ECCS accumulator system is intended to supply cold water at the core inlet and retain the primary coolant inventory when the primary pressure reduces below 4 MPa(when leaks occur). The system consists of four independent trains with redundancy of 4 x 50%. Each train includes an accumulator tank with boron solution under pressure; the pressure is created by a nitrogen cushion. The accumulators are connected to the reactor downcomer. The check valves are installed on the connecting pipelines to isolate the accumulators from the reactor when the primary pressure exceeds 4.0 MPa. The system operates in accordance with the passive principle, and no signal is required to activate the system.

XI — 3.2. ECCS tank subsystem

ECCS tanks (tanks of atmospheric type) are intended to flood the reactor core allowing long term residual heat removal when operating at a pressure below 0.29 MPa. The system consists of four independent trains with redundancy of 4 x 50%. Each train includes the tank filled with boron solution, valves, and pipelines. The ECCS tank is connected to the reactor downcomer by the pipeline with two check valves. The system operates under the hydrostatic force effect.