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The limits on tritium inventory in the vacuum vessel and the need for prevention of impurity ingress into plasma make plasma-surface interaction on tungsten an important issue. It is well known that plasma exposure on tungsten makes some kinds of blisters on the surface and increases the hydrogen inventory. O n the other hands, there is a possibility that plasma exposure would change the characteristic of surface and surface region in tungsten and cause the increase of tritium inventory. To understand the change of tritium inventory in the surface region and surface in tungsten by plasma exposure, tritium concentration in tungsten exposure by low-energy (3 8eV), high-flux D plasma with was examined with BIXS after thermal exposure of tritium gas. D plasma exposure was carried out at specimen temperature around 495 and 550K. After that, specimens were exposed to gaseous tritium diluted with deuterium at 473K for 3 hours. The tritium concentration was measured with BIXS. The tritium concentration in surface and surface region was found to be increased by plasma exposure. And its concentration of tungsten exposed at 495K was estimated to be twice higher than that of as-received tungsten.