ML20042G027
| ML20042G027 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 04/27/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20042G026 | List: |
| References | |
| NUDOCS 9005110003 | |
| Download: ML20042G027 (4) | |
Text
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/ p,. s f & '('g UNITED STATES NUCLE AR REGULATORY COMMISSION p
WASHINGTON D. C. 20566 f
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....l ENCLOSURE 3 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. m TO FACILITY OPERATING LICENSE NO. DPR-77
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AND AMENDMENT NO.122 TO FACILITY OPERATING LICENSE NO. OpR-79 TENNESSEEVALLEYAUTHORIE t
SEQUOYAH NUCLEAR PLANT, UNITS 1 AND 2 DOCKET NOS. 50-327 AND 50-328 I
1.0 INTRODUCTION
By letter dated October 5,1989 (Ref.1), the Tennessee Valley Authority (TVA) proposed changes to the Technical Specifications (TSs) for the Sequoyah Nuclear Plant (SQN), Units 1 and 2.
The proposed changes would clarify the actions to be taken when it is not possible to monitor or confirm the quadrant power tilt ratio when a power range instrument is inoperable.
These changes revise Action Statement "2" of Table 3.3-1 of TS 3.3.1.1 and add two action statements to TS 3/4.2.4.
In addition. TVA proposed to change Surveillance Requirement (SR) 4.2.4.2 to allow the use of a full core map to confirm the core power distribu-tion. This change would prevent an unnecessary plant derate in the event that 1
one of the instrument thimbles, which is needed to monitor the quadrant power i
tilt ratio, becomes inoperable.
-These proposed changes remove a perceived ambiguity in the interpretation of these TSs. Upon failure of a power range detector, TVA entered Action Statement "2.d" of TS 3.3.1.1 which requires that the quadrant power tilt ratio, as indicated by the remaining three power range detectors, be verified consistent with the normalized symmetric power distribution obtained by using the movable incore detectors in the four pairs of symmetric thimble locations at least once every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> when thermal power is greater than 75 percent of rated thermal' power. With 25 minutes remaining in the action statement time limit TVA had not successfully completed a flux map.
TVA then made a decision to invoke the provisions of TS 3.0.3, which is applicable when action statements can not be met. The appropriate flux @&surements were completed within the subsequent time allowance of TS 3.0.3, approximately 17 hours1.967593e-4 days <br />0.00472 hours <br />2.810847e-5 weeks <br />6.4685e-6 months <br /> after the failure of the power range detector. Another interpretation of these TSs is that TVA should have reduced power to less than or equal to 75 percent of rated thermal power, when Action Statement "2.d" of TS 3.3.1.1 could not be met.
This is discussed in License Event Report 89-022 for Unit 1 dated August 21, 1989 and in the staff's letters to TVA dated August 28 and December 4, 1989.
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9005110003 900427 PDR ADOCK 05000327 P
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L In its submittal dated April 9,1990, TVA stated that after discussions with the staff it agreed to revise the proposed Action Statement "e" for TS 3/4.2.4 to require the power level to be reduced to less than 50% of rated thermal power if SR 4.2.4.1 can not be met. This revision is conservative and does not
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change the substance of the proposed action in the Federal Register Notice (54 FR 46158) published on November 1, 1989 for the proposed amendments and does l
not affect the staff's initial determination of no significant hazards consider-ation in that notice.
2.0 EVALUATION TVA identified the possibility of multiple interpretations for the actions to be taken when the quadrant power tilt ratio is not monitored or confirmed in accordance with SRs 4.2.4.1 and 4.2.4.2.
TVA concluded that TS 3/4.2.4 does not specify actions to be taken when either SR 4.2.4.1 or 4.2.4.2 cannot be i
performed in the specified time interval.
Possible interpretations can lead to the application of TS 3.0.3 or the most limiting action in TS 3/4.2.4, with the final power level not clearly specified.
Possible interpretations on the final power level can include power levels below which TS 3/4.2.4 is not applicable or power levels below which the specific SR is not applicable.
TVA, therefore, has proposed two new action statements for TS 3/4.2.4 to specifically address situations when SRs 4.2.4.1 and 4.2.4.2 cannot be performed in the specified time interval.
The action statements apply any time the SRs cannot be performed, regardless of cause.
P TVA also evaluated Action Statement "2" of TS 3.3.1.1 for multiple interpreta-tions.
It stated that Action Statement "2.d" is apparently redundant to SR 4.2.4.2.
Action Statement "2.c" has two options that can be performed, one of which appears to apply different requirements than Action statement "2.d" when reactor power is below 75 percent of rated thermal power.
One interpretation is that Action Statement "2.c" requires a power reduction and a recalibration j
within four hours when Action Statement "2.d" cannot be met.
Another interpre-tation is that TS 3.0.3 applies when Action Statement "2.d" cannot be met because none of the conditions in Action Statement "2" specifically address the situation.
TVA also points out an ambiguity between similar actions in TS 3/4.2.4 and Action Statement "2.c" of TS 3.3.1.1.
