AOP-22 Pressurizer Level Control Malfunctions

Question 1

What are the entry criteria for AOP-22, Pressurizer Level Control Malfunctions?

Answer 1

• EK-0761, “PRESSURIZER LEVEL HI-LO”
• EK-0763, “PRESSURIZER LEVEL CH “A” LO-LO”
• EK-0764, “PRESSURIZER LEVEL CH “B” LO-LO”
• EK-0769, “PRESSURIZER HIGH LEVEL”
• Loss of level control program output signal causing a deviation from the calculated level control setpoint

Question 2

What are the AOP-22, Pressurizer Level Malfunction, automatic actions?

Answer 2

High Level - actual or indicated

• CV-2004 and CV-2005, Letdown Orifice Stop Valves, open
• P-55B and P-55C, Charging pumps, stop
• P-55A, Charging Pump, operates at minimum speed (33 gpm)
• Pressurizer Backup Heaters energize (in Auto position only)

Low Level - actual or indicated

• CV-2004 and CV-2005, Orifice Stop Valves, close
• P-55B and P-55C, Charging pumps, start
• P-55A, Charging pump operates at maximum speed (53 gpm)

Low Low Level - actual or indicated

• If “A”, “B” or “A & B” Pressurizer heater control is selected then all Pressurizer heaters trip.
• CV-2003, Letdown Orifice Stop Valve closes

Question 3

What are the trip crieria of AOP-22, Pressurizer Level Malfunctions?

Answer 3

Pressurizer Level less than 30% - Trip the Reactor

Question 4

What is the mitigating strategy and what are the main actions of AOP-22, Pressurizer Level Control Malfunctions?

Answer 4

MITIGATION STRATEGY

Respond to Pressurizer level control not operating correctly.
Operate Charging and Letdown as needed to maintain/restore Pressurizer level.

ACTIONS

1. Check if Pressurizer level is greater than 30% and less than 62.8%.
2. Verify Pressurizer level greater than or equal to 36%.
3. Operate Pressurizer level control or manually control Charging and Letdown.
4. Perform one of the following: (substeps alternate controller or place controller in Manual mode)
5. Procedure exit.

Question 5

What does HS 1/LRC-0101 do?

Answer 5

• Passes the normal and backup level signals from LIC-0101A or B to P-55A/B/C and orifices # 2 and # 3 starting and stopping pumps, opening and closing orifices as needed to control level.
• The signal from HS 1/LRC-0101 also activates the high/low level alarm and energizes the backup heaters if in auto (Backup heaters are procedurally required to be in Manual ie, always on), all based on a deviation from the program level setpoint.

Question 6

How does normal level control work?

Answer 6

Cascade mode of operations is the only mode that responds to the “normal” level control program.

Controller Output Signal Lowering - Normal Control

• 72.4 % Min Speed P-55A
• 69.3 % Close CV-2005
• 56.5 % Close CV-2004
• 50.0 % P-55A at required capacity CV-2003 is Open
• 30.8 % Start P-55B
• 27.6 % Max speed P-55A
• 24.3 % Start P-55C

Controller Output Signal Rising - Normal Control

• 37.3% Trip P-55C
• 43.5% Trip P-55B
• 50.0 % P-55A at required capacity CV-2003 is Open
• 69.3% Open CV-2004
• 72.4% P-55A at Max Speed
• 88.5% Open CV-2005

Question 7

How does backup level control given a deviation from setpoint?

Answer 7

~ +6% deviation

• Hi-Lo Level Alarm (EK-0761)

~ +5% deviation

• Backup Heaters On (Already ON)
• Open CV-2004 & CV-2005
• Trip P-55B & P-55C

~ +4% deviation

• Hi-Lo Level Alarm Off (EK-0761)

~ +2% deviation

• Backup Heaters Off
• Permit P-55B & P-55C Start
• Permit CV-2004 & CV-2005 Closure

~ - 4% deviation

• Hi-Lo Level Alarm Off (EK-0761)
• Permit P-55B & P-55C Stop
• Permit CV-2004 & CV-2005 Open

~ - 6% deviation

• Hi-Lo Level Alarm On (EK-0761)
• Start P-55B & P-55C
• Close CV-2004 & CV-2005

Question 8

How do you control pressurizer level outside the band of the level controllers?

Answer 8

Must take manual control of pumps and valves.

Question 9

What technical specification applies to AOP-22, Pressurizer Level Control Malfunctions?

Answer 9

T.S. 3.4.9

Applicable in Modes 1, 2 & 3

The pressurizer water level limit does not apply in MODE 3 until after a bubble has been established in the pressurizer and the pressurizer water level has been lowered to within its normal operating band.

The pressurizer shall be OPERABLE with:

1. Pressurizer water level < 62.8%;
2. ≥ 375 kW of pressurizer heater capacity available from electrical bus 1D, and
3. ≥ 375 kW of pressurizer heater capacity available from electrical bus 1E with the capability of being powered from an emergency power supply.

Question 10

When do the pressurizer heaters trip off? When might they not?

Answer 10

Trip Off at 36%

D-Bus heater breaker will not automatically re-energize. E-Bus will.

Loss of Y-01, protective trip feature of heaters is lost.

Question 11

EK-0735, CHARGING LO FLOW comes in on what?

Answer 11

25 gpm charging flow.

• CHECK Pressurizer level for confirmation of low flow condition.
• VERIFY Pressurizer Level Control System starts an available Charging Pump as applicable, and that alarm clears

Question 12

EK-0761, PRESSURIZER LEVEL HI-LO comes in on what?

Answer 12

5.75% Deviation from Setpoint on either LIC-0101A or LIC-0101B, whichever is selected.

High Level Alarm:

• CV-2004 and CV-2005, Letdown Orifice Stop Valves, open.
• P-55B, ‘B’ Charging Pump, and P-55C, ‘C’ Charging Pump, stop.
• P-55A, ‘A’ Charging Pump, operates at minimum speed (33 gpm).
• Pressurizer Backup Heaters energize (in AUTO position only).

Low Level Alarm:

• CV-2004 and CV-2005 close.
• P-55B and P-55C start.
• P-55A operates at maximum speed (53 gpm).

OPERATOR ACTION:

• CHECK Charging and Letdown response correct.
• IF Charging and Letdown response NOT correct, THEN REFER TO AOP-22 for applicable actions .
• IF selected TAVE input is inaccurate, THEN:
• REFER TO AOP-27 for Tave/Tref Controller failure actions.