Recent Advances In Actinide Science

by Iain May (Editor), N D Bryan (Editor), Rebeca Alvares (Editor)

Overview

The Special Publications Series is a collection of books produced from the proceedings of international symposia. Editors bring together contributions from authorities in the field and the books provide snapshots of the latest developments of that field.

Product Details

ISBN-13:	9780854046782
Publisher:	RSC
Publication date:	08/08/2006
Series:	Special Publications , #305
Pages:	836
Product dimensions:	6.15(w) x 9.20(h) x (d)

About the Author

R Alvarez:

Over eight years of research in environmental geochemistry including more than two years of postdoctoral research experience at The University of Manchester, UK studying analytical environmental separations of actinides in support of the Geoffrey Schofield Laboratories at BNFL, Sellafield. Currently undertaking research on the environmental biogeochemistry of depleted uranium.

PhD obtained in the area of analytical environmental geochemistry.

One year industrial experience at Australia’s National Medical Cyclotron facility at ANSTO, Sydney, producing radiopharmaceuticals.

Author of five refereed publications and two technical reports.

N D Bryan:

Following Ph.D. 5 years postdoctoral experience researching the colloidal properties of humic substances, their interaction with metal ions, particularly radionuclides, and their effects upon the transportation of pollutants in the environment.

In 1999, appointed as lecturer in Radiochemistry in the Centre for Radiochemistry Research, School of Chemistry, University of Manchester.

I May:

4 Years experience working for BNFL at Sellafield as a Research Associate on actinide chemistry of relevance to nuclear fuel reprocessing

Since 1999 employed as a Lecturer in the Centre for Radiochemistry Research, School of Chemistry, University of Manchester

Over 60 publications and numerous technical reports on actinide coordination chemistry and related subject areas.

Read an Excerpt

Recent Advances in Actinide Science

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By Iain May, Rebeca Alvares, Nicholas Bryan

The Royal Society of Chemistry

Copyright © 2006 The Royal Society of Chemistry
All rights reserved.
ISBN: 978-0-85404-678-2

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CHAPTER 1

Analysis, the Environment and Biotransformations

T. Ohnuki

Advanced Science Research Center, Japan Atomic Energy Research Institute, 2-4 Shirakata, Tokai, Ibaraki, 319-1195 Japan

1 INTRODUCTION

The presence of actinides in nuclear reactors and radioactive wastes is a major environmental concern, due to their long radioactive half-lives, their high energy radiation emissions, and their chemical toxicity. In order to estimate the potential impact of actinides on human beings, the mobility of actinides has been examined in terms of its interactions with soils and subsoils composed of abiotic and biotic components, principally minerals and bacteria. Among the biotic components, some microorganisms have cells whose surfaces sorb actinides. The high capacity of microbial surfaces to bind actinides may affect the migration of actinides in the environment. However, we have only limited knowledge of the role of microorganisms in the migration of actinides in the environment.

The interaction of actinides with microorganisms involves (i) adsorption, (ii) oxidation/reduction, (iii) degradation of actinide-organic component complexes and (iv) mineralization (Fig. 1). The interaction of actinides with microorganisms results in changes in their chemical state (biotransformation). The microbiology research group of JAERI is conducting basic scientific research on microbial interactions with actinides. Fundamental research on microbial transformations of actinides involves elucidating the mechanisms of dissolution and precipitation of various chemical forms, such as ions, oxides, and organic and inorganic complexes of actinides by aerobic or anaerobic microorganisms under relevant microbial process conditions. In the present report, recent findings from the heavy elements microbiology research group of JAERI are summarized.

2 ADSORPTION OF Pu(VI) AND U(VI) BY LICHEN AND YEAST

Lichens are symbiotic organisms consisting of fungal (mycobiont) and photosynthetic (photobiont) components, the latter of which may be a green alga or cyanobacterium. Lichens occur worldwide and on account of their dominance in certain terrestrial ecosystems (especially arctic/Antarctic tundra regions), play a major role in plant ecology and the cycling of some elements, such as C, N and P, and radionuclides. The ability of lichens to accumulate metals has led to their use in monitoring Pu fall-out from accidents, e.g. from Chernobyl and nuclear weapons tests. The concentration of Pu in reindeer lichen (Cladonia subgen. Cladina) has been studied, because Cladonia species form the first link of the lichen-reindeer-man subarctic food chain. These findings suggest that lichen affects the long-term migration of Pu in the environment. However, the accumulation mechanisms have not yet been identified.

Actinides can exist in different oxidation states of III, IV, V and VI in solution, and their chemical behaviour depends on the oxidation state. Actinides (V) and (VI) are more mobile than actinides (III) and (IV) in groundwater. Ohnuki et al. have studied the uptake of plutonium (VI) and uranium (VI) by lichen biomass of foliose lichen Parmotrema tinctorum to elucidate the migration behaviour of Pu and U in the terrestrial environment.

In accumulation experiments, discs 1 cm diam., weighing ca 9 mg cut from the outer margin of Parmotrema tinctorum (Nyl.) Hale were exposed to a Pu (VI) or U (VI) solution of 4.0x10-4 mol L-1 for 96 h at pH 3, 4 and 5. The oxidation states of Pu and U in the solutions were determined by UV/VIS absorption spectroscopy. The oxidation states of Pu and U accumulated by P. tinctorum were determined by UV/VIS absorption spectroscopy on extracts from the Pu/U-accumulated samples with 50% H3PO4 solutions.

