An algebraic collapsing acceleration in long characteristics transport theory

An acceleration technique for long characteristics discrete ordinates method is presented. The technique is based upon the developed representation of the transport sweep finite-difference operator as implicitly formulated sparse matrix operator in the space of the for the track averaged symmetrized angular fluxes. The collapsing technique is used to construct reduced sparse matrix with structure similar to block-diffusion in general case. That reduced matrix is applied to accelerate the scattering iterations. It is shown that for slab geometry case the simplest (one box collapsing) method is strictly equivalent to consistent diffusion acceleration method. Numerical results display high efficiency of the developed method (Authors)