Polish experience with application of the RSYST modular system

The higher requirement in both safety operation and optimal fuel management requires that more accurate computing techniques must be used in reactor analysis. The gadolinium bearing or high enriched fuel or tight fuel lattice needs more detailed treatment. The code which can be used successfully in analyses of the non-standard fuel lattices is the modular system RSYST. With RSYST the case dependent multigroup microscopic cross section library can be generated and the transport, diffusion and burnup calculations can be performed. The fact that RSYST is able to create its own microscopic library requires that the real material composition and geometry as well as the heterogeneous structure and overlapping of resonance for defined fuel lattice are taken into account. This means that the library is always adequate to the fuel lattice under consideration. In this paper the results of two benchmark problems are analysed: the Arkuszweski benchmark problem for square lattice with gadolinium bearing fuel and the Sidorenko benchmark problem for hexagonal fuel lattice with gadolinium as a burnable poison. 12 refs, 2 figs, 7 tabs