ML20239A604
| ML20239A604 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 09/09/1987 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20239A599 | List: |
| References | |
| GL-86-10, NUDOCS 8709170516 | |
| Download: ML20239A604 (3) | |
Text
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UNITED STATES
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NUCLEAR REGULATORY COMMISSION g
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g.....,o SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 10 TO FACILITY OPERATING LICENSE N0. NPF-37 I
1 AND AMENDMENT NO. 10 TO FACILITY OFPERATING LICENSE NO. NFP-66 COMMONWEALTH EDISON COMPANY BYRON STATION, UNITS 1 AND 2 l
DOCKET NOS. STN 50-454 AND STN 50-455
1.0 INTRODUCTION
By letter dated August 29, 1986, CommonwealthEdison(thelicensee) requested j
a revision to the Fire Protection License Conditions, 2.C(6) in NPF-37 and 2.E in NPF-66, and requested removal of the Fire Protection Technical Specifications.
By letter dated September 15, 1986, the licensee requested an amendment that replaces the requirernt to measure the source range neutron flux instrumentation high voltage plateau curve with a r'quirement e
to measure source range neutron flux instrumentation discriminator bias curves. The March 24, 1987 letter was submitted in response to the NRC's February 5,1987 request to clarify the original submittal and does not contain substantive changes.
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2.0 EVALUATION 2.1 Fire Protection Generic Letter 86-10. " Implementation of Fire Protection Requirements," dated April 24, 1986, provided guidance for a licensee to request an amendment to delete the Fire Protection Technical Specifications. The licensee, in its August 29, 1986, used that guidance and proposed a revision to the Fire Protection license condition and proposed an amendment that would remove the Fire Protection Technical Specifications.
The licensee stated that the fire protection program had been incorporated i
into the FSAR by reference, including limiting conditions for operation, action statements, and surveillance requirement for the fire protection program. The licensee also stated that its procedures provide a level of i
protection equivalent to that in the present Technical Specifications.
Therefore, the staff concludes that the proposed revision to the license condition and the removal of the Fire Protection Technical Specifications are acceptable.
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1 1 I 2.2 Source Range Instrumentation Source range neutron detectors monitor leakage flux at the lowest reactor l
shutdown. levels and provide output to indicating alarms and reactor trips.
j Source range detectors used in Westinghouse reactors are of the boron triflouride (BF ) type. These detectors emit a pulse rate output which is 3
proportional to the amount of thermal neutron flux to which they are exposed.
j These pulses are conditioned by electronic circuitry which provides amplifi-j cation and a means to discriminate between neutron flux and other types i
of radiation, primarily gamma. Gamma radiation stimulates the sensors to
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generate lower amplitude pulses. These low-level pulses are removed from i
I the detector signal by use of a pulse amplifier-discriminator.
The current channel calibration requirements of Technical Specification (TS) i j
Table 4.3-1 call for developing high voltage plateau curves for each BF detector ard comparing these curves with the manufacturer's recommendation.
These curves are obtained by varying the scpply voltage to the detectors and recording the corresponding change in voltage plateau (counting rate).
Any appreciable deviation in the curve's profile from that of the manufacturer's recommendation indicates probable detector degradation.
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Obtaining discriminator bias curves evolves a markedly different technique.
l This is done by varying the discriminator bias over a specified range of voltages and recording corresponding changes in the count rate. A graph 1
of count rate versus discriminator bias is then made. The discriminator bias operating point is determined from this graph and set on the channel.
l The count rate is then observed to determine if the correct operating point 1
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has been obtained.
If the correct point has not been determined, the l
procedure is repeated with increased voltage.
Detector degradation is determined by a downward shift in the discriminator bias curve from that of previous curves. This downward shift results because pulses detected by failing sensors have lower amplitudes; thereby, reducing the actual number of pulses counted at various bias voltages.
The intent of TS Table 4.3-1 functional Unit 6 is to assure, as reasonably as possible, that means are available to periodically assess the condition of source range detectors.
The TS refers to " voltage plateau curves" because these curves have traditionally been employed for the purpose.
In the staff's view, there is no reason an alternate method cannot be used as long as the stated purpose is accomplished. The licensee has presented a convincing argument in support of the TS change.
The staff finds acceptable the licensee's request to substitute " discriminator bias curves" for " voltage plateau curves" in TS Table 4.3-1, Functional Unit 6.
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ENVIRONMENTAL CONSIDERATION These amendments involve a change in the installation or use of the facilities components located within the restricted areas as defined in 10 CFR 20. The staff has determined that these 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 these amendments involve no significant hazards consideration 1
, and there has been no public coment on such finding.
Accordingly, these amend-i' ments meet the eligibility criteria for categorical exclusion set forth in 10 CFRSec51.22(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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CONCLUSION 1
We have concluded, based on the considerations discussed above, that: (1)there 1s 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 I
be conducted in compliance with the Commission's regulations and the issuance
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of these amendments will not be inimical to the common defense and security or to the health and safety of the public.
PRINCIPAL CONTRIBUTORS:
E.N. Fields L. N. Olshan Dated:
September 9, 1987
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