ML20101S263
| ML20101S263 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 06/29/1992 |
| From: | Murphy W VERMONT YANKEE NUCLEAR POWER CORP. |
| To: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| Shared Package | |
| ML20101S258 | List: |
| References | |
| NUDOCS 9207170032 | |
| Download: ML20101S263 (4) | |
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' VERMONT YANKEE NUCLEAR POWER CORPORATION
. Ferry Road, Brattleboro. VT 053017002 BYY 92-074 ENGINEERING OFFICE
$40 MAN $rREf t BoLTON, MA 01740 June 29,1992 United States Nuclear Regulatory Commission Regional 1-475 Allendale Road King of Prussia, PA 19406
- Attu: Regional Administrator
References:
a).
License No. DPR 28 (Docket No. 50-271)
- b)
NRC Memorandum from T.E. Murley, Director, Office of Nuclear Reactor Regulation, " Temporary Waivers of Comp 11ance', dated 2/22/90
Dear Sir:
Subject:
Request for Temporary Walycr of Compliance from Technical Specification LCO Requirements Pertaining to Emergency Diesel Generator The'perpose of this letter is to document our request, in accordance with the guidance provided
. In Reference b), for a temporary walver of compliance from Techalcal Specification LCO requirements fbr Emergency Diese! Generator operability.
1.-
Recuirements to be Walved:
Vermont Yankee Techrdcal Specillcation 3.5.H.1 statet:
During any period when one-of the standby diesel-generators is inoperable, continued reactor operation is permissible _ only during the succeeding seven-' days, provided that all of the Low Pressure Core
. Cooling and Containment Cooling Subsystems connecting to the operable diesel generator shall be operable, If this requirement cannot be met, an 2:
- orderly shutdown shall be initiated and the reactor sball be in the cold 4
shutdown condition within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
Vermont Yanicee la reques:Ing relief from the 7-day Limiting Condition for Operation of Section 3.5 H.1 for a period of 48 additional hours with an* emergency diesel generator. (EDG) inoperable. The walver.would extend -the available time to replace engine components and thorc;ghly test the unit prior to a return to operable status.
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I VERMONT YANKEE NUCt. EAR POWEQ CORPOFI ATON U.S. Nuclear Regula'ory Commission June 29,1992 Page 2 1
2.
Mnmlon of Clrnmutaneet 1
De "A" Emergency Diesel Generator was declared inoperable on June 23,1992 at 0457 a.m.
During a routine.rnonthly EDG surveillance, the engine tripped approximately 90 minutes into its scheduled 8-hout run from low Jacket cooling system pressure.
Due to extensive rework earlier in June to troubleshoot and replace two cylinder liners, leaking cylinder adapters were considered suspect. After an investigation of torque values for adapters, lapping of cylinder liner sealing surfaces and installationof new gaskets, hydro tests of theJacket coolmg system failed repeatedly. At this point, cylinder integrity was suspect and it was found that the #10 cylinder was leaking. A crack was discovered that originates in the threaded adapter connection in the cylinder liner.
Vermont Yankee determlaed that the most conservative approach to the repalt of this diesel engine was to replace eleven of the twelve cylinder liners with new imprcyod liners. De twelf1h liner in cylinder #3 was replaced a month ago.
3.
Compensatory Actions As required by Technical Speci6 cations, the alternate EDO was satisfactorily Iested and all of the Low Pressure Core Cooling and Containment Coolmg Subsystems connected to this operable EDG were verined as operable. Additionally, the Vernon Hydro Station was notided of this s tuation and the dedicated tie-line ", Vermont Yankee was verified as being available. The I
Station Manager concurred with our request not to do anything that would jeopardize the tic-line availability as well as to notify Vermont Yankee of any ch:mge in the tie-line status, it should be noted that use of the Vernon tie-line 1:. addressed in operating procedures and operatcres are trained in its use.
A thorough review of all planned surveillance activkles was conducted and only those determined to be of low risk will be allowed. Based upor. the short duration of this request, additional alternate testing of the *B" EDG and its subsystems was considered, and determined not to be necessary.
4; Safety Significance and Potential Consecuenegg The proposed 48 hout extension has no impact on the consequences of any previcasty analyzed event if off-site power remains available. 'Ite alternate EDG was tested for operablDty prior to requesting the 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> extension period. This gives assurance that the available EDG would function, if required. In addition, the Vernon tic-line, which has historically. demonstrated a very high reliability, Is available to supply power to the ernergency bus. The requirement.s of the Techideal' Specifications also require that during the LCO period, all remaining Low Pressure Core Cooling and Containment Coollag systems connected to the operable EDO will rema!n operable. The proposed extemion would allow the "A" EDG to remain inoperable for 48 additional hours. Any accident which coul.d occur during this 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> period conid have l
L occurred in the previous seven<tay period also. Therefore, the proposed change does not significantly increase the pmbability of an accident. Since this is an extension of only 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />, the increased risk associated with an accident during this period is not significant.
