CAC Flashcards
Which subsystems comprise CAC?
Nitrogen Makeup Pumpbakc system DW cooling DW Purge APCV
What is the purpose of the N2 Makeup system?
Provides pressure control support to Primary Containment as well as nitrogen feed and bleed vapability should combustible atmosphere develop post accident.
Provides makeup, inerting and NCAD flow paths
What is Nitrogen COntainment Atmospheric Dilution (NCAD)?
Provides more reliable source of nitrogen for combustivle gas controll following an accident - provides 29cfm through each line when normal makeup flow not available
What are the N2 low flow and high flow paths normally used for?
Low flow path - makeup
High flow path - Inerting post outag
How is DW inerting performed?
Using N2 Makeup High flow portion utilizing a steam heated vaporizer (from heating steam) which is capable of rapidly vaporizing liquid N2 at a nominal flow rate of 2500cfm
How is N2 Makeup performed?
Using the low flow portion of the system - used as makeup to PC for sligh leakages to maintain DW slightly higher than 1psig
What is the purpose of the Pumpback system?
Maintain slightly greater than 1 psid between DW and Torus and supply AOVs in DW via DW Pneumatics
How many Pumpback compressors are there per unit?
Power Supply?
Cooling?
2 per unit
pwr - 28-1/29-1(38-1/39-1)
ALL COOLED BY U2 RBCCW
What poweres DW Pneumatic Vlv Solenoids and how does a power loss impact valves?
Powered by IB - vlvs close on loss of IB (MSIV’s close w/in 1 minute)
What causes trip of Pumpback AIr Compressor?
Low Oil Pressure (15-17psig)
Hi RBCCW Temp (180F)
Lo Suction Pressure (5” Hg)
Breaker Trip
What is normal Pumpback flow path?
Suction from Torus to Torus to maintain 1pside
What happens to pumpback compressor on Grp II Isolation?
Runs unloaded and eventually trips on low suction pressure
How does the DW/Torus DP Control system function?
Pumpback compressors take suction on Torus and charge Pumpback receiver to 100psig and then air flows back to DW through PCV
What controls Pumpback flow and operation?
PCV to maitnain DW press ~1psig
What happens in Pumpback and DW pneumatic pressure drops?
N2 backup valve opens to maintain pressure to valves in DW. This is necessary to maintain MSIVs open for small period of time.
What powers Pumpback Receiver Digital Indicator and where is it?
902-4 powered from IB
What causes a change in containment pressure during normal operation?
Convective heating during startup or power reduction;
Malfunction of Pumpback system
Leak in DW pneumatics
Change in Ambient press(sensed relative to RB Press)
What signals cause closure of 57,58 and 59 Pmpback valves?
Grp II, loss of IB, Loss of IA
What does DW Pneumatics do?
Supplies pressure to operate AOVs in DW and AOVs that control DW pressure & DP
What is pressure set for N2 backup valve to open?
if Pumpback and DW pneumatic drops to ~80psig, valve 4723 opens to maintain pressure using backu supply
Which containment Dampers have fail safe accumulators?
1601-21, 22, 23, 24, 56, 60,63
What is the purpose of DW Air Cooling System?
maintains DW atmosphere temp less than those assumbed for DBA initiatl conditions
Temp between 135F and 150F
Where are the DW coolers and what are their power and cooling?
A-E on DW Basement F,G on 515 A,B, F, G powered by Bus 28 C,D,E powered by Bus 29 All cooled by RBCCW
What causes DW Cooer Trip?
Fans trip on ECCS Initiation (CS DWB Relay) and breaker trips
DO NOT TRIP ON UV LOAD SHED
(ECCS Trip may be defeated by lifting and taping leads)
What are the DW Purge Fans for? Power?
Designed to draw PC atmosphere through set of filters and discharge to RB Vent exhaust fans to RB Stack or SBGT
Normally used to de-inert DW for entry
Powered from MCC 28-1, 29-1
What happens to DW Purge Fans during Secondary Containment Isolation?
Both Unit Purge Fans trip and inlet and outlet dampers close
What is Augmented Primary Containment Vent?
APCV allows venting primary containment directly to 310 Chimney using IA and ESS for opening. fails closed on eitehr.
What is power supply for APCV?
ESS powers logic and valve solenoids
What is APCV design flow?
Equivalent to 1% rated thermal power (78910lb/hr) at 62psig torus bottom pressure and normal Torus water level
What are concerns fro SBGT Duct Work concerns?
Venting DW under high pressure (DBA) may result in failure of SBGT duct work in TB and contamination of TB areas.
