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1.
Literature data on distribution ratios (Dw) of Np(V) and Pa(V) for the AG1-X8 resin are scarce whereas those related on resin capacity factors (k′) values for TEVA, TRU and U/TEVA resins are absent. Therefore, batch extraction experiments for Pa(V) and Np(V) from HCl and HNO3 media were realized, at tracer scale, with AG1-X8 and EIChroM resins (TEVA, TRU and U/TEVA). Based on the new Dw and k′ values obtained in this study, a new protocol for Pa/Np separation has been developed leading to a better separation factor of 105 and a chemical yield of 97 ± 3% and 99 ± 1% for Pa and Np, respectively. A separation of 231Pa from uranium matrix was successfully tested. 相似文献
2.
Abstract Neptunium and plutonium monopnictides and monochalcogenides were studied by x-ray diffraction at pressures up to 57 GPa. All of them exhibit structural phase transitions under pressure. The arsenides and tellurides have a CsCl (B2) type high-pressure structure. Sb as an anion favours a tetragonal high-pressure structure. The compressibilities were determined for all of the compounds studied. The results are compared to those obtained for the corresponding thorium and uranium compounds. 相似文献
3.
Melissa A. Denecke Boris Brendebach Wout De Nolf Gerald Falkenberg Koen Janssens Rolf Simon 《Spectrochimica Acta Part B: Atomic Spectroscopy》2009,64(8):791
Spatially resolved X-ray absorption and fluorescence investigation with a micrometer-scale resolution on actinide-containing samples provide information necessary for safety assessment of nuclear waste disposal. In this paper one example of such an experiment is presented. This example entails neptunium speciation in a fractured granite bore core from the Swedish Äspö Hard Rock Laboratory following a radiotracer experiment using µ-XAFS and µ-XRF. In order to probe micro-volumes below the surface in the granite samples and thereby avoid potential changes in the Np speciation during cutting of the bore core, a confocal irradiation–detection geometry is employed. µ-XAFS results for a selected granite bore core cross section with ~ 3 nmol Np/g reveal that Np, originally introduced as Np(V) in the tracer cocktail, is present in the granite in its reduced Np(IV) form. The Np(IV) is often present as particles, tens of µm in size. Elemental distribution maps show the tracer Np to be located in fissures and permeable channels not larger than 100 µm. The Np distribution appears often correlated with Zn also present in some fissures. We observe small granite fissures containing Fe (presumably Fe(II)), where we do not detect any Np. It is feasible that inflowing Np(V) has a shorter residence time in large fractures, while in the smaller fissures migration is slower, leading to longer residence times, i.e., reaction times, where it is reduced to less soluble Np(IV) and becomes thereby immobilized. 相似文献
4.
Neptunium triselenide, NpSe3, was synthesized in high yield by the reaction of the elements in a Sb2Se3 flux at 1223 K. Its structure has been determined by single‐crystal X‐ray diffraction methods. Thecompound crystallizes with two formula units in space group C$\rm^{2}_{2h}$ –P21/mof the monoclinic system in the TiS3 structure type with cell constants at 100 K of a = 5.592(3) Å, b = 4.002(2) Å, c = 9.422(5) Å,β = 97.40(1) °. The asymmetric unit comprises one neptunium and three selenium atoms, each with site symmetry m. Np–Se interatomic distances range from 2.859(2) to 2.927(3) Å; the Se–Se bond length of 2.340(3) Å is typical of a single bond. The compound may thus be charge‐balanced and formulated as Np4+Se2–Se22–. 相似文献
5.
V. Brandel 《Journal of solid state chemistry》2004,177(12):4755-4767
The chemistry and crystal structure of tetravalent cation phosphates, including that of actinides was reviewed several times until 1985. Later, new compounds were synthesized and characterized. In more recent studies it was found that some of previously reported phases, especially those of thorium, uranium, and neptunium, were wrongly identified. In the light of these new facts, an update review and classification of tetravalent actinides phosphates is proposed in this two-part paper. Their crystal structure and some chemical properties are compared to non-actinide cation phosphates. 相似文献
6.
