基于在线耦合的球形燃料元件温度场计算

由于三层各向同性(TRISO)颗粒弥散型燃料元件结构复杂且其材料性能随着辐照水平不断变化，不同燃耗下燃料元件的等效热导率不易确定。本研究基于COMSOL软件完成了TRISO颗粒性能分析程序开发，并与BISON程序预测值进行了对比分析。随后，基于COMSOL软件与MATLAB联合仿真建立了球形燃料元件等效热导率的计算方法，实现了球形燃料元件和TRISO颗粒模型间的在线耦合计算。在此基础上，获得了不同边界温度、燃耗条件下燃料元件径向等效热导率分布及温度场分布。计算结果表明，快中子注量达到3×10²⁵m^–2时，TRISO等效导热率下降约20%，燃料等效热导率下降约15 W/(m·K)。为了验证本研究方法的有效性，用微分-有效介质理论模型(D-EMT)计算燃料的等效导热率，得到的球形燃料中心温度预测值相比本研究方法的预测值低约25 K。本文研究方法更能真实反映球形燃料元件在反应堆内的温度场变化。

Temperature Field Calculation of Spherical Fuel Element Based on Online Coupling

Due to the complex structure of TRI-Structural Isotropic (TRISO) dispersion fuel elements and its material properties that change under irradiation, it is difficult to determine the equivalent thermal conductivity (ETC) of fuel element under different burnup. In this study, the TRISO particle performance analysis program is developed based on COMSOL software, and compared with the predicted value of BISON program. Then, based on the joint simulation of COMSOL and MATLAB, the calculation method of equivalent thermal conductivity of spherical fuel element is established, and the online coupling calculation between spherical fuel element and TRISO particle model is realized. On this basis, the radial equivalent thermal conductivity distribution and temperature field distribution of fuel element under different boundary temperature and burnup conditions are obtained. The calculation results show that when the fast neutron flux reaches 3×1025 m–2, the equivalent thermal conductivity of TRISO decreases by about 20%, and the equivalent thermal conductivity of fuel decreases by about 15 W/(m·K). In order to demonstrate the effectiveness of this method, the equivalent thermal conductivity of fuel is calculated by differential-effective medium theory model (D-EMT). The predicted value of spherical fuel center temperature is about 25 K lower than that of this method. The research method in this paper can more truly reflect the temperature field change of spherical fuel element in the reactor.