ML20217F296
| ML20217F296 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 03/24/1998 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20217F290 | List: |
| References | |
| NUDOCS 9803310339 | |
| Download: ML20217F296 (6) | |
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NUCLEAR REGULATORY COMMISSION WASHINGTON, D c. 30666-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.155 TO FACILITY OPERATING LICENSE NO. DPR-28 VERMONT YANKEE NUCLEAR POWER CORPORATION VERMONT YANKEE NUCLEAR POWER STATION DOCKET NO. 50-271
1.0 INTRODUCTION
By letter dated October 10,1997, as supplemented by letter dated October 31,1997, the Vermont Yankee Atomic Power Corporation (W or the licensee) submitted a request to amend the Vermont Yankee Nuclear Power Station Technical Specifications (TSs). The proposed amendment would revise the TSs for the offsite power system. Currently, the backfeed through the main (step-up) transformer is being accomplished manually by disconnecting the main generator from the main transformer by removing the generator links and energizing the unit auxiliary transformer from the 345 kV switchyard through the main transformer. This backfeed takes up to six hours to establish. W is planning to install a new main generator no-load disconnect switch to reduce the time to establish this, backfeed. Upon installation of the backfeed switch, the licensee would remove the Vemon tie line as the second delayed access offsite power source from the TS. This requires revising existing limiting conditions for operation (LCOs) for normal plant operution and required action statements for plant operation with inoperable offsite power sources of the TS. The amendment also revises the relevant portions of the Bases Section to reflect modifications.
W is planning to install the main generator no-load disconnect switch during the Spring 1998 refueling outage. The licensee intends to update the TS to reflect installation of the above mentioned disconnect switch and to upgrade the delayed offsite access /offsite power source for startup in the spring outage.
2.0 EVALUATION W's final safety analysis report (FSAR) and TSs currently describe two delayed offsite power sources; one consisting of a backfeed through the main step-up transformer and the other (the Vemon tie line) consisting of a feed from the adjacent Vemon hydroelectric station capable of supplying power to only one of the two emergency buses. Recently, the licensee performed a review of the adequacy of the delayed offsite power circuits at W and its compliance with the station blackout (SBO) rule. The review indicated that the existing backfeed through the main step-up transformer would have sufficient capacity to supply the required safe shutdown loads under worst-case conditions, but, given its current physical configuration, this circuit cannot be established within sufficient time to meet the licensing basis as a delayed source of offsite power which ensures that specified acceptable fuel dosign limits and design conditions of the reactor coolant pressure boundary are not exceeded. The licensee preposed to hstall the main generator no-load disconnect switch in the generator leads (isolated phac bus duct) between the generator terminals and the tap to the unit auxiliary transformer. When W e disconnect switch 9003310339 980324 PDR ADOCK 05000271 P
. is opened, the generator and associated protective relays will be isolated from the main transformer and unit auxiliary transformer drcuitry. After switch installation, the backfeed to the station buses through the main transformer can be established in less than an hour after a unit trip. W analyses, performed to support operation of the altamate coolmg system, document that the plant can withstand an interruption of all ac power for at least one hour, therefore, the modified backfood can be established in sufficient time to " assure that specified acceptable tual design limits and design conditions of the reactor coolant pressure boundary would not be exceeded." The above satisfies the time requirement of the delayed access offsite power source. The licensee would no longer consider the Vemon tie as a delayed access offsite power source but will retain it as W's altemate ac power source to comply with the SBO rule.
The staff has reviewed the proposed changes to LCOs, surveillance requirements (SRs), and the appropriate Bases Sections of the W TS, and its evaluation is as follows:
Revision of TS LCO 3.10.A.4 and Raama section 3.10.A Offalta Power-Normal Ooerati.QD TS LCO 3.10.A.4.s and 4.b currently describe each of the two offsite power sources for normal plant operation; namely, one immediate pow *r source and two delayed offsite power sources respectively. With installation of the backfeed switch, there would be only one delayed offsite power source at W. Therefore, the licensee proposed to delete the two provisions in TS LCO 3.10.A.4 and combine them into one, with the following:
Two qualified off-site power sources consisting of the immediate access source and the delayed access source shall be energized and operable, i
The staff reviewed the proposed revision to TS LCO 3.10.A.4 as well as all of the changes proposed for Bases Section 3.10.A relative to the modification made to W's offsite power l
. sources. The staff finds that the backfeed (with the main generator disconnect switch installed) satisfies the requirement of the delayed offsite power source for W and that all the changes made to Bases Section 3.10.A are consistent with the proposals in TS LCO 3.10.A.4 regarding the offsite power system. Therefore, the staff concludes that the proposed TS LCO 3.10.A.4 and changes made to Bases Section 3.10.A are acceptable.
