The invention relates to a method for evaluating keff uncertainty caused by nuclear cross section deviation, and belongs to the technical field of
nuclear data evaluation. The method comprises the following steps: S1, selecting nuclides needing to be evaluated in a
nuclear system to be analyzed; S2, selecting a nuclear cross section, which needs to be evaluated, of each
nuclide; S3, respectively calculating the sensitivity of each nuclear cross section selected in the step S2; S4, selecting
covariance data corresponding to each kernel cross section, and adjusting or estimating the
covariance data; S5, respectively calculating the uncertainty Unck of each
covariance matrix to the keff; and S6, calculating the uncertainty Unc of the keff caused by the nuclear cross section deviation of the
nuclear system. According to the method provided by the invention, the influence of each
covariance matrix on the keff uncertainty is calculated through the nuclear cross section sensitivity data and the covariance data, so that the uncertain value of the keff caused by the nuclear cross section deviation can be quantitatively obtained, and design, analysis and evaluation can be guided.