Safety Systems Flashcards
State the functions of the Emergency Core Cooling System (ECCS).
The Emergency Core Cooling System (ECCS) protects the public & station personnel against the release of radioactive products from the RCS to the environment during accident conditions by delivering cooling water to the core.
State the functions of the Containment Heat Removal (CHR) System.
Removes heat & fission products from Containment atmosphere after an accident.
Ensures Containment design pressure & temperature limits are not exceeded following these accidents.
List the order that Emergency Core Cooling System (ECCS) subsystems inject into the Reactor Coolant System (RCS) as RCS pressure lowers.
Reactor Coolant System (RCS) as RCS pressure lowers.
High Pressure Safety Injection - ~ 1250 psig
Safety Injection Tanks - ~ 250[550] psig
Low Pressure Safety Injection - ~ 185 psig
Describe the Injection Phase flow path
All Safety Injection pumps start.
The pumps take suction from the Refueling Water Tank and discharge into each RCS cold leg through motor operated isolation valves, which open on a Safety Injection Actuation Signal.
Pump minimum recirculation flow lines connect to a common line, directing a small percentage of flow back to the Refueling Water Tank.
The Safety Injection Tanks are aligned to inject
Pressurized with Nitrogen with the outlet valves open.
Normally isolated from the RCS by check valves which are held closed by the differential pressure between the tanks and the RCS.
The check valves open if RCS pressure drops to less than tank pressure, allowing borated water in the tanks to flow into the RCS.
Describe the Recirculation Phase flow path
When the Refueling Water Tank water supply is exhausted, the Emergency Core Cooling System automatically realigns to circulate spilled RCS water from the Containment Sump back to the RCS.
The Containment Sump isolation valves open
The Refueling Water Tank isolation valves close
Minimum flow recirc isolation valves close to prevent discharging Containment Sump water to the Refueling Water Tank.
The Low Pressure Safety Injection pumps stop.
High Pressure Safety Injection continues to run.
The recirculation of coolant continues until such time as it is no longer needed (long term).
State the purpose(s) of the Refueling Water Tank (RWT)
Provides a borated water source for accidents and refueling
State the purpose(s) of the Containment Sump
Provides a large collection reservoir to supply water to the Containment Spray and Safety Injection Systems for recirculation after a RCS break inside Containment.
State the purpose(s) of the Spray Nozzles
Breaks up the Containment Spray flow from a stream into small droplets to maximize heat transfer from the Containment.
State the purpose(s) of the Iodine Removal System
Removes Iodine from the Containment atmosphere following an RCS break by adding Sodium Hydroxide [Hydrazine] to the Containment Spray System water.
State the purpose(s) of the Containment Fan Coolers
Maintain Containment average temperature less than 120°F during Normal Operations
Remove heat that is released during an accident in Containment.
