Radiation damage production in massive cascades initiated by fusion neutrons in tungsten

Neutrons in fusion reactors produce primary radiation damage from displacement cascades in tungsten (W) at an average PKA energy of 150 keV. We find, using molecular dynamics simulations, that cascades at this energy do not break up into subcascades. The massive amount of energy concentrated in the liquid-like heat spike facilitates a fairly high rate of formation of large dislocation loops and other defect structures, of sizes readily visible in today’s electron microscopes. We investigate the structures and distribution of the cascade debris in W predicted by different interatomic potentials. In particular, our simulations show the formation of 〈100〉-type dislocation loops, in agreement with recent experiments and in contradiction to the earlier held view that only 1/2〈111〉-type loops occur in W.