Preface. Acknowledgements. Foreword. I. Introductory material. Introduction Standards, conventions, and contents of tables. II. Tables of selected data. Selected neptunium data. Selected plutonium data. Selected auxiliary data. III. Discussion of neptunium data selection. Elemental neptunium. Neptunium aqua ions. Neptunium oxygen and hydrogen compounds and complexes. Neptunium group 17 (halogen) compounds and complexes. Neptunium group 16 compounds and complexes. Neptunium group 15 compounds and complexes. Neptunium group 14 compounds and complexes. Neptunium group 2 (alkaline-earth) compounds. Neptunium group 1 (alkali) compounds. IV. Discussion of plutonium data selection. Elemental plutonium. Plutonium aqua ions. Plutonium oxygen and hydrogen compounds and complexes. Plutonium group 17 (halogen) compounds and complexes. Plutonium group 16 compounds and complexes. Plutonium group 15 compounds and complexes. Plutonium group 14 compounds and complexes. Plutonium group 2 (alkaline-earth) compounds. Plutonium group 1 (alkali) compounds. Bibliography. List of cited authors. V. Appendices. Discussion of selected references. Ionic strength corrections. Assigned uncertainties. Index.

Chemical thermodynamics of neptunium and plutonium

Solution and solid-state structural chemistry of actinide hydrates and their hydrolysis and condensation products.

The paper describes the Rossendorf beamline (ROBL) built by the Forschungszentrum Rossendorf at the ESRF. ROBL comprises two different and independently operating experimental stations: a radiochemistry laboratory for X-ray absorption spectroscopy of non-sealed radioactive samples and a general purpose materials research station for X-ray diffraction and reflectometry mainly of thin films and interfaces modified by ion beam techniques.

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ROBL – a CRG beamline for radiochemistry and materials research at the ESRF

The availability of synchrotron radiation (SR) to the scientific community has literally revolutionized the way X-ray science is done in many disciplines, including low temperature geochemistry and environmental science. The key reason is that SR provides continuum vacuum ultraviolet (VUV) and X-ray radiation five to ten orders of magnitude brighter than that from standard sealed or rotating anode X-ray tubes (Winick 1987; Altarelli et al. 1998). Although SR was first observed indirectly by John Blewitt in 1945 (Blewitt 1946) and directly by Floyd Haber in 1946 at the General Electric 100-MeV Betatron in Schenectady, NY (see Elder et al. 1947; Baldwin 1975), it took 10 to 15 years before the first systematic applications of SR, which involved spectroscopic studies of the VUV absorption of selected elements (Tomboulian and Hartman 1956) using the 300-MeV synchrotron at Cornell University and of rare gases (Madden and Codling 1963) using the National Bureau of Standards SURF I synchrotron. As of September 2002, there are about 75 storage ring-based SR sources in operation, in construction, funded, or in advanced planning in 23 countries, with 10 fully dedicated SR storage ring facilities in the U.S.. A listing of these sources can be obtained at the following web site: http://www-ssrl.slac.stanford.edu/sr_sources.html .

The first SR experiments relevant to low temperature geochemistry and environmental science, although not performed on earth or environmental materials, were X-ray absorption fine structure (XAFS) spectroscopy measurements on amorphous and crystalline germanium oxide conducted on the SPEAR storage ring at the Stanford Synchrotron Radiation Project in 1971 by Dale Sayers, Farrel Lytle, and Edward Stern (Sayers et al. 1971). Prior to the availability of SR in the hard X-ray energy range (> 5 keV), XAFS spectroscopy measurements were impractical because of the high X-ray flux required and the need for a continuously tunable …

An Overview of Synchrotron Radiation Applications to Low Temperature Geochemistry and Environmental Science

http://server.ihim.uran.ru/files/info/2006/actinid%20sol.pdf

Solution coordination chemistry of actinides: Thermodynamics, structure and reaction mechanisms

Neptunium is the most problematic actinide element with respect to environmental migration because its solubility under typical groundwater conditions is expected to be high enough to be radiological concern, and its sorption on common minerals is expected to be relatively low Neptunium solubility in carbonate solutions is controlled by the formation of solids of general formula M{sub 2n-1}NpO{sub 2}(CO{sub 3}){sub n}, whose features have been reviewed The limited solubilities (10{sup -4}-10{sup -7} M) of these phases make the solution species in equilibrium with the solids very difficult to study using common structural methods We find that alkali free synthesis employing the tetrabutylammonium (TBA) cation provides 10{sup -3} M solutions of NpO{sub 2}(CO{sub 3}){sup -} and NpO{sub 2}(CO{sub 3}){sub 2}{sup 3-} These relatively high solubilities are unprecedented and afford the opportunity to determine the molecular structures of these environmentally important complexes employing EXAFS spectroscopy The near-IR absorption spectra of the neptunium electrolyte solutions are nearly identical, indicating that the same species are present in both solutions Known thermodynamic constants were used to prepare single-component solutions, and near- IR spectra were measured both before and after EXAFS analysis to confirm that each solution sample contained a single, pure neptunyl carbonato species 19more » refs, 1 fig, 1 tab« less

EXAFS studies of pentavalent neptunium carbonato complexes. Structural elucidation of the principal constituents of neptunium in groundwater environments

a Phillip D. Palmer

Papers

EXAFS studies of pentavalent neptunium carbonato complexes. Structural elucidation of the principal constituents of neptunium in groundwater environments

XAFS Structural Determination of Np(VII). Evidence for a Trans Dioxo Cation Under Alkaline Solution Conditions