Measuring the tritium concentration in the chamber wall of the thermonuclear reactor in the processes of its saturation and decontamination

Abstract

Diffusion of hydrogen isotopes in metals with a polycrystalline structure is investigated. The dif fusion conditions in stainless steel are analyzed as applied to the ITER operating conditions. The technolog ical regimes with the tritium propagation through the wall of the vacuum chamber are considered. It has been established that, in the expected reactor cycle, tritium permeates into the layer with a thickness much smaller than the thickness of the chamber wall. According to the experimental results of thermal decontamination of stainless steel samples (with the saturated thin tritium layer), the tritium inventory in a sample decreases in two phases. As a result, it is possible to monitor (by continuously measuring the tritium concentration in the reactor chamber) the process of chamber decontamination. In this case, it is expected that the effective depth of tritium permeation into the chamber wall in reactor cycles will be limited. It is proposed that the diffusion migration depth of tritium will be diagnosed by the time of occurrence of the velocity kink phase in the out going tritium flux in order to finish decontamination in the proper time or introduce new methods for limiting diffusion of tritium toward the exterior wall to avoid its leakage into the environment.