ML20073B345
| ML20073B345 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 03/28/1983 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20073B319 | List: |
| References | |
| NUDOCS 8304120241 | |
| Download: ML20073B345 (3) | |
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UNITED STATES
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- p WASHINGTON, D. C. 20856
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION j
SUPPORTING AMENDMENT NO. 76 TO FACILITY OPERATING LICENSE NO. DPR-28 VERMONT YANKEE NUCLEAR POWER CORPORATION VERMONT YANKEE NUCLEAR POWER STATION DOCKET NO. 50-271 l
i 1.0 Introduction By letter dated January 10, 1983, Vermont Yankee Nuclear Power Corporation (the licensee) proposed chai.ges to the Technical Specifications pertaining to limiting conditions of operation and surveillance requirements related to modifications of the scram discharge system and the analog trip system.
2.0 Evaluation 2.1 Scram Discharge System Modifications As a result of events involving common cause failures of Scram Discharge Volume (SDV) limit switches and SDV drain valve operability, the NRC staff issued IE Bulletin 80-14 on June 12, 1980.
In addition, the staff sent a i
letter dated July 7,1980 to all operating BWR licensees requesting that i
they propose Technical Specification changes to provide surveillance require-l ments for SDV vent and drain valves and LC0/ surveillance requirements on l
1 1
SDV limit switches.
The licensee's submittal dated October 5,1981, contained l
the proposed Technical Specifications requested by the staff, which were made part of the Vermont Yankee license by License Amendment No. 73 dated November 29, 1982. As described in the Safety Evaluation accompanying i
License Amendnent No. 73, the licensee planned to install a second instru-ment volume and provide four reactor protection system (RPS) level instruments for each of the two instrument volumes, for a total of eight instruments for the RPS.
The second instrument volume significantly improves the design and reliability of the SDV.
During the March 1983 refueling outage, the licensee is performing the planned i
modifications to provide two independent instrument ' volumes. Each volume will be monitored by four level transmitters. Signals from these transmitters feed into analog to digital trip units which provide reactor scram signals, when the-appropriate level is reached in either instrument volume. These analog instrument channels replace the float switches utilized in the previous design.
In addition to the scram signals described above, one of the transmitteis from each instrument volume feeds a separate analog to digital T
trip unit which provides a signal to the rod block actuation system.
8304120241 830328 PDR ADOCK 05000271 P
- The numerical trip point for the higfi scram discharge volume water level scram is lower than previous, due to the configuration of the new piping.
However, since only half assmany control rod drive units discharge into each volume, the reduced capacity should not create sprious signals. The numerical trip point for the control rod block will remain the same as it has been..
The surveillance and calibration requirements have been modified to agree with requirements which have previously been approved for similar analog instrumentation utilized at Vermont Yankee, as provided in License Amend-ment No. 58, dated November 3,1980.
Based upon our review of the licensee's January 10, 1983 submittal, we conclude that the licensee's proposed Technical Specifications satisfy staff requirements for limiting conditions of operation and surveillcace requirements for SDV level instrumentation. Consequently, we find the licensee's proposed Technical Specifications for SLV level instrumentation acceptable.
2.2 Analog Trip System By License Amendment No. 58, dated November 3,1980, the staff approved installation at Vermont Yankee of improved safety system instrumentation referred to as the analog trip system.
This analog trip system is similar to that developed by General Electric (GE) and described in GE's Topical Report NEDO-21617 of April 1977 and NEDG-21617-1'of Ja'nuary 1978 entitled,
" Analog Transmitter / Trip Unit System" (ATTUS).. GE submitted this topical report to the NRC staff for review and it was found acceptable by the staff as stated in the letter to SE dated June 27, 1978.
At the time o f the original installation of the analog trip system, the licensee converted certain reactor pressure and water level loops to analog loops. The licensee is now converting from pressure switch to analog loop design for drywell pressure instrumentation inputs to the reactor protection and emergency core cooling systems and reactor pressure instru-mentation for the emergency core cooling low pressure permissive.
The proposed Technical Specifications change the calibration frequency for channels converted to the analog trip system from once per three. months to once per operating cycle. The justification given for this change is that operating experience indicates that calibration drift and mechanical problems associated with mechanical float switches are not experienced with the analog equipment. Also, the overall accuracy and repeatability of the analog instrumentation is significantly better than the equipment-it will.re. place. We agree with this justification. We, consider that the daily.
instrument check and the monthly functional test of the analog system provides further assurance of the operability of this system when compared to the surveillante required for the system which it replaced. We approved identical :
changes in' calibration frequency for channels converted to the analog system in License Amendment No. 58, and we also find the revised surveillance requirements to be acceptable for this proposed Technical Specification charige.
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,i 3.0 Environmental Considerations j
We have determined that the amendrent does not authorize a change in effluent types or total amounts nor an increase in power level and will 1
not result in any significant environmental impact. Having made this determination, we have further concluded that the amendment involves an i
action which is insignificant from the standpoint of environmental impact, and pursuant to 10 CFR Section 51.5(d)(4) that an environmental impact statement, or negative declaration and environmental impact appraisal need not be prepared in connection with the issuance of the amendment.
i 4.0 Conclusion 1
We have concluded, based on the considerations discussed above, that:
(1) because the amendment does not involve a significant increase in the probability of consequences of an accident previously evaluated, does '
not create the possibility of an accident of a type different from any evaluated previously, and does not involve a significant reduction in a margin of safety, the amendment does not involve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (3) such activities will be conducted in compliance with the Commission's regulations and the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.
Dated:
March 28,1983 Principal Contributor:
V. Rooney e
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