中子辐照下EU固体增殖包层的热离散元分析
A Thermal Discrete Element Analysis of EU Solid Breeder Blanket subjected to Neutron Irradiation
摘要：
由于中子辐照，固体增殖包层经受复杂的热机械条件。在一个增殖单元中，陶瓷增殖床由球形原硅酸锂卵石组成，并且作为一种颗粒材料，它表现出温度场和应力场之间的强耦合。在本文中，我们研究这些热力学问题，通过开发一个热离散元法（Thermal-DEM）。该模拟工具将每个单独的陶瓷卵石建模为一个元素，并考虑元素之间的晶粒尺度热机械相互作用。HCPB中的一小部分固体增殖剂卵石床使用数千个单独的卵石建模，并根据ITER相关条件下的中子学计算体积加热剖面。我们认为在颗粒尺度之间的卵石通过固体-固体接触和间隙气相的热传递，我们计算所产生的应力从热膨胀的卵石。床的总有效电导率取决于在中子加热期间产生的压缩应力状态。本文提出的热-离散元方法提供了获得颗粒尺度信息的途径，有利于HCPB设计和增殖堆材料优化，并能更好地理解聚变相关条件下增殖堆单元的整体热-机械响应。
英文摘要：
Due to neutron irradiation, solid breeder blankets are subjected to complex thermo-mechanical conditions. Within one breeder unit, the ceramic breeder bed is composed of spherical-shaped lithium orthosilicate pebbles, and as a type of granular material, it exhibits strong coupling between temperature and stress fields. In this paper, we study these thermo-mechanical problems by developing a thermal discrete element method (Thermal-DEM). This proposed simulation tool models each individual ceramic pebble as one element and considers grain-scale thermo-mechanical interactions between elements. A small section of solid breeder pebble bed in HCPB is modelled using thousands of individual pebbles and subjected to volumetric heating profiles calculated from neutronics under ITER-relevant conditions. We consider heat transfer at the grain-scale between pebbles through both solid-to-solid contacts and the interstitial gas phase, and we calculate stresses arising from thermal expansion of pebbles. The overall effective conductivity of the bed depends on the resulting compressive stress state during the neutronic heating. The thermal-DEM method proposed in this study provides the access to the grain-scale information, which is beneficial for HCPB design and breeder material optimization, and a better understanding of overall thermo-mechanical responses of the breeder units under fusion-relevant conditions.
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