Week 5: Simulator Morning Questions

Question 1

What is the Point of Adding Heat?

Answer 1

The point at which Rx power impacts core components.

Question 2

A control rod drops into the core. The plant does not trip. Describe the plant response.

Answer 2

Tavg goes down to counteract the negative reactivity insertion.

Question 3

Describe how you would recover a dropped rod.

Answer 3

Lower power to 50%, open lift disconnect switches for the other RCCAs in the bank with the dropped rod, reset step counters to 0, pull dropped rod up and out.

Question 4

Describe the process of transferring house loads from the Unit Aux XFMR to the Startup XFMR on a plant shutdown.

Answer 4

Source selector switch to startup, close the PA01 startup XFMR breaker to PA01, then close the PA02 startup XFMR breaker to PA02. When the breaker closes for each bus, the unit aux breaker for that bus should automatically open.

Question 5

List all pumps that can add water to the SGs.

Answer 5

MFW Pumps
AFW Pumps
Startup FW Pump
Condensate Pump

Question 6

List all DNB-related trips.

Answer 6

OTDT
RCP Undervoltage/Underfrequency
RCS Flow
PZR Low Pressure
SG Low Level

Question 7

What criteria are needed to declare the reactor critical?

Answer 7

Constant positive SUR and increasing counts with no rod motion.

Question 8

You are at 5% power on a start-up. Explain in detail how you will raise power to 15%.

Answer 8

Critical at 5%
Pull rods - + reactivity
Raises power - Tavg > Tsteam
Steam dumps open to control pressure
Steam flow increases = Rx power at new high level

Question 9

You are conducting a startup. Explain how and why you will level power at 10^-8 amps.

Answer 9

Start critical, with a positive startup rate - drive the rods in until the SUR reads a little bit negative when power reads 10^-8 amps on the IR.

At this point, you are a few decades out of the source range, so you are less affected by fixed sources when taking critical data.

Question 10

You are critical at 10^3 cps. You pull rods to add 50 pcm of reactivity. What is the startup rate?

Answer 10

SUR = 26.06[(lambdarho)/(Beta-rho)]
lambda = slow up = 0.1
Beta = BOC = 0.0065
rho = 50 pcm = 50E-5
SUR = 0.217 dpm

Question 11

What are the auto SI signals?

Answer 11

SL pressure at 615 psig
PZR pressure at 1849 psig
CTMT pressure at 3.5 psig

Question 12

N43 fails high at 100%. Explain the plant and operator response.

Answer 12

Rod control thinks Rx power is much higher than Turbine power, begins to step in rods to compensate. Left alone, this will drive Tavg down and Rod control will not be able to recover due to C-2 being in. The RO will confirm with BOP that there is not a load rejection occurring, and will take manual control of the rods to prevent them from erroneously inserting.

Question 13

What is the minimum pressure for running a RCP?

Answer 13

320 psig

Question 14

I&C is performing maintenance on Channel 3 PZR pressure. Channel 1 vital instrument bus feeder breaker opens. Describe your operator actions.

Answer 14

Channel 3 is most likely in trip during maintenance; the channel 1 bus failing open will also put all channel 1 bistables in trip, leading to a Rx trip. Operators enter E-0.

Question 15

Plant is at 18% power. Main turbine trips on high S/G level. Describe the plant response.

Answer 15

MFW trips on the high SG level, FW isolates, SG level decreases due to shrink as turbine power goes to zero, AFW starts (due to either Lo SG level or loss of both MFW pumps).

Question 16

List the inputs to the OTDT setpoint calculation.

Answer 16

Tavg, RCS pressure, dI

Question 17

Describe the process of paralleling the main generator to the grid.

Answer 17

Sync all 3 phases to 25kV
Connect to grid when in phase and matching frequency as shown by the syncroscope

Question 18

What are indications that you are at the POAH? Why is this significant?

Answer 18

Tavg begins to increase, startup rate begins to drop due to temperature feedbacks, steam dumps will start to open.

This is significant because it indicates that a negative feedback loop has been established.

Question 19

Explain the changes in pump line-up going from 2%-100% power.

Answer 19

1.5% - Start MFW Pump
20% - Start 2nd Circ Water Pump
40% - Start both Heater Drain Pumps
50% - Start 3rd Condensate Pump, 2nd MFW pump, 3rd Circ Water Pump, 2nd Service Water Pump

Question 20

What is the minimum dP for the #1 RCP seal? Why?

Answer 20

200 psid, need that much to ensure the film riding seal isn’t rubbing on surface

Question 21

When do we put RHR in service on a SD/CD? How do we control the cooldown rate?

Answer 21

When the RCS reaches 350F / 360psig

Cooldown rate is controlled via the RHR Hx flow control valve increasing or decreasing the amount of RCS coolant that flows through the associated heat exchanger. Overall flow is kept constant at 3800 gpm via a RHR Hx bypass control valve.

Question 22

At 80%, we want to raise Tavg by 10F. How would you do this?

Answer 22

Withdraw rods or dilute

Question 23

Explain how to draw a bubble in the PZR.

Answer 23

With the PZR solid (PORVs shut), you raise the PZR liquid temperature via the backup heaters to the saturation point at your desired pressure. Then, you would decrease charging flow less than letdown, watching for level to decrease and pressure stabilize.

Question 24

Channel 2 pressure transmitter fails high. What will happen? What bistables must be tripped?

Answer 24

PZR sprays full open, a PORV opens, actual PZR pressure drops. PORV will close when the PORV Block setpoint of 2185 psig is met - however, spray will continue to drive pressure down unless operator action is taken.

The CH2 bistables for PZR high pressure trip, low pressure trip, low pressure SI, OTDT, and P-11 will need to be tripped.

Question 25

Why do we have P-12?

Answer 25

To prevent uncontrolled cooldowns via the steam dumps.

Question 26

What are the major Rx effects to be considered when shutting down plant from 100% to Mode 2?

Answer 26

Xenon
Power Defect

Question 27

List the Permissives that will change state when going from 100% to Mode 2.

Answer 27

P-9 - Blocks Rx trip on turbine trip at 50%
P-8 - blocks low flow trip in 1/4 loops at 48%
P-13 - 10% Turbine power
P-10 - When 3/4 PRs - Reset SR HV block, PR Hi flux trip at 25% and IR Hi flux at 25%
P-7 - when you get both P-13 & P-10, - Flow trips blocked, RCP UV/UF trips blocked, Pzr level Hi and LO Pzr P trip block

Question 28

What major electric plant change must be made when shutting down the plant?

Answer 28

Decreasing gen output, tripping Main turbine, auto bus xfr from Aux Xfr to SU Xfr PA01/02 after 30 sec. trip signal.

During downpower you manually close the PA01/02 feeds from SU Xfr which will open the Aux Xfr

Done before opening the MG Output breaker/trip turbine.

Question 29

What Main lube oil pumps will be needed to shutdown the turbine?

Answer 29

MSOP and TDOP initially to turbine trip, then TGOP when you trip the turbine as you decrease turbine speed

Need to start MSP and TGOP before tripping turbine.

Question 30

Sketch the xenon transient for 27 hrs after plant shutdown.

Answer 30

Xenon peaks at approximately 9 hours post-trip, returns to prior equilibrium at approximately 24 hours, and moves to 0 at approximately 72 hours post trip.