MT/MSR: Main Turbine and Moisture Separator Reheaters Flashcards
Which Main Stop Valve has an internal bypass? Why?
MSV #2
To pressurize the below seat area on all Main Stop Valves allowing them to open.
What is the RPM limit on the Main Turbine before vacuum can be broken?
1200 RPM
What is required to place Steam Blanketing in service?
Main Condenser vacuum
How does the Reheat Steam Low Load Valve (RSLLV) control 2nd Stage Reheat Steam pressure?
- Linearly with load from 15% to 65% - compares cross-around pressure to 2nd stage pressure
When does the local pushbutton for the Main Turbine Turning Gear work?
When the Control Room Switch for the TG must be in STOP or PULL-TO-LOCK. Cannot be in START or AUTO.
Describe how the Control Intercept Valves are constructed.
They of a stop valve and an intercept valve that share the same seat. The stop valve backs up the intercept valve.
What is the basis for the MSR reliefs?
Protection in the event the Combined Intermediate Valves shut and the Control Valves do not.
What is the setpoint for the High Exhaust Hood Temperature Trip of the Main Turbine?
225 F
What is bad about extended operation below 5% or the excessive use of Exhaust Hood Spray?
Last Stage Bucket Erosion
Why do the High Level Control Valves for the 1st and 2nd Stage stay open while at low powers?
To provide a constant vent to the 1st and 2nd stage tube bundles for the MSRs to the Main Condenser while coming up in power. 1st stage closes at 10% and 2nd stage closes at 20%
What kind of warming must be done to the MSRs prior to admitting reheating steam? Why?
At least 15% for 12 hours
Avoids thermal cycling
What does a Thrust bearing do?
Protects against axial thrust
Is the Master/Slave relationship applicable in the test mode?
No
What does a Journal Bearing do?
Rotary protection
What is differential expansion in regards to the Main Turbine?
Thermal expansion at different rates between the stationary and non-stationary parts of the turbine.
What is [Air] Purging in regards to the ED System? When is it performed?
A scavenging path aligned to the Main Condenser through vents on the 1st and 2nd Stage MSR Drain Tanks that pulls all the contents of the MSR tubes (be it steam, air, or non-condensibles) into the Main Condenser.
Performed just prior to admitting steam.
From where can you disarm a High Vibration Trip of the Main Turbine?
From the Turbine Supervisory Cabinet
Where are the Main Turbine Journal Bearings?
At the end of each turbine and generator
Why were CIVs #1, #2, #3 chosen as the Masters?
Rotor balancing concerns if one master were to fail
What is the setpoint for the Backup Overspeed Trip of the Main Turbine?
110.5%
What are the Controlling Steam Valves associated with the Main Turbine?
Main Stop Valve #2
Control Valves #1, #2, #3, #4
Control Intercept Valves #1, #2, #3
How are the MSR Relief valves distributed?
2 on A 1 on B 2 on C 1 on D
What is the setpoint for the Excessive Vibration Trip of the Main Turbine?
12 mils
To where do the 2nd Stage MSR tubes drain?
To the 2nd Stage MSR Drain Tank and then to the #7 HPFWH or the Main Condenser
What provides 1st Stage Reheat Steam for the MSRs?
3rd Stage Extraction Steam
How does the High Level Control Valve for the MSR Drain Tank behave while <10% power?
It its failed open as long as the Steam Blanketing Mode Selector Switch (MTN-HS-519) is in AUTO
How does the overspeed device work for the Main Turbine?
An unbalanced ring
centrifugal force puts the ring in an eccentric postion to strike a trip finger
What do you do if a tube breaks in the 2st Stage of an MSR?
Isolate the 2nd Stage Reheat steam to the MSRs.
What is unique about the Turning Gear motor for the Main Turbine?
It has a ‘piggyback’ motor.
Used to get the TG started so it can engage. Once engaged, #5 and #8 (bearings 7 and 10) oil lift pumps stop and the piggyback motor stops 10 seconds later.
