Experimental and numerical study on thermal-hydraulic characteristics of water-cooled fuel assembly irradiation device for HFETR

In this paper, in order to study the thermal-hydraulic behavior of fuel assembly irradiation device in HFETR (High-Flux Engineering Test Reactor), a fuel assembly irradiation device simulator with narrow channels and slit was developed. The thermal-hydraulic characteristics of the fuel assembly irradiation device was experimentally and numerically investigated. In the experiment, under the benchmarking high and low flow conditions, the overall heat leakage rate of the device is 1.54 % and 0.38 %, respectively, indicating that the thermal insulation performance of the experimental device is good. Under the two flow conditions, the corresponding total pressure drop in the experimental body is about 38 kPa and 11 kPa, respectively. Compared with the experiment, the maximum experimental body pressure drop error of the calculated results is 9.58 %. The calculated results show that there is a drastic exchange of velocities between the fluids during the movement of the fluid in the downcomer section. The flow velocity inside the slit channel is larger than that in the slit inlet and outlet area, and the velocity gradient at the slit outlet is larger. The existence of the slit makes a part of the fluid enter the outflow channel of the electric heating section, accounting for 2.4 %. The fluid mixing effect of the square box in the device is obvious, which is conducive to the flow distribution of the fluid into the heating channel. These findings provide critical insights for the design optimization of nuclear fuel irradiation devices in HFETR, particularly offering direct guidance for temperature measurement point arrangement, enhancing the thermal-hydraulic parameter measurement accuracy, and optimizing the narrow-channel flow control.

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