Abstract

A thermomechanical fuel performance analysis module is implemented in the Korea Advanced Institute of Science and Technology Monte Carlo (MC) neutron transport code iMC. The module is designed particularly for advanced three-dimensional (3-D) fuel concepts, so an unstructured tetrahedral mesh grid is adopted for geometry flexibility. The cellwise detailed power density distribution is tallied from the MC transport and transferred to the thermomechanics module for the heat transfer, thermal expansion, and stress analysis. In this paper, a recently proposed 3-D fuel concept called the centrally shielded burnable absorber (CSBA) model was considered for numerical studies. Several fuel models were solved by the iMC code: a single CSBA pellet, a three-ball–loaded CSBA pellet, and a CSBA fuel-loaded 17 × 17 fuel assembly. From the analysis results, it was discovered that the uncertainty of the detailed power density distribution hardly affects the uncertainty of the thermomechanical analysis due to dissipation via conduction. Also, the importance of using detailed intrafuel power distribution data in such a thermal neutron spectrum has been demonstrated, showing about 30 K overestimation of peak temperature compared to the conventional uniform power assumption.

摘要

韩国先进科学技术蒙特卡洛（MC）中子运输代码iMC中实施了热机械燃料性能分析模块。该模块是专为高级三维（3-D）燃料概念而设计的，因此采用了非结构化的四面体网格以提高几何灵活性。从MC传输中计算出沿单元的详细功率密度分布，并传输到热力学模块以进行热传递，热膨胀和应力分析。在本文中，考虑了最近提出的称为中央屏蔽可燃吸收器（CSBA）模型的3-D燃料概念，用于数值研究。通过iMC代码解决了几种燃料模型：单个CSBA燃料块，三球负载的CSBA燃料块和CSBA燃料负载的17×17燃料组件。根据分析结果，已经发现，由于通过传导耗散，详细功率密度分布的不确定性几乎不会影响热机械分析的不确定性。同样，已经证明了在这种热中子谱中使用详细的燃料内功率分布数据的重要性，与传统的均匀功率假设相比，峰值温度被高估了约30K。