Synthesis of unknowns for the interface partial current method

A synthesis technique is formulated as an alternative for the standard solution of the low order Interface Partial Current Equations, common in the within-group iteration schemes of Nodal Expansion and Response Matrix methods. This non-linear technique represents each node (mesh) in the iterations by its total partial in-current aiR), instead of the K partial in-currents at the nodal faces. At the same time, the distribution vectorf is introduced, whose elements are the fractions of jin entering through each face, which are assumed known from the previous fission-source iteration. This simple scheme, with no other non-linear feedback required, gives a nodal formulation of the inner problem with one unknown per node and energy group, while the problem still retains the original number of unknowns. The method has been tested on the IAEA-2D and -3D, and a 2D pressurized water reactor (Biblis) benchmarks. The results show savings of about 15% to 25 % of the CPU time, identical convergence despite the irregular nodal discretizations, and compatibility to the rest of the iteration strategy.