SG Blowdown Flashcards
What is SG Blowdown used for ?
-Used to maintain chemistry at power
-Used to maintain chemistry in SG while in wet lay-up providing: Mixing,Sampling, & chemical addition to SG
What’re the three blowdown lines tap off from on the SG ?
-Reactor Coolant Hot Leg Region
-Reactor Coolant Cold Leg Region
-Downcomer region
What will close the Blowdown Containment Isolation Valves ?
-MSIS
-AFAS
-SIAS
What source is used to operate the Blowdown Isolation Valves ?
-Air operated to open valve
- Spring loaded to close the valve
What’re the tech specs associated with the Blowdown Containment Isolation Valves & the Blowdown Sample Line Containment Isolation Valves?
Isolation valves must be checked on periodic basis to make sure they’re still operable
What’re the Blowdown Flow Control Valves used for ?
Control flow to either the flash tank or the main condenser
What’re the sizes of each blowdown line ?
Normal Rate: 2” Line
Abnormal Rate :4” Line
High Rate: 6” Line
How is a flow control valves normally aligned & operated ?
-AO must manually align the inlet & outlet valves for the Flow Control Valve
-Once FCV inlet & outlet valves are opened, control room control the FCV
Why are the inlet & outlet valves for the Normal & abnormal FCV aligned during irregular chemical activity ?
This allows control room to quickly switch between FCV as necessary
What’re the allowed SG Blowdown Lineups ?
-Both SG at normal rate to Blowdown Flash Tank or Main Condenser
-Both abnormal rate to Main Condenser
-One SG abnormal rate to Blowdown Flash Tank
-One SG High Rate to Main Condenser
What do the Blowdown FCV fail closed on ?
Fail close on:
-Loss of power to solenoid
-Loss of air supply to valves
When establishing blowdown lineup what needs to be locally controlled on the Blowdown Flash Tank ?
AO just manually control pressure to prevent lifting relief valve
What happens to the blowdown when it enters the Blowdown Flash Tank ?
It flashes to steam cooling down water & reducing pressure of blowdown
What temperature is blowdown at when it enters the Blowdown Flash Tank ?
550F saturation temperature
What does the Blowdown Flash Tank(BFT) pressure control valve do ?
It maintains BFT pressure at 200psig
Why is it important for the BFT to flash blowdown to steam ?
Cools the water down enough to be sent through Demineralizers to be cleaned
Where does the pressure relieve to from the BFT?
There is a set of Pressure Control Valves that send steam to either:
-HTR Drain Tank Equalizing line(Normal)
-Main Condenser (Alternate) path is used if normal path can’t maintain pressure
Who is supposed to control the Pressure Control valves for the BFT ?
-AO is supposed to manually control valve to maintain 200psig
-Changing blowdown alignments will need an AO to manually maintain pressure
What must happen to BFT Pressure Control Valves when plant power is changed by >5%?
AO must isolate HTR Drain Tank Equalizing Line Valves
Why do the HTR Drain Tank Equalizing Lines need to be isolated when plant power changes >5% ?
Helps reduce secondary chemical hideout by having all blowdown that goes to BFT end up in MainCondenser
What is the normal flow paths for the BFT Level Control Valves ?
1.)Blowdown HEX
2.)Blowdown Filters
3.) Blowdown demineralizers
4.) Main Condenser
What is the Alternate flow path from the BFT Level Control Valves ?
3 LPFWH shell side
How are the BFT Level Control Valves operated ? What do they fail closed on ?
-Automatically throttled to maintain level in BFT
- Fail closed on loss of power to solenoid
-Fail close on loss of air supply to valve
What is the Blowdown Heat Exchanger used for ?
Cool blowdown from the BFT prior to entering Blowdown Demins
What cools the Blowdown Heat Exchanger ?
Condensate pump discharge cools Blowdown in the HEX
When the Condensate cools blowdown where does it go after ?
-Goes to suction of FW pumps
-This helps plant efficiency
What is the Blowdown HEX outlet temperature maintained at when Demineralizers are in service ?
Temperature is controlled to <135F
What is Blowdown HEX outlet temperature maintained at when the Demineralizers aren’t in service ?
Condensate flow can be reduced & outlet temperature can be maintained up to 160F
How is the outlet temperature of the Blowdown HEX controlled ?
Manually throttling two condensate return FCV directed to HTR Drain Pump Discharge/ FW Pump inlet
Why must there be coordination when adjusting Blowdown HEX temperature ?
Coordination must be used to maintain balanced flow when throttling Condensate return FCVs
How many Blowdown Ion Exchangers are there ? How are they normally lined up with the BFT ?
-2 Blowdown Ion Exchangers
-Normally operated in series, but we can operate just one if needed
How is resin regeneration accomplished for the Blowdown Ion Exchangers? How often does Resin Regen. Occur ?
-Piping between Blowdown Ion Exchangers & Regen. Vessels in turbine building
-Occurs every 2 weeks
What does the Demineralizer Outlet Valve Control level on? What happens to Demineralizer Outlet Valve if the Demin Inlet valve sensed high temperature?
-Demineralizer controls BFT Level
-Demineralizer Outlet Valve will close on a high temperature
If the Demineralizers are taken out of service due to high temp, what must we do to blowdown flow?
-Blowdown will be taken to Bypass Demin Mode
-Blowdown will be sent through HV-3A to the #3 LP FW Heaters
What’re the Wet Layup Recirc Pumps used for ?
-Recirculates water in SG during shutdown conditions
-Also used for inventory transfer from SG
-Pump Isolated when unit is at power
What’re the Wet Layup Recirc Pumps powered by ? Where are they operated from ?
-Powered by 480VAC MCC (NH)
-Operated from local handswitch by an AO
During refueling outages how are the SGs aligned for Wet Layup?
-Fill SG to top of narrow rant by Aux. -FW & establishing 2-3psig nitrogen overpressure
-Wet layup pump or Wet Layup Cleanup pump will recirculate water & maintain SG chemistry
Why is it important to make sure Aux FW Pumps aren’t aligned to same SG that has Wet Layup Recirc pump running ?
Important because Aux FW Pump has higher discharge pressure
What SG Blowdown line can be used as suction line for Wet Layup Pump ?
All three of blowdown lines can be used:
-Hot Leg
-Cold Leg
-Downcomer
How are the Wet Layup Recirc pumps used when SG needs maintnence ?
Wet Layup Pumps will pump down SG during Drain & Refill required for maintnence
What is the Wet Layup Recirculation flow path ?
-Flows through blowdown line
-Bypasses blowdown flash tank
-Returns to SG via Downcomer FW
-Flow path allows chemical addition & mixing for water
What is SG Wet Layup Cleanup flow path ?
-Flows through blowdown lines
-Bypasses BFT
-Flows through Blowdown HEX
-Blowdown filters
-Blowdown Ion Exchangers
Why is the SG Wet Layup Cleanup flow path not normally used ?
-More effective & quicker to drain the SG & refill it with clean water
What happens to SG on loss of Blowdown ?
Corrosion will increase & can eventually cause immediate shutdown of the plant
What will have to happen to demand for FW Flow into the SG, if blowdown was lost ?
Demand of FW flow will drop due to reduction in inventory leaving the SG
