Week 8: Simulator Morning Questions Flashcards
List the major actions for a SG tube rupture.
Identify ruptured SG
Isolate ruptured SG
Cooldown RCS
Depressurize RCS
Terminate SI
When and why do you isolate feedwater to a ruptured SG?
Terminate at 4% level; this is done to prevent the steam of the SG from being in contact with bare SG tubes. If the tubes are bare, cooling down the RCS will also rapidly lower the pressure/temperature of the ruptured SG, making it difficult to equalize primary and secondary pressures
A Loss of all AC power (SBO) has occurred. Explain how you will cool the core.
Natural circulation and SG ARV dumps using nitrogen accumulators to manipulate the valves, TDAFW pump to maintain heat sink.
What was the historical problem with a SBO? How has this been addressed?
Loss of injection to RCP seals, results in a 20 gpm leak.
Loss of cooling water to seals means potential failure of seals, resulting in a much larger LOCA.
Safety seals have since been implemented - when they are exposed to RCS temps without cooling, they expand to fill the gap and prevent leakage.
Differentiate between a loss of offsite power and a SBO.
During a LOOP the emergency diesels pick up the safety related loads on the NB busses. A SBO involves a LOOP plus the failure of the EDGs.
List the major action categories of E-3.
Identify and Isolate ruptured SG
Cooldown RCS
Depressurize RCS
Terminate SI
Prepare for Cold Shutdown
Why do we cooldown before depressurizing on a SG tube rupture?
To maintain subcooling margin; if the RCS remains hot while we depressurize, we run the risk of boiling the coolant.
What criteria is used to determine whether the depressurization in E-3 will be done using spray or PZR porvs?
SG level, greater than 78% using the PORVs is required
When is the depressurization in E-3 stopped?
When one of the following is met:
RCS Pressure <= Ruptured SG Pressure and PZR level >4%
PZR level >76%
Subcooling margin < 30F
List two entry conditions to FR-S.1.
Power >5% or IR flux increasing post trip (RNO of Step 1 of E-0), Status trees in F-0
What are the inputs into the OTDT setpoint calculation?
Tavg, RCS pressure, dI
What does P-11 allow?
Below 1970 psig in the RCS, P-11 allows the operator to block the low SL pressure at 615 psig SI and MSI as well as the low PZR SI at 1849 psig
What conditions will isolate main steam?
CTMT High-2 (17 psig)
Low SL pressure (615 psig)
High SL rate (110 psig in 50 second)
Why do we program Tavg?
Maintain a balance between efficiency (constant Tsteam) and margin to DNB (constant Tavg).
List symptoms of a LOCA.
PZR level decreasing
PZR pressure decreasing
CTMT pressure increasing
CTMT sump level increasing
CTMT rad levels increasing
Tavg stable
Nuclear power stable
List symptoms of a SGTR.
PZR level decreasing
N-16 monitors alarming
SG process rad alarms
SG feedwater decreased in 1 SG
SG level rising after trip
List symptoms of a MSLB.
PZR level decreasing
PZR pressure decreasing
CTMT pressure increasing
CTMT sump level increasing
Tavg decreasing
SG pressure/level decreasing in all SGs
You are doing the cooldown phase of the SGTR procedure. Suddenly the steam flow to the steam dumps stops. List two possible causes.
Hit P-12
Hit low SL pressure/high SL pressure rate SI, closing MSIVs
FR S.1 has a transition to SAMG. What triggers this transition? What two other procedures have the same transition?
TCs >1200F
Loss of All AC
Loss of Core Cooling
You dilute 100 pcm (at 80% RTP). What is the resulting change in Tavg? (MTC is -20 pcm/F)
Tavg increases by 5F
Why do we perform a cooldown in the E-3 procedure?
We need to cooldown prior to depressurizing in order to maintain subcooling in the RCS. Depressurizing the RCS is needed to halt coolant flow into the ruptured SG.
Why is there a 4% Ruptured SG level requirement in E-3? Why is it 4% in other procedures?
The ruptured SG needs to have enough water to cover the tubes before isolating AFW. This provides a thermal barrier between the RCS and the ruptured SG. In other procedures, 4% NR level is a heat sink requirement.
We usually use 30F subcooling as a requirement. Why would we want more subcooling for SI reduction?
When you stop SI pumps, the loss of flow will cause a drop in pressure, which causes a drop in subcooling margin as well as a drop in PZR level.
You are in E-1. RWST level reaches 36%. What do you do?
Swapover to cold leg recirculation per the foldout page
Using Control Board meters, how do you determine if a temperature failure is Th or Tc?
Tavg on that loop tells you the direction of the failure (either instrument fails low, Tavg drops). dT tells which one once we know the direction of the failure (i.e. failed low CL = Th-Tc where Tc goes to 0, big dT)
Rx power is 28%. A SG level reaches 80%. What has happened/should have happened to plant?
FWIS, which trips the MFW pumps and isolates FW, turbine trip, no Rx trip
Rods in manual, moving from 60%-80% power. What happens to Tavg to Tref?
Tref increases, Tavg decreases
What is Tavg at 75%?
588.5-557 = 31.5, 31.5*0.75 = 23.6, 557+23.6 = 580.6
During a LBLOCA, containment pressure reaches 35 psig. Operators trip RCPs at 1621 psig. Was the the correct action?
Yes, we’ve received a CSIB signal from CTMT High-3, which has isolated CCW flow to the RCP heat exchangers and necessitates tripping the RCPs.
AFD is too negative. How can you AFD in a positive direction?
