Extraction Steam and Drains (ED) Flashcards
What is the purpose of the ED system?
Preheats condensate and feedwater prior to feedwater entering the Steam Generators to increase overall plant efficiency
What system has the ability to provide steam to the 4th point heater during startup?
AS
What is the purpose of the blowdown stack?
Provides a collection point for various steam traps, HP heater relief valves and miscellaneous aux steam header drains
When is DS added to the blowdown stack? What if DS is not available
When temperature of blowdown stack water volume exceeds 150F
If not available, there will be steam coming out of the blowdown stack and the north condenser area sump
How does GA interact with ED?
During long term shutdown conditions, the GA system supplies nitrogen for blanketing of the feedwater heater shells and heater drain tanks to protect against rust and prevent oxygen from dissolving in the water
How does IA interact with ED?
MT control system admits IA through Turbine Critical and Non-Critical Relay Dump Valves which provide a signal to control Bleeder Trip Valves
Provides motive force for all air operated valves in ED system
How are BTV’s affected by a loss of IA?
BTVs will lose their open permissives and go partially closed
They will remain open due to the extraction steam flow
Where are the Heater Drain Pumps powered from?
‘A’ from NBN-S02
‘B’ from NBN-S01
Where does the seal water for each Heater Drain Pump come from?
Directly from the Condensate Header at 375-500 psig
What provides cooling to each Heater Drain Pumps stuffing box?
Condensate service header at 50-100 psig
What positions the Heater Drain Pump mini-flow valves?
Heater Drain Pumps flow transmitter
What three signals would stop the Heater Drain Pumps?
A Heater Drain Tank lo-lo level alarm
Heater Drain Pump low flow after a time delay
Electrical protection signal
Where are the Heater Drain Pumps located?
100’ Turbine Building west of the Main Feed Pumps
Why does #5 Heater not have a level control system?
Does not contain a drain cooler region and drains directly to the Heater Drain Tank
Which Low pressure Feedwater heaters have four inlets?
1 and #2
Which heater has an input from S/G blowdown system?
3
What is the purpose of the Bleeder Trip Valves?
To prevent reversed steam flow when the Turbine is tripped
Closure of these valves will ensure the Turbine does not overspeed
What happens upon activation of the BTV test valve?
Valve equalizes the air pressure across the operator piston to allow partial closing of the valve disc by spring force
Why is there two BTVs installed on #4 heater extraction line?
4 heater, by itself, has enough energy to cause an overspeed trip
Which level control valves are reverse acting?
All of the high level control valves and #1 LP heater normal level control valves
At what air signals are the reverse acting valves full open and full closed?
Full open with 3#
Full closed with 15#
(Direct acting is the complete opposite)
What happens upon a hi-hi signal in a HP heater?
Isolates extraction steam
Closes the normal level control valve of the preceding heater
Opens the affected heater’s motor operated extraction steam line drain valve
In addition, for the HP heaters, the 1st and 2nd stage reheater drain tank vents isolate from the affected heater and vent to the main condenser
What happens upon a hi-hi signal in a LP heater?
Isolated entire LP heater train by closing the heater train isolation valves
Isolated extraction steam to #3 and #4 heaters
Opens the extraction line solenoid operated drain valves for #3 and #4 heaters
Below what power level may there be insufficient D/P between the heater shells to allow for proper operation of the normal level control valves?
20%
When is the first heater drain pump started? Second?
1st = 25% power
2nd = Between 30% and 40% power
During a plant shutdown, when are the Heater Drain Pumps secured?
First one at 40%, second one at 25%
How is the ED system affected by a loss of IA?
Heater Drain Pump discharge valve fails closed, recirc valve fails open, putting the pump on recirc
Heater Drain Tank, MSR Drain Tank, 1st and 2nd Stage Reheater Drain tank, and Feedwater heater High Level Dump valves will all fail open and the Normal Level Control Valves fail closed (Except #1 heater)
Heater Drain pump will eventually trip on low flow or Heater Drain tank lo lo level signals
The main steam supply to the 2nd stage reheater will isolate and the 1st and 2nd stage Reheater Drain Tanks and Tube Bundles will vent to the Condenser instead of their associated Feedwater heaters
How do you place an ED sight glass in service?