Plutonium and uranium uptake by P. tinctorum after 96 h incubation averaged 0.040 and 0.055 g gdry-1, respectively. SEM observations showed that the accumulated Pu is evenly distributed on the upper and lower surfaces of P. tinctorum. On the contrary, U(VI) was accumulated in medullary layers as well as both cortexes (Fig. 2). Interestingly, U in the region of the algal layer was below the detection limit. UV/VIS absorption spectroscopy demonstrated that a fraction of Pu(VI) in the solution was reduced to Pu(V), and the accumulated Pu on the surface was reduced to Pu(IV). Meanwhile, U(VI) maintained the oxidation state of VI in the solution and on the lichen.

Plutonium (VI) was reduced to Pu(V) in the exudates solution, in which P. tinctorum was immersed in a 0.01 M NaCl solution for 96 h and then P. tinctorum was removed. These results indicate that the exudates reduce Pu from VI to V in solution. Melanin can act as an electron donor. Approximately 5% Pu(VI) was reduced to Pu(IV) in the solution containing the exudates within 480 h contact. This reduction was caused by the exudates of organic substances released from P. tinctorum. Metabolites other than melanin may have a similar potential to melanin to be electron donors. These findings suggest that the organic substances on the cortical cortex directly transfer electrons from their functional groups to the sorbed Pu(VI) and Pu(V) to Pu(IV). This direct electron transfer is one of the possible mechanisms for the reduction of Pu(VI) and Pu(V). Since the solubility of Pu(IV) hydroxides is very low, reduced Pu(VI) does not penetrate to medullary layers, but is probably precipitated as Pu(IV) hydroxides on the cortical lichen surface.

Similar adsorption experiments have been carried out to examine the interactions of U(VI) and Pu(VI) with Saccharomyces cerevisiae and thereby elucidate the accumulation mechanism of actinides(VI) by microorganisms. In the accumulation experiments, precultured S. cerevisiae was exposed to 4x10-4 M U(VI) or Pu(VI) in 0.01 M NaCl solution with an initial pH between 3 and 5. Concentrations and oxidation states of U and Pu in the solutions were measured at predetermined intervals. Oxidation states of the sorbed Pu and U were determined by UV/VIS spectrometry and XANES, respectively.

Time courses of sorption of Pu(VI) and U(VI) by the yeast cells (Fig. 3) showed abrupt decreases in solution fraction with time after exposure to the yeast. Interestingly, the accumulation rate of Pu was higher than that of U. More than 90% of Pu and U were accumulated by the yeast under experimental conditions. These results indicated that the cell surfaces of the yeast also have high affinities for Pu and U.

Only one peak around 570 nm (Pu(V)) was distinguished in the UV/VIS spectrum of the Pu solution at 2 h after the exposure (Fig. 4a). No peak around 831 nm (Pu(VI) appeared. No peak for Pu was distinguished in the UV/VIS spectrum of the Pu solution at 24 h. These results indicated that the oxidation state of Pu in the solution changed from VI to V within 2 h. A sharp peak appeared around 831 nm, and small peaks around 642 and 667 nm (Pu(IV)) were distinguished in the UV/VIS spectrum of the extract from the Pu-accumulated S. cerevisiae at 2 h after the exposure (Fig. 4b). Peak intensity around 642 and 667 nm increased with the exposure time; by contrast, peak intensity around 831 nm decreased. It is known that Pu(V) in the acid solution changes its oxidation state to IV and VI by disproportionation, i.e.,

2Pu(V)O2+ + 4H+ = Pu(VI)O22+ + Pu4+ + 2H2O

Thus, the oxidation state of Pu was V at 2 h, and changed to IV with increasing time.

These results showed that Pu was highly accumulated in microorganisms after their exposure to it. Even though the oxidation state of Pu kept at VI in the solution without microorganisms, it changed from VI to V in solution after exposure to microorganisms, probably by released exudates. Direct electron transfer from functional groups of organic substances to the sorbed Pu(VI) and Pu(V) is one of the possible mechanisms for the reduction of Pu(VI) and Pu(V). The Pu(VI) reduction occurs by a two step reaction from VI to IV through V, and differs from that of U(VI), where no reduction occurred.

3 ADSORPTION OF Ln(III) AND An(III) ON CELL SURFACES OF MICROORGANISMS

Various microbial species have different cell-surface characteristics. Chrorella vulgaris is an autotrophic unicellular alga having cellulose as cell-wall components. Bacillus subtilis is a Gram-positive bacterium whose cell surface is composed of peptidoglycan and teicoic acid. Pseudomonas fluorescens is a Gram-negative bacterium. Its cell wall is more complex in both chemical and structural terms than that of a Gram-positive bacterium, and its external outer membrane is composed of protein, phospholipid and lipopolysaccharide. Halomonas sp., Halomonas salinarum and Halomonas halobium are halophic bacteria having highly hydrophobic cell surfaces. The association of Eu(III) and Cm(III) with these microorganisms was studied to elucidate the effects of cell surface structure on adsorption.

Ozaki et al. have studied the kinetics of Eu(III) and Cm(III) sorption by various kinds of bacteria at pH 3-5. The amounts of organic carbon exuded from C. vulgaris, Halomonas sp. and H. halobium were determined by measurements of the dissolved organic carbon (DOC). The kinetics of the adsorption of Eu(III) and Cm(III) on the cell surfaces of C. vulgaris indicated that adsorption reached a maximum in a very short time, and then decreased with increasing time. This decrease reflects the presence of exuded organic carbon, which desorbed Eu(III) and Cm(III) from the cell surfaces. A similar tendency was observed for Halomonas sp. at pH 5 and H. halobium at pH 4. These imply that exudates from bacteria enhance the mobility of actinides and lanthanides.

