ICS

Question 1

What are the power supplies for ICS?

Answer 1

RS-3/Y-02

Hand auto stations are fed from +/-24 V and 0 to 100% scale is +/- 10V

Loss of power to hand/auto station will result in a 50% output.

Question 2

What indications would be present on loss of AC or DC power to ICS?

Answer 2

Loss of AC or DC

• Loss of ICS power supply status lights on C03
• K07-A4 ICS/AUx Sys Power Supply Trouble Alarm
• Loss of H/A lights on ICS stations
• K07-A1 Unit master in track alarm

Question 3

How fast can H/A station move in auto? Manual?

Answer 3

In Auto hand/auto station can move full scale in 4 seconds

In Manual hand/auto station moves in 40 seconds or 2.5%/second

Question 4

What makes up the Integrated Master?

Answer 4

Turbine/bypass valve control, FW control and Rx control

Question 5

What is the purpose of the ULD? STAR module?

Answer 5

ULD - ULD provides means for the operator to set the desired electrical output of the turbine generator based on megawatt output.

STAR - STAR module calculates a CTP error and apply a correction to the requested ULD signal in a slow integral action based on setpoint input to plant computer. Takes into account efficiency gains/losses to maintain desired power setpoint.

Question 6

When will ULD revert to hand/manual based on cumulative error?

Answer 6

In auto, if cumulative correction/error reaches +/- 10 MW (seen on ULD station) the ULD will kick to manual.

Question 7

When will the STAR module kick SG/RX demand station to manual?

Answer 7

A processing failure in the STAR module will revert SG/RX demand to hand.

Question 8

What are the auto transfer permissives for the ULD?

Answer 8

• Setpoint < 100% and > 20%
• CTP setpoint is within 1% of CTP
• CTP inputs are good
• CTP calculation is good
• Communication link to STAR established

Question 9

What are the ICS runbacks and where do they input?

Answer 9

Runbacks input upstream of the SG/RX demand to the STAR module. If SG/RX demand is in hand, the operator is in control of applicable runback.

Question 10

What rates will the ULD hand station move when operated in manual?

Answer 10

Operating toggle switch < 3 seconds will move the hand station needle at a rate of 1.25 MW/sec. > 3 sec moves the station at 25 MW/sec.

Rate of power change will be dependent on Rate of Change station.

Question 11

What does the term “track” mean, what indications occur as a result and what causes it?

Answer 11

Track refers to transferring the generated megawatt signal to the input of the STAR module replacing the operator set demand. Actual generated megawatt signal is now the system demand.

When in track, both ULD lights will be illuminated and Unit Master in Track alarm.

Question 12

What is the turbine header pressure setpoint, how is it controlled and what range is the header pressure hand auto station?

Answer 12

Normal setpoint is 895# (49% on H/A station)

Current MW is compared to the ULD setpoint to generate a MW error. This MW error is added to the setpoint of 895 and then converted to a signal to modulate gov valves to bias SG pressure to store or borrow from SGs.

Hand auto station is 600 (0%) - 1200 (100%) psig scale

Question 13

How is energy borrowed and stored to control SG pressure?

Answer 13

If pressure demand is lowered (MW error), liar circuit kicks in to close governor valves to store energy in the steam generators as load is reduced.

When demand is raised, energy is borrowed (SG pressure will initially lower) by opening the gov valves.

This aids in maneuvering the plant in an integrated fashion.

Question 14

Describe turbine leading mode of operation.

Answer 14

Turbine establishes electrical load while the reactor and FW controls maintain the required steam conditions. (RX and FW are header pressure control).

Question 15

Discuss the MW calibrating integral and different modes of operation?

Answer 15

MW Calibrating integral applies demands to FW/RX controls in response to MW error due to efficiency changes, steam enthalpy changes or FW measurement errors. (Qin = Qout)

MW Calibrating Integral is in run mode if SG/RX demand in manual. Blocked if power moving > 2%/min and 2 min afterwards, Both SG on LL limits or Rx demand < 15%. If none of those apply, it is released to control.

Question 16

What happens to turbine controls when a 50# header pressure error exists?

Answer 16

Turbine will reject to Manual unless:

• Turbine is at valve pos limit
• Cross limit in effect
• Load limit in effect
• Runback in effect

Question 17

How do the turbine bypass valve biases work?

Answer 17

When one of the following conditions occur, turbine header pressure setpoint to the TBVs will be biased by 50#:

1) All TBVs closed and turbine header pressure within 10# of setpoint
2) Load demand in the integrated master system > 135 MW

A 100 psig bias is added when Rx trips to limit RCS cooldown and PZR inventory loss to to shrinkage

Question 18

What range is the Rx demand station?

Answer 18

0% = 520 deg F (Minimum Rx demand is 15%)

100% = 620 deg F

59% = 579 deg F (Auto Setpoint)

Question 19

What limiter is present on reactor demand station?

Answer 19

Rx demand has a limiter at 103% to prevent exceeding RPS setpoint of 104.9%.

Question 20

How does ICS generate a rod movement signal?

Answer 20

MW signal is converted to a rx demand signal of 15-125%. It is then modified by Tave integral to maintain at 579 deg F. This signal is then converted to a neutron error to control rods. A +/- 1% neutron error will cause rods to push/pull. -1% will pull rods, +1% will push rods.

Question 21

What are crosslimits and how do they work?

Answer 21

The purpose of crosslimits is to keep the heat production and heat removal within 5% of each other.

