Obtaining finite-difference equations for a heterogeneous reactor with spatial kinetics

An approach now called the method of surface harmonics is used to derive finite-difference equations describing the space-dependent kinetics of a heterogeneous reactor. The exposition is made for a three-dimensional geometry - a square lattice of blocks. The passage to the limit where Fick's law holds for the nonstationary problem is examined. The equations constructed in the general form contain six variables per cell. The main equation for the group neutron fluxes with some approximations is analogous to the equation obtained on the basis of a finite-difference approximation of the nonstationary diffusion equation.