ML17192A679

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Emergency Procedure DGA-20,Revision 0, Relief Valve Failure.
ML17192A679
Person / Time
Site: Dresden Constellation icon.png
Issue date: 12/20/1979
From:
COMMONWEALTH EDISON CO.
To:
Shared Package
ML17192A611 List:
References
DGA-20, NUDOCS 8005080525
Download: ML17192A679 (7)
v • d • e


Text

DGA-20

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RELIEF VALVE FAILURE

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A. SYMPTOMS

1. Electrom~tic Relief Yalve Open alarm.
3. Valve Leak Detect_or System High Temp alarm.
4. Acoustic Monitor Actuated alarm.
5. Torus tempera,ture increase.

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6. Torus water level increase.
7. OPEN indication for R~lief Valve.
8. Decrease in steam flow.
9. Generator load drop w~th no change in reactor power.
10. Change in reactor vessel water level.
11. Increase in torus pressure.

B. AUTOMATIC ACTIONS IF steaming to the Main Corl.denser, Turbine Control Valves or Bypass Valves would clo.se to compensate for relief valve flow.

C. IMMEDIATE OPERATOR ACTIONS

.CAllTION The reactor shall be scrammed from any ope~ating condition if torus temperature reaches ll0°F.

1. MONITOR torus water temperature and log every five minutes during heat addition and for a minimum of 30 minutes after heat *addition is believed terminated. RECORD data on Figure 1.
2. IF Relief Valve has sp~riously actuated or is stuck open,
a. Attempt to CLOSE valve by cycling control switch from AllTO(MANllAL) to OFF and OFF to AllTO (MANllAL) several times.

Apppr-.\'C;'\

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DGA-20

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  • ' ... CAUTION Valve position indication is de-energized when fuses are pulled. Confirmation of valve
  • closure must be made by observing Valve Leak Detection Temperature Recorder and Acoustical Monitor on Panel 902(3)~21.
b. IF cycling control switch does not close the valve, fuses listed in Tables I (Unit 2) and II (Unit 3) may be pulled to de-energize valve control circuit.
3. IF Relief Valve does NOT CLOSE,
a. Reduce recirculation flow to minimum.
b. TRANSFER auxiliary power to Transformer 22(32).
c. START the Main Shaft Suction Pump and Emergency Bearing Oil Pump.
d. ADJUST reactor water level to the High Level Alarm point.
e. Manually scram the reactor and follow the Scram Procedure (DGP 2-3).

D. SUBSEQUENT OPERATOR ACTIONS

1. IF available indications confirm that the Relief Valve is leaking through, consi.der an attempt to re-seat the valve as follows:
a. Reduce turbine load with LOAD SET until at least two Bypass Valves are OPEN.
b. Cycle the Relief Valve from AUTO to MANUAL and MANUAL to AUTO several times.
c. IF the Relief Valve will not re-seat, declare it inoperable.
2. MONITOR and maintain reactor water level by all available indications.

CAUTION VERIFY 2/3 core coverage before initi'ating containment cooling.

APPP(';\/~Q DEC 20*7;:,

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3.

-e Initiate torus cooling as soon as torus water temperature Revision-a exceeds the temperature of Containment Cooling Service Water.

4. . TL.RelieLValv.e ..:was ..spur.iousLy .actuated, was stuck open or.

failed to re-seat, ~~claie it inoperable and consult Technical Specifications Section 3.5 for limiting conditions for operation.

5. IF the torus temperature reaches 120°F during isolation conditions, depressurize the reactor to below 150 psig at normal cooldown rates.
6. IF Relief Valves are.actuated and torus temperature reaches 160°F or greater while t~e reactor pressure is above 150 psig, an external visual exam of the torus must be conducted before resuming power operation.

E. DISCUSSION This procedure is written assuming that there is one or more confirming indications that a Relief Valve is leaking, is stuck open or has been spurious~y actuated.

Relief Valves discharge below water level in the torus, whereas Safety Valves discharge to the. drywell atmosphere. If a Safety Valve were leaking in a ma:'nner sufficient to provide indication, i t would be handled in acc'ordance with Loss of Coolant (Slow Leak)

(DGA-2). If a Safety Valve were inadvertently lifted and/or stuck open, it would constitute the equivalent of a break and the response of the operator would be in accordance with Loss of

_.Coolant (Break Inside Drywell) (DGA-1).

Relief Valve stuck open or spuriously initiated is not a major transient from the standpo~nt of reactor or turbine operation.

