ML20029A882
| ML20029A882 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 02/27/1991 |
| From: | Hehl C NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Mroczka E NORTHEAST NUCLEAR ENERGY CO. |
| References | |
| NUDOCS 9103050051 | |
| Download: ML20029A882 (4) | |
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Docket No. 50-245 Northeast Nuclear Energy Company ATTN:
hir. E. J. hiroezka Senior Vice President - Nuclear Engineering and Operations P.O. Box 270 Hartford, Connecticut 06141-0270 Gentlemen:
Subject:
Regional Waiver of Compliance Related to the Operability of the hiillstone Unit 1 Containment Cooling System This responds to your February 26,1991, lettet requesting a temporary waiver of compliance from the blillstone Nuclear Power Station Unit No.1 lechnical SpeciGeation 3.5.B.5. The waiver was requested to permit reactor operation for up to an additional three days with one containment cooling subsystem inoperable. The waiver was requested to extend the available time to thoroughly evaluate and safely implement corrective actions to at least one of the low pressure coolant injection (LPCI) "B" and "D" pump motors which were recently declared inoperable based on motor vibration. A copy of your request is enclosed for reference.
After careful consideration of your request, the NRC has concluded that reactor operation beyond the four day Limiting Condition for Operation of Technical Specification 3.5 B.5 to seven days has a negligible additional effect on reactor safety.
A regional temporary waiver of compliance was granted from the four day time limit of Technical SpeciGcation 3.5.B.5, as discussed by hlr. E. Wenzinger of this ofGee and h1r. J.
Stolz of the Office of Nuclear Reactor Regulation with hlr. H. Haynes of your staff on February 27, 1991. The waiver was granted for a time period of three P.dditional days beyond the specified Limiting Condition for Operation, with the following two conditions:
- 1) A plant shutdown will be promptly commenced if, during the period covered by the waiver, it becomes evident that at least three LPCI pumps will not be operable by the expiration of the three days covered by this waiver of compliance.
OFFICIAL RECORD COPY
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2)' Continued operation'is contingent on the remaining active components of the other containment cooling subsystem, both core spray subsystems and both emergency power sources being operable.
Sincerely, Original Signed By
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6D Ch(rles W. IIchl, Director Division of Reactor Projects
Enclosure:
As Stated cc:
W. D. Romberg, Vice Pcesident, Nuclear Operations D. O. Nordquist, Director of Quality Services R. M. Kacich, Manager, Generation Facilities Licensing S. E. Scace, Station Director, Millstone H. Haynes, Nuclear Unit Director, Millstone Unit 1 Gerald Garfield, Esquire Public Document Room (PDR)
Local Public Document Room (LPDR)
Nuclear Safety Information Center (NSIC)
NRC Senior Resident Inspector State of Connecticut OFFICIAL RECORD COPY
Northeast Nuclear Energy Company 3
bec:
Region 1 Docket Room (with concurrences)
D. Haverkamp, DRP J. Shedlosky, SRI, Haddam Neck W. Raymond, SRI, hiillstone M. Boyle, PM, NRR T. Murley, NRR S. Varga, NRR E. Greenman, NRR J. Stolz, NRR M. Slosson, NRR C. Hehl, DRP J. Wiggins, DRP E. Wenzinger, DRP W. Hodges, DRS J. Durr, DRS RI:DRP RI:DRP RI:DRP h6fd' VEGEL HAVERKAMP WENZINGER 2/27/91 2/2f/91 2/27/91 RI:DRS NIgDRP RI:DRP
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- SEE PREVIOUS CONCURRENCE SHEET OFFICIAL RECORD COPY
State of ConnecticutNortheast Nuclear Energy Company 3
bec:
Region 1 Docket Room (with concurrences)
D. Haverkamp, DRP J. Shedlosky, SRI, Haddam Neck W. Raymond, SRI, Millstone M. Boyle, PM, NRR T. Murley, NRR S. Varga NRR
.B.-BogMRE E.Ce-w J. Stolz, NRR M. Slosson, NRR C. Hehl, DRP J. Wiggins, DRP E. Wenzinger, DRP
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February 2i,h:1 245 Rocket No. 50 A212 Re: TechnicIC Specifistion 3.5.8.5 U.S. Nuclear Regulatory Comission Attention: Documer.t Control Desk Washington, DC 205E5 F
l Gen {lemen MillstoneNuclearPowerStation,UnitNd; 1
Temporary Waiver of Compliance From Containment Cooling Subsystem Limitirla Condition for Goeration L
l Introduction 1
Millstone Unit No.1 is currently in a 4-day limiting co$dition for operation (LCO) due to inoperability of the 'B' and 'O' low pressd(e coolant injection (LPCI) pumps (i.e., one containment cooling subsystem) pdf Technical Specifi-cation 3.5.B.S.
