Radionuclide prediction

The retention of radionuclides within the containment was little accounted for by the RSS, but ranges from little to very substantial because of agglomeration and deposition. This leads to a large over prediction of the iodine risk, but substantial agreement with RSS for some other isotopes. 

For any given radionuclide, the rate of decay is a first-order process that is constant, regardless of the radioactive atoms present and is characteristic for each radionuclide. The process of decay is a series of random events temperature, pressure, or chemical combinations do not effect the rate of decay. While it may not be possible to predict exactly which atom is going to undergo transformation at any given time, it is possible to predict, on average, the fraction of the radioactive atoms that will transform during any interval of time. 

Pb-210 and the Cosmogenic Radionuclides. We noted earlier that our measurements of Pb-214 were really measurements of Po-214 decay, that is, the production of Pb-210. The mean AMAD of these measurements was about 0.16 um, with the AMAD of Pb-210 predicted to be 0.18 um after recoil. However, the summer AMAD of Pb-210, after aging in the atmosphere for about a week (Moore et al., 1980), was closer to 0.4 um, indicating that Pb-210 s AMAD approximately doubles during its lifetime in the atmosphere. The limited measurements reported here suggest that the AMAD of Pb-210 is smaller in winter than summer, possibly reflecting differences in aerosol growth rates. The summer measurements were also not different from simultaneous SoJ measurements. 

The vertical scavenging model also allows one to predict the distribution of particulate radionuclide profiles. Following Craig et al. [53] the particulate phase activity would be given by the solution of the equation ... 

Zavitkovski, J. and T.D. Rudolph. 1971. Predicted effects of chronic gamma irradiation of northern forest communities. Pages 1007-1014 in D.J. Nelson (ed.). Radionuclides in Ecosystems. Proceedings of the Third National Symposium on Radioecology. May 10-12, 1971, Oak Ridge, TN. Vol. 1. Available from Natl. Tech. Infor. Serv., Springfield, VA 22151. 

Hydrolysis. NMR results show that TBT carboxylates undergo fast chemical exchange. Even the interfacial reaction between TBT carboxylates and chloride is shown to be extremely fast. The hydrolysis is thus not likely to be a rate determining step. Since the diffusivity of water in the matrix is expected to be much greater than that of TBTO, a hydrolytic equilibrium between the tributyltin carboxylate polymer and TBTO will always exist. As the mobile species produced diffuses out, the hydrolysis proceeds at a concentration-dependent rate. Godbee and Joy have developed a model to describe a similar situation in predicting the leacha-bility of radionuclides from cementitious grouts (15). Based on their equation, the rate of release of tin from the surface is ... 

The level of radioactive contamination in the forest can be much higher than in open country (up to 10 times greater), but the density of radionuelide at forest ground level is very variable, because of the tree stands. Cs ground deposition in the zone affected by the Chernobyl aeeident ean vary up to 50 fold. This variability makes it difficult to predict the speeifie aetivity of radionuclides in particular components of the forest ecosystem, and forces a probabilistic approach. 

Disposal of spent nuclear fuel and other radioactive wastes in the subsurface and assessment of the hazards associated with the potential release of these contaminants into the environment require knowledge of radionuclide geochemistry. Plutonium (Pu), for example, exhibits complex environmental chemistry understanding the mechanism of Pu oxidation and subsequent reduction, particularly by Mn-bearing minerals, is of major importance for predicting the fate of Pu in the subsurface. 

Gomes JA, Winters SL, Stewart D, Horowitz S, Milner M, Barreca P. A new noninvasive index to predict sustained ventricular tachycardia and sudden death in the first year after myocardial infarction based on signal-averaged electrocardiogram, radionuclide ejection fraction and Holter monitoring. J. Am. Coll. Cardiol. 1987 10 349-57. 

The dose of radiation delivered by an internally deposited radionuclide depends on the quantity of radioactive material residing in situ. This quantity decreases as a function of the physical half-life of the radionuclide and the rate at which the element is redistributed or excreted (i.e., its biological half-life). Because the physical half-life is known precisely and the biological half-life can be characterized within limits for most radionuclides, the dose to a tissue that will ultimately be delivered by a given concentration of a radionuclide deposited therein can be predicted to a first approximation. The collective dose to a population that will be delivered by the radionuclide—the so-called collective dose commitment—serves as the basis for assessing the relevant long-term health effects of the nuclide. 

Metabolically, radionuclides are handled in the same way as stable elements of the same atomic numher. Thus radioactive iodine simulates stable iodine, being concentrated in the thyroid gland so predictably that its rate of uptake provides an accurate measure of thyroid function. The metabolism of other radionuclides also is sufficiently characteristic so that their patterns of uptake, distribution, translocation, and excretion are similarly predictable. 

Figure 9.5 compares the abundance ratios of short-lived radionuclides in the early solar system to the abundance ratios predicted by a standard model for galactic chemical... 

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