[en] Subassembly scale motion during the early fuel dispersal and extended fuel motion phases of an LMFBR loss of flow accident are examined with the SIMMER-II code. Results are compared and contrasted with previous analyses and selected experiments. The early fuel motion with a SIMMER-II model is calculated with the results given by the SLUMPY module of the SAS3A code. SLUMPY may greatly overpredict the extent and magnitude of fuel motion on the time scale of interest using the nominal SLUMPY parameters. By comparing with pin geometry fuel freezing experiments, SIMMER-II is calibrated to calculate the experimental fuel penetration distances