Annulus Ventilation(VE) Flashcards
What is the purpose of the Annulus Ventilation System?
- Produce and maintain negative pressure in the annulus during a LOCA
- Reduce radioactivity in the air
- Provide long term fission product removal
What is the system designator for the Annulus Ventilation System?
VE
What is the design/purpose of the Annulus Ventilation Fans?
- Two fans per unit, one in each train
2. Each fan is 100% capacity rated for 9000cfm
What are the power supplies to the Annulus Ventilation Fans?
A - EMXI
B - EMXB
What will cause the Annulus Ventilation Fans to automatically start?
The fans are automatically started by the D/G sequencer following a Safety Injection
What is the Annulus Ventilation Fan flowpath?
The fans suck from the top of the Annulus and return the air to the bottom to ensure proper mixing of air
What is the basic design of the Annulus Ventilation System?
- The Annulus Ventilation System will produce approximately a 1.5”H2O vacuum within 60 seconds following a Safety Injection.
- Discharges air from the Annulus to maintain a negative pressure
- Maintaining a negative pressure allows leakage from containment to enter the annulus for collection and filtration prior to release to the unit vent.
- Filtration reduces possible offsite dose rate
What is the design/purpose of the Filter Trains in the Annulus Ventilation System?
The Filter Train consists of:
- Prefilter
- Demister
- Heater
- HEPA filters
- Carbon filter
What is the purpose of the Prefilter?
Removes large particles from the flowpath
What is the purpose of the Demister?
Removes at least 99% of the incoming moisture
What is the purpose of the Heater?
The Heater reduces the relative humidity to increase the efficiency of the filters
What is the purpose of the HEPA filters?
- Inlet to Carbon Bed - Removes small particles
2. Outlet from Carbon Bed - Removes Carbon Filter material before it’s released to the system
What is the purpose of the Carbon Bed?
Removes radioactive iodine
When does the heater in the filter plenum energize?
The electric heater will energize when the fan starts with proper filter unit differential pressure
What is the power supply to the electric heater in the filter train?
A - EMXI
B - EMXB
How is pressure maintained in the Annulus by the Annulus Ventilation System?
The exhaust and recirculation dampers will modulate to control annulus pressure at approximately 1.5”H2O vacuum
What is the affect on the Recirculation and Exhaust Dampers on a loss of power?
- The recirculation damper will fail closed
2. The exhaust damper will fail open
What is the purpose of the Miniflow Dampers?
The Miniflow Dampers allow for cooling a hot carbon filter bed using the other train’s fan.
How will the Miniflow Dampers operated with their control switch in AUTO?
- They will close when the associated fan starts
2. They will open when the associated fan is stopped
How will the Miniflow Dampers fail on a loss of power?
The Miniflow Dampers are motor operated and will fail AS-IS
What is the design/purpose of the Manual Isolation Dampers?
The Manual Isolation Dampers are located downstream of each train’s exhaust damper. They prevent backflow from the Unit Vent(backdraft dampers).
What is the generic procedure for extinguishing a fire in the carbon filter?
- Ensure the associated fan is OFF
- Manually close the sprinkler drain valve
- Manually open the sprinkler deluge valve
How is an Annulus Ventilation Fan stopped following an automatic start?
- Ensure ECCS signal is reset
- Ensure D/G sequencer is reset
- Depress the OFF pushbutton
What is the Annulus Ventilation interrelationship with the Fire Protection System?
The Fire Protection System provides water for extinguishing fires in the carbon filter
What is the Annulus Ventilation interrelationship with the Demineralized Water System(YM)?
- The YM System provide automatic makeup to the Annulus floor drain loop seals
- The filter plenum has a loop seal on the pre-filter/demister drains which receives automatic makeup from YM