In hot conditions, the residual heat is removed through the steam generator. The steam is discharged to the atmosphere, and the Steam Generator is fed by the start-up shutdown system (SSS). The system is not safety grade. Then, at low temperature, the RRP with the air-cooling tower (RRPa) removes the decay heat.

When the vessel is opened, especially during the refuelling operating, decay heat is removed by the twelve RRPa cooled by chilled water in order to obtain a very low primary temperature compatible with the maintenance action conditions. The primary circuit operates in natural convection and the RRPa loops operate in active condition.

Chilled water is only used during the refuelling operation. In case of chilled water circuit or RRPa pump failure, the heat sink is backed up by the air-cooling tower of the RRPa. The RRP system replaces the normal residual heat removal system with an external loop like in standard PWRs.

XIX-4.3. Safety injection

Since large LOCAs are eliminated by design and since the primary system thermal inertia is larger than that of loop-type PWRs, the safety injection system requires devices with a small flow rate. Given the intrinsic low pressure option for the reactor, there is only one type of safety injection with a pressure of about 20 bars. The needed pump power for the safety injection is very small, about 35 kWe.