Preliminary Design and Thermal Analysis of Intermediate Heat Exchanger Based on Irradiation Test Loop with Alternative Coolants

Abstract

Irradiation test loop with alternative coolants is a new-concept test facility which can be used for irradiation of different types of reactor fuel elements. Intermediate heat exchanger is the key equipment of test loop, its heat transfer capacity directly affects the operating level of the loop. The intermediate heat exchanger based on irradiation test loop with alternative coolants adopts the typical shell-and-tube heat exchanger structure. The coolant on shell side which is connected to the secondary loop is lead-bismuth eutectic alloy (LBE), LBE can remove the heat released from irradiation vehicle through heat exchanger. The tube-side coolant is selected from sodium, lead, LBE, helium, and molten salt, according to the irradiation object. For different coolant conditions, the loop power level and the coolant temperature vary widely. Under the liquid metal sodium condition, the loop power can reach 1000 kW, and the sodium outlet temperature can reach 550 °C. While under the helium condition, the loop power is only tens of kilowatts, but the helium outlet temperature can reach 900 °C. In this study, the theoretical feasibility of the single heat exchanger to meet various coolant operating conditions is analysed, and the entire process from heat exchanger design to thermal calculation and analysis is accomplished. The research shows that flow of shell-side LBE has little effect on the heat transfer capacity of the heat exchanger. For different liquid metal conditions, adjusting the outlet temperature of shell-side LBE can adjust the heat transfer capacity to some extent to match the loop power. For helium or molten salt condition, due to the high coolant temperature and the low loop power, heat transfer tube adopts the double-layered tube structure and gas gap is arranged between tubes for heat conduction. By adjusting the thermal conductivity of gas, the heat transfer capacity can be matched with the low power condition of helium or molten salt.