The kinetics of Eu(III) and Cm(III) sorption showed no significant difference between Eu(III) and Cm(III) for C. vulgaris, B. subtilis, P. fluorescens, and H. halobium. However, a difference in the sorption kinetics of Eu(III) and Cm(III) by Halomonas sp. was observed. Higher amounts of Cm(III) than Eu(III) were accumulated at 20 min after exposure to Halomonas sp., suggesting a difference in the affinity of Eu(III) and Cm(III) to the functional groups of its cell surfaces. A slight higher fraction of Cm(III) was accumulated by H. halobium than Eu(III). These results suggest that halophilic bacteria have different sorption sites for actinides from non-halophilic bacteria.

4 EFFECTS OF METABOLITES ON THE SORPTION ACTINIDES

As mentioned above, exudates from microorganisms reduce the sorption of Eu(III) by bacteria. Naturally occurring chelating substances also have the potential to reduce the sorption of actinides and lanthanides by forming complexes in the environment. Siderophores, produced by microorganisms, access insoluble cations and form complexes, not only with Fe but also with actinides, causing their solubility to increase. Yoshida et al.' have studied the effects of desferrioxamine (DFO) B on the sorption of trivalent and tetravalent lanthanides and actinides by soil bacteria of P. fluorescens and B. subtilis.

The sorption density of Pu(IV) and Th(IV) on bacterial cells, and Fe(III) and Eu(III) on P. fluorescens in the presence of DFO (Fig. 5) indicated that sorption of Pu(IV) on P. fluorescens increased from 3 to 19 µM g-1 with a decrease of pH from 7.3 to 3.0, while sorption of Pu(IV) on B. subtilis and Fe(III) on P. fluorescens was smaller than 3 µM g-1 at about pH 3-8. Sorption of Th(IV) on P. fluorescens increased from 21 to 42 µM g-1 with a decrease of pH from 7.5 to 4.0, and sorption of Th(IV) on B. subtilis increased from 3 to 31 µM g-1 with a decrease of pH from 7.8 to 3.3. On the contrary, adsorption of DFO on both species was negligible at 3 hours after contact of the 1:1 Th(IV)-DFO complex with P. fluorescens or B. subtilis cells at pH 5.5. No DFO was sorbed on P. fluorescens cells from Eu(III)-DFO complexes. These results indicate that Th(IV)-, Pu(IV)- and Eu(III)-dissociate by contact with cells, after which the metals are sorbed.

Stability constants of the metal-DFO complexes decrease in the order of Pu(IV) (log K = 30.8) > Fe(III) (log K = 30.6) > Th(IV) (log K = 26.6) > Eu(III) (log K = 15). Adsorption density of Eu(III), Th(IV), and Pu(IV) on P. fluorescens cells decreased in the order Eu(III) > Th(IV) > Pu(IV), which corresponds to the increasing order of the stability constant of the DFO complexes. Adsorption of hydrated Eu(III) on P. fluorescens cells does not change significantly at pH 3 - 8, indicating that the affinity of P. fluorescens cell surfaces with metal ions is not changed significantly at these pHs. These facts indicate that pH dependence of adsorption density of metal ions on cells is dominated by the stability of the metal-DFO complexes.

Yoshida et al. investigated the influence of DFO on the sorption behavior of 11 rare-earth elements (REEs), La, Ce, Pr, Nd, Sm Eu, Gd, Tb, Dy, Ho, and Er on P. fluorescens cells at neutral pH. Pseudomonas fluorescens cell suspensions (1.3 g (dry wt.) L-1) in the suspensions were incubated for 30 minutes in 10 ml of 0.1 M Tris-HCl solutions containing 1.0 mg L-1 of each REE (La, 7.20 µM; Ce, 7.14 µM; Pr, 7.10 µM; Nd, 6.93 µM; Sm, 6.65 µM; Eu, 6.58 µM; Gd, 6.36 µM; Tb, 6.29 µM; Dy, 6.15 µM; Ho, 6.06 µM; Er, 5.98 µM) and 0.5 mM DFO in air at room temperature. The oxidation state of Ce was determined by X-ray absorption near edge structure (XANES) spectroscopy in fluorescence mode at the BL27B line at the High Energy Accelerator Research Organization (Tsukuba, Japan).

In the presence of DFO, the percent fraction of REEs in the solution after exposure to P. fluorescens cells (Fig. 6) showed a tendency to increase with increasing atomic number, except for Ce. The adsorption of Ce was significantly lower than those of the neighbouring REEs, La and Pr. On the contrary, no Ce anomaly in the sorption was distinguished in the solution with hydroxylammonium. XANES analysis of Ce in the Ce-DFO complex showed that Ce was in the tetravalent state. Adding hydroxylammonium reduced the tetravalent Ce in the complex to its trivalent form and erased the Ce anomaly (Fig. 6). These results show that DFO can oxidize Ce(III) to Ce(IV). Cyclic voltammetry revealed that the redox potential of the Ce(IV)/Ce(III) couple in the DFO complex was much lower than the standard redox potential, and that the stability of Ce(IV)-DFO is much higher than that of Ce(III)-DFO. These findings suggest that the observed Ce anomaly is due to the oxidation of the Ce(III)-DFO complex to the more stable Ce(IV)-DFO complex, and that naturally occurring organic ligands can contribute to this Ce anomaly in the natural environment.

