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Dispersed particle fuel is an advanced form of fuel. Due to the need for reactivity control, burnable poison particles and fuel particles are often dispersed in the matrix together. In order to prove the double dispersion mechanism of fuel and burnable poison particles with high calculation accuracy, a random dispersion model of burnable poison particles is constructed in this paper under the conditions of fuel homogenization and random dispersion of fuel particles. Compared with the random dispersion model, direct homogenization of fuel or burnable poison can cause large deviation in the calculation of system eigenvalues according to the MCX calculation. Under the same fuel phase volume, fuel enrichment and burnable poison loading, the maximum deviation can reach 1494pcm. The deviation increases with the increase of the loading mass of the burnable poison in the system, subject to fuel particle diameter of the order ∼100 μm. At a relatively high content of the burnable poison, the deviation decreases with the change of the content of the burnable poison. The calculation results show that the double heterogeneity effect of the system composed of fuel and burnable poison particles cannot be ignored, and the traditional homogenization calculation method must be corrected according to the actual situation. This paper is of valuable reference for the calculation and correction of dispersion fuel homogenization under the condition of strong absorber, and the program development and verification of using a new method to deal with the double heterogeneity effect.

Dispersed particle fuel is an advanced form of fuel with many advantages, which is safer than traditional fuel. But a strong double heterogeneity effect is formed, due to the random dispersion of fuel particles in the matrix. The homogenization and uniform distribution approximation models will thus leads to severe errors. In order to account for the influence of the double heterogeneity effect, a homogenization model, a uniform dispersion model and a random dispersion model are constructed in this paper. Then the MCX program was used for calculation, and the fuels were compared and analyzed, subject to high fuel phase volume and different enrichment. The effect of particle diameter variation on the eigenvalues of the system is revealed, and the errors introduced by the model approximation are also evaluated. It is demonstrated by the results that the double heterogeneity is negligible when the diameter of the fuel particles is less than 100μm. However, the double inhomogeneous effect is relatively enhanced under large diameter fuel particles and low enrichment, which requires high-precision calculations. This paper has a certain reference significance for the evaluation of the double heterogeneity effect of the dispersed particle fuel and the correction of the traditional homogenization calculation.