Characterization of a military training site containing 232Thorium

Contamination Measurements from Simultaneous Activated Potassium Bromide Radiological Dispersal Devices with a Collimated Vehicular Sensor

ABSTRACT

Surface contamination was quantified over a distributed source of activated potassium bromide from three detonations of Radiological Dispersal Devices (RDDs) at the Idaho National Laboratory Radiological Response Training Range, with a maximum sampled area of 19,900 m2, to provide a baseline comparison with other rapid, remote mapping methods. Measurements were obtained with a cerium bromide sensor collimated to a field of view of 3.14 m2, using lead shielding, and towed behind a ground vehicle. Sensor response correction factors for activated potassium bromide were calculated through simulation with SWORD to obtain activity per meter-squared. Continuous maps were produced by interpolating coverage from lawnmower raster scans. Radiological data was overlaid with aerial imagery from an automated unmanned aerial vehicle flight to provide contextual geological information relative to contamination levels. The contamination distribution measurements will be compared to unmanned aerial vehicle methods in future work.

Characterization of Thorium-Pyrazinoic acid complexation and its decorporation efficacy in human cells and blood

Thorium (Th) exposure to the human beings is a radiochemical hazard and the chelation therapy by suitable drugs is the major prevention approach to deal with. The present studies aimed at usage of pyrazinoic acid (PCA), which is a prodrug to treat tuberculosis, for its usage as decorporating agent for thorium from human body. The present studies provide a comprehensive knowledge on the chemical interaction and biological efficacy of pyrazinoic acid (PCA) for decorporation of Thorium from the human body. The thermodynamic parameters for Th-PCA speciation are determined by both experiment and theory. The potentiometric data analysis and Electro-Spray Ionization Mass Spectrometry (ESI-MS) studies revealed the formation of ML_i (i = 1-4) species with the decrease in stepwise stability constants. All the species formations are endothermic reactions and are predominantly entropy-driven. Biological experiments using human erythrocytes, whole blood and normal human lung cells showed cytocompatibility and decorporation ability of PCA for Thorium. Density functional calculations have been carried out to get insights on interaction process at molecular level. The experimental results and theoretical predictions found to be in line with each other. Present findings on complexation of Th by PCA and its evaluation in human cells and blood would further motivate determination of its safety levels and decorporation efficacy in animal models.

Insights into transport velocity of colloid-associated plutonium relative to tritium in porous media

Although faster transport velocities of colloid-associated actinides, bacteria, and virus than nonreactive solutes have been observed in laboratory and field experiments, some questions still need to be answered. To accurately determine the relative velocity (U_Pu/U_T) of ²³⁹Pu and tritium representative of the bulk water, a conceptual model of electrostatic interactions coupled with the parabolic water velocity profile in pore channels is developed. Based on the expression for U_Pu/U_T derived from this model, we study the effects of water flow rates and ionic strengths on the U_Pu/U_T. Also, the velocity relationship between Pu, tritium and Sr²⁺ is explored. The results show that U_Pu/U_T increased fairly linearly with decreasing water flow rates; U_Pu/U_T declined approximately exponentially with increasing Na⁺ concentrations; the charge properties of colloid-associated Pu (negative), tritium (neutral) and Sr²⁺ (positive) had a close association with their transport velocities as U_Pu : U_T : U_Sr²⁺ = 1.41 : 1 : 0.579.

Plutonium partitioning in three-phase systems with water, colloidal particles, and granites: new insights into distribution coefficients

The traditional sorption experiments commonly treated the colloid-associated species of low-solubility contaminants as immobile species resulted from the centrifugation or ultrafiltration, and then solid/liquid distribution coefficients (Ks/d) were determined. This may lead to significantly underestimated mobility of the actinides in subsurface environments. Accordingly, we defined a new distribution coefficient (Ks/d+c) to more adequately describe the mobile characteristics of colloidal species. The results show that under alkaline aqueous conditions the traditional Ks/d was 2-3 orders of magnitude larger than the Ks/d+c involving the colloidal species of (239)Pu. The colloid/liquid distribution coefficients Kc/d≫0 (∼10(6)mL/g) revealed strong competition of the colloidal granite particles with the granite grains for Pu. The distribution percentages of Pu in the three-phase systems, depending on various conditions such as particle concentrations, Na(+) concentrations, pH and time, were determined. Moreover, we developed the thermodynamic and kinetic complexation models to explore the interaction of Pu with the particle surfaces.