Search results for "Uranium"

Nuclear reactions in collisions of very heavy ions at energies below and near the barrier

2008

Structure of N >= 126 nuclei produced in fragmentation of (238)U

2009

The nuclear structure of neutron‐rich N⩾126 nuclei have been investigated following their production via relativistic projectile fragmentation of a E/A = 1 GeV 238U beam on a Be target. The cocktail of secondary beam products were separated and identified using the GSI FRagment Separator (FRS). The nuclei of interest were implanted in a high‐granularity active stopper detector set‐up consisting of 6 double sided silicon strip detectors. The associated gamma‐ray transitions were detected with the RISING array, consisting of 15 Euroball cluster Ge‐detectors. Time‐correlated gamma decays from individually identified nuclear species have been recorded, allowing the clean identification of isome…

First application of calorimetric low-temperature detectors in accelerator mass spectrometry

2004

Abstract For the first time, calorimetric low-temperature detectors were applied in accelerator mass spectrometry, a well-known method for determination of very small isotope ratios with high sensitivity. The aim of the experiment was to determine with high accuracy the isotope ratio of 236U/238U for several samples of natural uranium, 236U being known as a sensitive monitor for neutron flux. Measurements were performed at the VERA tandem accelerator at Vienna, Austria. The detectors consist of sapphire absorbers and superconducting transition edge thermometers operated at T≈ 1.5 K. The relative energy resolution obtained for 17.39 MeV 238U is ΔE/E=4–9×10−3, depending on the experimental co…

Total angular momenta of even-parity autoionizing levels and odd-parity high-lying levels of atomic uranium

2002

Using three-step resonance ionization spectroscopy, over 200 even-parity autoionizing (AI) levels of atomic uranium, including Rydberg series converging to the second lowest ionic level (6L 11/2o), were observed in the 49 930–51 200 cm−1 energy range. Total angular momenta (J values) of these levels were determined by a polarization combination method as well as a method based on the J-momentum selection rule. Using the AI levels of which J values were determined unambiguously, unique J values were also assigned for about 70 high-lying odd-parity levels. The observed J-dependence on autoionization linewidth is interpreted as being due to a centrifugal potential barrier.

Multidimensional Skyrme-density-functional Study of the Spontaneous Fission of 238U

2015

We determined the spontaneous fission lifetime of 238U by a minimization of the action integral in a three-dimensional space of collective variables. Apart from the mass-distribution multipole moments Q20 (elongation) and Q30 (left–right asymmetry), we also considered the pairing- fluctuation parameter λ2 as a collective coordinate. The collective potential was obtained self-consistently using the Skyrme energy density functional SkM∗ . The inertia tensor was obtained within the nonperturbative cranking approximation to the adiabatic time-dependent Hartree–Fock– Bogoliubov approach. The pairing-fluctuation parameter λ2 allowed us to control the pairing gap along the fission path, which sign…

Trace elements in native and transplanted Fontinalis antipyretica and Platyhypnidium riparioides from rivers polluted by uranium mining.

2017

The past uranium/polymetallic mining activities in the Sudety (SW Poland) left abandoned mines, pits, and dumps of waste rocks with trace elements and radionuclides which may erode or leach out and create a potential risk for the aquatic ecosystem, among others. In the present work four rivers affected by effluents from such mines were selected to evaluate the application of aquatic mosses for the bioindication of 56 elements. Naturally growing F. antipyretica and P. riparioides were compared with transplanted samples of the same species. The results demonstrate serious pollution of the examined rivers, especially with As, Ba, Fe, Mn, Pb, Ti, U and Zn, reaching extremely high concentrations…

Development of New Cationic Exchangers for the Recovery of Uranium (VI) from Concentrated Phosphoric Acid

2013

The extraction of uranium (VI) from 5.3 mol.L−1 phosphoric acid with a series of phosphoric, phosphinic, dithiophosphoric, or dithiophosphinic acid derivatives (0.5 mol.L−1) in mixture with 0.125 mol.L−1 TOPO in Isane IP 185 has been investigated. In the frame of the present work, eight acidic phosphorus and thiophosphorus compounds have been synthesized: bis(1,3-diisobutoxypropan-2-yl) phosphoric acid, bis(1,3-bis-(butylthio)propan-2-yl) phosphoric acid, bis(5,8,12,15-tetraoxanonadecan-10-yl) phosphoric acid, bis(1-butoxyheptan-2-yl) phosphoric acid, bis(undecan-6-yl) phosphoric acid, bis(2-(1,3-dibutoxypropan-2-yloxy)ethyl) phosphoric acid, bis(3-butoxy-2-(butoxymethyl)-2-methylpropyl) ph…

Quantum Chemical Calculations Predict the Diphenyl Diuranium Compound [PhUUPh] To Have a Stable1Ag Ground State

2006

A theoretical study of the gas-phase chemi-ionization reaction between uranium and oxygen atoms

2005

The U+O chemi-ionization reaction has been investigated by quantum chemical methods. Potential-energy curves have been calculated for several electronic states of UO and UO+. Comparison with the available spectroscopic and thermodynamic values for these species is reported and a mechanism for the chemi-ionization reaction U+O -> UO++e(-) is proposed. The U+O and Sm+O chemi-ionization reactions are the first two metal-plus-oxidant chemi-ionization reactions to be studied theoretically in this way.

Seasonal variation of air kerma in the "Vulcano Porto" area (Aeolian Islands, Italy).

2001

Abstract Air kerma was measured in the “Vulcano Porto” area of the Vulcano Island, belonging to the Aeolian Islands, in the Mediterranean Sea. Measurements were carried out using thermoluminescence dosimeters. The relationship between observed dose values and source lithology has been assessed. Data show a seasonal variation due to weather conditions but also probably related to features of the soils, making the variation more evident.