Heavy Water Release Experiments in a Greenhouse : Translocation of Deuterium into Unhulled Rice and Its Loss during Growth Process of Rice

Abstract

Among the chemical forms of tritium released in the environment, tritiated water (HTO) has a very high contribution to the dose. But, the dose due to organically bound tritium (OBT) is 2.3 times higher than that due to HTO. Heavy water (D₂O) vapor release experiments were carried out in a greenhouse using D₂O as a substitute for HTO and uptake and loss kinetics of D₂O in leaves and formation, translocation and retention of organically bound deuterium (OBD) in rice were investigated using different growth process of rice. Rate constants of D₂O uptake in leaves of rice plant in the daytime and nighttime release, rate constants and the half time of D₂O loss in leaves after release were determined. After D₂O release, OBD concentration in unhulled rice increased gradually until 4 days after the exposure and then decreased with time due to metabolic consumption in rice grain. [J Radiat Res 44:432 (2003)]