ML20087L467
| ML20087L467 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 08/22/1995 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20087L465 | List: |
| References | |
| NUDOCS 9508250267 | |
| Download: ML20087L467 (3) | |
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UNITED STATES 3
NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 2068H001 g,*....
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION i
RELATED TO AMENDMENT NO. 207 TO FACILITY OPERATING LICENSE NO. DPR-77 AND AMENDMENT NO.197 TO FACILITY OPERATING LICENSE NO. DPR-79 TENNESSEE VALLEY AUTHORITY SE000YAH NUCLEAR PLANT. UNITS 1 AND 2 DOCKET NOS. 50-327 AND 50-328
1.0 BACKGROUND
By application dated May 3, 1995, the Tennessee Valley Authority (TVA or the licensee) requested that the implementation dates for Amendments Nos. 188 and 180 for the Sequoyah Nuclear (SQN) Plant Units 1 and 2, respectively, be delayed until the related plant modifications and technical specifications (TS) can be revised and executed.
The initial amendments addressing the same changes to the TS were issued on May 24, 1994, as Amendment Nos. 182 and 174, for SQN Units 1 and 2, respectively, in response to the application dated October 1, 1993.
They required that the amendments for each unit be implemented during the Unit 2 Cycle 6 refueling outage.
Subsequently, by letter dated August 19, 1994, TVA 1
requested that implementation be delayed until the related plant modifications are executed during fiscal year 1995 when both units were operating. The exact timing was dependent on the preparation of appropriate staging and completion of detailed evaluations related to the modification.
The modifications involve changes to the setpoints and time delays for the auxiliary feedwater loss of power and the 6.9 kv shutdown board loss of j
voltage and degraded voltage instrumentation.
TVA considered performance of the modifications during power operation acceptable because it minimizes coordination of activities associated with a refueling outage. The delay would also allow additional time for planning the i
staged modification approach to meet TS action times and address any related issues.
In response to this request, the Commission issued Amendment Nos. 188 and 180 for SQN Units 1 and 2, respectively, indicating implementation would occur as soon as acceptable p.lant conditions and modification activities / procedures were established in 1995.
2.0 INTRODUCTION
The loss-of-voltage and degraded-voltage protection are provided to the 6900-volt shutdown boards to ensure that adequate voltage is available to the safety-related loads. A loss-of-voltage or a sustained degraded-voltage i
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a condition will start the emergency diesel generator (EDG) that will be connected to the shutdown board after tripping the normal and alternate feeders and shedding the major loads. After the EDG has been tied to the shutdown board, the loss-of-voltage relays continue to provide the load-shed functions and subsequent resequencing of the loads onto the EDG if necessary.
After the EDG has connected to the shutdown board and the load sequencing interval has been achieved, the loss-of-voltage load-shed feature of the 6.9 kv shutdown board initiates a motor-driven AFW pump start.
In addition, i
the load-shed actuation immediately activates a turbine-driven AFW pump start.
The reactor coolant pumps would not be available to provide forced coolant flow in the event of loss of voltage, but the turbine-driven AFW pumps start to initiate natural circulation and heat removal in the reactor coolant system via the steam generators. The AFW pumps provide sufficient heat-removal capability to prevent the pressurizer from filling during design-basis accidents.
The purpose of Amendment Nos. 182 (for Unit 1) and 174 (for Unit 2) is to revise the setpoints and time delays for the AFW loss of power and 6.9 kv shutdown board loss-of-voltage and degraded-voltage instrumentation. Also included are changes to the description, total number of channels, channels to trip, minimum channels operable, actions, trip setpoints, allowable values, channel checks, and channel functional test requirements for loss-of-power instrumentation.
3.0 EVALUATION TVA has performed additional evaluations necessary to implement the design changes related to the amendments and concluded that a significant risk to nuclear safety exists.
These risks result from placing various plant components in temporary configurations, numerous wire manipulations, and the need to extend the diesel generator allowed outage significantly.
Consequently, TVA concluded that implementation of the design change at this time was not in the best interests of safety. TVA is pursuing a new design i
change concept that will allow use of the alternate feeder breaker to the 6.9 kv shutdown boards while, at the same time, maintain the same level of voltage protection that was proposed in the original TS change request.
The j
revised modification is being developed in conjunction with consideration of
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the implementation requirements to ensure that the design can be reasonably i
and safely achieved.
It is expected that this may result in a need to submit another amendment to address changes to the technical aspects of Amendment l
Nos. 182 and 174 for SQN Units 1 and 2, respectively, in November 1995.
The result is that implementation of Amendment Nos. 182 and 174 for SQN Units 1 and 2 will not occur in 1995. This, in turn, led to the request to delay implementation until this process is completed.
The staff has evaluated the licensee's submittal and determined that i
sufficient justification has been provided to allow delaying implementation of TS Amendment Nos. 182 and 174 for SQN Units 1 and 2, respectively, until the safety issues related to implementation are thoroughly addressed.
In addition, the staff has concluded that maintaining the present plant configuration (i.e., not implementing the design change) is not detrimental to plant-safety since the present configuration complies with applicable i
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l 1 regulations. Therefore, the proposed change is acceptable.
Due to the uncertainty of the schedule, NRR and the Sequoyah Resident Inspector steif should be kept informed of significant changes to the design and implementation schedule.
4.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Tennessee State official was notified of the proposed issuance of the amendments.
The State official j
had no comments.
5.0 ENVIRONMENTAL CONSIDERATION
1 The amendments change a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20. The NRC staff has determined that the amendments involve no significsai 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 previously issued a proposed finding that the amendments involve no significant hazards consideration related to the i
original amendments, and there has been no public comment on such finding (59 FR 4947).
The Commission repeated the proposed finding that the amendments involve no significant hazards consideration in relation to the request to change the implementation date, and there has been no public comment on such finding (59 FR 47182) and (60 FR 27343). Accordingly, the amendments meet 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 4
issuance of the amendments.
6.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the i
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 the amendments will not be inimical to the common defense and security or to the health and safety of the public.
1 Principal Contributor: David E. LaBarge l
Dated:
August 22, 1995 l
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