Revision of TS LCO 3.10.B.3 and Bases Sect on 3.10.B Offsite Power-Operation With inoperable Components TS LCO 3.10.B.3.a currently states that, "From and after the date that both startup transformers and one diesel generator or associated buses are made or found to be inoperable for any reason, reactor operation may be continued provided the requirements of Specification 3.5.H.1 are satisfied," while TS LCO 3.10.B.3.b states that, "From and after the date that both delayed access offsite power sources become unavailable, reactor operation may continue for seven days provided both emergency diesel generators, associated buses, and all Low Pressure Core
. and Containment Cooling System are operable." Bases Section 3.10.B also states, "Therefere, reactor operation is permitted with the startup transformers out of service and with one diesel generator out of service provided the NRC is notified immediately of the event and restoration plans."
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s 3-With installation of the main generator no-load disconnect switch and subsequent deletion from the TS of the Vemon tie line as a delayed access offsite power source, the licensee proposed to revise TS LCO 3.10.B.3 as follows:
- TS LCO 3.10.B.3.a would state that:
From and after the date one offsite power source is made or found to be inoperable for any reason, reactor operation may continue for seven days provided the remaining offsite source, both emergency diesel generators, associated emergency buses and all Low Pressure Core and ContainmeM Cooling Systems are operable. If this requirement cannot be met, an ordetty shutdown shall be initiated and the reactor shall be in cold shutdown within -
24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> unless the conditions of Specifications 3.10.B.3.b are applicable.
.TS LCO 3.10.B.3.b would state that:
From and after the date that either offsite power source and one diesel generator are made or found to be inoperable for any reason, continued operation is permitted for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> as long as the remaining offsite power source, the remaining diesel generator, associated emergency buses and all Low Pressure Core and Containment Cooling Systems are operable. If this requirement cannot be met, an orderly shutdown shall be initiated and the reactor shall be in cold shutdown within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
The staff reviewed the proposed TS LCO 3.10.B.3.a, TS LCO 3.10.B.3.b, and Bases Section 3.10.B and noted the following:
1.
Exchangireg the contents of the current TS LCO 3.10.B.3.a (becomes TS LCO 3.10.B.3.b) with TS LCO 3.10.B.3.b (becomes TS LCO 3.10.B.3.a) is an administrative change and is acceptable.
2.
If one offsite power source (i.e., regardless of immediate or delayed) is made or found to be inoperable, the proposed TS LCO 3.10.B.3.a retains its current allowed outage time (AOT) of 7 days and adds action statements for the remaining offsite source, both diesel generators, associated emergency buses and all Low "ressure Core Cooling and Containment Cooling Systems to ensure its operability, and it further restricts reactor operation to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> if these requirements are not met.
3.
If one offsite power source and one diesel generator are made or found to be inoperable, the proposed TS LCO 3.10.B.3.b limits the reactor operation to continue for only 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. The current TS LCO allows the reactor operation for 7 days. Since the proposed TS LCO 3.10.B.S.b reduces reactor operation from its current 7 days to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> under the same condition, the ACT for the proposed TS LCO 3.10.B.3.b is more restrictive than the current TS LCO, and action statements have been added that if this requirement carinot be met, an orderly shutdown shall be initiated and the reacd.or shall be in cold shutdown within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
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4 4-4.
If one offsite power source and one diesel generator are made or found to be inoperable, Bases Section 3.10.B requires the licenses to notify the NRC of the event and of its restoration plans. The licensee proposed to delete this statement and replace it with a statement that would restrict the reactor operation for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, which has been incorporated irdo TS LCO 3.10.B.3.b.
Since the proposed provisions in TS LCO 3.10.B.3 and its Bases Section 3.10.8 restrict the plant operation by adding more action statements, the staff finds the proposed char.(,es to be more conservative, an improvemord over the current TS, and consistent with the improved standard i
TS (NUREG-1433) for General Electric plants. The staff concludes that the proposed TS LCO 3.10.B.3.a 3.10.B.3.b, and Bases Section 3.10.B are acceptable.
