ML20246F196
| ML20246F196 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 07/07/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20246F193 | List: |
| References | |
| NUDOCS 8907130148 | |
| Download: ML20246F196 (3) | |
Text
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i ENCLOSURE 2 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO.167 TO FACILITY OPERATING LICENSE NO. DPR-52 TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT, UNIT 2 DOCKET NO. 50-260
1.0 INTRODUCTION
By letter dated February 24, 1989, TVA requested an amendment to the Technical Specifications (TS) for Browns Ferry Nuclear Plant Unit 2 (BFN 2). The amendment would revise calibration frequencies for instrument lines containing transmitters manufactured by Tobar Inc. from the currently required 12 or 18 months to a more conservative interval of six months. The amendment also includes administrative changes to ten instrument numbers, and deletes daily instrument checks for four hi core isolation cooling (RCIC)gh pressure coolant injection (HPCI) and reactor instrument channels.
2.0 EVALUATION In general, surveillance frequencies are based on indu.etry accepted practice and engineering judgement considering the conditions required tc perform a given test, the ease of perfoming the test, and the likelihood if a change in the system / component status.
Instrumentation calibration" frequencies consist of an optimum selection of time versus drift. Setpoint scaling calculations are performed to provide assurance that there is adequate margin to account for all inaccuracies in the instrument loop between.the required trip setpoint and the limiting safety System settings.
Tober, Inc. has recomm.nded a calibration frequency of once every six months for transmitters they have manufactured. Three instrument lines at BFN 2 contain Tobar. Inc. transmitters and have calibration intervals less frequent than once every six months. Two of the instrument lines have calibration intervals of once every 18 months.
The third line has a calibration frequency of once every 12 months. NRC staff agrees with the proposed change to the more conservative calibration interval for all instrument lines containing Tobar transmitters.
The TS for one of the affected instrument lines, Reactor Low Pressure in Table 4.2.8, originally had a calibration interval of once every three months.
This was subsequently changed to once every 18 months when the licensee adopted the analog transmitter trip system (ATTS) design. The ATTS was developed by GE to offset operating disadvantages of the digital sensor switches of the original 890713014e 890707 PDR ADOCK 05000260 P
4 safety system instrumentation. The principal objective of the ATTS was to improve sensor intelligence and reliability while enhancing testing procedures.
The ATTS design was adapted to BFN 2 to replace the then existing mechanical switches which sensed drywell and reactor pressures with analog loops, and to modify the reactor water level indication loops to improve the reliability, accuracy, and response time of the instrumentation. The NRC reviewed and accepted this change in calibration frequency from three to eighteen months in August 1986. As stated earlier, the NRC staff supports the manufacturer's recommendation of the more conservative calibration interval of once every six months for the instrument line containing Tobar transmitters.
The other two instrument lines discussed earlier were not affected by the adoption of the ATTS design.
The changes to the ten instrument numbers are administrative in nature and do not change the function, setting or calibration interval of any of the instruments.
The instrument numbers are included in the technica?
specifications for completeness.
An instrument check is a qualitative determination of acceptable oehavior by observation of the instrument during operation.
The four HPCI/RCIC instrument channels for which daily instrument checks are presently required are pressure switches which have no indication function.
The functional test of this instrumentation which verifies operability, including the alarm and trip functions, is performed once every 31 days.
Based on the above, the staff concluded that the proposed changes to the TS regarding the changes to the instrument numbers and instrument checks for the HPCI/RCIC instrument checks do not affect safety and are therefore acceptable.
3.0 ENVIRONMENTAL CONSIDERATION
This amendment involves a change to 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 to the 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.
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 nor environmental assessment need be prepared in connection with the issuance of the amendment.
4.0 CONCLUSION
l The Commission made a proposed determination that the amendment involves no significant hazards consideration which was published in the Federal Reaister (54 FR 15838) on April 19, 1989 and consulted with the State of i
Alabama. No public comments were received and the State of Alabama did not have any comments.
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.The staff has concluded, based on the considerations discussed abcve, that:
(1) there is reasonable assurance that the health and safety of the
-willinot be endangered by operation in the proposed manner, and (2) public 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 nor to the health and safety of the public.
Principal Contributor:
N. Markisohn Dated:
July 7, 1989 S
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