板状燃料组件入口堵流事故下流场和温度场的瞬态数值计算

Numerical Analysis on Transient Flow and Temperature Field During Inlet Flow Blockage Accidents of Plate-type Fuel Assembly

板状燃料组件具有结构紧凑、换热效率高、深燃耗等特点,故被广泛应用在一体化反应堆和实验用研究堆中。在堆芯窄矩形流道中,冷却剂一般采用自上向下的强迫循环方式。在某些事故工况下,譬如由于燃料元件的辐照肿胀、堆内材料碎片或异物随冷却剂循环流入堆芯,可能引发堵流事故。该事故将造成燃料板失冷,板温升高,可能导致局部冷却剂蒸干,威胁燃料包壳的完整性,甚至造成放射性外泄,引发严重事故后果。本文采用CFD软件ANSYS FLUENT 12.1对板状燃料组件在入口95%部分堵塞和全部堵塞的工况进行了瞬态数值模拟。计算中考虑了冷却剂和燃料板的流固耦合传热问题,并对所得三维流场、温度场及影响因素进行了分析。

Due to its superior performances such as compact structure, higher heat transfer efficiency, and deeper fuel bum-up, plate-type fuel assembly has been more and more widely utilized in new type integrated reactors and experimental research reactors, of which coolant is forced passing through the typical narrow rectangular channels formed by plate-type fuel in the core. Under some postulated accident conditions, such as irradiation damage, materials debris or foreign objects dragged into the core with the coolant circulation, and coolant flow assembly blockage accidents could occur. The accident may cause the reduction of coolant flow, make the fuel plate temperature increased, result in the phenomenon of dry-out, threaten the integrity of fuel cladding, and even cause the release of radioactive material into the reactor coolant system. The transient thermal-hydraulic characteristics of plate-type fuel assembly under inlet 95% partial and total flow blockage transient accidents are numerical simulated using the commercial CFD software ANSYS FLUENT 12.1 code. The liquid-solid conjugate heat transfer between coolant and fuel-plates has been considered in this calcula- tion, and we analyzed the three-dimensional flow field, temperature field and the influencing factors.