An improved multi-assembly homogenization method is raised to deal with the environmental effect of the hexagonal fuel assembly in PWRs.In order to reduce the influence of environmental effect of fuel assembly on the calculation accuracy of two-step method,sensitivity analysis is carried out from the state variable of burnup depth,which expands the practicability of this method.In this method,the real core energy spectrum of the fuel assembly adjacent to the reflector is approximately obtained by establishing a multi-assembly model,and the heterogeneous correction factor is adopted to reduce the deviation of the calculation of few-group constants of the single-assembly model with reflective boundary due to environmental effects.At the same time,the traditional two-step calculation strategy is fine-tuned,which has little impact on the overall code framework.The calculation results show that this method can effectively improve the calculation accuracy of the traditional two-step method,and the eigenvalue deviation is reduced from-341pcm(1pcm=10-5)to-111pcm,and the root mean square deviation of assembly power is also reduced from 2.28％to 1.38％.
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