Fully ceramic microencapsulated (FCM) fuels with enhanced accident tolerance can provide an increased retention of fission products. In this study, a new method to model their irradiation-induced thermo-mechanical behavior is established. A fuel performance code called Thermo-mechanical Analysis of Inert Matrix Fuels (TMAIMF) is developed based on ABAQUS platform to enable the researchers to allow for all the irradiation effects in the three-dimensional large-deformation constitutive models of the involved materials. Especially, the important gas-release-induced thermal-mechanical effects are considered for the porous carbon layer. Finite element analysis is implemented for the thermo-mechanical coupling and multi-scale behavior in a FCM pellet, with the non-spherically symmetric thermal-mechanical interactions among all the coating layers in a TRISO particle, the TRISO particles and the matrix taken into account. Numerical simulation results indicate that (1) the irradiation shrinkage and gas-induced effective expansion strain in the porous carbon layer are responsible for the accommodation of kernel swelling, so the deformations of FCM pellets are dominated by the thermal expansion and irradiation swelling of SiC matrix; (2) the gas-induced effective expansion strains in the porous carbon layer together with the irradiation creep strains occurred in various materials protect the pellet from cracking during the whole irradiation process, with highly efficient heat transfer maintained. This study supplies a fundamental basis for advanced fabrication and optimization of FCM fuel pellets.

具有增强的事故耐受性的全陶瓷微囊化（FCM）燃料可以提高裂变产物的保留率。在这项研究中，建立了一种模拟其辐照引起的热机械行为的新方法。基于ABAQUS平台开发了一种称为“惰性基质燃料热机械分析”（TMAIMF）的燃料性能代码，以使研究人员能够在所涉及材料的三维大变形本构模型中考虑所有辐射效应。特别地，对于多孔碳层考虑了重要的由气体释放引起的热机械效应。对FCM颗粒中的热机械耦合和多尺度行为进行了有限元分析，考虑到TRISO颗粒，TRIOS颗粒和基体中所有涂层之间的非球对称热机械相互作用。数值模拟结果表明：（1）多孔碳层中的辐照收缩和气体诱导的有效膨胀应变是核溶胀的调节因素，因此，FCM颗粒的变形主要由SiC基体的热膨胀和辐照溶胀决定。 ; （2）多孔碳层中的气体诱导有效膨胀应变以及各种材料中发生的辐照蠕变应变可在整个辐照过程中保护颗粒免受破裂，并保持高效的热传递。该研究为FCM燃料芯块的先进制造和优化提供了基础。