ML20154M051

Forwards Info on Assessment of Station Battery Load Profile & Interim Response to Loss of Ac Power Event.Util Position That Svc Demand on Batteries Need Only Satisfy 1 H Load Profile Described in Original FSAR

ML20154M051
Person / Time
Site:	Fort Saint Vrain
Issue date:	09/16/1988
From:	Robert Williams PUBLIC SERVICE CO. OF COLORADO
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
P-88337, NUDOCS 8809270045
Download: ML20154M051 (6)

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Public Service ~ nya .

P.O. Box 840 Denver, Co 802010840 R.O. WILUAMS, JR.

NLER DONS September 16, 1988 Fort St. Vrain Unit No. 1 P-88337 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Docket No. 50-267

SUBJECT:

Loss of All AC Power Sources and Station Battery Load Profile Gentlemen:

Public Service Company of Colorado (PSC) hereby submits in the following attachment, information on the assessment of the Fort St.

Vrain station battery load profile and PSC's interim position in response to a loss of all AC power event until the requirements of 10CFR50.63 can be assessed for a high temperature gas cooled reactor.

It is PSC's position that the service load demand on the station batteries need only satisfy a one hour load profile as described in

! the original Final Safety Analysis Report (FSAR) rather than a four hour load profile as currently described in the Updated FSAR.

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. P-88337 September 16, 1988 Should you have any Mr. M. H. Holmes at (questions concerning this matter, please contact 303) 480-6960.

Very truly yours, R. O. Williams, Jr.

Vice President Nuclear Operations  ;

R0W/JCS:pa Attachment cc: Regional Administrator, Region IV Mr. Robert Farrell ATTN: Mr. T. F. Westerman Senior Resident inspector Chief, Projects Section B Fort St. Vrain L

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Q Attachment 1 to P-88337 September 16, 1988 BACKGROUND INFORMArION Section 8.2.3.4 of the FSV Preliminary Safety Anal stated that each station battery (Battery 1A or 18)ysis Report (PSAR) was adequate to supply the DC shutdown loads for not less than one hour following a loss of all AC power. This basis was retained up through Revision 3 to the Final Safety Analysis Report (FSAR). In Revision 4, Section 8.2.3.4 of the FSAR was revised to state that Battery 1A or 1B is adequate to supply the required shutdown DC Loads for four hours following a 'oss of all AC power, consist with the four hour load profile defined in Station Battery Design Criteria DC 92-1 and as reflected in the surveillance requirements of SR 5.6.2 of the Technical Specifications for battery testing. FSAR Figure 8.2-14 shows the single line diagram of the DC distribution panels for station batteries 1A and 18.

An assessment of the DC loads listed on the above referenced FSAR figure and the load profile defined in DC 92-1 finds that most of the critical safety functions beino performed which require battery power are occurring within the first n;lnute. These safety functions are those associated with the tripping of numerous circuit breakers and the actuation of numerous relays in the plant's control and PPS systems. Other critical safety functions occurring within the first hour are those associated with supplying standby diesel generator control power and with supplying inverter power for monitoring and control instruments and emercancy lighting. The remainder of the loads associated with the' battery are non-safety related such as plant computer power and items associated with equipment protection only (primarily associated with the main turbine).

PSC maintains the position that credit for the station batteries (batteries 1A, 18 and IC) need only be assessed for a one hour duration following a loss of all AC power event. Well within one hour of the loss of AC power event, the Alternate Cooling Method (ACM) diesel generator can be started and aligned to provide AC power for effecting a reactor shutdown and recharging of a station battery.

The following section provides the justification.

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Attachment 1 to P-88337 September 16, 1988 JUSTIFICATION The following discussion demonstrates sufficient justification that )

AC power can be restored within one hour in the event of a loss of all AC power. Restoration of AC power within this time ensures that AC and DC power will be available to those systems, equipment and components required for snutdown of the plant.

l (1) In a Station Blackout event (Loss of the Five Offsite Transmission Lines, Loss of the Main Turbine-Generator and Loss  ;

of Both Standby Diesel Generators), the ACM diesel generator .

