A study was made of the preparation of a uranium 10 w/o niobium alloy by the bomb reduction of a suitable form of niobium and uranium tetrafluoride with calcium. A compound with a probable formula of Na2NbOF5 proved to be most satisfactory as the source of niobium. High yields and good metal-slag separations were obtained. Chemical analysis and density determinations showed the composition to b...

A research effort was carried out at the Bhabha Atomic Research Centre (BARC), Mumbai, for developing laser-based techniques for enrichment of natural uranium to reactor-grade (2.5% to 3.0% U), with the potential to be economically scalable to industrial production. Three approaches – two molecular, namely CO2 laser-based approach and UF6-based approach, and one atomic, namely Atomic Vapour Las...

Uranium 236 is a long-lived radionuclide which is created from the naturally occurring trace isotope 235U (0.72% abundance) by thermal neutron capture. This process leads to a natural abundance of 236U in the range from 10-14—10-13 relative to the major 238U isotope (236U/238U). 236U is also created during the process of uranium enrichment for nuclear fuel or weapons, and as a waste product fro...

Oxidative dissolution controls uranium release to (sub)oxic pore waters from biogenic uraninite produced by natural or engineered processes, such as bioremediation. Laboratory studies show that uraninite dissolution is profoundly influenced by dissolved oxygen (DO), carbonate, and solutes such as Ca(2+). In complex and heterogeneous subsurface environments, the concentrations of these solutes v...

Bacillus sphaericus JG-A12 is a natural isolate recovered from a uranium mining waste pile near the town of Johanngeorgenstadt in Saxony, Germany. The cells of this strain are enveloped by a highly ordered crystalline proteinaceous surface layer (S-layer) possessing an ability to bind uranium and other heavy metals. Purified and recrystallized S-layer proteins were shown to be phosphorylated by...

Biological uranium reduction was investigated using bacteria isolated from a uranium mine in Limpopo, South Africa. Background uranium concentration in soil from the mine was determined to be 168 mgkg(-1) much higher than the typical background uranium concentration in natural soils (0.30-11.7 mgkg(-1)). Therefore it was expected that the bacteria isolated from the site were resistant to U(VI) ...

Water samples collected from 129 wells in seven of the nine sub-divisions of Ulaanbaatar were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) using Clean Lab methods. The levels of many trace elements were found to be low with the average concentrations (ranges in brackets) being 0.9 (<0.1-7.9) μg/L for As; 7.7 (0.12-177) μg/L for Mn; 0.2 (<0.05-1.9)μg/L for Co; 16 (<0.1-686) ...

Internal exposure from naturally occurring radionuclides (including the inhaled long-lived actinides (232)Th and (238)U) is a component of the ubiquitous background radiation dose (National Council on Radiation Protection and Measurements. Ionizing radiation exposure of the population of the United States; NCRP Report No. 160; NCRP: Bethesda, MD, 2009). It is of interest to compare the concentr...

Abstract Uranium isotopic signatures in the rock record are utilized as a proxy for past redox conditions on Earth. However, these display significant variability that complicates interpretation of specific conditions. Using model uranium-reducing bacterium, Shewanella oneidensis MR-1, we show abundance electron donors (e.g., labile organic carbon) controls uranium isotope fractionation, such h...