Week 3: Steam Generator/Steam Generator Level Control Flashcards
What is the function of the Steam Generators?
Heat exchanger between the Primary and Secondary systems
Steam supply for the Main Turbine
RCS Pressure boundary
Decay heat removal heat sink
What is the function of the SG Lower Head and Divider?
An inlet/outlet for RCS flow
Divider plate forces incoming flow up into the U-tubes for heat removal
What is the function of the Tube Sheet and U-Tubes?
To form the boundary between Primary and Secondary fluid and to act as a point of heat transfer.
What is the function of the Feedring?
To deliver feedwater to the SG via J-Tubes.
What is the function of the Feedring J-tubes?
To ensure that the feedring does not drain into the SG when FW is secured, as otherwise the feedring would fill with steam and pose a water hammer risk.
What is the flowpath of incoming feedwater through the SG?
The flow is directed into the downcomer region between the SG Shell and Wrapper; from there, it flows upward along the length of the U-tubes, turning into saturated steam.
What is the function of the SG Moisture Separators? How is this accomplished?
To dry the saturated steam as it rises through the SG. This is accomplished via a series of Swirl Vanes and Chevrons, which form a tortuous path for the steam to pass through. Moisture in the steam is pushed to the periphery, where it drains into the downcomer.
What is the function of the Anti-Vibration Bars?
To restrict vibration of the U-Tube bundle while allowing for thermal expansion.
What is the function of the SG Flow Restrictor?
To prevent rapid SG depressurization in accident conditions; does not restrict flow during normal ops.
What is the design basis of the Flow Restrictor?
To provide plant protection in the event of a SLB downstream of the restrictor
To provide minimum pressure loss during normal design full flow
To reduce the potential pipe whip in the event of pipe failure
To reduce the mass flow of steam that the main stop valve must resist during pipe failure
To provide a venturi to permit measurement of steam flow for control and protection instrumentation
What is the function of the Feedwater Control System?
To control the main feedwater valves automatically during operation from 15-100% power.
What is the function of the Feedwater Bypass Control System?
To control the feedwater bypass valves automatically during operation from 0-20% power.
What is the function of the Feedwater Pump Speed Control System?
To regulate the speed of the MFPs automatically when above 15% power.
What is the SG Level Control program?
78% - Hi-Hi Setpoint
50% - Nominal
15% - Lo-Lo Setpoint
What are the inputs to the SG Level Control program?
Nominal Level vs Measured Level
Steam Flow vs Feedwater Flow (Note that steam flow has a pressure sensor to correct for density)
These signals are used to generate an error signal which will open/close the FWCV accordingly
