ML20086C286
| ML20086C286 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 06/29/1995 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20086C282 | List: |
| References | |
| NUDOCS 9507060397 | |
| Download: ML20086C286 (3) | |
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 205 TO FACILITY OPERATING LICENSE NO. DPR-77 AND AMEND!iENT NO. 195 TO FACILITY OPERATING LICENSE NO. DPR-79 TENNESSEE VALLEY AUTHORITY SE000VAH NUCLEAR PLANT. UNITS 1 AND 2 DOCKET N05. 50-327 AND 50-328
1.0 INTRODUCTION
By application dated April 6,1995, and supplemented May 26, 1995, the Tennessee Valley Authority (the licensee) proposed an amendment to the Technical Specifications (TS) for Sequoyah Nuclear Plant (SQN) Units 1 and 2.
The proposed changes would revise the Action statement for Technical Specification 3.8.1.1 by inserting a new Action a, relabeling and modifying existing Action a to become Action b, adding a footnote referenced to Action b, renumbering the subsequent action statements, and adding information to the Bases that amplifies the action statements.
The May 26, 1995, letter provided clarifying information that did not change the initial proposed no significant hazards consideration determination.
The proposed new Action a would no longer address required actions for diesel generator testing.
It would require that, should one of the ac electrical power sources listed be inoperable, operability of the remaining offsite ac circuit be demonstrated by performing Surveillance Requirement 4.8.1.1.1.a (verification of correct breaker alignment) within one hour and at least once per 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> thereafter.
If two offsite circuits cannot be restored with 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, the requirement to place the unit in hot standby within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in cold shutdown within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> would continue to be applicable.
The proposed change to Action b would address the testing requirements should a diesel generator become inoperable.
It would (1) eliminate the requirement for demonstrating operability by starting diesel generators when an offsite circuit is 1. operable, (2) eliminate the requirement for demonstrating operability by starting the remaining diesel generators if it can be determined within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> that there is no common cause failure between the inoperable diesel generator and the remaining operable diesel generators, (3) require testing of operable diesel generators if the inoperability of the affected diesel generator has the potential to be the result of a common cause failure, and (4) clarify in a footnote that the common cause determination must be completed regardless of how long the diesel generator inoperability persists or Surveillance 4.8.1.1.2.a.4 must be completed to verify diesel ganerator operability.
9507060397 950629 PDR ADOCK 05000327 P
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. TVA supplied the following as a basis for the changes:
a.
The 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> completion time is based on Generic Letter 84-15.
b.
The 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> completion time provides a reasonable time to confirm that the operable diesel generators are not affected by the same problem as the inoperable diesel generator.
The new action provides allowance to avoid unnecessary testing of c.
operable diesel generators.
d.
If it can be determined that the cause of failure does not exist on the remaining operable diesel generators, the remaining diesel generators do not have to be started to confirm no common cause failures.
e.
If it cannot be determined that the cause of failure does not exist on the remaining diesel generators, starting of the remaining diesel generators suffices to provide assurance of no common cause failures.
f.
If it is determined that the cause of failure does exist on the remaining redundant diesel generators, the failure must be repaired or plant shutdown must be initiated within two (2) hours.
If the failure is repaired, the required action to determine no common cause failures is satisfied.
For the situation when the inoperable diesel generator is returned to operable status (within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />) before the remaining diesel generators are either demonstrated or determined operable, TVA proposed adding a note referenced to the new Action b to indicate that the required actions to verify that the operable diesel generator sets are not inoperable due to common cause failure determination starting the diesel generators be completed if the Action item is entered.
In the submittal, TVA indicated that this requirement is intended to assure that all diesel generator inoperabilities are investigated for common cause failures.
A proposed change to the Bases would provide guidance on the use of common cause failure determination to eliminate unnecessary diesel generator testing and would define when testing is required to verify diesel generator operability.
In justification for the proposed TS changes, TVA stated that testing of operable diesel generators when there is no possibility of a common cause l
failure with the inoperable diesel generators, does not provide a benefit and increases the degradation of the diesel generators unnecessarily.
In i
addition, TVA indicated (1) that the proposed changes are consistent with the standard TS (NUREG 1431) and (2) that Generic Letter 84-15 recommended that licensees take actions to reduce unnecessary starts of the diesel generators because of the degradation that results.
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.. Moreover, in their May 26, 1995 letter, TVA indicated that the normal routine testing (that is, once per 31 days) provides adequate assurance of diesel generator operability and that this position is supported by the overall reliability of the diesel generators. Of the 190 diesel generator tests conducted in 1994, there has been only one failure.
Based upon this exhibited reliability, TVA indicated that the likelihood of diesel generator failure is judged to be sufficiently low during the time when the plant is operating with either an offsite circuit or a diesel generator inoperable.
In addition, TVA indicated that the future implementation of the maintenance rule will further ensure that diesel generator reliability remains high.
EVALVATION In NRC's program for enhancing the safety impact of TS (NUREG-1366 and Generic Letter 93-05), the staff recommended that the diesel generator (s) should be start tested only once (not every 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />) and within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> of a failure unless the absence of any potential common mode failure can be demonstrated.
Generic letter 93-05 also recommended that when an offsite circuit becomes inoperable, start testing of the diesel generator should be deleted from TS requirements.
In addition, NUREG-1366 indicated that diesel generator testing appears to be an area that would benefit from a reliability-based testing program.
The report indicated that unnecessary testing may be further reduced by a reliability based program which includes a detailed root-cause analysis procedure, a good preventive maintenance program, detailed monitoring, and trending.
Therefore, the staff concludes that an additional start test will not significantly improve the level of assurance that the plant is not being operated with more than one ac power source inoperable.
In addition, the drawbacks of testing may offset this benefit; that is, the potential for increased unavailability, unnecessary shutdowns, and diversion of operating personnel time and attention due to testing may eliminate or counter this benefit.
The staff therefore considers the proposed elimination of the additional start test to be acceptable.
Also as part of the proposed TS change, TVA indicated that the additional start test will continue to be required if the existence of common cause failure cannot be established, in order to clarify common cause failure, changes to the surveillance requirement and its bases were also proposed.
The staff considers these additional changes to be clarifications of existing requirements that are not being eliminated.
These proposed changes do not alter existing requirements and are, therefore, acceptable.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Tennessee State official was notified of the proposed issuance of the amendment.
The State official had no comments.
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4.0 ENVIRONMENTAL CONSIDERATION
The amendment changes 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 amendment involves no significant increase in the amounts, and no significant change in the types, q
of any effluents that may be released offsite, and that there is no i
significant increase in individual or cumulative occupational radiation
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exposure. The Commission has previously issued a proposed finding that the amendment involves no significant hazards consideration, and there has been no public comment on such finding (60 FR 20529). 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 or environmental assessment need be prepared in connection with the issuance of i
the amendment.
5.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities W,il be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
John L. Knox J
Dated: June 29, 1995 i
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