] would be available to provide power to the essential 480 VAC

buses, so that forced circulation cooling could be established wit;. either condensate or firewater. This is supported by the following

A. In a Station Blackout event, PSC considers that operators could implement the Restoration of Power To Essential 480

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Volt Buses procedure, SSC-01, and supply ACM diesel i generator power to these buses within 45 minutes.

Establishing a one hour battery load profile requirement is i conservative. i j A walkdown of SSC-01, performed in 1987 as documented in PSC

. Internal Memo PPS-87-T!05, demonstrated operators could ,

perform the nece:sary steps to establish ACM diesel generator power to a 480 VAC essential bus in less than 20 minutes. PSC recognizes that during a Station Blackout event, operators will initially work toward starting one of j the Standby Olesel Generators (SDGs) and bringing in off-

, site power from one of the five offsite connections to FSV.

However, since establishing a source of electrical power is  :

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. the primary objective, it is not unreasonable to credit the '

operators with the ability to implement SSC-01 and power the i essential buses from the ACM Diesel Generator in 45 minutes

! should power be unavailable from one of the other sources.

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l B. With power supplied to the essential buses at one hour.

I operators can perform the necessary actions to establish l

forced circulation cooling with condensate (Fire Protection [

Shutdown /Cooldown Train A - Safe Shutdown Cooling Procedure '

550-03) or firewater (Safe Shutdown Cooling Procedure SSC- ,

05) in 90 minutes. Provided adequate forced circulation is started at 90 minutes and maintained in operation, analyses [

l demonstrate that peak core fuel temperatures will not exceed l 1  !

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Attachment 1 to P-88337 September 16, 1988 2900 degrees F (a temperature well below that at which rapid fuel deterioration is anticipated) and no significant fuel particle coating failure will occur. Analyses also demonstrate that the reactor coolant pressure boundary .and containment boundary will remain intact, prevencing the release of significant amounts of primary coolant to the -

atmosphere. This assures that offsite doses resulting from a Station Blackout event will be a very small fraction of 10CFR100.

(2)The FSV Technical Specifications govern the ACM diesel generator and provide assurance it will be available to "backfeed" the 480 VAC essential buses folicwing a Station Blackout event.

Limiting conditions for operation and surveillance requirements applicable to the ACM diesel generator are defined in LC0 4.2.17, SR 5.2.20 and SR 5.2.21.  ;

(3) The original licensing basis as defined in the PSAR and subsequent SAR updates up to Revision 4 of the Updated FSAR established battery capacity basis to supply the required i shutdown DC loads for one hour following a loss of all AC power. >

(4)The existing batteries and DC bus configuration are adequate to r power the loads needed for one hour. After one hour the ACM diesel generator will be available to supply power to the i essential buses for charging the batteries even in the event of a Station Blackout.

COMMITMENTS '

In view of the above discussed justification, PSC cormiits to the following.  ;

A. Issuance of a change notice (CN) to revise the Station Battery Design Criteria, DC 92-1, to change the four hour load profile to a one hour load profile. Issuance of the CN will also incorporate the one hour load profile for Battery IC, which is not currently addressed. This CN will be completed prior to restart following the 4th refueling.  ;

B. Revise the surveillance procedure which implements Technical i Specification SR 5.6.2 surveillance to reflect the one hour load profile for battery testing requirements prior to the next  !

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Attachment 1 to P-88337 September 16, 1988 scheduled battery surveillance test following the current outage testing requirements.

C. Generate an interim procedure to address plant operation with only DC power available for up to one hour prior to restart from the current outage. This procedure will provide assurance that forced circulation is placed in effect at no later than 90 minutes after the loss of all AC power.

All of the above commitments will serve as the baseline for the future FSV assessment against the Station Blackout requirements defined in 10CFR50.63.