Potential impact of releases from a new molybdenum-99 production facility on regional measurements of airborne xenon isotopes

The monitoring of the radioactive xenon isotopes (131m)Xe, (133)Xe, (133m)Xe, and (135)Xe is important for the detection of nuclear explosions. While backgrounds of the xenon isotopes are short-lived, they are constantly replenished from activities dominated by the fission-based production of (99)Mo used for medical procedures. At present, one of the most critical locations on earth for the monitoring of nuclear explosions is the Korean peninsula where the Democratic People's Republic of Korea (DPRK) has announced that it conducted three nuclear tests between 2006 and 2013. This paper explores the backgrounds that would be caused by the medium to large scale production of (99)Mo in the region of the Korean peninsula.

Interactions of Np(V) and U(VI) with dipicolinic acid

To complement earlier studies of the complexation kinetics of Np(V) and U(VI) by oxydiacetic acid and several diphosphonic acids, the rate of complexation of these metal ions by dipicolinic acid (pyridine-2,6-dicarboxylic acid, DPA) has been investigated by stopped-flow spectrophotometry. This ligand is distinguished from the previously studied species by the rigid planar arrangement of the ligand functional groups and the presence of a pyridine nitrogen donor atom. Reactions of DPA with UO22+at p[H] 1 and NpO2+at p[H] 1 and 3 adhere to the comparatively simple first-order approach to equilibrium kinetic model used to describe the earlier results. At p[H] 3, the UO22+reaction is characterized by consecutive pseudo-first order reactions. The first is an apparent approach to equilibrium while the second process demonstrates a saturation effect, indicating the existence of a stable intermediate complex. Relative rates and activation parameters are discussed in comparison with the previous results.

Chromatographic separation and characterization of hydrolyzed Cr(III) species

Both macroscale and microscale methods to separate hydrolyzed Cr(III) species from acidic to near-neutral pH solutions have been developed. The macroscale approach is based on ion exchange, and involves separating monomeric, dimeric, trimeric, tetrameric, and higher order Cr(III) oligomers from such solutions using a gradient elution with increasing cationic charge. With this approach, the concentration of a given fraction can be maximized, and complete resolution between these species can be achieved. In addition, complete recovery of Cr(III) from the column is achievable. For the microscale approach, capillary electrophoresis with indirect detection is used to isolate and uniquely identify the same smaller oligomers and a fraction of larger Cr(III) species that are not uniquely identified. Capillary electrophoresis also provides indirect structural information for the Cr(III) trimer, suggesting that it exists in a triangular configuration rather than as a linear species. These methods are described in detail, and possible applications are discussed.