Recent Developments of Lattice Physics Code STREAM

Three new advanced features have been implemented in the lattice physics code STREAM for higher accuracy and performance in the analyses of Light water reactors (LWRs). First, In this paper, the RIF library has been extended to include more isotopes to analyze a variety of fuel types including UO₂ and MOX fuels. With the application of the new RIF library and method to the UO₂ and MOX pin depletion problems, STREAM shows reactivity errors of less than 80 pcm at all burnup steps. Second, the inflow transport approximation has been implemented. In LWRs analyses, the anisotropic scattering effect is generally treated by the transport corrected cross section (XS) with an isotropic scattering approximation. Therefore, a more rigorous inflow transport correction method is implemented in order to mitigate this problem. Three new advanced features are implemented in the lattice physics code STREAM. STREAM with the upgraded RIF library can analyze both of UO₂ and MOX fuel depletion problems with errors less than 80 pcm for all burnup steps. The inflow transport approximation and high order scattering model make it possible to treat highly anisotropic scattering accurately. The results from the inflow transport approximation and high order scattering treatment are accurate and consistent each other