Main Steam Flashcards
What components & systems does main steam provide steam to ?
-HP turbine
-MSRs
-MFWP Turbines
-Steam seal system for Main Turbine & FW Pump Turbines
-Aux. FW Pump Turbine
-Aux. Steam system
What does Main Steam provide during startup, shutdown& abnormal, or emergency operations?
Provides means of dissipating heat generated from Nuclear Steam Supply Systems(NSSS) to either condenser or atmosphere
What is provided for cooldown of SG when condenser isn’t available ?
ADVS are provided for when the condenser isn’t available
What happens to RCS, if SG loses ability to remove heat from RCS ? What happens if it’s an extended loss of SG ability to remove heat ?
-Result in High Pressure & Temperature in RCS, which could lead to reactor trip
-Extended loss could result in core damage due to inability to lose decay heat
What could happen on a loss of FW to the SG ?
Results in inability to cool RCS, which could lead to plant trip due to low SG Water levels or High Pressure
What does the Steam Bypass Control system control ?
Employs 8 Steam Bypass Control Valves to control heat removal from SG during normal & abnormal operations
What does the Steam Bypass Control System(SBCS) control during startup ?
SBCS controls Main Steam Pressure either automatically or manually by adjusting bypass valves as needed to maintain steam header pressure
What happens on a loss of SBCS during startup,post trip, or whenever it’s controlling steam pressure ?
Results in high steam pressure & if not corrected by ADVs,Turbine Load, or Reactor Power Cutback could result in reactor trip
What’re Nitrogen accumulators used for ?
-Used for backup supply to ADVS,Downcomer FWIV, & Downcomer FW Control valves,
-Used to SG for blanketing during shutdown
What happens on a extended loss of nitrogen ?
Won’t affect valve operation because of accumulator, but if accumulators runs out while supplying them valves could shut
N2 IS ONLY USED ON A LOSS OF IA
What’re the SG Downcomer Valve Upstream Block Valves used for ?
Provided for remote isolation of the Downcomer Control Valves
How are the Downcomer Block Valves operated? What is the normal position of them ?
-Motor operated operated by handswitch in Control Room
-Downcomer Block Valve are normally opened gate valves
What’re the FW Downcomer Control valves normally controlled by ? Where is another alternate way they can be controlled by ?
-Normally controlled automatically by Digital Feed water Control System
-Alternately can be controlled by operator in Control Room
What position do the Feedwater Downcomer Control Valves fail in on loss of air or power to solenoid ?
They fail in the as-is position, on loss of air or power to solenoid
What is the flow percentage passing through Feedwater Downcomer Control Valves during Low Power operation ?
100% of flow is passing through Downcomer Control Valves
Why during low power operation does 100% of Feedwater flow pass through Downcomer Control Valves ?
Supplied sufficient preheating for incoming feedwater at lower power
What percentage of power do the Feedwater Downcomer Control Valves throttle close ?
At 15% power & increasing, the Downcomer Control Valves will throttle close
When Downcomer Control valves are throttled closed at 15%, what valve is throttled OPEN at 15% power?
Economizer Control Valves are throttled open sending ALL FW through Economizer lines
What is it called when the Downcomer Control Valves are closed at 15% power, & the Economizer Control Valve is opened at 15% power ?
It’s called “Feedwater Swapover”
What happens to the Downcomer Control Valves at 50% power ?
-Downcomer Control Valves are throttled set position to supply 10% of feed flow
-Between 50%-100% power
What does throttling the Downcomer Control Valve to 10% when at 50% power provide for the system ?
Provides sub cooling for Recirc water& promotes increased Recirc ratio in S/G
How are the Downcomer Control Valve Bypass Valves operated? What position are they normally in ?
-Motor operated valves operated from control room & is normally closed
When & why are the Downcomer Control bypass valves used ?
Used in Mode 3 to control SG water level being supplied by
Non-Essential Aux FW Pump (AFN-P01
How does the Downcomer Control Valve Bypass Valves switch in the Control Room work ? What position does the valve in ?
-Three position switch is used to either jog the valve close or open
-Valve fails as-is on loss of power