Tight-binding Theory Study on the First Wall Material Tungsten in Fusion Reactor

In order to study the structural evolution and thermodynamic properties of the first wall material tungsten (W) in electronic excited state during irradiation, the physical properties of W in fusion reactors were studied theoretically by using tight-binding potential model. It is found that the electronic excitation induced by the irradiation of energetic particles leads to the events such as spontaneous appearance of micro-voids, sharp expansion of the lattice, and decrease in the melting point of the irradiated regions in W. Specifically, the lattice expansion of W is mainly driven by lattice temperature under the medium temperatures (~5 000 K). But the lattice expansion effect caused by electronic temperature cannot be ignored at the higher temperatures. Especially when the electronic temperature is rather high (>10 000 K), the electronic temperature will cause a large degree of lattice expansion, even if the lattice temperature is low for the irradiated regions. These findings bring benefit to gain deep understanding in the physical performance of W in fusion reactors during service.