5 SORPTION OF U(VI) BY THE MIXTURES OF MICROORGANISM AND CLAY

Soils and subsoils are composed of abiotic and biotic components, principally minerals and bacteria. It is therefore important to elucidate the role of microorganisms on the accumulation of actinides in such mixtures. Ohnuki et al. assessed the accumulation of uranium (VI) by a bacterium, Bacillus subtilis, suspended in a slurry of kaolinite clay, to elucidate the role of microbes on the mobility of U(VI). Various mixtures of bacteria and the koalinite were exposed to solutions of 8x10-6 M and 4x10-4 M-U(VI) in 0.01 M NaCl at pH 4.7. After 48 h, the mixtures were separated from the solutions by centrifugation, and treated with a 1 M CH3COOK for 24 h to determine the associations of U within the mixture. The mixture exposed to 4x10-4 M U was analyzed by a transmission electron microscope (TEM) equipped with EDS.

The accumulation of U by the mixture increased with an increase in the amount of B. subtilis cells present at both U concentrations. Treatment of kaolinite with CH3COOK removed approximately 80% of the associated uranium. However, in the presence of B. subtilis the amount of U removed was much less. TEM-EDS analysis confirmed that most of the U removed from solution was associated with B. subtilis. XANES analysis of the oxidation state of uranium associated with B. subtilis, kaolinite, and with the mixture containing both revealed that it was present as U(VI). These results suggest that the bacteria have a higher affinity for U than the kaolinite clay mineral under the experimental conditions tested, and that they can immobilize significant amounts of uranium.

CHAPTER 2

MICROBIAL TRANSFORMATIONS OF ACTINIDES IN TRANSURANIC- AND MIXED-WASTES: IMPLICATIONS FOR RADIOACTIVE-WASTE DISPOSAL

A.J. Francis

Environmental Sciences Department Brookhaven National Laboratory, Upton, New York 11973, USA

1 INTRODUCTION

The presence of actinides (U, Np, Pu, Am), organic- (cellulose, plastics, rubber, chelating agents) and inorganic- (nitrate and sulfate) compounds in transuranic (TRU) and mixed wastes are a major concern, because of their potential for migration from the waste repositories and contamination of the environment. The primary causes of this disquiet are the toxicity of the actinide elements and the long half-lives of their isotopes. The radionuclides may be present in TRU wastes in various forms, such as elemental, oxide, co-precipitates, ionic, inorganic-, and organic-complexes, and also as naturally occurring minerals, depending on the process and waste stream.

The actinides existing in various oxidation states that are the ones of concern are III (Am, Pu, U), IV (Pu, U), V (Np, Pu), and VI (Pu, U). Significant aerobic- and anaerobic-microbial activity is expected to occur in the waste because of the presence of electron donors and acceptors. The actinides initially may be present as soluble- or insoluble-forms but, after disposal, may be converted from one to the other by microorganisms. The direct enzymatic or indirect non-enzymatic actions of microbes could alter the speciation, solubility, and sorption properties of the actinides, thereby increasing or decreasing their concentrations in solution. Dissolution of radionuclides reflects changes in the Eh and pH of the local environment caused by the microorganisms, by their production of CO2, or of extra cellular metabolic products, such as organic acids, and sequestering agents such as siderophores. Immobilization or precipitation of radionuclides is due to changes in the Eh of the environment, enzymatic reductive precipitation (reduction from a higher to lower oxidation state), biosorption, bioaccumulation, biotransformation of radionuclide-organic and -inorganic complexes, and bioprecipitation. Free-living bacteria suspended in the groundwater fall within the colloidal size range and may have a strong radionuclide sorbing capacity, giving them the potential to transport radionuclides in the subsurface. Further, gases generated from the biodegradation of TRU wastes, thereby pressurizing the containment areas, with subsequent reduction in the volume of the waste and subsidence in the repository. Microbial corrosion of the waste canisters also is a major concern.

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Excerpted from Recent Advances in Actinide Science by Iain May, Rebeca Alvares, Nicholas Bryan. Copyright © 2006 The Royal Society of Chemistry. Excerpted by permission of The Royal Society of Chemistry.
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Table of Contents

