Some peculiar features for kinetics of fission gas release from nuclear fuel on fast heating up

This paper presents studies of some anomalies observed in kinetics of fission products based on the model of porous fuel. A nonmonotone two-peak structure of a fission product flux is shown to be determined by the effect of the system of open pores. It has been established that on heating, an explosive growth of a flux in the region of relatively high temperatures is associated with a high nonlinearity of the time dependence of phenomenological parameters describing a fission gas release from a solid phase. The analysis has been performed. of the processes accompanying a decay of a fission product solid solution. The possibility of a fuel material dispersion has been noted under the conditions of a fast reactivity accident due to a sharp rise of the gas phase pressure in the system of closed pores.