Annulus Ventilation(VE)

Question 1

What is the purpose of the Annulus Ventilation System?

Answer 1

1. Produce and maintain negative pressure in the annulus during a LOCA
2. Reduce radioactivity in the air
3. Provide long term fission product removal

Question 2

What is the system designator for the Annulus Ventilation System?

Answer 2

VE

Question 3

What is the design/purpose of the Annulus Ventilation Fans?

Answer 3

1. Two fans per unit, one in each train

2. Each fan is 100% capacity rated for 9000cfm

Question 4

What are the power supplies to the Annulus Ventilation Fans?

Answer 4

A - EMXI

B - EMXB

Question 5

What will cause the Annulus Ventilation Fans to automatically start?

Answer 5

The fans are automatically started by the D/G sequencer following a Safety Injection

Question 6

What is the Annulus Ventilation Fan flowpath?

Answer 6

The fans suck from the top of the Annulus and return the air to the bottom to ensure proper mixing of air

Question 7

What is the basic design of the Annulus Ventilation System?

Answer 7

1. The Annulus Ventilation System will produce approximately a 1.5”H2O vacuum within 60 seconds following a Safety Injection.
2. Discharges air from the Annulus to maintain a negative pressure
3. Maintaining a negative pressure allows leakage from containment to enter the annulus for collection and filtration prior to release to the unit vent.
4. Filtration reduces possible offsite dose rate

Question 8

What is the design/purpose of the Filter Trains in the Annulus Ventilation System?

Answer 8

The Filter Train consists of:

1. Prefilter
2. Demister
3. Heater
4. HEPA filters
5. Carbon filter

Question 9

What is the purpose of the Prefilter?

Answer 9

Removes large particles from the flowpath

Question 10

What is the purpose of the Demister?

Answer 10

Removes at least 99% of the incoming moisture

Question 11

What is the purpose of the Heater?

Answer 11

The Heater reduces the relative humidity to increase the efficiency of the filters

Question 12

What is the purpose of the HEPA filters?

Answer 12

1. Inlet to Carbon Bed - Removes small particles

2. Outlet from Carbon Bed - Removes Carbon Filter material before it’s released to the system

Question 13

What is the purpose of the Carbon Bed?

Answer 13

Removes radioactive iodine

Question 14

When does the heater in the filter plenum energize?

Answer 14

The electric heater will energize when the fan starts with proper filter unit differential pressure

Question 15

What is the power supply to the electric heater in the filter train?

Answer 15

A - EMXI

B - EMXB

Question 16

How is pressure maintained in the Annulus by the Annulus Ventilation System?

Answer 16

The exhaust and recirculation dampers will modulate to control annulus pressure at approximately 1.5”H2O vacuum

Question 17

What is the affect on the Recirculation and Exhaust Dampers on a loss of power?

Answer 17

1. The recirculation damper will fail closed

2. The exhaust damper will fail open

Question 18

What is the purpose of the Miniflow Dampers?

Answer 18

The Miniflow Dampers allow for cooling a hot carbon filter bed using the other train’s fan.

Question 19

How will the Miniflow Dampers operated with their control switch in AUTO?

Answer 19

1. They will close when the associated fan starts

2. They will open when the associated fan is stopped

Question 20

How will the Miniflow Dampers fail on a loss of power?

Answer 20

The Miniflow Dampers are motor operated and will fail AS-IS

Question 21

What is the design/purpose of the Manual Isolation Dampers?

Answer 21

The Manual Isolation Dampers are located downstream of each train’s exhaust damper. They prevent backflow from the Unit Vent(backdraft dampers).

Question 22

What is the generic procedure for extinguishing a fire in the carbon filter?

Answer 22

1. Ensure the associated fan is OFF
2. Manually close the sprinkler drain valve
3. Manually open the sprinkler deluge valve

Question 23

How is an Annulus Ventilation Fan stopped following an automatic start?

Answer 23

1. Ensure ECCS signal is reset
2. Ensure D/G sequencer is reset
3. Depress the OFF pushbutton

Question 24

What is the Annulus Ventilation interrelationship with the Fire Protection System?

Answer 24

The Fire Protection System provides water for extinguishing fires in the carbon filter

Question 25

What is the Annulus Ventilation interrelationship with the Demineralized Water System(YM)?

Answer 25

1. The YM System provide automatic makeup to the Annulus floor drain loop seals 2. The filter plenum has a loop seal on the pre-filter/demister drains which receives automatic makeup from YM