- Obtain gloves, tape measure, hose/bucket, a wrench
- Check for leaks and ensure drain and vent valves are closed
- Remove cap off vent and make sure hose is on drain
- Open lower and upper instrument valves slowly
- Fill the sightglass by opening vent slighty to raise liquid level
- Continue to do so until liquid is around 200 deg F
- Fully open upper and lower instrument isolation valves and install vent cap
What I&C does with the ED?
Operations asks them to make level controller adjustments on the robot heads
What happens when securing HDP?
We have to cross tie the suctions of the pumps in order to remain >50% power but also, securing a pump can lower condenser hotwell level by as much as 9” hence why we keep hotwells at 41” and lo lo is 30”)
What happens on a hi/hi hi HDT level?
Hi hi isolated all inputs into the HDT
Hi should open the hi level dump and dump to the condenser
Where does the HDT high level control valve discharge go to?
Condenser
How many strings of HP heaters? LP heaters?
HP: 2 strings of 3 heaters
LP: 3 strings of 4 heaters
What can cause high level in a HP FW heater? LP FW Heater?
Both:
Tube rupture in the heater
Dump valves fail to open backing up the water
What is the normal outlet temperature from #7 FW heater?
450 F
How many BTVs and where are they?
15 BTVs
HPFWH ones are on either side of the control valves
LPFWH ones are on the south side of the turbine building on like 155’
Moving high level dump valves?
When manually stroking the high level dump valves, you want to make sure the valve is not open or the controller being stroked. The bail on the robot head will be pressed down ¼ - 3/8 in and you will observe the air output signal lowering and let go of the bail
To observe the valve locally the bail will be pressed slowly and when an operator says the valve is moving, the bail is let go
If there is any problems, notify CRS, I&C and engineering
What to do on high level MSR drain tank?
The turbine will trip when it reaches 3 inches below the MSR
What are the load limits on LP heater?
According to 40OP-9ZZ14, Appendix I, the power limitations for one string of LPFWH out is 1109 MW (80%) and two out is roughly 50% power.
What is some OE on robot heads?
The robot heads may create a crevice where the little arrow goes and it will get caught sometimes and wont move the valve
The air input isn’t accurate and pressing the bail wont do anything either
What are the level alarms for FW heaters?
There is a ED trouble for just a high level in any of the heaters but then there is a HiHi alarm on each of the heaters in the CR as well as the MSR drain tank and HDT
Orientation of the FW heater within condenser?
LPFWH are at the top of the condenser going in horizontally with 1 and 2 on the top and 3 and 4 on the bottom although steam goes through it 4->1, the pressure difference allows flow to do so
How do you ensure vacuum breakers are full?
We fill the vacuum breakers during rounds by adding seal water (condensate service header) to it and when the pipe start to feel hot, close the valve.
The procedure says to close the valve when there is water discharging from the overflow, however, the temperature difference between the condensate service header and the atm is enough to feel when it is full to maintain the water air seal on the breaker
How do the LCV and HLCV work to control ED tank levels? Interlocks?
Normal level control valves open based on the air input from the controller to maintain less than 4 inches.
The high level control valve will open when there is a high level in the tank and dump the level to the condenser.
High level control valves don’t open until the normals are completely open.
How does colder FW affect Primary (esp RX power/Reactivity)?
Colder FW going in to the SG’s will pull more heat away from the RCS which then cools the RCS which then will cause power to increase.
Colder water is denser which will cause more interactions with neutrons and power will increase
Where are the normal and high level control valves for the LPFWH?
High Level control valves for LPFWH are on the north side by the respective heaters
Normal Level control valves for LPFWH are on the south side again by the respective heaters
