Actinide Chemistry Research Articles

Chemical applications of topology and group theory. 27. Covalent bonding in actinide derivatives

The d-block transition metals are characterized by forming strong cvalent bonds involving the d orbitals in a nine-orbital spherical sp[sup 3]d[sup 5] manifold thereby leading to the familiar 18-electron rule for the stable electronic configurations of transition metal coordination and organometallic complexes. On the other hand the 4f orbitals in the lanthanides appear to participate very little in covalent bond formation so that the chemistry of the lanthanides is governed largely by electrostatic considerations similar to the chemistry of the alkali and alkaline earth metals but with a predominant +3 oxidation state. The chemistry of the actinides from at least uranium through americium exhibits some features of both the predominantly covalent bonding of the d-block transition metals and the predominantly electrostatic bonding of the lanthanides since both the 5f and 6d orbitals of the actinides can function as valence orbitals leading to an unusual 12-orbital spherical d[sup 5]f[sup 7] manifold. This paper uses elementary group theory to explore how such a d[sup 5]f[sup 7] manifold can participate in the types of covalent bonding prevalent in actinide chemistry.

核燃料サイクルバックエンドを支えるアクチノイド元素の基礎化学

核燃料サイクルバックエンドを支えるアクチノイド元素の基礎化学

Separation Chemistry for the Nuclear Industry

A review of the actinide and lanthanide extraction chemistry by N, N-dialkylamides and N, N'- tetraalkylamides is given. It includes the extraction equilibria of inorganic acids. The prospects of using. these completely incinerable extractants in the nuclear fuels cycle is discussed.

Latest achievements in the analytical chemistry of actinides

New methods for separation and determination of actinides, widely used in analysis of actinides in technological and environmental samples are reviewed. Special attention is paid to obtaining and stabilizing transplutonium elements. (TPE) in extreme oxidation states. Their use in analytical practice resulted in expanding possibilities of methods for separation and determination of TPE. Solvent extraction, sorption and extraction chromatography are the basic methods for separation of TPE. Solvent extraction, sorption and extraction chromatography are the basic methods for separation of TPE. Methods of separation in gas phase and some other methods such as precipitation and coprecipitation are applied, however, to a lesser degree. Trends of development of these methods including those of various types of membrane extraction that succeeded in separation of TPE in both trivalent and other valence states have been shown. Attention is paid mainly to consideration of modern methods for determination of actinides, special distinction of such methods being low limits of determination, high precision and selectivity. Alpha- and beta-spectrometric methods with semiconductor detectors are the most advanced among various methods based on registration of nuclear radiation. Tremendous success has been achieved in development of emission-spectrometric methods for determination of trace amounts of actinides and various impure elements occurring in samples of actinides. Sensitive mass-spectrometric methods are widely used for determination of both isotope composition and content of elements in various samples including those which are highly radioactive. More simple and precise titrimetric methods based on using oxidizing-reducing or complexing agents are developed successfully. A large number of coulometric methods for determination of americium and berkelium, characterizing high precision and selectivity as well as luminescence methods have been developed.

Radiochemistry and actinide chemistry

The paper deals with radiochemistry of tracer amounts of radionucli des with N=1 to 100 or several hundreds of species/cm3.

Radiation chemistry of actinides

The paper presents data on the development of a mathematical model describing the radiation-chemical behaviour of plutonium in 3–6 mol/l HNO3 with uranium present and absent. Using experimental data on the kinetics of Pu(VI) reduction and Pu(IV) oxidation, and comparing them with the calculated values, we succeeded in finding the previously unknown rate constants of many reactions between plutonium ions and HNO3 radiolysis products, between plutonium ions and between plutonium ions and uranium ions. The mechanism of the radiation-chemical processes has been established.

Coordination chemistry of actinides in molten salts

The problems of actinide molten salt coordination chemistry are considered in terms of spectroscopic parameters as functions of melt composition and temperature. Parameters connected with energy, intensity and fine structure of 5f-5f transitions have been obtained for molten alkali metal chlorides, fluorides and chloride-fluoride mixtures. The regularities of variation of both actinide-chlorine distances and actinide fluorocomplex stability have been studied.

