ML20094L926

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Proposed Tech Specs,Extending AOT When Offsite Circuit Inoperable from 72 H to 7 Days
ML20094L926
Person / Time
Site: Millstone Dominion icon.png
Issue date: 11/15/1995
From:
NORTHEAST NUCLEAR ENERGY CO.
To:
Shared Package
ML20094L910 List:
References
NUDOCS 9511210188
Download: ML20094L926 (5)
v • d • e


Text

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May 17,1995 3/4.s' ELECTRICAL POWER SYSTEMS -

BASES The OPERABILITY of the A.C. and D.C. power sources and associated distribution systems during operation' ensures that sufficient power will be available to supply t'se safety related equipment required for 1) the safe shutdown of the facility and 2) the mitigation and control of accident conditions within the facility. The minimum specified indepen-dont and redundant A.C. and D.C. Power sources and distribution systems satisfy the requirements of General Design Criteria 17 of Appendix 'A' I to 10 CFR 50.

The ACTION requirements specified for the levels of degradation of the power sources provide restriction upon continued facility operation commensurate with the level of degradation. The OPERASILITY of the power i sources are consistent with the initial condition assumptions of the i accident analyses and are based upon maintaining at least one of each of 1 the onsite A.C. and D.C. power sources and associated distribution systems 0PERA8LE during accident conditions coincident with an assumed loss of offsite power and single failure of the other onsite A.C. source. l The OPERABILITY of the minimum specified A.C.and D.C. ower sources and associated distribution systems during shutdown and ref eling ensures '

that 1) the facility can be maintained in the shutdown or refueling condition for extended time periods and 2 sufficient instrumentation I and control capability is available for mo)nitoring and maintaining thel '

facility status.*

( g The non-safety grade 125V D.C. Turbine Battery is required for ,

accident mitigation for a main steam line break within containment with a  !

coincident loss of a vital D.C. bus. The Turbine Battery provides the alternate source of power for Inverters 1 & 2 respectively via non-safety grade Inverters 5 & 6. For the loss of a D.C. event with a coincident steam line break within containment, the feedwater regulating valves are l required to close to ensure containment design pressure is not exceeded.  ;

The feedwater regulating valves require power to close. On loss of a vital '

D.C. bus, the alternate source of power to the vital A.C. bus via the Turbine Battery ensures power is available to the affected feedwater regulating valve such that the valve will isolate feed flow into the faulted generator. The Turbine _ Battery is considered inanerable when hue (f voltage is issa snan un vous v.5, snereoy ensuring adequate capacity for isolation functions via the feedwater regulating valves during the onset of a steam line break.

The Turbine Battery Charger is not required to be included in Technical specifications even though the Turbine Battery is needed to power backup Inverters 5 & 6 for a main steam line break inside containment )

coincident with a loss of a Class IE D.C. bus. This is due to the fact [

that feedwater isolation occurs within seconds from the onset of the event. -

vv ev ADD TocsTWOTE"w# c NE%T* fpq.E NILLSTONE - 1st!T 2 8 3/4 8-1 Amendment No.188

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Docket No. 50-336 B15445 Attachment 2 Millstone Nuclear Power Station, Unit No. 2 Proposed Revision to Technical Specifications One-Time Only A.C. Sources Allowed Outage Time Extension Retyped Pages November 1995

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$ 3/4.8 ELECTRICAL POWER SYSTEMS IASES The OPERABILITY of the A.C. and D.C. power sources and associated distribution systems during operation ensures that sufficient power will i be available to supply the safety related equipment required for 1) the  ;

safe shutdown of the facility and 2) the mitigation and control of  ;

accident conditions within the facility. The minimum specified indepen- l dent and redundant A.C. and D.C. power sources and-distribution systems  ;

satisfy the requirements of General Design Criteria 17 of ~ Appendix "A"  :

to 10 CFR 50. I The ACTION requirements specified for the levels of dvdation of l the power sources provide restriction upon continued facility operation  ;

commensurate with the level of degradation. The OPERABILITY of the power i sources are consistent with the initial condition assumptions of the  !

accident analyses and are based upon maintaining at least one of each of the onsite A.C. and D.C. power sources and associated distribution systems ,

OPERABLE during accident conditions coincident with an assumed loss of I offsite power and single failure of the other onsite A.C. source. i The OPERABILITY of the minimum specified A.C.and D.C. power sources

. and associated distribution systems during shutdown and refueling ensures that 1) the facility can be maintained in the shutdown or refueling condition for extended time periods and 2) sufficient instrumentation ,

and control capability is available for monitoring and maintaining the i facility. status.* l 1 The non-safety grade 125V D.C. Turbine Battery is required for accident mitigation for a main steam line break within containment with a coincident loss of a vital D.C. bus. The Turbine Battery provides the alternate source of power for Inverters 1 & 2 respectively via non-safety grade Inverters 5 & 6. For the loss of a D.C. event with a coincident '

steam line break within containment, the feedwater regulating valves are .

required to close to ensure containment design pressure is not exceeded. j 1

The feedwater regulating valves require power to close. On loss of a vital  !

D.C. bus, the alternate source of power to the vital A.C. bus via the Turbine Battery ensures power is available to the affected feedwater regulating valve such that the valve will isolate feed flow into the faulted generator. The Turbine Battery is considered inoperable when bus

  • A probabilistic safety assessment has examined the affect of extending the allowed outage time to seven (7) days for the electrical cross-tie from ,

Unit I to Unit 2 during the Unit 1 Refueling Outage 15. The results shows s that the risk is negligible provided that two diesel generators are i available.

Amendment No. Jpp.  !

MILLSTONE - UNIT 2 B 3/4 8-1 0222 4

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3/4.8 , ELECTRICAL POWER SYSTENS BASES voltage is less than 125 volts D.C, thereby ensuring adequate capacity for isolation functions via the feedwater regulating valves during the onset of a steam line break.

The Turbine Battery Charger is not required to be included in Technical Specifications even though the Turbine Battery is needed to power backup Inverters 5 & 6 for a main steam line break inside containment coincident with a loss of a Class IE D.C. bus. This is due to the fact that feedwater isolation occurs within seconds from the onset of the event.

NILLSTONE - UNIT 2 8 3/4 8-2 Amendment No. Jpp, 02%t

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