' Addition of TS BR 4.10.A.4.b and its Raams Racelan 4.10.A - Normal Ooer=*ian With installation of the main generator no-load disconnect switch at W, the licensee proposes to demonstrate the ability to establish the delayed access offsite power source within the allowable time limit once every operating cycle. Thus, the licensee proposed to add a new TS provision (4.b) in SR 4.10.A.4, which states:
Once per operating cycle, the delayed access source shall be established within one hour.
The licensee also revised the Bases Section 4.10.A to reflect the above SR change.
With proposed TS SR 4.10.B.3.a and Bases Section 4.10.A, the licensee establishes that the delayed access power source can be established within the required 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and its operability will be demonstrated once every refueling outage. The reduction of the new time required for esteblishing the backfeed from six hours to one hour will ensure that fuel design limit and design conditions of the reactor coolant pressure boundary would not be exceeded. This modification allows the licensee to remove the statement regarding the second delayed offsite line (the Vemon tie line) from the TS and its Bases Section.
The staff finds the. proposed addition of SR 4.10.A.4.b and changes to the Bases Section 4.10.A for the delayed access offsite power source to be an improvement over the current TS requirements, and acceptable.
Revision of TS SR 4.10.B.3 and Bases Section 4.10.B - Operation With inoperable Components The current TS SR 4.10.B.3.s states that, "When one of the diesel generators or associated buses is made or found to be inoperable, the requirements of the Specification 4.5.H.1 shall be satisfied," while TS SR 4.10.B.3.b states that, "When both delayed access offsite power sources are unavailable, both diesel generators and associated buses shall have been or shall be -
' demonstrated to be operable within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />."
Since the requirements for an inoperable diesel generator are addressed in other sections
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(SR 4.10.B.1) of W's TS, the licensee proposed to revise TS SR 4.10.B.3.a for an inoperable offsite power source (either immediate or delayed) as follows:
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.. When one offsite power source is unavailable, the remaining power source, both emergency diesel generators, associated emergency buses and all Low Pressure Core and Containment Coolmg Systems shall have been or shaN be venfied operable within one hour and once per eight hours thereafter.
The staff has reviewed the proposed TS SR 4.10.B.3.s that addresses required surveillance for an inoperable offsite power source and finds the performance of SRs for the remaining power sources to be more conservative than the similar provision in the improved standard TS. The improved standard TS no longer requires verification of operability of the diesel generators if one offsite power source is found inoperable.
The licensee also proposed to clarify the verification of operability of the above equipment in Bases Section 4.10.B by inserting the following paragraph:
Verification of operability within one hour and once per eight hours thereafter, may be performed as an administrative check by examining logs and other information to determine that required equipment is available and not out of service for maintenance or other reasons. It does not require performing the surveillance needed to demonstrate the operability of the equipment.
The licensee proposed to change TS SR 4.10.B.3.b as follows:
When either offsite power source and one diesel or associated buses are unavailable:
1.
The other offsite power source and all Low Pressure Core and Containment Cooling Systems shall have been or shall be verified operable within one hour and once per eight hours thereafter.
2.
The remaining diesel generator shell have been or shall be demonstrated to be operable within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
Since the plant is allowed to operate for only 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> when one offsite and one diesel generator are found to be inoperable according to TS LCO 3.10.B.3.b and Bases Section 3.10.B. the staff finds that use of the proposed TS SR 4.10.B.3.b is prudent to verify operability of the offsite power source and all Low Pressure Core and Containment Cooling Systems within one hour and once every eight hours and the remaining diesel generator within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. This change is an improvement over the current TS because it now addresses the required surveillances for an inoperable offsite power source and one diesel generator. The staff also fim's that the proposed TS SR 4.10.B.3.b is addressing the pertinent action statement of TS LCO 3.10.8.3.b.
Based on the above, the staff concludes that the proposed revisions of TS SR 4.10.B.3.a, TS SR 4.10.B.3.b, and Bases Section 4.10.B are acceptable.
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m i 3.0 STATE CONGULTATION in accordance with the Commission's mgulations, the Vermont State official was notified of the proposed issuance of the amendment. The State official had no comments.
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 and changes surveillance requirements. The NRC staff has determined that the amendment involves no significant increase in amounts, and no significant change in the types of any effluents that may be released i
offsite, and that there is no significant increate in individual or cumulative occupational radiation exposure. The Commission has previoust! issued a proposed finding that the amendment involves no significant hazards consideration, and there has been no pub 8!c comment on such
- finding (62 FR 68319). Accordingly, the amendment meets the e8)gibility 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 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 will 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: P.J. Kang Date: March 24, 1998 4..
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