ML17285A553
| ML17285A553 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 06/06/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17285A552 | List: |
| References | |
| NUDOCS 8906150087 | |
| Download: ML17285A553 (8) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 7OTO FACILITY OPERATING LICENSE NO.
NPF-21 WASHINGTON PUBLIC POWER SUPPLY SYSTEM NUCLEAR PROJECT NO.
2 DOCKET NO. 50-397
1.0 INTRODUCTION
2.0 By letter dated March 8, 1989, Washington Public Power Supply System proposed certain changes to the Technical Specifications for Nuclear Project No. 2.
Technical Specification Table 4.3.2.1-1, Isolation Actuation Instrumentation Survei llance Requirements, would be modified to reduce requirements for periodic functional testing of temperature switches in the leak detection system.
This reduction in surveillance reflects enhanced operating capabilities of the leak detection system due to replacement of the present equipment (based on Riley Model 86 temperature switches) with General Electric Nuclear Measurement Analysis and Control (NUMAC) micro-computer based instrumentation.
EVALUATION During the fourth refueling outage, which started on about April 29, 1989, the Supply System intends to replace the Riley temperature switches in the leak detection system with General Electric Nuclear Measurement and Control instrumentation.
The NUMAC equipment will receive signals from the presently installed thermocouples and provide alarm and trip signals to existing circuitry.
All functions of the leak detection system will remain unchanged.
The replacement is being made to enhance overall system reliability.
The NUMAC instrumentation incorporates a
number of diagnostic and self-test features as well as significantly better total channel. drift characteristics.
The proposed amendment to the technical specification requirements is based on these enhanced capabilities and is acceptable.
Presently the technical specification requires channel checks on a twelve hour frequency and channel functional tests on a monthly frequency.
The licensee proposes to amend the technical specifications to eliminate the channel check requirement and to change the channel functional test frequency from monthly to semi-annually.
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The channel check of the instrumentation requires that an operator read the output of each channel and compare the reading to expected and similar channel readings on a 12-hour basis.
Fifty nine thermocouples are presently manually selected and assessed to complete the channel check.
The NUMAC replacement instrumentation, guality Class 1 and seismically qualified, has the following diagnostic and self-test features:
o Continually senses an open thermocouple (no input signal) and provides a'rouble alarm.
o Continually monitors two internal power supplies and provides a trouble alarm should one fail.
The monitors remain functional with one power supply.,
o Continually monitors power input to the module and provides a trouble alarm on loss of power.
o Self-checks each channel utilizing a micro-pulse signal through the channel to confirm functionality on a 30-minute frequency and provides a trouble alarm on failure of the self test.
o Provides a trouble alarm if the module is left in an inoperable condition (card-out-of-file, instrument left in an instrument-out-of operate mode).
These design features provide a more comprehensive assessment of system operability every 30 minutes than that presently provided by the Ri ley instrument channel check on a 12-hour basis.
Essentially, a 30-minute channel check feature is inherent in the'design that far surpasses and precludes the necessity of the channel check presently performed.
Utilization of the NUMAC instrumentation channel check feature provides greater and more frequent assessment of system operabi lity, is more resistant to human error, and will avoid the use of an operator's time for an obsolescent function (channel checking manually).
The licensee's proposal to perform channel functional testing on a
semi-annual frequency instead of monthly is based on (I) the manufacturer's total channel drift as compared to that experienced by the presently installed Riley instruments and (2),
an analysis of the minimum changes in temperature between trip setpoint and allowable value allowed by the technical specifications compared to the manufacturer's specified total channel drift.
Observed drift values on the Riley instrumentation have been as high as 7' per month.
The NUMAC equipment drift specification is less than 0.7' per month, which is one-tenth of that observed in the Riley equipment.
Additionally, the minimum margin between Trip setpoint and Allowable Value for the temperature monitoring system variables as noted in Technical Specification Table 3.3.2-2, Isolation Actuation Instrumentation Setpoints, is 10'.
Using this
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value and the manufacturer's specified drift (less than 0.7'), the.
changing of channel functional testing from monthly to semi-annually for the new system will leave a margin to the allowable value of greater than 5.8'.
Using this same drift value, the new instrumentation could be channel functional tested each 10 months and provide approximately the same margin observed, at times, with the present instrumentation.
As discussed above, failure mode diagnostic features are continuous and preclude the necessity of confirmation during channel functional testing.
- Hence, the diagnostic and drift characteristics of the NUMAC equipment assure greater confidence in system operability when functionally tested on a semi-annualy basis than the Riley equipment tested monthly.
- 3. 0 ENVIRONMENTAL CONS IDERATION This amendment involves a'hange'in the installation and 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 this 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.
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.
4.0 CONTACT WITH STATE OFFICIAL The Commission made a proposed determination that the amendment involves no significant hazards consideration (54 FR 18962, May 3, 1989) and consulted with the State of Washington.
No public comments were
- received, and the State of Washington did not have any comment.
5.0 CONCLUSION
Due to the diagnostic, self-test, and channel drift features, system operability is assessed more frequently and accurately, failure is identified more readily, operator efficiency is increased and presently recognized margins are conservatively preserved.
The margin of safety is increased through the use of the NUMAC equipment.
The diagnostic and self-test functions in lieu of a manual channel
- check, and semi-annual functional testing ensure the NUMAC equipment functions as intended.
Hence, there is no impact to safety due to this proposal and it is acceptable.
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We have 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 regula-tions 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 Contr ibutor:
R. Samworth, PD5 Dated:
June 6, 1989
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