Practical environment-corrected discontinuity factors and homogenized parameters for improved PT-SCWR neutron diffusion solutions

Abstract

A novel application of practical discontinuity factors in coarse-mesh finite-difference solutions of heterogeneous multi cells with Pressure Tube Supercritical Water-cooled Reactor (PT-SCWR) type fuel and moderator cells has been investigated. In addition to discontinuity factors, homogenization schemes have also been studied and applied to reflector-adjacent-fuel cells and reflector cells. A 49 node inner-core multi cell model containing only fuel and a 40 node outer-core multi cell model containing reflector and fuel cells were simulated. In addition to nominal conditions, various discontinuity factors and homogenization techniques, along with conventional techniques, were applied to static beyond-nominal condition scenarios to evaluate the error associated with neutron power changes from nominal conditions, relative to reference transport solutions. The use of novel mean reference discontinuity factors and environment homogenized reflector-adjacent-fuel cells, over conventional methods, reduces core-wide reactivity errors, RMS neutron power errors, and maximum channel specific power errors by up to 2.6mk, 2.9%, and 6.7%, respectively.