Relative abundance of HT and HTO in the accelerator tunnel air and atmospheric air

The relative abundance of tritiated-airborne species was studied for the air of the beam-line tunnel at high-energy accelerators as well as atmospheric air. The tritium produced via nuclear spallation reactions in the accelerator-tunnel air exists in the chemical forms of HTO and HT. The HT-to-HTO ratio was about 2 x 10-2 on the average, being appreciably smaller than that in atmospheric air. The reaction mechanisms of accelerator-produced tritiums were discussed on the basis of the similarity to the reactions by cosmic-generated tritium. HT is likely to be formed directly through the reaction of a recoiling tritium with H2O. On the other hand, the HT-to-HTO ratio for the present atmospheric air indicates that tritium distributions have been largely modified by the release of man-made tritium into the air. (author)