B4C is the material that will be used as neutron absorber in the future ASTRID reactor. In operating conditions it will be submitted to several irradiation fields. Here we want to study solely the damage produced by neutron capture on 10B. For that purpose, neutron diffraction patterns in reflection mode will be measured on a flat B4C sample as a function of time. Thus we aim at characterizing the damage created by neutron absorption in a surface layer by the progressive changes it induces in the diffusion pattern measured at small angles. A set of a few samples with different 10B enrichment will be first tested in order to determine the best experimental conditions for this original experiment.