ALL RIGHTS RESERVED iii ABSTRACT Ghassan Badri Hamra: Bayesian methods for the evaluation of Tritium: Relative Biological Effectiveness and cancer risk. Tritium is a radioisotope of hydrogen that releases -energy, which is a form of ionizing radiation. Tritium is understudied due to a lack of epidemiological data on human exposure, despite the fact that exposure to low energy ionizing radiatio...

Previous experiments have shown that tritium is produced in deuterated titanium. To better define the phenomenon a series of tests have been performed using various metals and alloys and different deuterating conditions. Sheets and shavings of titanium, zirconium, hafnium, tantalum, Zircaloy 2 and Ti-Zr 50% alloy have been tested. A statistical analysis of the tritium production shows that sign...

A method of general tritium labeling is described which is applicable to a broad range of organic compounds of biological interest, including amino acids, peptides, and proteins. The method is rapid, inexpensive, and nondestructive, thereby making the purification of labeled material relatively uncomplicated. The reaction apparatus consists of a closed system in which tritium gas at a pressure ...

Tritium from methyl-H(3)-thymidine was found to be incorporated into proteins in mice. This incorporation in the mouse as a whole represented between 1 and 10% of the injected tritium. Tritiated water was not an intermediate. Transmethylation reactions are proposed as a means whereby certain amino acids might have acquired the tritium from thymidine at some stage of its catabolism. The initial ...

The major pathway of testosterone oxidation by human liver microsomes is the formation of 6beta-hydroxytestosterone, which is catalyzed by CYP3A4/5 and which accounts for 75-80% of all metabolites formed. In the present study, we describe a non-high pressure liquid chromatography assay (HPLC) of CYP3A4/5 activity based on the release of tritium (with formation of tritiated water) upon incubatio...

An estimate of the diffusion loss of tritium from iron meteorites in space cannot be based, in a direct manner, on the results of diffusion measurements in the laboratory, because the hydrogen content of the samples in the laboratory is always higher by many orders of magnitude than is the tritium content of iron meteorites in space, which results f rom bombardement by cosmic rays. This is true...

Retardation of tritium migration in the Chinese loess media was studied through column experiments by comparison of the migration velocity with other three “non-adsorptive” tracers of Br, Tc, and I. Results showed that the transport peak of Br was 1.25 times earlier than that of tritium when the tracers were simultaneously injected into the column, and the migration of Tc was even 1.60 times fa...

An unavoidable category of molecular species in large-scale tritium applications, such as nuclear fusion, are tritium-substituted hydrocarbons, which form by radiochemical reactions the presence (circulating) and carbon (mainly from steel vessels tubing). Tritium-substituted methane species, CQ4 (with Q = H,D,T), often precursor for higher-order reaction chains, thus particular interest. Here w...

Isotopic fractionation of tritium is a highly relevant issue in radiation protection and requires certain radioecological considerations. Sound evaluation of this factor is indeed necessary to determine whether environmental compartments are enriched/depleted in tritium or if tritium is, on the contrary, isotopically well-distributed in a given system. The ubiquity of tritium and the standard a...

Environmental releases of tritium oxide at a number of Department of Energy nuclear weapons facilities contribute to a significant portion of environmental dose. Several conversion factors are utilized in the estimation of human impact from these releases, e.g., dispersion coefficients, consumption rates, uptake factors, transport factors, dose conversion factors, and risk coefficients. A proba...