Investigation of the approximate method efficiency for calculating neutron field profiles

Considered are the most widely used modifications of homogeneous-diffusion and heterogeneous-diffusion methods for calculating neutron fields in nuclear reactor cores. Results obtained by these methods have been compared with the results of exact calculation of hexagonal lattice carried out by the Monte-Carlo method to determine the errors of these methods. It is underlined that both methods are equivalent from the point of view of the idea, but the application of finite-difference approximation of differential operators gives a considerable error to homogeneous lattice calculations. An option of a concrete calculational method is determined predominantly by technological differences of an assembly under consideration. Also if in the tasks with hexagonal cells and considerably different diffusion coefficients (WWER) homogeneous programs are preferable, in the tasks with square cells containing comparatively thin channels (RBMK), homogeneous five-point algorithm will give an appreciable error and a heterogeneous algorithm, especially effective in a monopole version, will be preferable