Dose-dependent irradiation embrittlement in tungsten: A predictive model based on grain plasticity mechanisms

This paper presents a radiation embrittlement model applicable to polycrystalline BCC tungsten, in the context of fusion reactor technology. BCC tungsten fracture response is temperature and dose-dependent, due to critical sub-grain plasticity mechanisms and their interaction with brittle fracture initiators. Mesoscale plasticity effects are treated using a comprehensive, close-form analytical expression, accounting for thermally activated slip and cross-slip influences. In practice, the number of slip bands generated in all the grains of a macroscopic grain aggregate is calculated first, for a given plastic strain increment. The results associated with different temperature and dose conditions are then side-by-side compared with corresponding experimental fracture toughness data up to 1100 °C. To demonstrate the predictive model capability, we successfully apply our methodology to the case of tungsten irradiated by neutrons up to 1 dpa. The proposed approach to predict the embrittlement does not use any data adjustment, is based on the SEM-EBDS microstructure of the investigated material, possesses distinctive predictive capacities and is directly applicable in support of advanced design rules to ensure safety during nuclear operation of fusion reactors.