Civil Engineering Reference
In-Depth Information
Fig. 3.13
Automatic depressurization system, safety coolant water injection and residual heat
removal of AP1000 [
2
,
9
]
3.2.5.2 Passive Residual Heat Removal
After depressurization below 0.18 MPa the IRWST provides long term cooling of
the core by the opening of squib valves. For passive residual heat removal a passive
residual heat removal heat exchanger (PRHR HX) is connected through inlet and
outlet lines to one of the main reactor coolant loops. The heat sink for the PRHR HX
is provided by the large water volume of the IRWST. In this way the PRHR HX can
also counteract to temperature transients caused by imbalances on the steam
generator and feedwater side.
3.2.5.3 Passive Containment Cooling
In case of boiling water in the IRWST the steam in the atmosphere of the inner steel
containment condenses at the inner wall. The resulting water is collected and
flowing back into the IRWST. The heat is transferred by heat conduction through
the wall and removed by the air or water flowing at the outer surface. In this way all
decay heat released in the molten core can be transferred to the outside atmosphere
(Fig.
3.12
).