What is the Turning Gear used for on the Main Turbine?
To rotate the shaft to prevent distortion on a cooldown
Jack the rotor for inspection
Rotor breakaway on Main Turbine startup
What is the setpoint for the Low EHC Pressure Trip of the Main Turbine?
1100 psig
What would have to happen if a Control Valve failed open on a Turbine Trip? Why?
All Main Stop Valves would have to close due to the fact that they are all connected via a below seat equalizer.
What is the setpoint for the Overspeed Trip of the Main Turbine?
110%
What are the Non-Controlling Steam Valves associated with the Main Turbine?
Main Stop Valves #1, #3, #4
Control Intercept Valves #4, #5, #6
Intercept Stop Valves #1, #2, #3, #4, #5, #6
When the CIVs close, to what are they isolating steam?
To the Low Pressure Turbines from the large capacity cross-around piping.
What happens to the ED system on a loss of Instrument Air?
Normal Level Control Valves fail closed (except for the #1 LPFWH which fails open)
High Level Control Valves all fail open
What happens if you take the Scavenging Mode Select Switch (EDN-HS-615 or EDN-HS-715) to the ‘Steam Blanket’ position at 100% power?
The vents for the associated MSR Drain Tank go closed
Where does drainage from the MSR shell go?
To the MSR Drain Tank and then to the Heater Drain Tank or the Main Condenser.
In the ‘Steam Blanket’ Mode, how do the RSSV and the RSCV behave?
They both close to allow blanketing steam to be admitted from Aux Steam.
What is the danger in valving in 2nd Stage Reheat steam when Reactor Power is > 95%?
2nd Stage Reheat steam flow to the MSRs is approx. 5% of total steam flow. Valving it in with power > 95% could result in exceeding 100% Reactor Power.
What is the RSCV?
Reheat Stop Check Valve
Block valve for the 1st Stage reheating steam to the MSRs
What is the setpoint for the Loss of 125 VDC Control Power Trip of the Main Turbine?
Loss of both speed signals
From where do the MFPs get their steam?
At 100% power, from Hot Reheat Steam from the D MSR. At low powers, Main Steam is used.
What do you do if a tube breaks in the 1st Stage of an MSR?
Isolate both stages of reheat to the MSRs
You cant have 2nd stage in without the 1st stage in
What’s special about the MTLO supply and return piping around the Main Turbine?
“Pipe within a pipe”
What components make up the Controlling Valve PACs?
A Servo for controlling valve position with control oil
A pressure controlled shut off valve
A fast acting solenoid for tripping the Main Turbine and testing
What is the RSSV?
Reheater Supply Stop Valve
Block valve for the 2nd Stage reheating steam to the MSRs
For what specific reason do we purge the MSRs prior to admitting steam?
It prevents the top half of the MSR tube bundles from expanding first which would result in severe differential expansion.
If in AUTO, when will the Main Turbine Turning Gear automatically start?
When rotor speed is < 2 RPM
When does the High Level Control Valve for the 1st Stage MSR Drain Tank open?
High level in the #6 HPFWH
< 10% power with HS-519 in AUTO
HS-519 in PURGE
What is the setpoint for the Low Vacuum Trip of the Main Turbine?
7.5” HgA
What provides 2nd Stage Reheat Steam for the MSRs?
Main Steam
What requirements must be met to start the Main Turbine turning gear ‘piggyback’ motor from the Control Room?
- The Main Generator Output breakers or Motor Opereated Disconnects must be open
- At least one bearing oil lift pump running
- Bearing lube oil pressure is adequate
- The TG motor is not running
- The TG is not already engaged
What specific type of damage do the MSRs help to prevent?
Last Stage Bucket Erosion
What components make up the Non-Controlling Valve PACs?
A solenoid test valve
A pressure controlled shut off valve
A fast acting solenoid for tripping the Main Turbine and testing
What is the setpoint for the Low MSLO Pump Discharge Pressure Trip of the Main Turbine?
