一种针对三维瞬态多群中子扩散方程的非结构网格变分节块方法，首先使用非结构VNM对稳态中子扩散方程计算后初始化中子通量密度、缓发中子先驱核以及动力学截面，然后在瞬态计算的每个时间步内通过迭代更新反应截面以及更新动力学频率并重构响应矩阵后，使用非结构VNM求解刚性限制法(SCM)方程，实现任意几何形状下的中子的瞬态过程的模拟；本发明提高瞬态计算下变分节块法的几何适应性，并通过刚性限制法(SCM)减少VNM在时间推进中的响应矩阵重构次数以提高瞬态计算效率，能够准确模拟实际不规则几何的复杂问题。

An unstructured variational nodal method for three-dimensional transient multigroup neutron diffusion equations begins by using the unstructured VNM to compute the steady-state neutron diffusion equation, initializing neutron flux density, delayed neutron precursor, and dynamic cross sections. Subsequently, at each time step of the transient calculation, the reaction cross sections are iteratively updated along with the dynamic frequencies, and the response matrix is reconstructed. The unstructured VNM is then used to solve the stiffness confinement method (SCM) equations, achieving simulation of neutron transient processes under arbitrary geometries. This invention improves the geometric adaptability of the variational nodal method under transient calculations. By using the SCM, it reduces the number of times the response matrix needs to be reconstructed during time advancement, thus enhancing the efficiency of transient calculations. This method can accurately simulate complex problems with irregular geometries in practical scenarios.