ML20209H460

Provides Basis for Operating Bypass of ATWS Mitigation Sys Actuation Circuitry Below 40% Turbine Load,Per 870227 Commitment

ML20209H460
Person / Time
Site:	Beaver Valley
Issue date:	04/24/1987
From:	Sieber J DUQUESNE LIGHT CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
2NRC-7-091, 2NRC-7-91, TAC-62942, TAC-62943, NUDOCS 8705040019
Download: ML20209H460 (3)

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'Af Tefephone (412) 393-6000 No.'*e*E[l" April 24, 1987 Shippingport, PA 15077-0004 2NRC-7-091 U.

S. Nuclear Regulatory Commission Attn:

Document Control Desk Washington, DC 20555

Reference:

Beaver Valley Power Station, Unit No. 1 and No. 2 BV-1 Docket No. 50-334, License No. DPR-66 BV-2 Docket No. 50-412 10 CFR 50.62, ATWS Rule Implementation Gentlemen:

On February 27, 1987 we provided a design report on the ATWS mitigation system actuation circuitry (AMSAC) to be installed in Beaver Valley 1 and 2 as required by 10 CFR 50.62.

In this report we committed to provide the basis for the operating bypass of AMSAC below 40%

turbine load after the Westinghouse Owners Group (WOG) assembled the information.

The WOG submitted the basis for the operating bypass (i.e., C-20 permissive) setpoint to the NRC by letter number OG-87-10 dated February 26, 1987 as Addendum 1 to WCAP-10858-P-A.

Consequently, the basis for the operating bypass setpoint for Beaver Valley 1 and 2 is as follows:

OPERATING BYPASS BASIS Operating bypass of AMSAC is accomplished by the C-20 permissive.

This signal is derived from two existing turbine impulse chamber pressure transmitters (one from each impulse chamber) in the reactor protection system.

The signals are isolated by existing isolators and routed to the AMSAC cabinet as non-safety grade signals.

When the pressure signal on both channels exceeds the setpoint (2 out of 2), AMSAC is immediately armed.

When the pressure signal on either of the channels decreases below the setpoint (1 out of 2),

AMSAC will be disarmed only if the signal remains below the setpoint for a pre-determined time.

The setpoint for the C-20 permissive is 40% turbine load with a time delay of 120 seconds on disarming.

The basis for this value is provided in Addendum 1 to WCAP-10858-P-A submitted by the WOG on February 20, 1987.

8705040019 870424

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• Beaver Valley Power -Station, Unit No.1 and Unit No. 2 Docket No. 50-334, License No. DPR-66 Docket No. 50-412 I

10 CFR 50.62, ATWS Rule Implementation Page 2 l

In

summary, the C-20 permissive setpoint is based on limiting reactor coolant system voiding to that predicted by previous

}

analysis.

With the 40%

turbine load permissive, the AMSAC actuation setpoint was reduced to 25%

feedwater flow, and as shown in the WOG submittal, with this reduction in the setpoint I

the reactor coolant system pressure is maintained below the ASME Service Level C Stress Limits.

i If you_ have any questions on -this subject, please contact my i

office.

Very truly yours, ll J

a Y

J. D. Sieber Vice President, Nuclear l

cc: Mr. S. M. Pindale, Resident Inspector U. S. Nuclear Regulatory Commission

)'

Beaver Valley Power Station Shippingport, PA 15077 U. S. Nuclear Regulatory Commission Regional Administrator Region 1 l

631 Park Avenue King of Prussia, PA 19406 Mr. Peter S. Tam U. S. Nuclear Regulatory Commission Project Directorate No. 2 Division of PWR Licensing - A i

Washington, DC 20555

- Mail Stop 316 Addressee only Director, Safety Evaluation & Control Virginia Electric & Power Company _

i P.O. Box 26666 One James River Plaza Richmond, VA 23261

)

i

• Beaver Valley Power Station, Unit No. 1 and Unit No. 2 Docket No. 50-334, License No. DPR-66 Docket No. 50-412 10 CFR 50.62, ATWS Rule Implementation l

Page 3 cc: (cont.)

Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Attn: -Harold R. Denton, Director Office of Nuclear Reactor Regulation Washington, DC 20555 Mr. J. Beall, Sr. Resident Inspector U. S. Nuclear Regulatory Commission Beaver Valley Power Station P. O. Box 4 Shippingport, PA 15077 INPO Records Center 1100 Circle 75 Parkway suite 1500 Atlanta, GA 30339 l

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