Diffusion kinetics of gaseous fission products arising under uranium fuel irradiation

A physical mechanism underlying the diffusion migration of gaseous fission products near the triple joints of grain boundaries during nuclear fuel burnout is suggested and mathematically substantiated. The diffusion kinetics is analyzed with regard to the first invariant of the stress tensor for a given structural defect. The results of mathematical simulation are of interest for analysis of nuclear fuel swelling due to the growth of intergranular pores and formation of channels for fission product migration along the grain boundaries.