alignment and calibration procedure for the integral j
bias curve uses a pulse height method to determine the detector high-voltage setpoint. This procedure counts the statistically expected minimum pulse height that exceeds the discriminator setting and also counts the 9501190184 950109 DR ADOCK 05000482 PDR
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statistically expected maximum' pulse height that will not saturate the source range pulse amplifier electronics.
j The gas multiplication efficiency for the source range detector is determined from the performance of the integral bias curve and a subsequent comparison of the present high-voltage operating point with the high-voltage operating point obtained from previous integral bias curves. The gas multiplication l
efficiency of the source range detector provides information regarding the life expectancy of the detector. As the detector ages, the pulse amplitude decreases because the gas multiplication is less efficient.
The decrease in i
the pulse amplitude for a given high voltage setting can be adjusted by increasing the detector high voltage to compensate for the lower gas multiplication efficiency.
t The NRC staff has verified that the new Revised Standard Technical i
Specifications reflect the applicability of the integral bias curves as a method for source range instrumentation calibration. The staff has reviewed the. proposed change to the Wolf Creek TS and finds it consistent with the staff's position. Therefore, the staff has concluded that the proposed change is acceptable. The detector plateau curves will continue to be used to calibrate intermediate range and power range channels.
3.0 STATE CONSULTATION
In accordance with the Comission's regulations, the Kansas State Official was notified of the proposed issuance of the amendment. The State official had no i
coments.
4.0 ENVIRONMENTAL CONSIDERATION
The amendment changes surveillance requirements. The NRC staff has determined that the amendment involves no significant increase in the amounts, and no l
significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative i
occupational radiation exposure. The Comission has previously issued a l
proposed finding that the amendment involves no significant hazards consideration, and there has been no public comment on such finding (58 FR 62159). 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.
5.0 CONCLUSIDH l
The Comission 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 Comission's regulations, and (3) the issuance of the amendment will not be inimical to the comon defense and security or to the health and safety of the public.
Principal Contributor:
J. Stone Date:
January 9, 1995
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