Extension of KIN3D, a kinetics capability of VARIANT, for modeling fast transients in accelerator driven systems

The time-dependent second-order PN equation is discretized by a fully implicit finite-difference scheme; the obtained pseudo-steady-state PN equations are then used in the framework of the Variational Nodal Method (VNM). This scheme is implemented in the VARIANT/KIN3D code. A new code option is presented that takes in account neutron wave phenomena The code has been validated for a very simple case against an analytic solution; other simple tests are performed in order to investigate differences compared to the original version of KIN3D/VARIANT. (authors)