Transport and Release of Radioactive Fission Products in Nuclear Fuels: The New Analytical Method of the MITRA Code

The transport and release of radioactive fission products in nuclear fuels are described with detailed reaction-rate equations including intragranular precipitation, radiation re-solution, biased diffusion, and nuclear transmutations. An analytical procedure is found to solve these equations that makes it possible to calculate the release and redistribution of the radionuclides with greater accuracy and with much more speed than conventional numerical methods. The method was implemented in the computer code MITRA for the calculation of the radionuclide behavior during stationary and nonstationary reactor operating conditions. The structure of this code is described, and recalculations of experiments are presented. The analytical solutions of the rate equations are reported in the Appendix.