COMPARISON OF PANTHER NODAL SOLUTIONS IN HEXAGONAL-Z GEOMETRY

The reactor physics code PANTHER has been extended to hexagonal geomet ries. Steady-state, depletion, and transient calculations with feedbac k can all be performed. Two hexagonal nodal flux solutions have been d eveloped. In the first method, transverse integration is performed exa ctly as in the rectangular case. The resulting transverse integrated e quation has singular terms, which are simply ignored. The second appro ach applies a conformal mapping that transforms the hexagon onto a rec tangle. Pin power reconstruction has also been developed with both met hods. For a benchmark VVER-1000 reactor depletion problem, both method s give accurate results for standard depletion calculations. In the mo re extreme situation with all rods inserted, the simpler method breaks down. However, the accuracy of the conformal solution was found to be excellent in all cases studied.