In order to estimate the internal exposure dose in an experiment using tritiated thymidine, the rate of volatile3H-decomposition of several tritiated thymidine samples was measured. The decomposition rate of [methyl-3H] thymidine in water was over 80% in less than one year after initial analysis. [methyl-3H] thymidine was decomposed into volatile and non-volatile3H-decomposition products. The ratio of volatile3H-decomposition products increased with increasing the rate of the decomposition of [methyl-3H] thymidine. The volatile3H-decomposition products consisted of two components, of which the main component was tritiated water. Internal exposure dose caused by the inhalation of such volatile3H-decomposition products of [methyl-3H] thymidine was assumed to be several μSv.
Three kinds of charcoal (LH2C20/48, WH5C8/32 and X-7100-3), three kinds of ion exchange resin (DE52, MB5113J and RG501 /X8), and one metal chelater (MC75) were tested for their ability to remove [α-32P] dCTP as a standard RI using a small column system. The most efficient absorber was DE52. However, DE52 was not suitable for practical treatment of the waste because flow rate was slow. LH2C20/48, WH5C8/32 and MB5113J also showed high absorption ability and their absorption efficiency was not affected by a pH range from 5 to 9 of the solution. On the basis of this result, a practical trial of the radioisotope waste treatment was also made. It was concluded that among the tested absorbents MB5113J was the most applicable for removing32P-labeled nucleotides from experimental waste.