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On february 22, 1991, at approximately 1110 hours0.0128 days <br />0.308 hours <br />0.00184 weeks <br />4.22355e-4 months <br />, the'
'B' LPCI pump was declared inoperable and a 30 day LCO entered based on w increased level of The 'B' LPCI motor measured about 1.25 in/sec and was vibration in the motor.
trending towards the last measured (approximately 1.6 in/dec) value of the 'M An immediate boroscopic LPCI motor prior to its failure on December 4, 1990.
inspection of the 'B' LPCI motor was performed to 6etermi ne whether any rotor The results -of this inspectior were inconclusive.
damage had been sustained.
Subsequently, on Thuary 23,1991, the '0' l.PCI pud m tagged out for At approximately 0920 hours0.0106 days <br />0.256 hours <br />0.00152 weeks <br />3.5006e-4 months <br />, t x pump was conserva-boroscopic inspection.
of about 0.85 fn/sec tively declared inoperable based on its vibration level and the 4 day LCO entered.
The results of this boroscopic. Inspection were also inconclusive.
1991, and appraised General Electric (GE) was contacted late on February 22,om GE were dispatched of the status of the LPCI motors. Two representatives fr to the Millstone Station and arrived on-site the rext day (fobruary 23,1991).
ie 'A' LPCI motor in GE presented the results of their failure analysis of t order to determine whether a common cause f ailure mecher 1sm existed.
It was determined that the failure of the ' A' LPCI motor was iriduced by high vibra-tion. The high vibration caused the rotor to rub against the stator which in turn caused the rotor bars to melt.
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E U.S. Nuclear Regulatory Commission B13758/Page 2 February 26, 1991 On February 24, 1991, after ovaluation of the availabit information, NNECO determined that its proposed course of action would be as follows:
E o
Attempt to balance the
'O' LPCI motor in place to reduce vibration and realignmotortothepump.
o Remove the 'B' LPCI motor from the pump and visually inspect for rotor
- damage, o
Ship the 'B' LPCI rotor to a repair Qcility for mini: halancing, o
Reinstall the 'B' LPCI motor anerable, the change would increase slightly the probability of failure of the 'ontainment cooling subsystem should l{ be regulred to operale to mlk gate a DBA.
The probability of core melt during the 3 day period has been calculated in the Millstone Unit No.1 Probabilistic Safety Study to increase by 2E 7, which is less than a 1 percent increase in risk.
This slight increase in ri3k is not deemed largc enough to warrant consideration as a new or different kind of accident.
3.
Involve a significant reduction in any margin of safet/
As discussed above, the consequences of any DBA are no ; adversely affect-ed if no single failures are assumed. With a single Tailure, the conse-quences and input on margin of safety are no different during an 4 day LCO as for a 7-day LC0; the only difference is in the period of time alloved.
This small increase in risk (less than 1 pe rent) is deemed not to resalt in a significant red Atton in any margin of, Lafety.
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U.S. Nuclear Regulatory Commission
.913758/Page5 February 26, 1991 Basis for No f rreyersible [nvirenmental Conseouanct1 The proposed temporary w.t'ver of' compliance has no environmental impac; since the waiver simply allows nillstone Unit Nc. I to continue power o an additional 3 days with one containment cooling system oserable.peration for Protective boundaries are not directly affected.
Sumarv i
l The Millstone Unit No.1 Plant Operations Review Comittoq and Nuclear Review Board have approved this request for a temporary waiver of compliance and concur with the abuve determinations.
1 We wish to emphasize our conclusions that this proposed request for a tempo-i rary waiver involves no undue safety risk nor irrever tible environmental consequen>fs.
We are therefore requesting this action to allow continued plant operation as there is no sdfety issue threatening sa fe plant operation.
i Avoiding an unnecessary plant shutdown is in the best int prest of the health and safety of the public, our customers, and shareholders.
W9 belifVG the abOVQ inf0PMtion proVides a complete bas {s for approval of the requested terrporary waiver of compliance from Technical Spqcification 3.$.D.S.
We will continue to keep you informed on matters relevant to this request.
Should the Staff require any additional information to proposs this temporary waiver of compliance on an expedited basis, NNECO remains available to provide i
suchinformationpromptly.
l Very truly yours.
NORTHEAST NUCl. EAR ENERGY COMPANY FOR:
E. J. Mroctb Senior Vice $ resident By:
N i
C. F. 5 ears Vice Preside,t cc:
E. C. Wenzinger, Chief, Projects Branch No. 4, Division of Reactor j
Projects J. f. Stolz, Direttur, Project Directorate 1 4 T. T. Martin, Region 1 Administrat9r O. H. Jaffe, NRC Project Manager, Millstone Unit Nos., I and 3 W. J. Raymond. Senior Resident inspector, Millstone Unit Nos. 1, 2, and 3 l
Mr. Kevin McCarthy, Director Radiation Control Unit Department of Environmental Protection Hartford, C1 05106 e-.o n..
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