Fission gas release and swelling model of metallic fast reactor fuel

A mechanistic model of fission gas release and swelling for the U-Pu-10Zr m etallic fuel in a fast reactor, GRSIS (Gas Release and Swelling in ISotropi c fuel matrix), was developed. Fission gas bubbles are assumed to nucleate isotropically from gas atoms in the metallic fuel matrix since they could n ucleate at both the grain boundaries and the phase boundaries, which are ra ndomly distributed inside the grain. Bubbles can grow to larger sizes by ga s atom diffusion and coalescence with other bubbles. When bubble density or swelling due to bubbles reaches a threshold value, bubbles are assumed to be interconnected to each other to form an open channel to the external fre e space and then the fission gases inside the interconnected open bubbles a re released instantaneously. During the irradiation, fission gases are succ essively released through the open bubbles. The GRSIS model was validated b y comparison with the irradiation test results of U-Pu-10Zr fuels as well a s parametric studies of the key variables in the model. (C) 2001 Elsevier S cience B.V. All rights reserved.