100 psig
List the Main Turbine Trips
- Overspeed
- Backup Overspeed
- Low Vacuum
- Excessive Thrust Bearing Wear
- Reactor Trip
- Generator Trip
- Excess Vibrations
- High Exhaust Hood Temperature
- MSR Hi-Hi Level
- Loss of Stator Cooling Water
- Low EHC Pressure
- Loss of 125VDC Control Power
- Low Bearing Pressure
- Low MSLO Pump Discharge Pressure
- Power Load Unbalance
- Manual from Control Room
- Manual from Front Standard
What is the setpoint for the Hi-Hi MSR Level Trip of the Main Turbine?
3 inches below the bottom of the MSR
When does the High Level Control Valve for the 2nd Stage MSR Drain Tank open?
High level in the #7 HPFWH
< 20% power with HS-519 in AUTO
HS-519 in PURGE
To where do the 1st Stage MSR tubes drain?
To the 1st Stage MSR Drain Tank and then to #6 HPFWH or the Main Condenser
Why do the 2nd Stage Reheat Steam lines have control valves (RSHLV and RHSLLV) and the 1st Stage Reheat Steam lines do not?
Because the temperature and pressure of 1st Stage Reheat Steam varies with Turbine load and is therefore self-regulated through the Reheater Stop Check Valve (RSCV).
What is the setpoint for the Loss of Stator Cooling Water Trip of the Main Turbine?
549 gpm
What is the setpoint for the Low Bearing Oil Pressure Trip of the Main Turbine?
12 psig
When do the Main Stop Valves open?
When a Main Turbine speed is selected on B06 (EHC)
They’ll remain open until a Turbine Trip occurs.
Where is the Main Turbine Thrust Bearing?
Between the HPT and the first LPT
Explain the Master/Slave relationship with the CIVs.
CIVs #4, #5, #6 are slaves to CIVs #1, #2, #3.
CIVs #4, #5, #6 will trip completely closed when CIVs #1, #2, #3 reach 50% closed.
CIVs #4, #5, #6 will open completely when CIVs #1, #2, #3 reach 90% open.
Describe Steam Blanketing for the MSRs.
Pressurizes the MSR tube bundles with AS (52.3 psia which corresponds to 283F) to keep air and condensation out of the tubes.
What is the maximum temperature for the cross-around (Hot Reheat) when power is < 10%?
400F
What is Scavenging Steam?
Steam flow from the MSR tubes to the feed water heaters through an orifice that sweeps condensate out of the MSR tubes.
How does the Reheat Steam High Load Valve (RSHLV) work with the Reheat Steam Low Load Valve (RSLLV)?
Fully opens at 65% and bypasses the RSLLV.
What is the setpoint for the Excessive Thrust Bearing Wera Trip of the Main Turbine?
40 mils
When does the Main Shaft Oil Pump sufficiently supply the Main Turbine bearings?
When Main Turbine speed is > 90%
What happens when you take the Steam Blanketing Mode Selector Switch (EDN-HS-519) at full power?
The Reheater Steam Source Valve (RSSV) and the Reheater Stop Check Valve (RSCV) close, isolating 1st and 2nd stage reheating steam to the MSRs
What would be the result if the Normal LCV and the High LCV for the MSR Drain Tank failed closed?
The Main Turbine would trip on High MSR Level at -3”
What happens to the Bearing Oil Lift Pumps when the Turning Gear is engaged?
Two of the Bearing Oil Lift Pumps trip off to prevent the turbine from speeding up and slipping off the Turning Gear.
What is the reason for the High MSR Level Turbine Trip?
To protect the Main Turbine from moisture carryover
What function do the CIV servos perform?
They control the EHC flow to and from the valve actuators
What is the status of the Stop and Control valves during Chest Warming for the Main Turbine?
Stop Valve #2 is throttled and all the Control Valves are shut
