Drywell Cooling Flashcards
What is the purpose of the Drywell recirc fans?
Circulate air from the upper to lower elevations of the drywell to prevent thermal stratification
What cools the drywell chill water?
PSW
What’s the purpose of the Drywell Chilled water pumps?
circulate drywell chilled water through the chillers and drywell coolers
How many chillers are normally in service?
2 in service and 2 in stby
what are the trips for all the fans?
no trips!
What will start the stby fan?
low flow through associated cooler
Where does leak-off from the coolers go?
unidentified leakage
When does high leakage flow come in?
> 3 gpm or increase by 2 gpm in 24 hours
what’s the tech spec limit for leakage?
5 gpm
when will CTMT drywell isolation valves go closed for chill water?
when is it bypassed?
- 41.6” Rx level
1. 23 psig drywell pressure
bypassed 30 seconds after initiation so valves can be re-opened from the control room, but will re-close if an isolation signal is received again
What are the trips for the drywell chillers?
Low compressor oil level (bypassed 60 seconds for startup)
Low evaporator Refrigerant pressure 58 psig
High oil temp 212 F
High condenser refrigerant pressure 250 psig
High motor winding temp 267 F
Low chilled water flow 300 gpm
Low chilled water temp
how do chillers respond to a LOP?
A will be without power
B will auto start align to SSW B, but undervoltage relays will need to be reset
How do chillers respond to a LOCA?
A locked out on isolation
B will trip on LSS load shed, It is locked out from Electrical power and SSW B
When will the STBY chiller auto start?
> 60 deg F, Chilled water supply
When will the STBY drywell chilled water pump auto start?
< 300 gpm
What are the power supplies for the recirc fans?
A - 15B42
B - 16B42
What are the power supplies for the DW chillers?
A - 14AE
B - 16AB
What is the high temp for CRD cavity?
145 deg F
What activities occur when high temp alarm is reached?
F006 and F014 close and F009 and F016 open to divert cool air to CRD cavity.
(6 + 14 = 20) (9 + 16 = 25)
What temp does Drywell system return to normal? (after CRD cavity high temp alarm reached)
140 deg F
How do the drywell recirc fans operate?
they start when flow is sensed through associated cooler
they secure when no flow is sensed through associated cooler after 20 second time delay
How do drywell cooler fan out dampers fail on a LOP?
All 6 “A” fail CLOSED
All 6 “B” fail OPEN
Will 15B42/16B42 auto sequence back to power Drywell fans after a LOCA?
no
How will drywell be cooled in a LOCA?
AMBIENT losses only
