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Systems > SG Blowdown > Flashcards

SG Blowdown Flashcards

1
Q

What is SG Blowdown used for ?

A

-Used to maintain chemistry at power
-Used to maintain chemistry in SG while in wet lay-up providing: Mixing,Sampling, & chemical addition to SG

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2
Q

What’re the three blowdown lines tap off from on the SG ?

A

-Reactor Coolant Hot Leg Region
-Reactor Coolant Cold Leg Region
-Downcomer region

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3
Q

What will close the Blowdown Containment Isolation Valves ?

A

-MSIS
-AFAS
-SIAS

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4
Q

What source is used to operate the Blowdown Isolation Valves ?

A

-Air operated to open valve
- Spring loaded to close the valve

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5
Q

What’re the tech specs associated with the Blowdown Containment Isolation Valves & the Blowdown Sample Line Containment Isolation Valves?

A

Isolation valves must be checked on periodic basis to make sure they’re still operable

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6
Q

What’re the Blowdown Flow Control Valves used for ?

A

Control flow to either the flash tank or the main condenser

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7
Q

What’re the sizes of each blowdown line ?

A

Normal Rate: 2” Line
Abnormal Rate :4” Line
High Rate: 6” Line

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8
Q

How is a flow control valves normally aligned & operated ?

A

-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

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9
Q

Why are the inlet & outlet valves for the Normal & abnormal FCV aligned during irregular chemical activity ?

A

This allows control room to quickly switch between FCV as necessary

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10
Q

What’re the allowed SG Blowdown Lineups ?

A

-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

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11
Q

What do the Blowdown FCV fail closed on ?

A

Fail close on:
-Loss of power to solenoid
-Loss of air supply to valves

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12
Q

When establishing blowdown lineup what needs to be locally controlled on the Blowdown Flash Tank ?

A

AO just manually control pressure to prevent lifting relief valve

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13
Q

What happens to the blowdown when it enters the Blowdown Flash Tank ?

A

It flashes to steam cooling down water & reducing pressure of blowdown

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14
Q

What temperature is blowdown at when it enters the Blowdown Flash Tank ?

A

550F saturation temperature

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15
Q

What does the Blowdown Flash Tank(BFT) pressure control valve do ?

A

It maintains BFT pressure at 200psig

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16
Q

Why is it important for the BFT to flash blowdown to steam ?

A

Cools the water down enough to be sent through Demineralizers to be cleaned

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17
Q

Where does the pressure relieve to from the BFT?

A

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

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18
Q

Who is supposed to control the Pressure Control valves for the BFT ?

A

-AO is supposed to manually control valve to maintain 200psig
-Changing blowdown alignments will need an AO to manually maintain pressure

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19
Q

What must happen to BFT Pressure Control Valves when plant power is changed by >5%?

A

AO must isolate HTR Drain Tank Equalizing Line Valves

20
Q

Why do the HTR Drain Tank Equalizing Lines need to be isolated when plant power changes >5% ?

A

Helps reduce secondary chemical hideout by having all blowdown that goes to BFT end up in MainCondenser

21
Q

What is the normal flow paths for the BFT Level Control Valves ?

A

1.)Blowdown HEX
2.)Blowdown Filters
3.) Blowdown demineralizers
4.) Main Condenser

22
Q

What is the Alternate flow path from the BFT Level Control Valves ?

A

3 LPFWH shell side

23
Q

How are the BFT Level Control Valves operated ? What do they fail closed on ?

A

-Automatically throttled to maintain level in BFT
- Fail closed on loss of power to solenoid
-Fail close on loss of air supply to valve

24
Q

What is the Blowdown Heat Exchanger used for ?

A

Cool blowdown from the BFT prior to entering Blowdown Demins

25
Q

What cools the Blowdown Heat Exchanger ?

A

Condensate pump discharge cools Blowdown in the HEX

26
Q

When the Condensate cools blowdown where does it go after ?

A

-Goes to suction of FW pumps
-This helps plant efficiency

27
Q

What is the Blowdown HEX outlet temperature maintained at when Demineralizers are in service ?

A

Temperature is controlled to <135F

28
Q

What is Blowdown HEX outlet temperature maintained at when the Demineralizers aren’t in service ?

A

Condensate flow can be reduced & outlet temperature can be maintained up to 160F

29
Q

How is the outlet temperature of the Blowdown HEX controlled ?

A

Manually throttling two condensate return FCV directed to HTR Drain Pump Discharge/ FW Pump inlet

30
Q

Why must there be coordination when adjusting Blowdown HEX temperature ?

A

Coordination must be used to maintain balanced flow when throttling Condensate return FCVs

31
Q

How many Blowdown Ion Exchangers are there ? How are they normally lined up with the BFT ?

A

-2 Blowdown Ion Exchangers
-Normally operated in series, but we can operate just one if needed

32
Q

How is resin regeneration accomplished for the Blowdown Ion Exchangers? How often does Resin Regen. Occur ?

A

-Piping between Blowdown Ion Exchangers & Regen. Vessels in turbine building
-Occurs every 2 weeks

33
Q

What does the Demineralizer Outlet Valve Control level on? What happens to Demineralizer Outlet Valve if the Demin Inlet valve sensed high temperature?

A

-Demineralizer controls BFT Level
-Demineralizer Outlet Valve will close on a high temperature

34
Q

If the Demineralizers are taken out of service due to high temp, what must we do to blowdown flow?

A

-Blowdown will be taken to Bypass Demin Mode
-Blowdown will be sent through HV-3A to the #3 LP FW Heaters

35
Q

What’re the Wet Layup Recirc Pumps used for ?

A

-Recirculates water in SG during shutdown conditions
-Also used for inventory transfer from SG
-Pump Isolated when unit is at power

36
Q

What’re the Wet Layup Recirc Pumps powered by ? Where are they operated from ?

A

-Powered by 480VAC MCC (NH)
-Operated from local handswitch by an AO

37
Q

During refueling outages how are the SGs aligned for Wet Layup?

A

-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

38
Q

Why is it important to make sure Aux FW Pumps aren’t aligned to same SG that has Wet Layup Recirc pump running ?

A

Important because Aux FW Pump has higher discharge pressure

39
Q

What SG Blowdown line can be used as suction line for Wet Layup Pump ?

A

All three of blowdown lines can be used:
-Hot Leg
-Cold Leg
-Downcomer

40
Q

How are the Wet Layup Recirc pumps used when SG needs maintnence ?

A

Wet Layup Pumps will pump down SG during Drain & Refill required for maintnence

41
Q

What is the Wet Layup Recirculation flow path ?

A

-Flows through blowdown line
-Bypasses blowdown flash tank
-Returns to SG via Downcomer FW
-Flow path allows chemical addition & mixing for water

42
Q

What is SG Wet Layup Cleanup flow path ?

A

-Flows through blowdown lines
-Bypasses BFT
-Flows through Blowdown HEX
-Blowdown filters
-Blowdown Ion Exchangers

43
Q

Why is the SG Wet Layup Cleanup flow path not normally used ?

A

-More effective & quicker to drain the SG & refill it with clean water

44
Q

What happens to SG on loss of Blowdown ?

A

Corrosion will increase & can eventually cause immediate shutdown of the plant

45
Q

What will have to happen to demand for FW Flow into the SG, if blowdown was lost ?

A

Demand of FW flow will drop due to reduction in inventory leaving the SG

Systems (62 decks)

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