Borate the rods out
You have lost RC subcooling. Discuss how this affects the relationship between PZR level and RCS inventory.
Level and inventory are no longer intrinsically linked, as the potential now exists for voids to form in other areas of the RCS, forcing level into the PZR
You have just blocked the SR trip at P-6 and are increasing in power. N36 fails high. What is your immediate action?
E-0, since you just tripped
You are at 300 psi and 220F and COPS is armed. A temperature input to COPS fails high, what happens?
Nothing; COPS is protecting off of a High Pressure/Low Temperature situation - it runs off of Auctioneered High Pressure and Auctioneered Low Tavg
You are in FR H-1. A Red Path on FR C-1 occurs. What do you do?
Immediately transition to FR C-1
List the entry paths to SAMG.
> 1200F on TCs from ECA 0.0, FR C-1, or FR S-1
You discover that you have violated the core safety limit curve. What is your action per TS?
TS 2.2 - restore compliance and be in Mode 3 in 1 hour
Discuss the QPTR TS.
QPTR shall be less than 1.02; if violated, RTP must be reduced 3% by every 1% over 1.00 you are.
When are you required to emergency borate? When do you stop?
When more than 1 rod is stuck out of the core post-trip, 100ppm per rod
Rod banks below the RILs, until the rod bank clears the RIL
Uncontrolled reactivity addition, borate until the reactivity increase stops, then 100 ppm more
Makeup System Failure
Discuss priorities among optimal recovery procedure, FRPs, and contingency procedures.
FRPs > Contingencies > Optimal Recoveries
What role does the loop seal play in SBLOCA progression?
The loop seal hinders the ability of the break to pass steam, limiting the amount of energy removed by the break. This means that the SGs will still be needed as a heat sink until the water level in the core reaches midplane, clearing the liquid from the loop seal and allowing steam to reach the break, removing more energy.
List the immediate actions of ECA 0.0.
Verify Rx and Turbine trip
What concern do we have when depressurizing the RCS to inject accumulators in FR C-1?
We don’t want to inject the nitrogen in the accumulators into the RCS, since the gas will pool in the top of the SG U-tubes and hinder natural circulation.
Generally describe the difference between loads sequenced by the shutdown sequencer compared with the LOCA sequencer.
Pumps needed for Safety Injection loaded on the LOCA sequencer, they won’t be for the Shutdown sequencer
What are the shutoff heads for the CCP, SIP, and RHR pumps?
CCP - 2690 psig
SIP - 1538 psig
RHR - 195 psig
Controlling PZR pressure channel fails high with the plant at 8% power. With no operator action what will happen?
PORV opens, sprays open fully. P-7 is not in, so the Rx trip at 1885 would not occur. However, we would get SI at 1849, which will trip the reactor.
Source Range counts are 500 cps with CB at 1200 ppm.
Later, SR counts are 1000 cps with CB at 1150 ppm. At what boron concentration will the plant go critical?
Counts have doubled, which indicates we are halfway to criticality. We’d expect to go critical at 1100 ppm.
Rx critical at 17% power with turbine synced to the grid. Operator raises turbine load. Describe response of steam dump.
Steam dumps close in accordance with the opening of the Turbine Control Valves
Discuss bulk boiling, nucleate boiling, and DNB.
Bulk boiling is a condition where the entirety of the coolant is at saturated temperatures.
Nucleate boiling is a condition where steam bubbles are forming on the surface of the cladding, break off, and then collapse in the coolant.
DNB is the point at which a steam film forms on the surface of the clad, inhibiting heat transfer.
Plant trips and ECP is calculated. Describe how the following will affect the actual rod height at criticality compared to the ECP: CB down, Tavg up, time from trip up.
CB Down: rods lower than predicted
Tavg up: rods higher than predicted
TfT up: rods lower than predicted
What signals start the AFW pumps?
Motor Driven:
LOCA/Shutdown sequencer
AMSAC
SG lo-lo level on 2/4 detectors on 1/4 SGs
Both MFW pumps trip
Turbine Driven:
Shutdown sequencer
AMSAC
SG lo-lo level on 2/4 detectors on 2/4 SGs
What is the setpoint for the MS isolation on negative rate?
110 psig in 50 seconds
What is the AMSAC actuation setpoint?
3/4 NR SG levels below 5% for 25 seconds
Describe the OTDT and OPDT setpoints.
OTDT is 110% +/- penalties due to Tavg, RCS pressure, and dI
OPDT is 109% - penalties due to Tavg
What additional pumps need to be started when raising power past 50%?
Circ water, Service water, Condensate, Feedwater
Describe what needs to be done at a RCS pressure of 1970 psig on plant shutdown.
P-11 is in, we will need to block the PZR Pressure Lo SI and Lo SL pressure SI
Letdown is 75 gpm and charging is 140 gpm. Seal injection/return is normal. What is happening?
Charging flow is normally 87 (Letdown of 75 + 3 per RCP seal leakoff), so there is an RCS leak of 140-87=53 gpm
Describe how you would calculate the required boron change in going from 70% to 100%, using 20% rods/80% boron.
Use the power defect to determine the total negative reactivity resulting from the power change, then using DBW and IRW determine the positive reactivity needed via dilution and rod withdrawal
Tavg is 4F lower than program. Describe how you calculate new CB to return to program.
Take the MTC times the desired temperature change to determine the amount of negative reactivity this maneuver will add. Translate this into a dilution amount by using the DBW.
What are the symptoms of a vapor space LOCA?
Pressure dropping, Level rising, PRT pressure/level rising
