Studies on 129I in bovine thyroid glands and investigations on revolatilization of iodine

In order to study fall out effect, deposition and revolatilization of iodine in the field and 129I activity in bovine thyroid glands were studied. Deposition velocity of I2 was 0.15 to 7 cm/sec, which was 100 times higher than that of CH3I. Biological half-life of iodine was 7.5 +- 0.5 d. In the contaminated plants, indifferent to the environmental conditions. However, the decrease of iodine concentration was not observed when the plants were cut off immediately after deposition of iodine. A sample of soil with or without plants was contaminated with iodine and re-emitted iodine was trapped by a charcoal filter. Iodine concentration was determined by I-specific electrodes after 1, 2, 4, and 8 hrs. In any case, I2 was re-emitted immediately after the contamination. Bovine thyroid glands were dried by deep freezing and ground after the addition of KOH. Organic compounds were decomposed by stepwise heating up to 6000C. Then iodine was extracted by concentrated H2SO4 and heated at 1100C. Evaporating iodine was adsorbed by a pure charcoal filter. By neutron activation analysis of the filter the activity of 129I was 1.2 pCi/g iodine, which would be about 5 times higher than that measured in animals living far from nuclear installations. The distribution of stable iodine in thyroid gland was inhomogeneous. (Nakanishi, T.)