以工业汞灯为光源,在硝酸体系中采用光化学方法控制镎(Np)价态的研究中,应用分光光度法对Np的价态及Np的定量测定分析,探讨了Np的光化学机理,得出了Np(Ⅵ)的光化还原速率方程,为光化学分离和提纯Np提供了必要的信息。 相似文献
7.
Fully relativistic, four-component Dirac–Fock calculations and quasirelativistic pseudopotential calculations at different
ab initio levels are used to study the bonding trends among the naked, triatomic [OAnO]
q+
groups or the oxyfluorides [AnO
n
F
m
]
q
with f
0 configurations. The triatomic f
0 series is suggested to range from the bent ThO2 via the linear OPaO+ to at least NpO2
3+, a possible new gas-phase species. The neutral oxyfluoride molecules include the experimentally unknown NpO2F3 and PuO2F4. The latter is a candidate for the so far unknown oxidation state Pu(VIII), which is found to lie considerably above Pu(VI),
but to be locally stable. Their all-oxygen isoelectronic analogues are NpO5
3−, known in the solid state, and the unknown PuO6
4−. Further possible candidates for Pu(VIII) are PuO4(D
4h
) and the cube-shaped PuF8(O
h
). Isoelectronic UF8
2− is calculated to be D
4d
, in agreement with experiment.
Received: 18 May 2001 / Accepted: 21 June 2001 / Published online: 11 October 2001 相似文献
8.
Kaitlyn S. Otte Dr. Julie E. Niklas Chad M. Studvick Andrew C. Boggiano Dr. John Bacsa Prof. Ivan A. Popov Prof. Henry S. La Pierre 《Angewandte Chemie (International ed. in English)》2023,62(34):e202306580
The study of the redox chemistry of mid-actinides (U−Pu) has historically relied on cerium as a model, due to the accessibility of trivalent and tetravalent oxidation states for these ions. Recently, dramatic shifts of lanthanide 4+/3+ non-aqueous redox couples have been established within a homoleptic imidophosphorane ligand framework. Herein we extend the chemistry of the imidophosphorane ligand (NPC=[N=PtBu(pyrr)2]−; pyrr=pyrrolidinyl) to tetrahomoleptic NPC complexes of neptunium and cerium ( 1-M , 2-M , M=Np, Ce) and present comparative structural, electrochemical, and theoretical studies of these complexes. Large cathodic shifts in the M4+/3+ (M=Ce, U, Np) couples underpin the stabilization of higher metal oxidation states owing to the strongly donating nature of the NPC ligands, providing access to the U5+/4+, U6+/5+, and to an unprecedented, well-behaved Np5+/4+ redox couple. The differences in the chemical redox properties of the U vs. Ce and Np complexes are rationalized based on their redox potentials, degree of structural rearrangement upon reduction/oxidation, relative molecular orbital energies, and orbital composition analyses employing density functional theory. 相似文献
9.
10.
T.Z. Forbes 《Journal of solid state chemistry》2009,182(1):43-6303
The compound (NpO2)2(SO4)(H2O)4 was synthesized by evaporation of a Np5+ sulfate solution. The crystal structure was determined using single crystal X-ray diffraction and refined to an R1=0.0310. (NpO2)2(SO4)(H2O)4 crystallizes in triclinic space group P-1, a=8.1102(7) Å, b=8.7506(7) Å, c=16.234(1) Å, α=90.242(2)°, β=92.855(2)°, γ=113.067(2)°, V=1058.3(2) Å3, and Z=2. The structure contains neptunyl pentagonal bipyramids that share vertices through cation-cation interactions to form a sheet or cationic net. The sheet is decorated on each side by vertex sharing with sulfate tetrahedra, and adjacent sheets are linked together through hydrogen bonding. A graphical representation of (NpO2)2(SO4)(H2O)4 was constructed to facilitate the structural comparison to similar Np5+ compounds. The prevalence of the cationic nets in neptunyl sulfate compounds related to the overall stability of the structure is also discussed. 相似文献