It is significant in that it constitutes an unreplenished drain from the steam cycle. It is also significant because -0f the resulting heatup of torus water and the temperature restrictions encountered with such a heatup.

The Immediate Actions are concerned with torus temperature limita-tions and with attempts to.:close a spuriously actuated or stuck open Relief Valve. The requirement to monitor torus temperature for a ~ininum of 30 minutes after heat addition terminates is intended to provide backup indication that the valve has fully closed or fully re-seated.,

For a stuck open Relief Valve, the steps to cycle the control switch and pull fuses would be of little or no help if the failure were mechanical in nature. However, if the valve stuck open because of an electrical contact failure, those steps would be meaningful.

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DGA-20 Revision 0

r. The actions to be performed prior to manual scram presume time to perform them. With significant degradations this time may not exist and under such circumstances the operator should initiate an iillJI1ediate scram signal**:

The Subsequent Actions deal first with the more probable failure, a leaking Relief Valve. Determination of a leaking valve versus a spuriously opened valve is not easy. Temperature indication and acoustic monitor indication* will probably indicate the same in both cases. If the valve position indication which senses air pressure to the valve actuator indicates the valve is closed, the valve is probably leaking. through. A backup indication might be the rate of temperature increase in the torus. The only exception to valve position as confirmation would be the Target Rock* Relief Valve. The target rock if actuated on mechanical pressure set would still indicate closed.

The actions for re-seating a leaking Relief Valve are only suggestions due to the possibility of having the valve stick open while cycling. A more probable course of action would be to declare the valve inoperable and shutdown for repair.

The remainder of the Subsequent Actions deal with maintaining reactor water level, torus temperature limitations and limiting conditions for operation with an inoperable Relief Valve. If the Relief Valve is adding significant heat to the torus, torus cooling should be initiated as soon as torus water -temperature exceeds the temperature of Containment Cooling Service Water.

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Re.vision 6 TABLE I (UNIT 2)

..(Pr.ints:* 12E2461 and 2462)

Panel 902-32 Fuses Target Rock Valve 203-3A Normal (125V DC Turb Bldg Main) F-19 287-705A F-22 287-706A Reserve (125V DC Turb Bldg Reserve) F-37 287-713A F-44 287-714A Electromatic Relief Valve 203-3B Normal (125V DC Turb Bldg Main) F-20 287-705B F-23 287-706B Reserve (125V DC Turb Bldg Reserve) F-38 287-713B F-45 287-714B Electromatic Relief Valve 203-3C Normal (125V DC Turb Bldg Hain) F-25 287-707A F-28 287-708A Reserve ( 125V DC Turb Bldg: Reserve) F-39 287-li3C F-46 287-714C Electromatic Relief Valve 203-3ti Normal (125V DC Turb Bldg Main) F-26 287-707B F-29 287-708B Reserve ( 125V DC Turb Bldg:Reserve) F-40 287-713D F-47 287-714D Electromatic Relief Valve 203-3E Normal (l 25V DC Turb Bldg Main) F-33 287-707C F-34 287-708C Reserve (125V DC Turb Bldg Reserve) F-41 287-713E F-48 287-714E APPROVED 5 o'f 7

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Revision O

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  • TABLE II (lTNIT 3)

... (pr.ints*:, 12E3461 and 3462)

. Panel 903-32 Fuses Target Rock Valve 203-3A Normal (12SV DC Turb Bldg Main) F-11 287-717A F-16 287-718A Reserve (i25V DC Turb Bldg Reserve)* F-1 287-713A F-6 287-714A Electromatic Relief Valve 203-3B Normal (125V DC Turb.Bldg Main) F-12 287-717B F-17 287-718B Reserve (125V DC Turb Bldg Reserve) F-2 287-713B F-7 287-714B Electromatic Relief Valve 203-3C Normal (125V DC Turb Bldg 'Main) F-13 287-717C F.:..18 287-718C Reserve (125V DC Turb Bldg Reserve) F-3 287-713C F-8 287-714C Electromatic Relief Valve 203-3D Normal (125V DC Turb Bldg Main) F-14 287-717D F-19 287-718D Reserve (125V DC Turb Bldg Reserve) F-4 287-713D F-9 287-714D Electromatic Relief Valve 203-3E Normal (125V DC Turb Bldg Main) F-15 287-717E F-20 287-718E Reserve (125V DC Turb Bldg *Reserve) F-5 287-713E F-10 287-714E A0Dun, 1*r:""\

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