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.