DW Ventilation - 1.0

Question 1

What buses power the drywell ventilation and do they lose power on a LOP?

Answer 1

10B252 and 10B262, and yes

Question 2

When does drywell ventilation get power back after a LOP and how are they restored?

Answer 2

13 seconds after the LOP, the D/G’s will restore power to MCCs (13 = 3 sec for LOP initiation & 10 sec for EDG start and closure). All 16 DW fans start (first thing on the load sequencer) in Fast speed (if non-faulted) when bus is restored)

Question 3

What supplies cooling flow to DW ventilation normally and what provides it during a LOP?

Answer 3

Cooling supply to coolers is swapped from Chilled water to RACS. (Chilled water is isolated immediately (T=0, 13 seconds after LOP), RACS supply valves will receive an open signal at the same time the RACS pumps are started (72 seconds after EDG is restored (72 + 13 = 85 seconds after LOP - this is nearly the last thing sequenced))

Question 4

What happens to DW ventilation during a LOCA and what signals does this occur?

Answer 4

Fans Shed on Load Shed
LOCA Signals
* -129” RPV Level
* 1.68psig drywell
* CS Manual pushbutton (A or B)

Question 5

During a LOCA can you restore drywell ventilation? if so, then how?

Answer 5

Fan MCCs can be overridden and restored (Press the LOCA over-ride PB and reclose the 1E breaker, fans must be manually restarted at 10C651E)

Question 6

What is the automatic start function for DW fans during normal operations?

Answer 6

A drywell cooling fan will automatically start in High Speed if the following conditions exist:
a) Low flow experienced by the running fan
(< 1.2 inches of water dP), and
b) Standby fan control switch is in the AUTO position

Question 7

Will a running drywell fan trip under low flow conditions under all circumstances?

Answer 7

The low flow condition will only trip the operating fan if it is running in High Speed.

Question 8

What happens when the DW fan fails to auto start?

Answer 8

The “Start Hi” Pb will be flashing.

Question 9

What are the DW fan trips?

Answer 9

1. Overcurrent
2. Low flow (if in Fast Speed)
3. LOCA (loss of MCC)
4. LOP (trips fans on UV until sequenced on signal received)

Question 10

What are the DW fan trips?

Answer 10

1. Overcurrent
2. Low flow (if in Fast Speed)
3. LOCA (loss of MCC)
4. LOP (trips fans on UV until sequenced on signal received)

Question 11

What precautions must you take when manually switching between CW and RACS?

Answer 11

A transfer of inventory from the higher pressure RACS to the lower pressure CW may occur, resulting in a subsequent low RACS Head Tank Level / Alarm. To prevent this HV-9532-1 and 2 (CHW Isln RTN/SPL) should be closed prior to performing any swap

Question 12

What are the power supplies for the CW INBD/OUTBD isolation valves and the DW A and B fans?

Answer 12

CW to Containment INBD Isolation Valves – 10B232
CW to Containment OUTBD Isolation Valves – 10B242
‘A’ Fans – 10B252 - ‘A’ CS Logic
‘B’ Fans – 10B262 - ‘B’ CS Logic

Question 13

What effects will the channelized properties of the CW supplies to the DW fans and the DW fans themselves have when initiating CS manually?

Answer 13

Individual CS manual initiations will have various effects based on the bus it drops. i.e, ‘A’ will secure all ‘A’ fans while ‘C’ will secure all CW flow to the coils etc.

Question 14

What are the temperature limitations?

Answer 14

• DW AVG: <135°F
• Around RR pumps: 135°F
• Below 162’: <150°F
• Above 162’ up to 208°F for hot spots.

Question 15

What are the power supplies for HV-9531’s?

Answer 15

• HV-9531 B1-B4 Ch C (inboard valves).
• HV-9531 A1-A4 Ch D

Question 16

What are the power supplies for HV-9531’s?

Answer 16

• HV-9531 B1-B4 Ch C (inboard valves).
• HV-9531 A1-A4 Ch D