FASTRAN. A computercode for the analysis of recriticality accidents

The code FASTRAN is appropriate for the analysis of recriticality accidents caused by the loss of control rods after a successful shut down of a fast reactor. FASTRAN bases on a factorization method and has an option to use time dependent shape factors. The shape factors as well as the reactivity are calculated by a discretization scheme basing on the mesh grid which may be distorted by the hydrodynamic displacement of the core material. This method permits the direct calculation of the reactivity. Therefore the interaction of outer reactivity, Doppler reactivity and disassembly reactivity is taken correctly into consideration. It is shown on examples that the introduction of time dependent shape factors may considerably improve the results