ML20027D205

Forwards Safety Evaluation Re Effect of Dc Power Supply Failure on ECCS Performance.Min ECCS Equipment & Support Sys Will Provide Sufficient Cooling Capacity for Safe Reactor Shutdown for All Breaks

ML20027D205
Person / Time
Site:	Pilgrim
Issue date:	10/01/1982
From:	Vassallo D Office of Nuclear Reactor Regulation
To:	Morisi A BOSTON EDISON CO.
References
NUDOCS 8211030116
Download: ML20027D205 (5)

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Dc D-o I 'o Dietribution:

fnntkat" r4 D NR PD Docket No. 50-293 0CT 1 - LW 9 cal DR ORB #2 D. Eisenhut i

0 ELD Mr. A. Victor Morisi Manager 01&E (1)

Nuclear Operations Support Department KEccl eston Boston Edison Company S. Norris 25 Braintree Hill Park NSIC Rockdale Street ACRS (10)

Braintree, Massachusetts 02184 JHeltemes, AE0D

Dear Hr. Morisi:

Your letter of September 16, 1980 confirmed that General Electric analyses regarding minimum ECCS equipment available with a DC power supply failure are conservative with respect to the system availability combinations at Pilgrim Nuclear Power Station.

We have completed our review of your submittal and conclude that there is adequate assurance that DC power will be available for the combination of ECCS equipment and systems as stated in your letter assuming a single DC power supply failure. We have further concluded that the minimum ECCS equipment and support systems available assuming a single DC power supply failure will provide sufficient cooling capacity for a safe reactor snutdown for all breaks. The enclosed Safety Evaluation documents our findings.

Consequently, we consider this issue resolved for Pilgrim.

Sincerely.

OrI#.na.a.

.l S.~8. Vassille Domenic B. Vassallo, Chief Operating Reactors Branch #2 Division of Licensing

Enclosure:

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Mr. A. Victor Morisi Boston Edison Company i

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Mr. Richard D. Machon U. S. Environmental Protection Pilgrim Station Manager Agency Boston Edison Company Region I Office RFD #1, Rocky Hill Road Reoional Radiation Representative Plymouth, Massachusetts 02360 JFK Federal Building Boston, Massachusetts 02203 Resident Inspector c/o U.S. NRC P.O. Box 867 Ronald C. Haynes Plymouth, Massachusetts 02360 Regional Administrator, Region I U.S. Nuclear Regulatory Comission 631 Park Avenue Henry Herrmann, Esquire Massachusetts Wildlife Federation King f Prussia, PA 19406 151 Tremont Street Boston, Massachusetts 02111 i

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Massachusetts Department of Public Health ATTN:

Comissioner of Public Health i

600 Washington Street Boston, Massachusetts 02111 Water Quality & Environmental Commissioner Department of Environmental Quality 1

Engineering i

100 Cambridge Street Boston, Massachusetts 02202 Mr. David F. Tarantino Chaiman, Board of Selectmen I

11 Lincoln Street Plymouth, Massachusetts 02360 1

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SAFETY EVALUATION EFFECT OF A DC POWER SUPPLY FAILURE ON ECCS PERFORMANCE PILGPIM 1 NUCLEAR POWER STATION

Background

The loss of direct current (dc) power supply can disable several Emergency Core Cooling System (ECCS) components. This can result in a limiting single failure condition for some breaks. Pilgrim 1 Nuclear Power Station belongs to the category of plants, as indicated in Reference 1, which has retained low pressure coolant injection (LPCI) loop selection logic (non-LPCI mode plants) and in accordance with a General Electric Company study must have the following equipment and support systems available for all breaks:

1 core spray (CS) pump + 2 LPCI pump + 1 automatic depressurization (ADS)

The de power to these systems should be available at all times regardless of 1

I any de supply failure to ensure that the above equipment is capable of pro-vioing safe reactor shutdown. Also, ECCS equipment should not be lost due to water spillage.

The referenced letter is the licensee's response to an NRC inquiry to assure that the system combinationr,, as indicated above, are available at all times for small and large breaks. The above equipment as indicated in the licensee's submittal are supplied by two redundant buses and regardless of any postulated dc power supply failure, power is available to the minimum ECCS equipment.

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Analysis and Evaluation i

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The 125-volt de po..er system supplies power and control through two control

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buses, A and B and two distribution panels A and B which are associated with le each bus, respectively.

Each bus is supplied by an independent battery and 9

battery charger. Each-battery charger is fed from a separate 480-volt ac

]3 emergency service load center. Buses A and B are connected via interlocked circuit breakers to a common backup battery charger which is fed from the j

480-volt ac common emergency service load center. Each battery charger has li adequate capacity to restore its battery to full charge from a totally dis-j charged condition while carrying the normal steady state de load. Each y

battery has adequate capacity to safeguard the station until ac power sources 3

are restored. Each battery is located in a separate ventilated battery room jl as are the chargers for each battery. Any loss of de power is annunciated j

in the control room, a

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1 The 125V-dc power system supplies de power to the selected safeguard system loads. Each bus supplies de power to its associated ECCS equipment consisting of ccre spray, residual heat removal (RHR) and automatic depressurization system. Power to the core spray, residual heat removal and automatic depressurization systems is available regardless of which de power supply is lost. Also, the reactor core isolation cooling (RCIC) system is supplied by Bus A and the high pressure coolant injection (HPCI) is supplied by Bus B.

Therefore in addition to the 1 CS + 2 LPCI + ADS system, either RCIC or HPCI system is available for safe reactor shutdown depending on which de supply is lost. As listed in the licensee's submittal the following equip-ment is available in the event of a single failure of a de power supply:

CS System P-215A atsociated circuit breaker A507 plus logic "A" or P-215B associated circuit breaker A607 plus logic "B" l

LPCI System P-203A associated circuit breaker.A-503 plus logic "A" P-203C associated circuit breaker A-506 plus logic "A" a

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P-203B associated circuit breaker A603 plus logic "B" P-203D associated circuit breaker A606 plus logic "B" ADS System j

SV-203-3A SV-203-3B SV-203-3C SV-203-4B Logic for all

'The de equipment associated with the above mentioned systems are located outside the containment and therefore are unaffected by water spillage resulting from the location of the break.

Our evaluation indicates that the minimum ECCS equipment and support systems available will provide sufficient cooling capacity for safe reactor shutdown for all breaks.

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3-I Based on our review of the licensee's submittal, FSAR (Sections 7 and 8) and single line relay and meter diagrams for the 125V and 250V de systems, we conclude that there is an adequate level of assurance that dc power will be available for the combination of ECCS equipment as stated in the licensee's submittal.

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Date : October 1,1982 Principal Contributor:

A. Gill i

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I Re ference 1.

I Boston Edison Company letter #80-223 to T. A. Ippolito dated September 16, 1980.

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