Proceeding of M&C2005, Sept 12-15, 2005
The subgroup method for resonance treatment is formulated for applications to nonuniform
temperature conditions which are frequently encountered in the direct whole core transport
calculation at power generating conditions. The problem of using a constant subgroup level
across the problem domain in the subgroup resonance fixed source problem is identified first
which is to obtain the heterogeneous flux distribution for a given subgroup level. A scheme to
adjust the subgroup level according to the local temperature is then proposed as a fix to the
problem. Another scheme is to use the effective fuel temperature defined for each fuel pin. The
problem of neglecting of the nonuniform temperature in the resonance fixed source problem
formulation is demonstrated with a simple 2-D pin cell problem which involves a nonuniform
temperature profile and the improvement obtained by these fixes are shown. Then the solution
accuracy of the DeCART whole core transport code in which the proposed subgroup resonance
treatment method is implemented is verified through an extensive comparison with the results of
a continuous Monte Carlo code for a wide range of problems spanning from a two-dimensional
pin cell to a three-dimensional core at both uniform and nonuniform temperature conditions.