Feedwater is reactor limited indicates reactor power is > +/-5% from reactor demand. As a result, when difference is > 5%, signal will be sent to FW to keep within 5% of actual reactor power. Opposite for FW limited.

Example: RX power 90%/RX demand 96%, FW Flow demand will hold at 95% independent of how high rx demand gets.

Question 22

What is mode referred to when rx demand and diamond are in hand?

Answer 22

Referred to as “Mini Track”. This mode keeps output of rx demand equal to rx power and minimizes chance of getting a cross limit because neutron error remains at zero.

Indicated by both lights illuminated on rx demand station.

Question 23

When is Tave control transferred to FW?

Answer 23

Tave control is transferred to feedwater when rx demand OR diamond is in hand unless both SGs are on LL limits or both FW demand stations in hand.

Question 24

How is the FW demand signal generated in ICS?

Answer 24

MW demand is converted to a total FW demand. The demand is then modified by FW temperature error. It is then split to each individual FW loop. Normally 1/2 will go to A and 1/2 to B unless a Delta Tc or RCS flow difference exists.

Question 25

How does FW demand respond during RCP trip?

Answer 25

If ICS senses RCP breaker trip, FW demand will **re-ratio** to lower flow in the loop that the RCP tripped. 2/3 of total flow will be in loop with 2 RCPs and 1/3 flow will be in other loop. Ultimately the loop with both RCPs should stay the same with no runback and other loop should cut in half. Delta Tc should then fine tune FW flow to bring delta Tc to zero. If re-ratio circuit is failed, Delta Tc will still adjust flows to correct the delta.

Question 26

When will Delta Tc integral be blocked? When bled to zero?

Answer 26

Question 27

How does the total flow controller in FW circuit function?

Answer 27

When 1 SG reaches LL limits, the delta Tc correction signal is blocked and total FW flow error is used to adjust loop FW demand signals. The SG on LL limits flow will remain the same while the other loop's flow will continue to decrease to meet the new FW demand. In this case, Delta Tc is sacrificed to achieve the reduced FW flow demand.

Question 28

What would be the effect of MFW temperature instrument reading lower than actual temperature?

Answer 28

The associated FW demand to that loop would lower.

Question 29

What indications can be read on the Delta Tc H/A station?

Answer 29

In position, Delta Tc controller reads 0 to 100%. Normal value is 0 deg F. If above 50% then means loop A demand is \> Loop B because A Loop is hotter. 0 to 100% equates to -10 to +10 deg. If both FW demands are placed in hand, then Delta Tc station reverts to hand.

Question 30

What is the purpose of BTU limits and what 4 parameters does it monitor?

Answer 30

The purpose of BTU limits is to monitor for a minimum of 35 deg F of superheat leaving SG. 1) Selected Thot 2) Individual SG Pressure 3) Loop FW temp 4) RCS flow in that loop

Question 31

What is the purpose of the high level limit? When is it sensed and what action occurs?

Answer 31

Hi level limit @ 90% operate level which prevents flooding aspirating steam ports in the OTSG. Will lower FW demand to prevent overfill.

Question 32

What indications are present on the MFP H/A station?

Answer 32

In **position**, 0 to 100% equates to 3000 - 5900 RPM. **Measured variable** reads MFW block valve DP which is used when block valves are closed.

Question 33

What are the different modes of Feedwater Pump Controls?

Answer 33

Question 34

Discuss startup and LL control valve operation.

Answer 34

Question 35

What will close the LL Block valve? What signals are overridden when ICS control switch is in override position?

Answer 35

- SU valve at 50% and going closed - Rx Trip (**Overridden by ICS override switch)** - Both MFPs trip - All RCPs trip

Question 36

What speeds do the MFW block valves operate?

Answer 36

Slow Speed (8"/min) - Opens in slow speed when FW demand is 50% and rising or when closed at 45% and lowering. Fast (72"/min) - Closes in fast speed if rx trip or MFP trip with power \< 80% until 95% closed. If, MFW X-over valve is closed FW flow error \> 10% will stop block valve movement until error \< 5%.

Question 37

What causes RFR (rapid fw reduction) and what occurs?

Answer 37

RFR occurs as a result of a reactor trip. **What occurs?** - Zero demand signal inserted below each loop FW demand running loop demands to 0. - MFW pump control is taken away from the operator as indicated by both lights lit on MFP H/A station and both pump control stations are run to zero demand (minimum speed). - SU and LL control valves are closed. **RFR is released** when: 1) SG level \< 45" for MFPs to be released (If \> 45" MFP drive to minimum again). 2) \< 40" SU and LL valves released to control (Will stay released if goes back above 40"). **If RFR failed**, overfeeding would occur but would be limited by crosslimits due to difference between rx demand and rx power which would drive MFW down to minimum.

Question 38

What occurs in ICS when MFP trips?

Answer 38

- MFW x-tie valve will open - PZR spray valve is biased 125# to open \> 80% - MFW Block valve closure is blocked \> 80% - Other MFW pump will reach max demand - Rx demand is biased down (at 100% is biased to 70%, at 90% -\> 75%, no bias @ 80% and below) RUNBACK to 40% @ 50%/min

Question 39

What is ICS response during reactor trip?

Answer 39

ICS will go to **track** (diamond to manual, turbine to manual, Gen output bkrs open), Generator output is zero so ULD signal will go to **0 at 20%/min** (track). **RFR** is initiated, **MFW blocks** close in fast speed and LL block valves go closed. **5" bias** is applied to low level limit setpoint by RFR (decays over approximately 10 minutes). **TBV** control header pressure at ~995# due to 100# bias (547 deg F saturation temp).