Chapter One: Analysis, the Environment and Biotransformations; Biotransformation of Actinides; Microbial Transformations of Actinides in Transuranic- and Mixed-Wastes: Implications for Radioactive-Waste Disposal; A Brief Review of the Enzymatic Reduction of Tc, U, Np, and Pu by Bacteria; Actinides - A Challenge for Nuclear Forensics; Non-Exchangeable Binding of Radionuclides by Humic Substances: A Natural Chemical Analogue; On the Multi-Spectroscopic Approach for Radionuclide/Mineral Interaction Modelling in Aqueous Solutions; Compact Accelerator Mass Spectrometry: A Powerful Tool to Measure Actinides in the Environment; Interaction Mechanisms of Uranium with Bacterial Strains Isolated from Extreme Habitats; High Sensitivity Plutonium Isotopic Analysis in Environmental and Monitoring Samples; Speciation of the Oxidation States of Np and Pu in Aqueous Solutions by CE-ICP-MS and CE-RIMS; Soft X-Ray Spectromicroscopy of Actinide Particulates; Uranium Colloid Analysis by Single Particle Inductively Coupled Plasma - Mass Spectrometry; Status of The European Network for Actinide Sciences, ACTINET; Using Surface Imaging and Analytical Techniques to Study the Calcite Surface in Contact with Aqueous UO22+ Ions; Production of High-Purity 236Pu From 237Np by a Photonuclear Reaction; Decontamination of Soils in Liquid O2; A Novel Hydrogen Uranyl Phosphate-Based Bio-Inorganic Ion Exchanger for the Removal of 60Co, 85Sr And 137Cs from Aqueous Solutions; Effect of Closo-Dodecacarborane Ion Exchangers on the Potentiometric Response of Ionophore-Based Ion-Selective Electrodes; Geochemical and Microbial Controls on Decomposition and Dispersion of Depleted Uranium (DU) in the Environment: An Overview of Current Research and the Development of Methods for Handling DU Microparticulates; Fibrous "Filled" Sorbents for the Preconcentration of Actinides and Technetium; Np(V) Sorption to Goethite in the Presence of Natural and Hydroquinone-Enriched Humic Acids; Sorption of Np(IV) and Np(V) by Depleted Uranium Dioxide; The Recommended Values of 239Pu and 240Pu Concentrations in IAEA Standard Reference Material Estimated by Three Measuring Methods: Isotope Dilution-Thermal Ionizaton Mass Spectrometry, Inductively Coupled Plasma Mass Spectrometry and Alpha Spectrometry; A Sequential Separation Procedure for Pu, Am, U and Np Isotopes in Soils and Liquid Samples; Combination of Alpha Track Analysis, Fission Track Analysis with SEM-EDX and SIMS to Study Spatial Distribution of Actinides; Aspects of UO3 Dissolution Kinetics; Determining the Radiation Damage Effect on Glovebox Glove Materials; Plutonium-Humate Complexation in Natural Groundwater by XPS; Uranium Sorption and Solubility Under Conditions Relevant for the Radioactive Waste Repository in Morsleben / Germany; The Application of Colloidal Photocatalysis in Actinide Photoredox Chemistry; Study of the Chemical Scheme of δ-TUPD Solid Solution Alteration; Solubility Studies of Uranium(IV) by Laser-Induced Breakdown Detection (LIBD); Resonance Ionisation Mass Spectrometry for Element- and Isotope-Selective Trace Analysis of Actinides in Environmental Micro-Particles; The Romanian Uranium Industry- Its Past and Future in the Context of The Strengthening and Integration of the European Research Area; Uranium and Neptunium Sorption onto Magnetite Under Suboxic Conditions; The Application of Avalanche Photodiodes for the Measurement of Actinides by Alpha Liquid Scintillation Counting; The Effect of Uranium on the Corrosion of Stainless Steel in High Temperature Molten Salts in the Presence of Moisture; Reactions of the Feldspar Surface: Surface Composition and Microtopography After Contact with Radionuclides and Heavy Metals; The Influence of Oxalate on the Partitioning of Trivalent f-Elements to Hematite; Mechanisms for the Reduction of Actinide Ions by Geobacter Sulfurreducens; Oxidation and Surface Complexation of Actinyl Species by Oxides; Chapter Two: Coordination and Organometallic Chemistry; Structure-Property Relationships in Novel Actinide Compounds with Heavy Oxoanions; On the Role of f-Obitals in the Bonding in f-Element Complexes: the "Feudal" Model as Applied to Organoactinide and Actinide Aquo Complexes; New Catalytic Reactions Promoted by Organoactinides; Octacoordinate Soft Donor Complexes of Trivalent and Tetravalent Lanthanide and Actinide Cations; Structure and Stability of Peroxo Complexes of Uranium and Plutonium in Carbonate Solution; Sequestered Plutonium: Structural Characterisation and Complex Formation of Pu(IV) Complexes with Siderophore-Like Ligands; Extraction of Actinides by Functionalised Calixarenes; 5f Element Complexes with 'Soft' Donor Atom Ligands: Eight Coordinate Pu(III) Pyrazinyl and Thioether Complexes; Plutonium(V) Chemistry in Neutral Aqueous Complexing Media: New Crystal Compounds Synthesis and Study of their Structure and Properties; Management of Transuranic Actinide Containing Materials in Nuclear Clean up in the UK; Extending the Chemistry of the Uranyl Ion: {UO2}2+ Acting as a Lewis Acid and a Lewis Base; Covalency in Uranium Complexes and New f-Element Chemistry that Exploits Soft Organometallic Carbene Ligands; Variability in the Crystal Structures of Uranium(VI), Neptunium(VI) and Plutonium(VI) Phthalates; Novel Neptunyl(V) and Plutonyl(V) Bi-Oxalate Compounds: