The passive containment cooling system is a nuclear power plant cooling method for the transfer and dissipation of the reactor heat. It uses a steel primary containment vessel. In this system, pressure reduction is relatively slow as it depends on the partial pressure of non-condensable gases in the containment. Meanwhile, a series of sprays perform and improve external cooling.
The AP1000 passive containment cooling system consists of an inner steel containment shell or vessel, which is enveloped by an external concrete shield building. The inner steel containment acts as a barrier for radioactive release, serving also as an integral part of the heat release system. Its passive containment cooling system provides natural circulation air draft cooling between the steel containment shell and the concrete building surrounding it. This prevents it from overheating. In some power plant, there is an annulus between the two shells through which air circulates naturally.
Steel containment shell gives the advantage of good heat removal characteristics, which can be fitted with passive heat removal systems. When concrete is used as the sole form of containment, it needs additional heat transfer systems, such as heat exchangers of condenser systems to help in the removal of heat from the interior to the exterior of the containment.
Below, a drawing and diagram of a passive containment cooling structure in a nuclear power plant.
