Search results for " uranium"
showing 10 items of 24 documents
Depleted uranium induces human carcinogenesis involving the immune and chaperoning systems: Realities and working hypotheses
2019
Abstract Cancer is caused by a combination of factors, genetic, epigenetics and environmental. Among the latter, environmental pollutants absorbed by contact, inhalation, or ingestion are major proven or suspected culprits. Depleted uranium (DU) is one of them directly pertinent to the military and civilians working in militarized areas. It is considered a weak carcinogen but its implication in cancer development in exposed individuals is supported by various data. Since not all subjects exposed to DU develop cancer, it is likely that DU-dependent carcinogenesis requires cofactors, such as genetic predisposition and deficiencies of the chaperoning and immune systems. It is of the essence to…
Uranium(VI) sequestration by polyacrylic and fulvic acids in aqueous solution
2011
Stability data on the formation of dioxouranium(VI) species with polyacrylic (PAA) and fulvic acids (FA) are reported with the aim to define quantitatively the sequestering capacity of these high molecular weight synthetic and naturally occurring ligands toward uranium(VI), in aqueous solution. Investigations were carried out at t = 25 °C in NaCl medium at different ionic strengths and in absence of supporting electrolyte for uranyl–fulvate (\( {{\text{UO}}_{2}}^{2+} \)–FA) and uranyl–polyacrylate (\( {{\text{UO}}_{ 2}}^{ 2+ } \)–PAA, PAA MW 2 kDa) systems, respectively. The experimental data are consistent with the following speciation models for the two systems investigated: (i) UO2(FA1),…
Isotope selective ultratrace analysis of plutonium by resonance ionisation mass spectrometry
2006
Abstract Resonance ionisation mass spectrometry (RIMS) is a sensitive and selective method for isotopically resolved ultratrace analysis of long-lived radionuclides. For the routine analysis of plutonium three titanium–sapphire lasers pumped by a pulsed Nd:YAG laser in combination with a time-of-flight mass spectrometer are used. The detection limit of this system is as low as 106–107 atoms for the plutonium isotopes 238Pu to 244Pu. The RIMS technique was applied to investigate the isotopic composition and the content of plutonium in a depleted uranium penetrator as used during the Balkan conflict delivering important information on the origin of the depleted uranium in this type of ammunit…
Building future nuclear power fleets: The available uranium resources constraint
2013
Abstract According to almost all forward-looking studies, the world′s energy consumption will increase in the future decades, mostly because of the growing world population and the long-term development of emerging countries. The effort to contain global warming makes it hard to exclude nuclear energy from the global energy mix. The availability of natural uranium resources is a major constraint in terms of meeting this demand. In line with the scenarios floated by various international organisations and taking into consideration only current uranium-consuming light water reactors technologies with slow neutrons, 4 to 7 Mt of uranium could be consumed by 2050, namely, all identified or know…
New measurement of the 242Pu(n,γ) cross section at n_TOF
2016
The use of MOX fuel (mixed-oxide fuel made of UO2 and PuO2 ) in nuclear reactors allows substituting a large fraction of the enriched Uranium by Plutonium reprocessed from spent fuel. With the use of such new fuel composition rich in Pu, a better knowledge of the capture and fission cross sections of the Pu isotopes becomes very important. In particular, a new series of cross section evaluations have been recently carried out jointly by the European (JEFF) and United States (ENDF) nuclear data agencies. For the case of 242 Pu, the two only neutron capture time-of-flight measurements available, from 1973 and 1976, are not consistent with each other, which calls for a new time-of flight captu…
(Supplement Table S2) Results of 230Th/U-dating
2016
We compared the suitability of two skeletal materials of the Atlantic brain coral Diploria strigosa for 230Th/U-dating: the commonly used bulk material comprising all skeletal elements and the denser theca wall material. Eight fossil corals of presumably Last Interglacial age from Bonaire, southern Caribbean Sea, were investigated, and several sub-samples were dated from each coral. For four corals, both the ages and the activity ratios of the bulk material and theca wall agree within uncertainty. Three corals show significantly older ages for their bulk material than for their theca wall material as well as substantially elevated 232Th content and (230Th/238U) ratios. The bulk material sam…
High-resolution triple-resonance autoionization of uranium isotopes
2005
Abstract The near-threshold autoionization (AI) spectrum of uranium has been investigated by triple-resonance excitation with single-mode continuous lasers. Spectra were recorded over the first ∼30 cm − 1 above the first ionization limit at a resolution of 3 × 10 − 4 cm − 1 using intermediate states with different J values (6, 7, 8) to assign AI level total angular momentum J AI = 5 to 9. Resonances with widths ranging from 8 MHz to 30 GHz were observed; the strongest ones have J AI = 9 and widths of ∼60 MHz. Hyperfine structures for 235 U and isotope shifts for 234, 235 U have been measured in the two intermediate levels and in the final AI level for the most favorable excitation path. T…
Alpha decay study of 218U; a search for the sub-shell closure at Z=92
2006
Neutron-deficient uranium isotopes were studied via α spectroscopic methods. A low-lying α-decaying isomeric state was found in 218U. The new isomeric state was assigned spin and parity I π = 8+. The isomer decays by α emission with an energy E = 10678(17) keV and with a half-life T 1/2 = (0.56 -0.14 +0.26 ) ms. The known alpha-decay properties of the ground state of 218U was measured with improved statistics. The ground-state α-decay has an energy E = 8612(9) keV and a half-life T 1/2 = (0.51 -0.10 +0.17 ) ms.
Uranium from German Nuclear Power Projects of the 1940s— A Nuclear Forensic Investigation
2015
Here we present a nuclear forensic study of uranium from German nuclear projects which used different geometries of metallic uranium fuel. Through measurement of the (230)Th/(234)U ratio, we could determine that the material had been produced in the period from 1940 to 1943. To determine the geographical origin of the uranium, the rare-earth-element content and the (87)Sr/(86)Sr ratio were measured. The results provide evidence that the uranium was mined in the Czech Republic. Trace amounts of (236)U and (239)Pu were detected at the level of their natural abundance, which indicates that the uranium fuel was not exposed to any major neutron fluence.
α decay studies of the nuclidesU218andU219
2007
Very neutron deficient uranium isotopes were produced in fusion evaporation reactions using $^{40}\mathrm{Ar}$ ions on $^{182}\mathrm{W}$ targets. The gas-filled recoil separator RITU was employed to collect the fusion products and to separate them from the scattered beam and other reaction products. The activities were implanted into a position sensitive silicon detector after passing through a gas-counter system. The isotopes were identified using spatial and time correlations between the implants and the decays. Two $\ensuremath{\alpha}$-decaying states, with ${E}_{\ensuremath{\alpha}}=(8612\ifmmode\pm\else\textpm\fi{}9)$ keV and ${T}_{1/2}=(0.{51}_{\ensuremath{-}0.10}^{+0.17})$ ms for t…