Nodal interpolation of surface flux and current distributions

An interpolation scheme is introduced for use in deriving local flux and current distributions in light water reactor calculations. It is developed as a consistent extension of the nodal method and is used in conjunction with this approach. Standard nodal quantities of surface and node averaged fluxes can be interpolated, leading to a complete distribution with little further loss of accuracy. This is the case even in the harsh environment found in two group calculaions at one node per assembly. A second application is in the interpolation of surface currents during a nodal calculation. This requires the explicit modelling of some known asymptotic behaviour but the effect is a considerable improvement in the transverse leakage approximation and thus in the accuracy of the nodal flux values and the reactor eigenvalue