TVA, therefore, proposed (1) revisions to Action Statement "2.c" of TS 3.3.1.1 to eliminate requirements that are redundant to SRs 4.2.4.1 and 4.2.4.2 and (2) the addition of two new action statements for TS 3/4.2.4. These changes should remove the ambiguities in the interpretation of the required actions to be taken when, for example, a power range detector is not operable.
The proposed changes are evaluated as follows:
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_ Proposed Specification 3.2.4, Action Statement "d" L
This proposed action statement requires a power reduction to less than 75 percent of rated thermal power within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> if the quadrant power tilt ratio is. not confirmed as required by SR 4.2.4.2.
This SR is applicable when
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! one power range detector is inoperable and the reactor power is above 75 percent of rated thermal power.
TVA has chosen a time interval of six hours to complete the requirements of the action statement because Action Statement "d" applies only to cases where monitoring capability is affected.
- Although, the time interval for action is four hours in the existing Action Statement "2.c" of Table 3.3-1, the difference between the proposed six hours and the existing four hours is not considered significant.
The proposed six hours is used in other action statements in the TSs for the time interval to reduce power.
Based on our review, we conclude that new Action Statement "d" of TS 3.2.4 is acceptable because it is consistent with current NRC requirements on monitoring the quadrant power tilt ratio and because it eliminates ambiguity in the current TSs.
proposed Specification 3.2.4 Action Statement "e" This revised proposed action statement requires a power reduction to less than 50 percent of rated thermal power within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> if the quadrant power tilt ratio is not monitored, as required by SR 4.2.4.1.
SR 4.2.4.1 is applicable at all times when the reactor power is above 50 percent of rated thermal power and has provisions for when the alarm on quadrant power tilt is either operable or inoperable.
TVA has chosen time intervals for this action statement that it deems appropriate because only monitoring capability is affected.
Based on our review, we conclude that the new Action Statement "e" of TS 3.2.4 is acceptable because it is consistent with current NRC requirements on monitoring the quadrant power tilt ratio and because it eliminates ambiguity in the current TSs.
Revised Surveillance Requirement 4.2.4.2 TVA proposed a change to SR 4.2.4.2 to allow the use of the movable incore detectors to obtain a full core flux map in addition to the four pairs of symetric thimble locations currently used to monitor the quadrant power tilt ratio. The longer time interval that would be required to take a full core flux map is well within the time interval required to complete SR 4.2.4.2.
Therefore, this change to SR 4.2.4.2 is acceptable because a full core flux map is just as capable as the four pairs of symetric locations for providing infor-mation on the quadrant power tilt ratio.
Revised Table 3.3-1, Action Statements "2.c" And "2.d" TVA has evaluated Action Statements "2.c" and "2.d" of Table 3.3-1 in TS 3.3.1.1.
TVA concluded that Action Statement "2.d" is redundant to SR 4.2.4.2 in that both apply to monitoring the quadrant power tilt ratio when a power range detector is inoperable.
TVA also concluded that Action Statement "2.c,"
which has two options, appears to apply different requirements than Action Statement "2.d" when reactor power is below 75 percent of rated thermal power.
TVA proposed to eliminate Action Statement "2.d" and to rewrite Action State-ment "2.c" to refer to TS 3/4.2.4 for requirements on monitoring the quadrant power tilt ratio.
Based on our review, we conclude that the proposed changes to Action Statements "2.c" and "2.d" of TS 3.3.1.1 are acceptable because monitoring of the quadrant power tilt ratio will be performed in
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ambiguity in the current TSs.accordance with the provisions of TS 3/4.2.4 and bec 3.0 _CONCL310NS TVA has requested changes to the TSs that will clarify the requirements on monitoring the quadrant power tilt ratio of the core whenever a power range detector is inoperable.
i Our review has concluded that these proposed because present NRC requirements on monitoring the qu i
are maintained by the t
ambiguity in the TSs. proposed changes and the proposed changes reduce
4.0 ENVIRONMENTAL CONSIDERATION
These amendments involve a change to a requirement with respect to the inst 61-lation 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 amendments involve no significant increase in be released offsite, and that there is no sithe amounts, and no signif cumulative occupational radiation exposure. gnificant increase in individual or The Commission has previously issued a proposed finding that these amendments involve no significant hazards consideration and there has been no public comment on s Accord-setforthin10CFR51.22(c)(9).
Pursuant to 10 CFR 51.22 innpact statement nor environmental assessment need be prepa(b), no environmenta with the issuance of these amendmentt.
red in connection 5.0 CONCLUSI0N_
The Commission made a proposed determination that the amendment involves no significant hazards consideration which was published in the Federal Register (54 FR 46258 public commen)ts were received and the State of Tenness Congnents.
The staff has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will l
not be endangered by operation in the proposed manner, and (2) such activities I
will be conducted in compliance with the Commission's regulations, and the issuance of the amendments will not be inimical to the common defense security nor to the health and safety of the public.
6.0 REFERENCES
1.
Letter from M. J. Ray (TVA) to NRC,
Subject:
Technical Specification (TS)
Change 89-36, dated October 5, 1989.
l 2.
Letter from M. J. Ray (TVA) to NRC,
Subject:
Technical Specification (TS) Change 89 Additional Information, dated April 9, 1990.
Principal Contributor:
D. Fieno Dated: April 27, 1990