Using laser remote heating to simulate extreme thermal loads on nuclear fuels

International audienceUnderstanding the behaviour of nuclear fuel materials in relation to the different thermal loads to which they can be subjected, i.e. from normal operation through severe conditions, is of critical importance in the nuclear field. Experimental studies can be performed with dedicated integral experiments conducted in-pile (i.e. in Materials Testing Reactor) with the corresponding cost and constraints, or at the laboratory scale with annealing tests that can produce representative thermal conditions. In this context we are developing an experimental platform to perform annealing tests on irradiated nuclear fuel samples involving very high temperatures (up to 3000°C), with control of radial and axial thermal gradients and temporal dynamics, coupled with on line analysis of gas and fission product releases, microstructure evolution and fuel fragmentation kinetics. This experiment is based on a high power laser (1.5 kW) used to generate heat on the sample, implemented in an experimental chamber with controlled atmosphere, associated with different diagnostics. Based on the spatial beam profile and temporal power function of the laser, such a system allows producing complex spatiotemporal temperature gradients, relevant for addressing different research needs. It provides access to extreme thermal conditions that are very difficult to reach with other means. Particularly, one of the objectives of this work is to investigate conditions of Reactivity Initiated Accident (RIA)