Synthesis, Properties and Structure; Synthesis and Crystal Structure of a New Np(V) Oxalate, Na4(NpO2)2(C2O4)3.6H2O; Plutonyl(V) Malonate Compounds: Synthesis and Properties; Crystal Compounds of Plutonyl(V) Monooxalate Complex; Solid Compounds of Np(V) with 2,4,6-Tri-(2-Pyridyl)-1,3,5-Triazine: Crystal Structure, Spectral and Thermal Properties; Complex Formation of Np(V) with Picolinic, Nicotinic and Isonicotinic Acids; The Stability of a Uranyl(V) Benzoyl Acetonate Complex in Dimethyl Sulfoxide; Preparation of Uranium(III) Perchlorate in N,N-Dimethylformamide and Other Aprotic Media; Bent Metal Carbenes - Electrostatic Bonds vs Covalency in Organometallic Actinide Chemistry; Uranyl Complexation by a Hinged Polypyrrolic Macrocycle; Hydrogen Bonding with the Uranyl Oxo Atom and Enforced π-Stacking in the Equatorial Plane; Structure of Trivalent Americium and Lanthanide Complexes with Phosphoryl Acetic Acid Amides; Surprising Activity of Organoactinide Complexes in the Polymerization of Cyclic Mono- and Diesters; The Affinity of N Donor Ligands in AnO22+ Complexes and Synthetic Routes to New Neptunyl Chemistry; Synthesis and Crystal Structure Determination of Some Mixed Oxalates of Actinide(s) and/or Lanthanide and Monovalent Cations (NH4+ or N2H5+); Complexation of a B-Type Unsaturated Polyoxoanion, [BiW9O33]9-, to Actinyl, {UO2}2+, {NpO2}+ and {PuO2}2+, Cations; Uranium Coordination to Environmentally Relevant Polyhydroxycarboxylate Ligands; Co-Crystallisation Processes in a Study of Physiochemical Properties of Actinides and Lanthanides in Lower Oxidation States; Monocarboxylate Complexes of Uranyl: a Relativistic Density Functional Study; Coordination Chemistry of Americium: Synthesis, Structure of Am(III) Iodates; The Performance of Time-Dependent Density Functional Theory in the Simulation of the Electronic Spectra of Molecular Uranium Complexes; The Effect of Solvent on the Modelling of the Geometry and Vibrations of UO2(H2O)52+; Chapter Three: Heavy Elements; Chemistry of Transactinides; Unusual Volatility of Oxides Formed by Some Actinides; SISAK Liquid-Liquid Extraction Studies of Rutherfordium and Future Plans to Study Heavier Transactinides; Development of a System for Chemical Studies of Rutherfordium by Liquid-Liquid Extraction From Sulphuric Acid Solutions with SISAK; Influence of KCl on the Extraction of Rutherfordium Homologues Hafnium and Zirconium from Sulphuric Acid with Tri-Octylamine in Toluene; Thermochromatographic Adsorption Studies of Curium and Berkelium; Self-Diffusion Coefficients and Structure of the Trivalent f-Element Ions, Eu3+, Am3+ and Bk3+ in Aqueous Solution; Ceramic Plutonium Target Development for the MASHA Separator for the Synthesis of Element 114; Chapter Four: Nuclear Fuels, Materials and Waste Forms; Understanding and Predicting Self-Irradiation Effects in Plutonium Alloys: A Coupled Experimental and Theoretical Approach; Identifying and Quantifying Actinide Radiation Damage in ZrSiO4 Minerals and ceramics with Nuclear Magnetic Resonance; Lessons Drawn From Studies of the Transmutation of Fuels Carried Out in the Framework of the French Law of December 1991 on the Management of Long Lived Waste; Properties of Minor Actinide Compounds Relevant to Nuclear Fuel Technology; Transformation Characteristics of Isothermal Martensite in Pu-Ga Alloys; Reactivity of Mixed Uranium and Plutonium Nitride with Silicon Carbide as Materials for Gas Cooled Fast Reactors; Confinement of Plutonium and Thorium in Monazite/Brabantite, in View of Actinide Conditioning; Physical and Electronic Properties Changed by Aging Plutonium; Corrosion Resistance of Uranium Metal Surface with CO and SCCO2 Treatment; Pyrochemical Processing of Plutonium at AWE; Uranium Ion Valences in Perovskite, Zirconolite and Pyrochlore from Near Infrared Diffuse Reflectance Spectroscopy; Thermal and Mechanical Properties of Simulated High Burnup Uranium Oxide Fuels; Thermodynamic Modelling and Analyses of Molten Salt Reactor Fuel; Structure of the Americium Pyrochlore Am2Zr2O7 and its Evolution Under Alpha Self-Irradiation; Local Structure of Th1-XMXO2 Solid Solutions with M = U, Pu; First-Principles Phase Diagram of the Ce-Th System; Crystal Stability and Equation of State for Am: Theory; XPS Study of High Temperature Oxidation of a Plutonium Alloy Under Vacuum; Phase Relation of Mixed Oxide Fuel Containing Np and Am; Study on Corrosion Resistance Improvement of U and U-Nb Alloys by Ion Implantation with Niobium; Simulation by External Irradiation of Self-Irradiation Effects on Thorium Phosphate Diphosphate (δ-TPD) - Consequences for Its Dissolution; From Thorium Phosphate-Hydrogenphosphate Hydrate to Thorium Phosphate-Diphosphate : A New Way of Preparation of—TPD and Associated Solid Solutions with Actinides; Invariant Equilibria in Binary Plutonium Phase Diagrams, Relationships; Photoemission and Secondary Ion Mass Spectrometry Study of Uranium Passivation by C+ Implantation; Optical Metallography of Plutonium; New Family of Intermetallic Hydrides: U2T2InHx and U2T2SnHx; Self-Propagating High-Temperature Synthesis of Actinide-Containing Pyrochlore-Type Matrices; Relation Between Solubility and Local Environment of Actinides and Surrogates in Borosilicate Glasses; Electrochemical Studies of Uranium Metal Corrosion Mechanism and Kinetics in