基于COMSOL的板状燃料组件流道堵塞事故研究

Research on Flow Blockage Accident of Plate-Type Fuel Assembly Based on COMSOL

板状燃料组件结构紧密,冷却剂流道狭窄,各流道中的冷却剂无法交混,发生流道堵塞事故将引起堆芯局部温度升高,并可能导致堆芯熔毁.为了研究板状燃料组件发生流道堵塞事故后的严重性,选取国际原子能机构的材料测试堆标准燃料组件作为对象,应用COMSOL软件模拟堵塞条件下燃料组件内的热工水力特性的变化.结果表明,稳态运行条件下,冷却剂和燃料板温度沿着流动方向逐渐上升,组件底部区域温度达到342.73 K;单流道发生不完全堵塞将造成冷却剂流动情况发生改变,堵塞流道内形成的涡流将影响传热;相比不完全堵塞,单流道发生完全堵塞造成的传热恶化更严重,燃料包壳的最高温度为362.74 K,仍处于安全范围之内.计算结果为板状燃料组件的尺寸设计和流道堵塞事故预防提供了参考依据.

The structure of the plate-type fuel assembly is compact and the coolant channel is narrow. Meanwhile, the coolant in each channel cannot be mixed with each other. The blockage accident of flow channel will cause the rise of local temperature in the core and may further cause the meltdown. In order to study the severity of flow channel blockage in the plate fuel assembly accurately, the standard fuel assembly of IAEA Material Test Reactor was selected as the object, and the change of the thermal and hydraulic characteristics in the fuel assembly under the condition of blockage is solved by the COMSOL program. The results show that the temperature of the coolant and the fuel assembly rise gradually along the flow direction and reach the maximum temperature 342.73 K at the bottom of the assembly under the steady state operation condition. The incomplete blockage of flow passage will cause the change of coolant flow, and the turbulence will be formed in the blocked flow passage to affect the heat transfer. Compared with the incomplete blockage, the deterioration of heat transfer caused by the complete blockage of the single flow channel is more serious. The maximum temperature of the fuel cladding is 362.74 K within the acceptable range. The results provide an important reference for the designs of the plate fuel assembly and the prevention of flow channel blockage accidents.