New technique for in-situ tritium measurement in future fusion reactors

To establish a new technique for in-situ measurements of high-level tritium, applicability of the new measuring technique that is based on utilization of X-rays induced by β-rays from tritium was examined for three physical states of tritium such as gaseous tritium, aqueous tritium, and solid tritium retained on the surface and/or in bulk of the tritium-exposed materials in fusion reactors. It was found that the intensity of X-rays induced by β-rays was well proportional to tritium partial pressure in a mixture gas and also to tritium concentration in water in a wide range. In addition, it was seen that this technique is applicable to evaluate the amount of tritium retained in a sub-surface layer of materials and to determine a depth profile of tritium in the bulk of materials. This measuring technique was named β-ray-Induced X-ray Spectrometry (BIXS), and it was concluded that BIXS is widely applicable to in-situ measurements of high-level tritium in future fusion reactors as well as ITER. (author)