Water; The Effect of Oxygen Potential on the Sintering Behaviour of MOX Fuel Containing Americium; Variation of Lattice Parameter and Thermal Expansion Coefficient of (U,Er)O2 as a Function of ErO1.5 Content; An Experimental Investigation of Effects of Americium Addition to (U, Pu)O2-X on Phase Relation; Molecular Dynamics Studies of Uranium-Plutonium Mixed Oxide Fuels; Thermodynamic Modelling of the Uranium-Zirconium-Iron-Oxygen System; Nanoindentation Studies of Uranium Intermetallic Compounds; Self-Irradiation of Ceramics and Single Crystals Doped with Plutonium-238; Actinoid Phosphates of Kosnarite Structure; Monazite and Kosnarite-Based Ceramics Containing Uranium and Plutonium; Application of Ceramicrete Matrices for Low-Temperature Solidification of Liquid Actinides-Containing Wastes; Ab Initio Study of Uranium and Plutonium Carbides and Nitride; Effect of High Static Pressure on Crystaline and Electronic Structures of Transition, Lanthanide and Actinide Metals; Positron Annihilation Spectroscopy: A Powerful Tool to Investigate the Early Stages of Self-Irradiation Effects in δ-Pu Alloys; High Pressure X-Ray Diffraction Study of a Pu0.92Am0.08 Binary Alloy; Calculation of the Critical Concentration of Helium Release From Uranium Tritide; Recycle of Calcium in Incineration Process of Low Level Radioactive Wastes; Vaporization Behaviour of Pu-Cd Intermetallic Compounds; Development of the Scientific Concept of the Phosphate Methods for Actinide-Containing Waste Handling (Pyrochemical Fuel Reprocessing); Synthesis and Investigations of the Phosphates of Th, U, Np, Pu, Am and Lanthanides with Monazite, Zircon, Kosnarite and Langbenite Mineral-Like Structures; Basic Concept of Hydro-Pyro Hybrid Type Sulfide Process for Spent Fuel; Low Temperature Selective Reduction of U3O8 in the Presence of Sulfurizing Agents; Chapter Five: Separation and Solution Chemistry; Actinide Solution Chemistry And Chemical Separations: Structure-Function Relationships In The Grand Scheme Of Actinide Separations Science; X-Ray Absorption Spectroscopy of Actinides Involved in Toxicological Processes; Solubility and Redox Reactions of Plutonium(IV) Hydrous Oxide in the Presence of Oxygen; Uranium Speciation in Molten Salts from X-Ray Absorption and Electronic Absorption Spectroscopy Measurements; The Separation of Plutonium from Uranium by Solvent Extraction: Recent Developments for Advanced Fuel Cycles; Ternary Complex Formation and Coordination Modes of Am, Cm and Rare Earths with EDTA+NTA: Stability Constants, TRLFS and 13C NMR Studies; Influence of Temperature and Ionic Strength on the Hydration of Curium(III) in Aqueous Solution Studied with TRLFS; Insights into Third Phase Formation Using Neptunium; Investigation of the Behavior of Am (IV), (V) And (VI) in Alkaline Media; A Comparative Study of the Complexation Of Uranium(VI) with Oxydiacetic Acid and its Amide Derivatives; Actinide Electrochemistry in Low Temperature Ionic Liquids; New Data on Extraction of Nitric Acid with 30% TBP from Solutions Containing Uranyl Nitrate; New Data on Extraction of Tetravalent Uranium With 30% TBP from Solutions Containing Uranyl Nitrate; Behaviour Of Some Anhydrous U(IV) Complexes in Hydrophobic Room Temperature Ionic Liquids; The Hydrolysis of Protactinium(V): Equilibrium Constants and Determination of the Standard Thermodynamic Data; The Study of Polymerization of Pu(OH)4 and its Solubility in 0.01M NaCl Solutions at Various pH Values; Dissolution Of Actinide Oxides In Some Organic Reagents Saturated With Nitric Acid; Separation of Uranium and Plutonium by the Method of Countercurrent Chromatography; Alkaline Sequestrants in Hanford Tank Waste Processing; Anion Control in Hanford Leachates by Solid-Liquid Separation; Uranium Removal From Process Effluents Containing Chromate And Aluminum Nitrate; Diffusion Coefficients of Actinide and Lanthinde Eleents in Liquid Metal for Reductive Extraction; Electrochemical and Spectroscopic Characteristics of Uranium Ions in a Hydrate Melt; Spectroscopic Study for the Oxychloride Precipitation of Neodymium and Uranium in Chloride Melts; Extraction of Transuranium Elements and T?(VII) from Acid Solutions by Neutral Phosphorous Compounds; Transuranium, Rare Earth Elements and Technetium (VII) Extraction by Calix[4]Arenes From Acidic and Alkaline Media; Adsorption Properties of Amidoxime Resins for Uranium(VI) and Some Fission Products Soluble in Aqueous Carbonate Solutions; Solubility of UO2(δ-Diketonato)2DMSO Complexes (δ-Diketonate = Acetylacetonate, Trifluoroacetylacetonate, Hexafluoro-Acetylacetonate; DMSO = Dimethyl Sulfoxide) In Supercritical CO2; Kinetic Study on Exchange Reaction of Hexafluoroacetyl-Acetonate in Bis (Hexafluoroacetylacetonato) (Dimethyl Sulfoxide) Dioxouranium(VI) in Supercritical CO2 by 19F NMR; Heat Oscillating Extraction of Rare Earth Elements; Mathematical Model of Extraction Separation of f-Elements in Non-Stationary Conditions; Final Tests using the BNFL Electrorefiner at Harwell; Behaviour Of FPs And TRU in a Fluoride Volatility Process; Specific Features of Kinetics and Mechanism of Np(IV) Oxidation with Nitric Acid in Aqueous and TBP Solutions; Lanthanide Salt Solutions: Representation Of Osmotic Coefficients Within the Binding Mean Spherical Approximation; The Reduction of Np(VI) by Acetohydroxamic