Application of the surface harmonics method for the solution of the neutron-physical problems with the double heterogeneity of the cell - fuel assembly - reactor type

General approaches to by-step calculation of reactors with heterogeneity of the cell - fuel assembly - reactor type using the surface harmonics method are developed. Serviceability of the technique suggested and its advantages in computation efforts as compared with direct calculations using the fine mesh ensuring the same accuracy are demonstrated taking as an example the calculation results for the RBMK assemblies. The comparison with traditional homogenization method is made. Much attention is paid to calculating different reactions, namely, transfer of reaction matrices from the stage of cell calculation via the stage of polycell calculation to the stage of course-mesh calculation. The algorithms described are realized in the SUHAM computer code