AOP-12, LOSS OF PREFERRED AC BUS EY-10

Question 1

What is the mitigating strategy of AOP-12, LOSS OF PREFERRED AC BUS EY-10?

Answer 1

1. Trip Reactor if greater than 80% power and CV-0711, Feed Pump P-1A Recirculation is not isolated.
2. Isolate CV-0711, Feed Pump P-1A Recirculation Valve.
3. Determine if an actual fault exists on EY-10, Preferred AC Bus No 1.
4. If a fault does not exist, supply power to EY-10 with the Bypass Regulator.
5. If a fault does exist, perform compensatory actions for lost indicators and equipment.
6. Restore EY-10.

Question 2

What are the entry conditions of AOP-12, LOSS OF PREFERRED AC BUS EY-10?

Answer 2

EK-0543, “PREFERRED AC BUS NUMBER 1 TROUBLE”

AND

Channel ‘A’ RPS Trip Ladder Logic Lights Illuminated

Question 3

What are the automatic actions of AOP-12, Loss of Preferrend Instrument AC Bus Y-10?

Answer 3

• P-8A, Motor Driven Auxiliary Feedwater Pump, control circuitry transfers to EY-30, Preferred AC Bus No 3.
• P-8B, Steam Driven Auxiliary Feedwater Pump, control circuitry transfers to EY-30, Preferred AC Bus No 3.
• Main Feedwater control for E-50A, ‘A’ S/G, transfers to EY-30, Preferred AC Bus No 3.

Question 4

What are the Reactor Trip Criteria of AOP-12, Loss of Preferred Instrument AC Bus EY-10?

Answer 4

Greater than 80% power, trip the reactor.

• CV-0711, Feed Pump P-1A Recirculation Valve, fails open with Reactor power greater than 80%

Question 5

What are the immediate actions of AOP-12, Loss of Preferred Instrument AC Bus EY-10?

Answer 5

None

Question 6

How is RIA-1805 impacted by a loss of EY-10, Preferred AC Bus? What could happen?

Answer 6

RIA-1805 fails to tripped status.

One other 1806-1808 monitor trips and containment will isolate.

While left channel CIS is deactivated by a Loss of Y-10, CV-2009 is actuated by either channel.

CV-2009 closing isolates the letdown line and will result in lifting RV-2006.

PCS leak. 3.4.13 PCS Operational LEAKAGE. MODES 1, 2, 3, and 4.

4 Hours to Limit.

PCS operational LEAKAGE shall be limited to:
a. No pressure boundary LEAKAGE;
b. 1 gpm unidentified LEAKAGE;
c. 10 gpm identified LEAKAGE; and
d. 150 gallons per day primary to secondary LEAKAGE through any
one steam generator (SG).

Question 7

How is HS1/LIC-0101 impacted by the loss of Y-10?

Answer 7

HS1/LIC-0101, Heater Select Switch is normally in the “A+B” position.

It passes the low level signal (<36%) from A&B controllers to trip off the pressurizer heaters and close CV-2003, letdown orifice stop valve.

If Y-10 fails, LIC-0101A fails to low level. System goes to maximum charging, isolates letdown and shuts down the heaters.

HS1/LIC-0101, Heater Select Switch, is taken to ‘B’ channel.

Ensures affected components (Charging Pumps and Letdown Orifice Stop Valves) are provided a neutral process signal (50% Pressurizer Level Controller process output signal). Remember: OOS controller is placed in manual with output signal at 50% to avoid saturating the controller.

Question 8

What happens on pressurizer level on loss of EY-10, Preferred AC?

Answer 8

Pressuizer level begins to rise. You have approximately 3 minutes before reaching the 62.8% limit of T.S. 3.4.9. when at full power (57% starting level)

With ‘A’ Channel PPCS and PLCS in service, Charging Pumps P-55B and P-55C will start and P-55A will go to maximum speed and Letdown will be isolated. This results in PZR level rising ~ 1.95 %/min. (133 gpm - 4 gpm) / 66 gal/% = 1.95 %/min.

Question 9

What happens to T_ave on loss of Y-10?

Answer 9

Loop 1 T_ave signal fails low.

Causes Pressurizer Level to be calculated as 42%.

Switch to Loop 2 to provide Pressurizer Level Control with a valid signal.

Question 10

What do you do if T_ave/T_ref deviation is not within 5 degrees?

Answer 10

REDUCE Reactor Power or Turbine load to lower TAVE/TREF deviation within 3F.

Question 11

For West ESG sump, what must you do and why must you do it?

Answer 11

MONITOR West ESS Room Sump Level locally every 4 hours.

Due to the loss of power to the West EES Sump level and Sump Pump pressure instruments.

Question 12

Why are all fuel or irradiated component handling activities stopped?

Answer 12

Proactively implements LCO 3.7.10 actions due to loss of FIC-1711 which prevents opening of Damper D-20, Air Filtering Unit V-26A Modulating Damper, which in turn prevents V-26A, Air Filter Unit VF-26A Fan, from starting.

Question 13

Why is T cold verified greater than 460F?

Answer 13

If it were not, LTOP would be in service.

Due to loss of power to TT-0112CA, Temperature Input to Channel ‘A’ LTOP could result in spurious actuations.

A channel is defeated if in service so that spurious actuations will not complicate event recovery when power is restored to EY-10.

Question 14

Why must you bypass the A Channel Trips?

Answer 14

If the reactor is reset, then spurious RPS channel actuations can occur when
a trip unit is reenergized.

Question 15

What happens to Left Channel CIAS on loss of Y-10?

Answer 15

A valid CHP or CHR signal results in Right Channel CIAS initiation only.

For a valid CHP you will need to:

1. PRESS PB1-1, (LEFT) Injection Initiate, to manually actuate Left Channel SIS.
2. OPEN CV-3001, Containment Spray Valve.
3. START Containment Spray Pumps: P-54B & P-54C
4. PERFORM EOP Supplement 6, “Checksheet for Containment Isolation and CCW Restoration.” to ENSURE CLOSED Left Channel CIAS valves.

For a valid CHR you will need to:

1. PERFORM EOP Supplement 6, “Checksheet for Containment Isolation and CCW Restoration.” to ENSURE CLOSED Left Channel CIAS valves.
2. PLACE the following ESS Sump Pump handswitches to OFF.

• 42-155B/SS, P-72B
• 42-165B/SS, P-73B

Question 16

What happens to the ASDV on loss of Y-10?

Answer 16

Atmospheric Steam Dumps are inoperable due to loss of EY-10.
Turbine Bypass Valve Controls and S/G Code Safety Valves are still available.

Question 17

How do you tell there is or is not a fault on the Preferred AC Bus?

Answer 17

Loss of the preferred AC bus due to the Inverter Output breaker opening indicates
that there is likely a fault on the preferred AC bus.

Loss of the preferred AC bus due to a tripped DC Input breaker when the AC
Output breaker remains closed indicates that the Preferred AC Bus is likely free of
a fault.

Question 18

What are some key equipment losses from Y-10 deenergizing?

Answer 18

A Channel Pressurizer Level Control

A Channel Pressurizer Pressure Control

Left Channel CIAS

ASDV Controller - HIC-0780A, 0780B, 0781B

West Safeguards Sump Level/Auto Pump

NI-5, Power Range NI

LTIR-0101A, RV Level/Qualified CETs

Auto Start Low Pressure on A & C CCW Pumps

Condenser Off-Gas Monitor