The noble gases helium, krypton and xenon are generated or implanted in many materials employed in or developed for fission or fusion nuclear reactors (e.g. UO2, neutron absorbers, high-level waste matrices, etc.). Taking the example of the usual fission nuclear fuel UO2, the in-pile generation of noble gases is greatly responsible for the unfavorable microstructure and thermal properties...
Atomistic modelling of materials is typically achieved by using Molecular Dynamics (MD). However, due to the fact that MD needs to resolve atomic vibrations, a very large number of small time steps are needed and the total simulation time is therefore often limited to less than one microsecond. The timescale limitation can be overcome by using Adaptive Kinetic Monte Carlo (AKMC) methods....
This work discusses advances in phase-field modelling of multiphase nuclear materials with a focus on incorporating bulk equilibrium thermodynamics and interfacial phenomena. Tools have been developed for the automated construction of explicit multiphase, temperature dependent composite potentials from those of the pure phases obtained from CALPHAD-type databases. The interfacial energy is...
A combination of materials modelling techniques and targeted experimental investigations have identified the manner in which non-stoichiometry is accommodated in both crystalline and amorphous ZrO$_2$. Not only is excess oxygen possible in both crystalline and amorphous ZrO$_2$, but it is found that there is a high propensity for significant deviations–especially in the amorphous...
Advanced Generation-IV nuclear reactors, which should excel in the areas of sustainability, economics, safety & reliability and proliferation resistance, are currently being developed to replace the Light Water Reactors (LWRs) at the end of their operating licenses. Among the various designs selected by the Generation-IV International Forum, research has been focused in Europe on fast neutron...
Abstract: Fuel performance modeling and analysis plays an important role in fuel design and performance optimization, especially accurate fuel rod modeling and analysis in 3D. Fuel thermal behaviors are very complex and are strongly coupled with other factors. For example, with the increase of burnup, fuel thermal conductivity decreases which further increases the pellet central temperature,...
For the future Sodium-cooled Fast Reactors, uranium-plutonium mixed dioxide (U,Pu)O2-x, with the plutonium content ranging between 19 to 40 mol.%, is foreseen as potential fuel. The pellets have to match various physico-chemical specifications: physical integrity, chemical homogeneity, to be oxygen hypostoichiometric (Oxygen/Metal ratio included in 1.94 and 1.99 range). However, for a Pu...
Under irradiation in nuclear reactors, the microstructure of oxide nuclear fuel changes. To improve the modeling of the UO2 fuel behavior under irradiation, it is necessary to understand the elementary mechanisms of fission products diffusion. Among them, rare gas Xenon and Krypton represent 30% of created elements moreover fission products such as Iodine and Caesium are corrosive for the...
Uranium dioxide (UO$_2$) is an important industrial material which is employed as a fuel in most nuclear reactors world-wide. The doping of UO$_2$ with small amounts of chromium oxide Cr$_2$O$_3$ is technically applied to obtain a larger average grain size after the fuel sintering process. In this study the local environment of chromium in UO$_2$ was investigated using X-ray absorption...
Uranium mononitride (UN) has been considered a potential accident tolerant fuel (ATF) mainly because its high uranium density, high melting point, and high thermal conductivity. Composite fuels like UN-UO2 have been proposed so as to combine the good properties of both fuels. This study is focused on analysing the first results regarding the sintering behaviours and the microstructures of an...
The thermodynamic modelling of the U-Pu-Am-O system is proposed by using the CALPHAD method. The aim is to provide basic thermodynamic data (melting temperature, heat capacity …) on the (U,Pu,Am)O2 mixed oxide fuel to be used as input data in Fuel Performance Codes. In 2011, a CALPHAD model was developed in the TAF-ID database. An update of some of the binary and ternary sub-systems is...