Actinide and lanthanum toxicity towards aCitrobacter sp.: Uptake of lanthanum and a strategy for the biological treatment of liquid wastes containing plutonium

Recent attention has focused on the discharge of actinide species into the environment as wastes from nuclear power and nuclear fuel reprocessing activities, in addition to the more traditional hazards posed by the discharge of native uranium in mining wastes. The chemistry of uranium, plutonium and other actinides is complex and is complicated by the co-existence of a variety of oxidation states each displaying a different pattern of pH-dependent hydroxylation behavior. This study formed a preliminary investigation to assess the comparative toxicity of the three valency states with the ultimate aim of predicting which forms of waste discharge would be the most amenable to biological detoxification. The microbiological component of this test system, a Citrobacter sp., has been extensively studied. The organism overproduces a phosphatase enzyme which liberates HPO{sub 4}{sup 2{minus}} to precipitate with heavy metals as cell-bound MHPO{sub 4}. One present aim is to assess the toxicity of actinide valency states anticipated to be present in environmental situations and process outflows. These studies indicate that the An(VI) state is by far the most toxic. These findings are discussed in terms of the likely speciation behavior of the three metals. It is suggested that the An(III) forms are amenable tomore » biological desolubilization; implications in the treatment of plutonium wastes are considered.« less

Second international conference on chemistry and migration behavior of actinides and fission products in the geosphere

Second international conference on chemistry and migration behavior of actinides and fission products in the geosphere

Chemistry of Actinides in the Environment

Chemistry of Actinides in the Environment

Solvent extraction for the chemical separations of the 5f elements

After a brief account of the needs for new extractants in actinide chemistry, interesting possibilities for N,N-dialkylamides and N,N'-tetraalkylmalonamides are discussed. Results dealing mainly with the properties of N,N-dialkylamides as an alternative to TBP in irradiated fuel reprocessing are presented. They are: the selection of amides of which the uranylnitrato adducts are soluble in alkanes; the extraction of: U(IV), Pu(IV) and fission products; the radiolytic and hydrolytic stability of amides and a bench-scale test of N,N-di(2-ethylhexyl)hexanamide in a first reprocessing cycle. Extractive properties of the N,N'-tetra- or pentaalkyl malonamides are described. They indicate that these completely incinerable extractants are very promising for the recovery of actinides from radio- active wastes. The needs for basic research which could lead to a better understanding of actinide extraction chemistry are illustrated by some examples.

New trends in the structural chemistry of actinide and lanthanide coordination compounds

The structural chemistry of the actinide and lanthanide elements has recently undergone considerable development and a wide variety of coordination numbers and geometries have been observed. This structural versatility arises from the lack of strong crystal field effects for the 4f and 5f electronic configurations, as well as from the large ionic radii of these metal ions which change markedly with either oxidation number or atomic number for both the lanthanides and the actinides. Accordingly, the coordination numbers and geometries of actinide and lanthanide complexes are determined primarily by the denticity, geometry and steric bulk of the ligands. Examples are the monodentate, sterically hindered substituted ureas and amides and, more importantly, the wide variety of polydentate sequestering ligands such as the coronates, cryptates and podates. A critical survey of the various structures observed for these complexes is presented and the relevant structural trends are related to steric and electronic effects.

Authors

Authors

Superacid chemistry of actinide and lanthanide metals, oxides and fluorides

Superacid chemistry of actinide and lanthanide metals, oxides and fluorides

4656014 Process for reducing the nox content in waste gases

After a brief account of the needs for new extractants in actinide chemistry, interesting possibilities for N,N-dialkylamides and N,N'-tetraalkylmalonamides are discussed. Results dealing mainly with the properties of N,N-dialkylamides as an alternative to TBP in irradiated fuel reprocessing are presented. They are: the selection of amides of which the uranylnitrato adducts are soluble in alkanes; the extraction of: U(IV), Pu(IV) and fission products; the radiolytic and hydrolytic stability of amides and a bench-scale test of N,N-di(2-ethylhexyl)hexanamide in a first reprocessing cycle.Extractive properties of the N,N'-tetra- or pentaalkyl malonamides are described. They indicate that these completely incinerable extractants are very promising for the recovery of actinides from radio- active wastes. The needs for basic research which could lead to a better understanding of actinide extraction chemistry are illustrated by some examples.

