Main Steam and Steam Bypass Control Systems

Question 1

List two functions of the Main Steam System.

Answer 1

1.Supply steam to the turbine generator.
2.Supply steam to the following sub-systems:
Moisture separator reheaters
Main condenser steam air ejectors
Gland Sealing Steam System
Steam driven auxiliary feed pump
Auxiliary Steam System
3.Provides RCS Heat Removal using Atmospheric Dump Valves & Steam Bypass Control System.

Question 2

State the function of the Atmospheric Dump Valves

Answer 2

Provide a means of plant cooldown & decay heat removal when MSIV’s are closed.

Question 3

List two functions of the Steam Bypass Control System.

Answer 3

Accommodate load rejections of up to ~57% of full steam flow without tripping the turbine or reactor or lifting the PZR or main steam safety valves.
Maintain the RCS at hot zero power conditions.
Provides a means for manual control of the RCS temperature during heatup or cooldown.
Provides a condenser vacuum interlock which will block steam bypass flow if condenser pressure to high.

Question 4

Identify the Steam Bypass Control System’s response to a loss of condenser vacuum.

Answer 4

All Steam Bypass Valves close on loss of condenser vacuum

Question 5

State the function of the Main Steam Safety Valves

Answer 5

Protects Steam Generators & Main Steam System from over pressurization.

Question 6

State the function of the Main Steam Isolation Valves (MSIV)

Answer 6

Isolates steam flow from steam generator to turbine
Containment isolation function

Question 7

State the function of the Main Steam Header

Answer 7

Header supplies steam to high pressure turbines, steam bypass, auxiliary steam, & moisture separator reheaters.

Question 8

State the function of the Moisture Separator Reheaters (MSR)

Answer 8

MSRs reheat exhaust steam from the high pressure turbine before the steam enters the low pressure turbine.