Experimental study on flow characteristic of thimble heat exchanger applied to passive residual heat removal system of molten salt reactor

In advanced fourth generation reactor Molten Salt Reactor (MSR), thimble heat exchanger projected into the drain tank is the key equipment in the Passive Residual Heat Removal System (PRHRS). In the present work, a full-scale thimble heat exchanger for 2 MW MSR have been designed and fabricated to investigate the flow performance as well as further understand the flow process for single and two phase flow in natural circulation at the operation of the PRHRS. The key parameters are measured to evaluate the flow performance mechanisms and friction pressure drop model for both single and two phase flow. Meanwhile, the traditional correlations are further compared with the experimental data of the thimble heat exchanger in the system. It is also observed that the periodic oscillations may occur in the course of operation at relative low pressure and temperature. The validated correlations provide applicable and effective references for the actual operation and safety analysis of the PRHRS in the later commercial MSR.