Transformation laws for probabilities in the interface current method and its application to cluster geometry

In the collision-probability (CP) method, the calculation of probabilities by numerical methods is very expensive. Within the generalized CP formulation, Takahashi (1966) derived the transformation law between the generalized first-flight CPs in two geometrically identical systems with different cross-sections. Its potential for the real reactor problems has not yet been demonstrated. In this paper, we derive a similar transformation law for the various probabilities within the interface current formulation. We then apply these relations in the burnup calculations for a pressurized heavy-water reactor (PHWR) lattice cell. It is shown that these calculations represent an ideal example for the application of these transformation laws.