ML20059C356
| ML20059C356 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 12/28/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20059C353 | List: |
| References | |
| NUDOCS 9401050121 | |
| Download: ML20059C356 (2) | |
Text
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j NUCLEAR REGULATORY COMMISSION WASHINGTON. D.C. 20556 4001 k.....,/
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 87 TO FACILITY OPERATING LICENSE NO. NPF-30 UNION ELECTRIC COMPANY 1
CALLAWAY PLANT. UNIT 1 DOCKET NO. 50-483 i
1.0 INTRODUCTION
By application for license amendment dated November 3,1992, and clarifying information dated December 4,1992, Union Electric Company (the licensee) requested changes to Technical Specification Table 4.3-1, " Reactor Trip Instrumentation Surveillance Requirements," Note 5 for Callaway Plant, Unit 1.
The change reflects that integral bias curves, rather than detector plateau
{
curves,areusedtocalibratethepourcerangeinstrumentation. Both calibration methods measure the BF gas multiplication in the Nuclear Instrumentation detectors.
Integral bias curves have been used to calibrate the source range instrumentation at Callaway since the initial startup of the plant.
2.0 EVALUATION The implementation of the Boron Dilution Mitigation System into the NIS at Callaway, Unit 1, caused the source range to add a " low noise" preamplifier to i
the original (pre-operating license) design. The Westinghouse NIS manual recommends the integral bias curve as the required calibration method for source range instrumentation calibration in NIS systems which have low noise preampl i fiers. The integral bias curve is considered to be a more inclusive calibration which provides the same information as the detector plateau curve (i.e., high voltage setpoint).
i According to Westinghouse, the source range high voltage setting cannot be acquired by using the detector (high voltage) plateau curves in systems which have low noise preamplifiers used with source range NIS channels. The 4
detector plateau curves are a charge sensitive design with the purpose of integrating the pulses in the area under the curve which could result in erroneous settings if 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 hundred 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 bias curve utilizes a pulse height method to determine the detector high 1
voltage setpoint. This procedure counts the statistically expected minimum pulse height that exceeds the discriminator setting and also counts the statistically expected maximum pulse height that will not saturate the source range pulse amplifier electronics.
9401050121 931220 PDR ADOCK 05000483 P
o f The gas multiplication efficiency for the source range detector is determined e
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 efficiency of the source range detector provides information regarding the life expectancy of the detector..As the detector ages, the pulse amplitude decreases due to a reduction in the gas multiplication. The decrease in 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.
The NRC staff has verified that the new Revised Standardized Technical Specifications (RSTS) 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 Callaw y Technical Specifications and finds it consistent with the staff's position. Therefore, the staff has concluded that the proposed change is acceptable.
The intermediate range and power range instrumentation will continue to be calibrated using the detector plateau curves.
3.0 STATE CONSULTATION
1 In accordance with the Commission's regulations, the Missouri 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 the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes surveillance requirements. The 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 this amendment involves no significant hazards consideration and there has been no public comment on such finding (58 FR 601). Accordingly, this 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 this amendment.
5.0 CONCLUSION
lhe 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,'(2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributors:
K. R. Marcus L. R. Wharton Date: December 28, 1993