Material testing nuclear reactors, which allow materials to be subjected to neutron irradiation, have very high power densities. This requires the use of fuel elements with a very high load of fissile material, historically obtained thanks to high enrichment in 235U. Due to international non-proliferation agreements, it is now necessary to develop less enriched fuels, and therefore maximizing the uranium concentration. A solution mainly adopted and studied is based on U3Si2 particles dispersed in an aluminum matrix. However, under irradiation, an interaction compound U(Al,Si)3±x is formed. Its low thermal conductivity tends to increase the temperature of the fuel, thus degrading its behavior in service.
The objective of this thesis is to improve experimental knowledge of the evolution of the thermal conductivity of dispersed U3Si2-Al fuels during their irradiation, and ultimately to correlate their microstructure to their thermal properties, which will be measured at different scales. Non-irradiated U3Si2-Al plates will be subjected to heat treatments intended to obtain variable fractions of U(Al,Si)3±x compound and their thermal properties will be measured and correlated to the fraction and volume distribution of this compound. A specific study will also be carried out around the synthesis and measurement of the thermal properties of amorphous U(Al,Si)3±x compounds, as observed in reactor.
The data acquired during this thesis will feed the modeling of the behavior of dispersed U3Si2-Al fuels Under irradiation: they will serve as validation data for the models and calculation codes.
This work will be performed at the Fuel Research Department (IRESNE institute, CEA Cadarache). It will allow the doctoral student to acquire skills in the manufacturing and characterization of fuels (microstructure and thermal properties), which will be transposable to other materials. He (she) will also have to use “heavy” experimental devices such as synchrotron beamlines and ion beams. He/she will have the opportunity to present his/her work at national and international conferences, as well as through the publication of articles.