ML19344F588
| ML19344F588 | |
| Person / Time | |
|---|---|
| Site: | Farley  |
| Issue date: | 09/08/1980 |
| From: | Clayton F ALABAMA POWER CO. |
| To: | Schwencer A Office of Nuclear Reactor Regulation |
| References | |
| TAC-12391, TAC-12963, NUDOCS 8009150484 | |
| Download: ML19344F588 (4) | |
Text
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- Alabama Power Company 600 North ICh street Post Office Box 2641 Birmingham. Alabama 35291 1.i., eon. 20s m.,o=
h I.kor'sc" r"8.'nt Alabama Power the southem electnc system September 8, 1980 Docket No. 50-364 Director, Nuclear Reactor Regulation U. S. Nuclear Regulatc'y Commission Washington, D. C.
20! 5 Attention: Mr. A. Schwencer Gentlemen:
Farley Nuclear Plant - Unit 2 Auxiliary Feedwater System - Train Separation of the Power Supply to the AR1 Flow Control Solenoid Valves Attached is a description of Alabama Power Company's proposed modification to the auxiliary feedwater flow control solenoid valves.
- The proposed change is to satisfy the NRC requirement set forth in the i
Farley Unit 2 License for Fuel Loading and Low Power Testing.
If you have any questions, please advise.
Very truly yours, 3 %9 U;p.
ma r
F. E. Clayton, r.
TLC:de Attachment cc: Mr. R. A. Thomas Mr. G. F. Trowbridge Mr. L. L. Kintner Mr. W. H. Bradford
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h FARLEY NUCLEAR PLANT
, UNIT 2 f
AUXILIARY FEEDWATER INITIATION AND INDICATION (II.E.1.2)
REQUIREMENT Prior to installation, Alabama Power Company shall submit a description of the design modifications to provide train separation of the power supply for the auxiliary feedwater flow control solenoid valves. Prior to operation above zero power, the revised power supply shall be installed and operable.
RESPONSE
Following is a description of the proposed design modifications to provide train separation of the power supply for the auxiliary feedwater flow control solenoid valves. This modification will be made prior to operation above zero power.
t General - Addition of Train B Solenoid Valve Attached is a simplified P. & ID depicting the auxiliary feedwater discharge valves for both the motor driven and turbine driven AFW pumps. SV-A and SV-B are the existing ficw control solenoid valves and are powered from an A-train power supply. SV-C represents the y
solenoid valve to be added to each discharge valve and will be powered from a B-train power supply. The control circuits of the motor driven and turbine. driven pump valves are very similar and the following discussion is applicable to both.
Description of Valve Operation Under normal operating conditions above 5% power the AFW discharge valves are closed. During plant startup or normal cooldown the valves are placed in the modulating mode and the positioner in the air supply line is used to position the valves to obtain the desired flow rate.
Initiation of an emergency signal'(" Safety injectior." for the motor driven AFW pumps and "Lo-Lo steam generator level" or " reactor coolant pump bus undervoltage" for the turbine driven AFW pump) will result in the valves moving to the full-open position regardless of which mode (valves in open, close, or modulate position) the system is in at the time of the emergency signal initiation.
The three discharge valves (HV3227A, B, and C) for the motor driven pumps and the three discharge valves (HV3228A, B, and C) for the turbine driven pump'are all air-to-close. Placement of either SV-A (A-train) l or SV-C (B-train) in the vent position (de-energized) will remove air l
from the valve and cause it to move to the full-open position.
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The design as shown is such that SV-C.(B, train) is redundant to and serves as a backup for SV-A (A-train). Failure of either will not
. prevent the discharge valve from being placed in the full open position, whether initiated by operator action or an automatic signal. This is true for any possible failure mode of either solenoid valve whether it be due to loss of. power, an overvoltage condition, or other.
SV-B (A-train) is used only for positioning the valve when in the modulating mode and its failure will not preclude opening of the discharge valve.
Local and Remote Operation-Remote hand switches are provided on the main control board for normal control of the discharge valves. Control of the valves from the hot shutdown panel is provided by placement of.the selector switches located on the hot shutdown panel into the local position.
Each train of solenoid valves is provided with separate power supplies for remote (normal) and the local (hot-shutdown) control. The power.
supply to the hot shutdown panel for local contral does not pass through the cable spreading room and originates from a separate distribution panel than the power supply to the main control board for remote control. This will allow the operator to modulate the discharge valves from the hot shutdown panel in the event of a fire in the cable spreading room.
Reset Capability
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Upcn initiation of an emergency signal the discharge valves will move to the full-open position. Following mitigatica of the abnormal or accident condition that initiated the emergency signal, the operator may want to regain control of the discharge valves to regulate the AFW flow. A reset capability (reset switches located on the main control board) is provided to the operator to accomplish this. Two operator actions are required to move the valves from their emergency open mode. This prevents the valves from inadvertently closing follow-ing reset of the emergency signal by the operator. An additional margin of safety in this regard is provided by the standard operating procedure which requiNs the valve positioner to be placed in the full open position during normal operation (valves closed).
Summary The proposed modification provides two trains of emergency power to AFW discharge valve controls such that a single failure of the solenoid valves or their power supply will not cause a loss of auxiliary feed-water to the steam generators.
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