Study of tissue free water tritium and tissue bound tritium in neem tree leaves (Azadirachta indica) around Madras Atomic Power Station, Kalpakkam

Tritium, one of the isotopes of hydrogen, is a pure beta emitter and is released as HTO through 100 metre stack during the operation of Madras Atomic Power Station at Kalpakkam, located in Tamilnadu state. Depending on the proximity and wind direction, the released tritium activity in the atmosphere gradually decreases with distance due to dilution and dispersion and has the ability to exchange with nearby surface soil water, vegetation etc. In the vegetation, tritium is present in two forms namely Tissue Free Water Tritium (TFWT) and Tissue Bound Tritium (TBT). This paper presents the level of TFWT and TBT in the neem tree leaves (Azadirachta indica) of Kalpakkam. Specific activity ratio (SAR) of TBT and TFWT for neem tree leaves was computed and is presented in this paper. It was mainly observed in the present study that high tritium activity in ground water plays a major role for the contribution of TBT. It was observed that SAR was greater than unity in a location where the ground water tritium was comparatively higher than atmospheric tritium, which may be due to dynamic tritium environment in both ground water as well as in atmosphere. In other locations where there was less or negligible tritium activity in the ground water, the observed SAR was less than 1 irrespective of atmospheric moisture tritium. (author)