Characterization of Tritium Retention in Plasma Sprayed B_4C/Mo Coatings

Quantification of the amount and depth of tritium retained on plasma facing materials(PFMs) surface is of great importance for selecting PFMs with high safety in the nuclear system. In the present study, potential PFMs of B4 C/Mo coatings were prepared and the depth profiles of tritium in the coatings were measured both by imaging plate(IP) technique and β-ray induced X-ray spectrometry(BIXS). The IP images showed that the amount of adsorbed tritium in the coatings followed the order of B4 C BM15 BM5 Mo, which was along with the X-ray spectra also illustrating that most tritium penetrated into the bulk of the B4 C coating while on the surface only for the other three coatings. The cross-sectional morphologies of the coatings were observed by scanning electron microscope(SEM), which demonstrated that B4 C coatings had the highest porosity while the other three coatings were denser despite of the existence of smaller-sized pores and cracks. All the results suggest that pores and microcracks in the as-sprayed coatings provide passageway for tritium penetration and adsorption, which are the key factors that affect the amount of tritium adsorbed. Furthermore, the content of Ti contamination in the coatings also plays an important role in controlling tritium adsorption.