On the efficiency of a modified variable directions method

Amodification is suggested of variable directions method for resolving the neutron diffusion difference equation in which the terms describing leakage are transposed to the left or to the right side of the equation depending on the leak sign. The modified equation enables to restrict oneself to accomplishing only one inner iteraction on each outer one in majority of practical cases. This decreases sufficiently the counting rate. Results of calculation of reactors with various energy spectra are presented. Calculation were conducted for a fast reactor, inermediate critical uranium-beryllium assembly and critical uranium-water assembly. Calculations were conducted in two-dimensional (z, Z) geometry according to the PENAP-21 program in 5-, 21 and 4-group approximations. The effective multiplication factor and neutron flux agree to high accuracy