Changes in structure of the surface and edges of beryllium plates as a result of thermal cycling tests

•TGP-56 beryllium has a high resource durability for operation under conditions of heat exposure in ITER.•The “normal” and “increased” heat flux in ITER will not have a critical effect on the destruction of the edges of beryllium.•In the normal operation mode of ITER (2.0–4.7 MW) the edges of beryllium have good resistance to heat load.•The large-scale changes in the structure and shape of the surface occur at a maximum temperature of ∼ 1200 °C. In this paper, experiments were conducted on the thermal effect of an electron beam on beryllium of the TGP-56 grade in vacuum, at the values of the surface temperature of beryllium ∼360, ∼800 and ∼1200 °C with the number of pulses 10 and 100 with the same pulse duration – 500 s. A complex of material research such as microanalysis, x-ray diffraction analysis, determination of microhardness was conducted. The experimental data on changes in mechanical properties and melting conditions of beryllium at the boundary between gaps of the plates of the ITER first wall as a result of heat loads were obtained. It was found that in the normal operation mode of ITER (2.0–4.7 MW) the edges of beryllium have good resistance to spraying. Under critical conditions, closer to the melting point, beryllium is strongly sprayed.