Containment - Air Control Flashcards
What systems support Containment Air Control?
Nitrogen Makeup, Pumpback System, DW Cooling, DW purge, Augment Primary Cotnainment Vent (APCV
What is the prupose of the Nitrogen Makeup System
Provides pressure control support to primary containment.
Also performs feed and bleed to prevent combustible atmosphere;
May be used as system to inert the DW - vaporizing liquid N2 at flow rate of 2500cfm.
What is the purpose fo the Nitrogen containment atmospheric Dilution (NCAD?
Provides more reliable combustible gas control
Used as backup makeup flow path during accident conditions
What is the Pumpback System?
Used to maintain DP at slightly greater than 1psid between DW and torus via supply air operated vavles in DW.
Where are the Pumpback Air Compressors?
North of West (East) HCU Bank on U2 (U3)
What is the power source for the Pumpback air compressors?
MCC 28-1 (38-1) and 29-1 (39-1)
What provides the cooling for the Pumpback Air Compressors?
U2 RBCCW cools all of them for both units.
What are the trip setpoints for the Pumpback Air Compressors?
Low oil pressure (15-17psig) High RBCCW temp 180F Low Suctio Pressure 5"Hg Breaker Trip ***If one compressor trips, the other must be started manually
What happens to the pumpback air compressor on a group II isolation?
It will run unloaded due to Air isolation and will likely trip on low suction pressure.
What is normal flow for pumpback air compressor?
Suction from Torus and discharge to DW
How does the DW/Torus DP control System Function?
Pumpback Compressors suction off Torus and charge receiver to 100psig, then supplies flow back to DW via PCV
PCV used to control flow and set to maintain DW Pressure slightly higher than 1psig.
Receiver also supplies a line to the DW pneumatic system dryer and to DW Pneumatic receiver to support AO isolation valves and DW valves
What happens with degraded pressure on Pumpback and Drywell Pneumatics?
N2 backup valve opens to maintain pressure to valves in DW.
This is requried to maintain MSIV’s
What may cause changes to DW pressure during normal Operation?
Convective heating during startup or power reduction
Pumpback malfunction
DW pneumatic leak
Change in ambient pressure (relative to RB pressure
What is the purpose of DW Pneumatics?
Supplies pressure to DW AOVs
How do the Containment Dampers respond on loss of pumpback?
Fail safe accumulators provide pressure to operate valve through a couple of cycles if pumpback lost.
What is normal setpoint for DW temperature?
135 to 150F - maintained by DW coolers
What provides cooling to DW cooler fans?
RBCCW
What powers the DW Cooler Fans?
Bus 28 for A, B, F, G; Bus 29 C, D, E
How do the DW Coolers respond to ECCS initiation?
Trip and breakers trip.
Do not trip on load shed.
What is the purpose of the DW purge fans? Power?
Draw primary containment atmosphere through set of filters and dischage to RB vent exhaust fans and out RB Stack or SBGT.
Powered by MCC 28-1 and 29-1
How does DW Purge Fan Respond eto Secondary Containment Isolation?
Both Units purge fans trip and inlet and outlet dampers close
What is the Augmented Primary Containment Vent System (APCV)?
Provides capability to vent Primary Containment following accident should all primary containment cooling be lost and containment pressure approach design limit by providing rapid vent means.
What is the design flow for APCV?
Equivalent to 1% rated thermal power at 62psig torus bottom pressure and maximum normal Torus water level
What provides power to APCV?
ESS supplies power to logic and valve solenoids (valves fail closed).
What happens to Nitrogen Makeup on Group 2 isolation?
Signal to close dampers (57 through 59)
How may the Drywell Cooling ECCS trip signals by bypassed?
Lifting and taping leads per DEOP 500-02
If there is a loss of Instrument Bus or Air how will Pumpback Respond?
DW to Torus DP PCV fail closed;
DW Pneumatic to DW Isolation valve fail closed;
DW Pneumatic N2 Backup Valve Fails Closed;
Loss of Instrument Bus will cause AOVs supplying DW pneumatics to fail closed and Inboard MSIVs fail closed on loss of N2.
Loss of Pumpback will…..
Cause DW to Torus DP to drift and exceed design/TS limits
