First-order perturbation theory for the multiplication coeffi cient based on the method of characteristics in the form used in the MCCG3D code is presented. Finite-difference analogs of the perturbation theory formulas are derived using the difference scheme of the MCCG3D code. Test calculations were performed. It is shown that the results obtained by perturbation theory and direct calculations converge.

中文翻译：

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特征法中的微扰理论

提出了基于MCCG3D代码形式的特征方法的乘法系数的一阶微扰理论。微扰理论公式的有限差分模拟是使用 MCCG3D 代码的差分方案导出的。进行了测试计算。结果表明，微扰理论和直接计算得到的结果是收敛的。