A Test of Main Stream Pin Power Reconstruction Methods

Preliminary to implementing a pin power reconstruction scheme in the nodal core calculations of the ELCOS system, the “main stream” methods and elements thereof were tested against fine-mesh calculations of a number of benchmark “small cores” consisting of uranium, controlled uranium, and mixed-oxide assemblies. Overall, the results do not clearly favor one of the methods. However, test details conduce us to prefer the 32-term expansion for corner-point fluxes over their determination by the separability assumption, and the 21-term expansion of the intranodal flux over the 13-term expansion. There is little difference whether the factorization of the pin power distribution into global and form factors is imposed on the group fluxes or on the power. Data transfers and matrix inversions connected with the many-term flux expansions slow down the nodal calculation. This condition may be alleviated in some cases by an approximation leading to fewer matrix inversions.