1976/01/01 by J. K. Soldat, J.K. Soldat · 1 citation
Environmental Science · Health Professions · Engineering · #Radioactive contamination and transfer #Radioactivity and Radon Measurements #Nuclear and radioactivity studies
paper · doi:10.1097/00004032-197601000-00006
Recently, renewed attention has been drawn to 129I, a radionuclide which, because of its long half life (1.6 × 107 yr), has a potential for long-term accumulation in the environment from low level chronic releases at nuclear facilities. The transfer of 129I through the biosphere and the resultant radiation doses to man are discussed. Metabolic parameters are tabulated for four ages; 1, 4, 14 and adult. These parameters include fractional uptake via inhalation and ingestion, breathing rate, mass, radius and iodine content of the thyroid, and the energy absorbed per disintegration of 129I vs thyroid size. Factors are presented for calculation of doses from intake or concentration of 129I in the thyroid. Factors are also derived for estimating thyroid doses from 129I air concentration via the inhalation, leafy vegetable, milk or meat pathways. Analysis of the atom ratios of 129I:127I in the thyroid required to yield a dose rate of 1500 mrem/yr reveals that on this basis the adult thyroid reaches the limiting dose rate at a ratio of 1:48 (3.6 μCi 129I/g iodine). However, a higher ratio of 1:11 (15 μCi/g I) is required for the infant thyroid to receive the same dose rate. The reason for this difference is the higher stable iodine concentration in the adult thyroid (350 ppm) than in the infant thyroid (90 ppm). In all instances, however, a dose rate of 1500 mrem/yr would result from a concentration of 1.3 × 10−3 μCi 129I/g of thyroid.