Placa 3D: a three-dimensional code to simulate the irradiation behaviors of Disperse/Monolithic nuclear fuel for research and test reactors

A. SOBA; A. DENIS

Bariloche

Congreso; IGORR 2014; 2014

Since 2005 the Code and Models Section of the Nuclear Fuel Cycle Department of CNEA has been working in the development of a complete tool to simulate the behaviour under irradiation of nuclear fuel plates for research reactors. The two-dimensional finite element code PLACA/DPLACA, dedicated to the simulation of the behaviour of monolithic/disperse fuel plates under irradiation was presented in the past years. A significant improvement has been recently introduced in the code which is now capable of simulating the complete three- dimensional domain involved in the research nuclear fuel. The three-dimensional code version, PLACA3D, employs the finite element method to discretize the domain. It makes possible a detailed simulation of the evolution of the more relevant physical parameters of a plate-type fuel element during its permanence within a reactor. The code contains more than thirty models, theoretical or empirical, interconnected and mutually dependent which simulate the heat and mass diffusion, stress-strain distributions in the elastic and plastic domains, fission gas generation and its effect on the volume change and the thermal conductivity of the plate core. The thermal- hydraulic behaviour of the reactor and the growth of the oxide layer on the cladding surface are taken into account to simulate the temperature distribution over the plate. The modular character of the code makes it appropriate for diverse cladding and fuel materials and designs, both monolithic and dispersed fuels. Among the latter, the code has been tuned to simulate fuels of U3Si2-Al, U-Al, UMo-Al, and UMo-AlSi. In particular, it contains models to predict the growth of the interaction layer between the UMo particles and the surrounding Al, and the swelling induced by this growth. Specific models are included for the simulation of monolithic fuels. PLACA3D was applied to simulate several irradiation histories and the results, when compared with the experimental data, evidence the correct performance of the models involved and a good coupling of the ensemble.