Total loss of flow accident characteristics of Super FR with new coolant flow

Total loss of flow accident characteristics of the supercritical-pressure light water-cooled fast reactor (Super FR) with all upward flow core cooling in two paths is investigated at supercritical pressure. Upward flow cooling has advantage that flow stagnation does not occur at total loss of coolant flow accident due to the buoyancy of the coolant. It is found that maximum cladding surface temperature (MCST) is sensitive to the volume of the gap between two paths the. By open the automatic depressurization system (ADS), depressurization will induce flow in the RPV, and it can improve the MCST in this accident.

► MCST is high at the total loss of reactor coolant flow accident in Super FR.
► The new coolant flow pass scheme gives lower MCST than the old coolant flow.
► Distance between shroud and outer core needs to be limited for safety.
► Opening ADS is effective to decrease MCST.