Examination of tritium retention in boron-coated graphite by β-ray-induced X-ray spectrometry

Tritium retention in boron-coated graphite (B/Graphite) irradiated with tritium ions at room temperature and at higher temperatures was examined by β-ray-induced X-ray spectrometry (BIXS). The results of analyses by X-ray diffraction and X-ray photoelectron spectroscopy for an unirradiated sample suggested that boron coated on the graphite surface formed an amorphous structure and that it contained impurities such oxygen and carbon. Both a sharp intense peak and a broad weak peak induced by β-rays appeared in the observed X-ray spectra. It was seen from the X-ray spectra that most of tritium implanted into the B/Graphite at room temperature was retained on the surface and in subsurface layers. In addition, it was seen that the implanted tritium can be easily removed at a relatively low temperature and that the retention amount decreased to 1/3 by heating at 300degC for 30 min. However, a considerable increase in tritium retention was observed when the irradiation temperature was increased to more than 300degC, indicating adsorption of tritium on the bare surface of graphite. (author)