ChemInform Abstract: Cone Packing Model ‐ a Geometrical Approach to Coordination and Organometallic Chemistry of Lanthanides and Actinides.

Chemischer InformationsdienstVolume 17, Issue 43 Physical Organic Chemistry ChemInform Abstract: Cone Packing Model - a Geometrical Approach to Coordination and Organometallic Chemistry of Lanthanides and Actinides. X.-F. LI, X.-F. LISearch for more papers by this authorX.-Z. FENG, X.-Z. FENGSearch for more papers by this authorY.-T. XU, Y.-T. XUSearch for more papers by this authorH.-T. WANG, H.-T. WANGSearch for more papers by this authorJ. SHI, J. SHISearch for more papers by this authorL. LIU, L. LIUSearch for more papers by this authorP.-N. SUN, P.-N. SUNSearch for more papers by this author X.-F. LI, X.-F. LISearch for more papers by this authorX.-Z. FENG, X.-Z. FENGSearch for more papers by this authorY.-T. XU, Y.-T. XUSearch for more papers by this authorH.-T. WANG, H.-T. WANGSearch for more papers by this authorJ. SHI, J. SHISearch for more papers by this authorL. LIU, L. LIUSearch for more papers by this authorP.-N. SUN, P.-N. SUNSearch for more papers by this author First published: October 28, 1986 https://doi.org/10.1002/chin.198643050AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume17, Issue43October 28, 1986 RelatedInformation

Solid-state actinide chemistry and physics symposium sponsored by division of nuclear chemistry and technology co-sponsored by division of inorganic chemistry, American Chemical Society

Solid-state actinide chemistry and physics symposium sponsored by division of nuclear chemistry and technology co-sponsored by division of inorganic chemistry, American Chemical Society

Cone packing model — a geometrical approach to coordination and organometallic chemistry of lanthanides and actinides

By projection of the ligands to a unit sphere centred at the metal ion, steric effects, both local and overall, can be studied quantitatively in terms of solid angle factor ( SAF), fan angle ( FA), coordination vector, gap and hole. The packing saturation rule and the packing centre rule have been determined by treatment of more than 400 structures of lanthanide and actinide coordination and organometallic compounds. A ligand packing model was thus adopted with cones joined at the same apex. ‘Coordination Saturation’ in f-block chemistry was clarified to be saturation in coordination space, implying an equilibrium between bonding and steric effects. Molecular structures could be simulated on the basis of a uniform packing principle. The cone packing model has been applied to inorganic preparation, synergistic extraction and structure prediction. These predictions have been clearly substantiated experimentally, and the results are reported. A dynamic packing model was also suggested to study the reaction pathways by simulating the relative positions during the reaction process and the size and shape of holes, which correspond to the reaction areas in the coordination sphere. Lewis base association and dissociation, and the metal- carbon bond thermolysis of structural pattern MCp 3L were explained as examples.

Solid-state actinide chemistry and physics symposium sponsored by division of nuclear chemistry and technology co-sponsored by division of inorganic chemistry, American Chemical Society : 192nd National Meeting, Anaheim, California, USA, September 7–12, 1986

Solid-state actinide chemistry and physics symposium sponsored by division of nuclear chemistry and technology co-sponsored by division of inorganic chemistry, American Chemical Society : 192nd National Meeting, Anaheim, California, USA, September 7–12, 1986

Solid-state actinide chemistry and physics Symposium sponsored by Division of Nuclear Chemistry and Technology Co-sponsored by Division of Inorganic Chemistry, American Chemical Society : 192nd National Meeting, Anaheim, California, USA, September 7–12, 1986

Solid-state actinide chemistry and physics Symposium sponsored by Division of Nuclear Chemistry and Technology Co-sponsored by Division of Inorganic Chemistry, American Chemical Society : 192nd National Meeting, Anaheim, California, USA, September 7–12, 1986