Nondestructive Measuring Technique of Tritium Retained On/in Plasma-Facing Materials

Dynamic behavior of tritium implanted into Ni-based alloys (Inconel, Hastelloy and Monel) was nondestructively examined by β-ray-induced X-ray spectrometry (BIXS) at room temperature. The observed X-ray spectra consisted of several sharp characteristic X-ray peaks and a broad bremsstrahlung X-ray peak. It was seen that the normalized intensity of the former X-ray peaks corresponded well to each composition of constituent elements in the alloy. Changes in intensity and shape of X-ray spectra observed at room temperature for a long time suggested that most of the implanted tritium was strongly trapped in the surface layers and it was gradually released from the surface with little diffusion into the bulk. This was also confirmed by change in depth profiles determined from computational analyses of the observed X-ray spectra. Such tritium behavior was interpreted by the formation of metallic oxides on the surface of the alloys.