Acid in Nitric Acid Solution; Photoreduction Of UO2F2 Enriched with 18O in Isopropanol Solution; Electrorefining of Plutonium in Calcium Chloride; Separation of Minor Actinides and Lanthanides from Nitric Acid Solution by R-BTP Extraction Resin; UC Electrochemical Behaviour in Aqueous Solution; Redox Behaviour of Plutonium(IV) in Acidic Solutions; The Effect of Fission Product Elements on the Chlorination of Uranium Metal in Molten Salts; Spectroelectrochemical Studies of Uranium Behavior in (Li-K)Cleut Based Melts At 450° C; Evaluation of Nuclear Fuel Cycle Systems for Actinide Recycle in Feasibility Study on Commercialized Fast Reactor Cycle Systems; Extraction of Transplutonium and Rare-Earth Elements with the use of Zirconium Salt of Dibutyl Phosphoric Acid; The Effect of Dibutylphosphoric Acid on Actinide (IV) Extraction by 30% TBP from Solutions Containing Uranyl Nitrate; Sorption Properties of New Solid Extractants Based on Malonamide Compounds; Direct Extraction of Uranium and Plutonium with Supercritical Carbon Dioxide from MOX Fuel; Modelling the Hydrolysis of Actinide Complexed Hydroxamic Acid Ligands; A New Approach for Estimating Stability Constants Between Actinides and Organic Ligands by Semi-Empirical Gibbs Energy Fragmental Method; Measurement of Some Actinides Redox Potentials in TBP Medium With Ultramicroelectrode; Development of High Throughput Electrorefining of Uranium in the Metallic Fuel Cycle; Experimental Data Points to Existence of Plutonium (VIII) in Alkaline Solutions; Control of Neptunium Routing During the Reprocessing of Spent Nuclear Fuel Using PUREX; Crystallization Behavior of Uranium and Plutonium in Nitric Acid Solution; A Hot Test on Minor Actinides Separation from High-Level-Waste by CMPO/SiO2-P Extraction Resin; Recovery Of Uranium and Plutonium Metals Through Cathode Processing of Electrodeposits from Reduced Oxide Fuel Anodes; Kinetics of Electrochemical Generation of Silver(II); Ionic Liquids for Actinides and Lanthanides Chemistry; Solvent Extraction of Actinides by Tetraalkylpyridine-N-Oxide-Bis Phosphine Oxide Complexants; Kinetics and Mechanism of Actinide Complexation by Polydentate Ligands; The Significance of Minor Actinide Based Fuel Cycles in Advanced Fuel Cycles; Separation of Uranium from Radioactive Waste using Supercritical Carbon Dioxide with Nitric Acid - Tri-n-Butylphosphate Complex; Chapter Six: Spectroscopy and Magnetism; Spectroscopic Actinide Speciation for Nuclear Waste Disposal; Superconductivity in Actinide Materials; Neutron Scattering Studies of NpTGa5 (T = Fe, Co, Ni and Rh); Tuning the Superconducting Behaviour of the PuTGa5 Compounds; The Electronic Structure of the Pu-Based Superconductor PuCoGa5: LSDA and LSDA+U Investigations; Ground State and Solution Behaviour of Actinide Ions Investigated by Nuclear Magnetic Resonance Methods; Polarization Effects in EXAFS Spectra at the Uranium L1 and L3 Edge - A Comparison Between Theory and Experiment; A Study of the Competition Between Delocalization and Spin-Orbit Splitting in the Actinide 5f States; A Crossover Effect of the 5f Electrons of Uranium Compounds: From Itinerant to Localized, With Increasing Temperature; Localization of 5f Electrons and Phase Transitions in Americium; Orbital Ordering in Actinide Oxides: New Perspectives on Old Problems; Electronic Structure of δ-Pu: Theories and PES Experiments; Magnetic Properties of Radiation Damage in Pu and Pu Alloys; A Photoelectron Spectroscopy Investigation of the Early Stages of Neptunium Oxidation; Electronic Structure of Molecular Actinide Compounds Through Spectroscopic Experiments Combined with Theoretical Modelling; Influence of Self-Irradiation Damage on the Superconducting Behaviour of Plutonium-Based Compounds; MARS Beamline, A New Facility for Studying Radioactive Matter from a Synchrotron Source; Solid State Synthesis and X-Ray Diffraction Characterization of Pu3+(1-2x)Pu4+xCa2+xPO4; Chemiluminescence in Solid-Phase Reactions of Uranium (IV) and Terbium (III) Compounds; Chemiluminescent Reactions of Uranium and the Role of UO2+; Magnetic Anisotropy of U2Co17-xSix Single Crystals; High-Field Magnetization of a UIrGe Single Crystal; Comparative Photoemission Study of Actinide Metals, Nitrides and Hydrides; Cathodoluminescence of Actinide Ions in Crystalline Host Phases Electronic Structure of the Americium Monopnictides: Ab Initio Calculations and Photoemission Experiments; Using Nano-Focussed Bremstrahlung Isochromat Spectroscopy (nBIS) to Determine the Unoccupied Electronic Structure of Pu: A Proposed Study Fluorescence Spectroscopy of Protactinium(IV); Pu, Np and U Valence States and the Determination of their Molecular Form by Chemiluminescence and Pulsed Laser Spectroscopy; Air-Oxidation Behaviour of UO2 and Gd-Doped UO2 by XAS; Speciation Of Radionuclides With Bioligands Using Time-Resolved Laser-Induced Fluorescence (TRLIF) and Electrospray Mass Spectrometry (ES-MS); Magnetic Diagrams of PuGa3 Under Pressure; Magnetic Ordering of U and Co Moments in (Th,U)Co2X2 (X = Si, Ge) Solid Solutions; Spectroscopic Investigations of Uranium Species in Alkali Chloride Molten Salts; Magnetic and Electrical Properties of UCu3M2Al7 Alloys; X-Ray Photoelectron Spectroscopy Study of Neptunium-Containing Ceramics on the Basis of Ferrite and Titanate (6P23); Subject Index