Abstract:Fission gas release (FGR) has an extremely important influence on the thermo-mechanical behavior of a fuel element. Accurate simulation of FGR in reactors is one of the most basic contents in the development of fuel element performance analysis program, and it is also an important evaluation criterion. In this paper, we discuss the FGR behaviors in fast reactors in detail. The FGR model is based on the equations modeling the behavior of gas atoms and bubbles. The behaviors such as the generation, free diffusion, capture and re-dissolution of gas atoms in the grain are modeled in detail, and the nucleation, growth, coalescence, and migration of bubbles in the grain are simulated. Moreover, the growth, connection, channel formation, and gas release of intergranular bubbles are modeled. We develop a model for FGR calculation, using a method of numerical discrete and iteration calculation. The calculated results are compared with those of experiments and physical theories, which shows very good agreement. Therefore, the model can predict the gas release and swelling in the fuel and the concentration and size of intragranular bubbles, indicating that this model is appliable in a fuel element analysis code.
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