When fuel rods melt during a severe accident, the movement of the structural and fuel materials along fuel assemblies can be spatially non-uniform, so that a three-dimensional thermohydraulic model is implemented in the EVKLID/V2 code as part of the HYDRA-IBRAE/LM module. The transport of the same sets of components and their mixtures as in the one-dimensional version of the HYDRA-IBRAE/LM module can be calculated in the model: liquid sodium, sodium vapor or vapor-gas mixture of sodium vapor and non-condensable gases, solid lead, liquid lead, solid uranium dioxide, liquid uranium dioxide, hard stainless steel, liquid stainless steel, steel vapor. The three-dimensional model is implemented in a cylindrical coordinate system, which makes it easier to include the geometric dimensions and parameters of a particular fuel assembly (number and diameter of fuel rods, lattice pitch, and others) and the core. A description is given of the basic system of equations describing the motion of the components of the destroyed core in the three-dimensional r–z–φ geometry, and its numerical realization. Examples of test calculations showing the serviceability of the model are presented.

中文翻译：

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严重事故的 3D EVKLID/V2 代码辅助模拟

当燃料棒在严重事故中熔化时，结构和燃料材料沿燃料组件的运动可能在空间上不均匀，因此在 EVKLID/V2 代码中实施了三维热工水力模型，作为 HYDRA-IBRAE 的一部分/LM 模块。可以在模型中计算与一维版本的 HYDRA-IBRAE/LM 模块中相同的组分及其混合物的传输：液态钠、钠蒸气或钠蒸气和不可冷凝的蒸气-气体混合物气体、固体铅、液体铅、固体二氧化铀、液体二氧化铀、硬质不锈钢、液体不锈钢、钢蒸气。三维模型是在圆柱坐标系中实现的，这使得包含特定燃料组件的几何尺寸和参数（燃料棒的数量和直径、晶格间距等）和堆芯的几何尺寸和参数变得更加容易。描述了在三维 r-z-φ 几何中描述被破坏核心部件运动的基本方程组及其数值实现。给出了显示模型适用性的测试计算示例。