Proton and gamma irradiation of novel tungsten boride and carbide candidate shielding materials

Abstract

Low-activation cWC and RSBs show considerable promise as broad-spectrum radiation-dense materials suitable for use in compact spherical tokamaks (cSTs). The radiation response of novel radiation dense materials cemented tungsten carbide (cWC) and reactive sintered borides (RSBs) at ambient and non-ambient temperatures is investigated for the first time in this work.Sample irradiation consisted of 1.5 MeV protons at 408 K and at 873 K and 60Co gamma irradiation at 293 K and 77 K. Evaluation of radiation-induced damage via electron backscatter diffraction (EBSD) and TEM observed that cWCs have greater radiation attenuation than RSBs but RSBs have more diffuse dislocation distributions. Temperature at irradiation was observed to have a significant impact on dislocation presence with more diffuse dislocation presence in RSBs at 873K but with a well-defined damage front in cWCs as determined by changes in band contrast and indexing in EBSD and by dislocation presence in TEM. Dislocation presence observed to be significantly phase-dependant, particularly for cWC where the WC phase acts to absorb the bulk of radiation-induced dislocations. Both cWC and RSBs demonstrated significant γ-ray attenuation at 77 K with most radiation-induced changes confined to the top 25 µm from the incident face.