Experimental Investigation on Natural Circulation Characteristics of Core Make-Up Tank Under Rolling Conditions

In the floating nuclear power plant, Core Make-up Tank (CMT) is one of the passive safety facilities, has been widely used in nuclear engineering. Under emergency conditions, natural circulation occurs and consequent thermal stratification appears in CMT system. However, rolling motion will directly affect the natural circulation and destroy the formation of thermal stratification, so there will be uncertain and unknown change of the safety injection capacity of CMT. Based on above analysis, this work carried out experiments under rolling conditions to reveal natural circulation and thermal stratification characteristics in CMT. A temperature detecting matrix formed by thermocouples is deployed in CMT. It is concluded that thermal stratification distribution is affected by the rolling conditions. Rolling conditions increase the thickness of thermal stratification and reduce the temperature gradient. The CMT natural circulation has two stages, the influence of rolling motion on the average flow in the first stage of natural circulation is very weak, but rolling motion will significantly affect the second stage of natural circulation and advance the decline time of direct vessel injection (DVI) flow rate. The transition time of natural circulation stage and the flow change in the second stage of natural circulation are related to the thermal stratification in CMT. The impact of rolling conditions should not be ignored when evaluating the performance of CMT.