U.S. Nuclear Regulotory Commlulon VERMONT YANKEC NUCLEAR POWER CORPORATK>N June 29,1992 Page 3 5,
(htcld2n.cL8ttml The proposed walver of compliance is for approval of reactor operation for up to nine (9) days with the EDG inoperable, ne current Vermont Yankee Technical Specifi:ations allow reactor operation for seven (7) days with the EDG inoperable. Vermont Yankee believes that the additional 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> will provide sufficient margin to repalt and thoroughly test the EDG without compromising the continued safe operation of the plant. It sbovM be noted that a significant pertion of the extra LCO time would be for "run in" of the new components and operability testing, The EDG would be available during this period, but not considered operable.
Following approx!mately nine (9) hours of continuous opera:lon at 70,73, 87.5 and 100% load, it is our intent to allow the EDG to cooldown for a minimum of twelve (12) hours.
The return of the "A" EDG to operable status would then occur aner a t.ucce.uful elght (8) hcur operability rtmi Following restoration of the 'A' diesel generator to operable status it is cut intent to conduct an additional surveillance test of the "A" diesel generator w! thin one week.
This testing would be conducted with careful monitoring of key diesel engine parameters to further substantiate satisfactory operation. Additlocally,if any significant, related problems are discovered during these test periods, such thst the Jacket cooling system problems do not appear to be corrected, an orderly shutdown ot' the plant would be initiated.
The "B" EDO will also be tested for eight houn, aAer declaring the "A" EDG operable, per the normal monthly surveillance procedure.
6.
S]g0]Acant limrds Consids.ct1193 Vermont Yankee has concluded that the request does not involve a significant huards considoration in that the reques would not:
(i) involve a signl6 cant increase in the probability or consequences of an accident previously evaluated. As discussed in section 4, a 48 hout extension to an already existing seven i
(7) day Limiting Condition for Operation would involve an insign icant la. Jesse in the W
probability of occurrence and consequences of a des!gn basis accident during the extension period.
(ii) create the possibility of a new or different kind of accident from those previously evaluated. The proposed change can have no impact on the possibility of a new or different initiating event. Any previously analyzed event postulated during the 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> extension period can be mitigated by the systems powercJ by the Vernon tie-line.
(111) involve a significant reduction in the margin of safety. As disettued above, approval of this request involves an insignificant reduction in the marglu of safety because of the availability of other plant electrical systems and the short duration of the extension period.
l In summary, the waiver of compliance would provide approval of reactor operation for up to an additional 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> with the " A" EDG inoperable. The waiver of compliance would extend the existing Technical Specification LCO throt.gh Juh 2,1992 at 0457 am. The walver of comp!!ance will allow an additional 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> to repair components and thoroughly test the EDO prior to returning it to service.
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U.S. Nuclear Regulatory Cornmission VERMONT YANKEE NUCLEAR POWER CORPORATON hme 29,1992 Page 4 s
The Vermont Yankee Plant Operations Review Committee (PORC) and Nuclear Safety Audit and Review Committee (NSARC) have reviewed this request for a temporary walver of compliance -
and concur W.th the determinations presented.
4 7.
Environmental Consequences No environmental consequences will result from approval of this request.
8.
~ Eptification of Statt Vermont Yankee has notified the State of Vermont of the content of this request and ha:
forwarded a copy of this document to the Vermont State Nuclear Engineer.
It is our understanding that this request for a 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> temporary walver of compliance has been
-authorized by telecon on June 29,1992 by James C. Linville (USNRC) to Donald A. Reid (VYNPC).
We trust that the information provided adequately supports our request; however should you have any questions regarding this rpatter, please :cntact this office.
Very tmly yours, Vermont Yankee Nuclear Power Corporation Ah Warren P. Mu hy Senior Vlec P esident, Opefa o lt h
WFM/dm -
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USNRC Document Control Desk J
USNRC Dirxtor, NRR USNRC Director, Reactor Projects, NRR USNRC Director, Offlee of Enforcement y
L USNRC Technical Assistant, Reae:or Projects, NRR USNRC Resident Impector, VYNPS
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