Main Condensers

Question 1

Describe the design of the main condensers

Answer 1

• 3 vertical shells: 1 for each low pressure turbine
• Main condenser water boxes are split so you can isolate 1 half for maintenance
• unit 1 has equalizing ducts to avoid temp and pressure differences across bearings
• unit 2 each shell is separate

Question 2

What loads input in to the condensers

Answer 2

• Turbine section
• normal blowdown flashtank
• MFP ELOS
• makeup from cst
• drip receivers
• msr drain tank
• hotwell pump suction and discharge vents

Question 3

How does the hotwell level control system operate

Answer 3

• Level controller references leg a or c differential pressure
• 1 level controller controlls all hotwells
• crv 155 opens to let down water
• crv 55 opens to raise water level
• on loss of reference leg
  
  • indicated level rises crv 155 opens actual level lowers, hotwell pump suction is challenged

Question 4

How will a high level in the condenser hotwell affect the operation of the plant

Answer 4

Lowers vacuum because the high level reduces surface area for the heat transfer on the tubes

Question 5

How will low hotwell level affect the operation of the plant

Answer 5

• reduces NPSH to the hotwell pump allowing it to cavitate and potentially steam bind
• if it causes low flow to the MFP suction the MFP will trip
  
  • this will require a reactor trip in Unit 2