Development of advanced nodal methods for hexagonal geometry reactors

It is proposed to develop a multigroup, three-dimensional nodal neutron diffusion method for hexagonal geometry reactors. The proposed method differs from all existing hexagonal nodal diffusion methods by its use of net currents rather than partial currents and differs from all but one by its use of a local analytical solution rather than a polynomial approach. These two differences are expected to yield a faster, more accurate method that is easily vectorizable and concurrency capable. The method will treat feedback and depletion induced homogeneities explicitly via in-node variable cross sections. It will also incorporate discontinuity factors and thermal hydraulic feedback via coupling to a newly developed semi-analytical thermal-hydraulic code. The use of a tight coupling algorithm will allow the method to treat transients very efficiently. The research will also include the development of a hexagonal geometry, burnup-corrected, depletion method. The issue of compatibility of the variable cross section methods (and of kinetic feedback) with current formulations of the equivalence theory will be addressed and a resolution of the issue sought