Week 4: Auxiliary Feedwater

Question 1

What is the function of the Auxiliary Feedwater System?

Answer 1

To supply water to the SGs when the main feed system is not available.

Question 2

What normal operating conditions utilize AFW?

Answer 2

Startup
Hot Standby
Cooldown

Question 3

What emergency operating conditions utilize AFW?

Answer 3

LONF
FLB
SLB
LOCA
LOAC
Control Room Evacuation

Question 4

Describe the major components of the AFW system.

Answer 4

3 pumps in total, 2 Motor-driven and 1 Turbine-driven. The MD pumps are sized such that 1 can supply the necessary FW to remove 100% of the decay heat load. The TD pump is capable of twice the flow of a single MD pump.
The condensate storage tank is the preferred source of water for the AFW pumps; during normal operation all 3 AFW pumps are lined up to the CST.
The ESW system is the safety-related, backup source of feedwater in the event that the CST is unavaliable.

Question 5

What signals will automatically start the Motor-driven AFW pumps?

Answer 5

Shutdown sequencer actuation
LOCA sequencer actuation
AMSAC actuation
MD AFAS

Question 6

What conditions will initiate a MD AFAS?

Answer 6

Manual Actuation
SG lo-lo level on 2/4 detectors on 1/4 SGs
Both MFW pumps trip

Question 7

What signals will automatically start the Turbine-driven AFW pump?

Answer 7

AMSAC actuation
TD AFAS

Question 8

What conditions will initiate a TD AFAS?

Answer 8

Manual Actuation
SG lo-lo level on 2/4 detectors on 2/4 SGs
Undervoltage on either NB buses

Question 9

What is the minimum amount of feedwater needed to assure ultimate heat sink capability?

Answer 9

260,000 lbm/hr