Investigation of ammonium diuranate calcination with high temperature X-ray diffraction

The thermal decomposition of ammonium diuranate (ADU) in air is investigated using in-situ high-temperature x-ray diffraction (HT-XRD), thermogravimetry, and differential thermal analysis (TG/DTA). Data have been collected in the temperature range from 30 to 1000 °C, allowing to observe the sequence of phase transformations and to assess the energy changes involved in the calcination of ADU. The starting material 2UO3•NH3•3H2O undergoes a process involving several endothermic and exothermic reactions. In situ HT-XRD shows that amorphous UO3 is obtained after achieving complete dehydration at 300 °C, and denitration at about 450 °C. After cooling from heat treatment at 600 °C, a crystalline UO3 phase appears, as displayed by ex-situ XRD. The self-reduction of UO3 into orthorhombic U3O8 takes place at about 600 °C, but a long heat treatment or higher temperature is required to stabilize the structure of U3O8 at room temperature. U3O8 remains stable in air up to 850 °C. Above this temperature, oxygen losses lead to the formation of U3O8-x, as demonstrated by subtle changes in the diffraction pattern and by a mass loss recorded by TGA.JRC.E.6-Actinide researc

A TRLFS study on the complexation of Cm(III) and Eu(III) with 4-t-butyl-6,6´-bis-(5,6-diethyl-1,2,4-tiazin-3-yl)-2,2´-bipyridine in a water / 2-propanol mixture

The complexation of Cm(III) and Eu(III) with 4-t-butyl-6,6´-bis-(5,6-diethyl-1,2,4-tiazin-3-yl)-2,2´-bipyridine(t-Bu-C2-BTBP) in water / 2-propanol solution is studies.JRC.E-Institute for Transuranium Elements (Karlsruhe

50 Years Institute for Transuranium Elements: An Illustrated History

This illustrated book gives a chronological overview of the history of the Institute for Transuranium Elements, highlighting the main achievements, milestones, events and visits of the last 50 years.JRC.E-Institute for Transuranium Elements (Karlsruhe

Euratom contributions in Fast Reactor reearch programmes

Fast reactors are the basis for a long term sustainable energy policy, as has been recognized at Euroepan level within the Strategic Energy Technology (SET) Plan. On the initiative of the Sustainable Nuclear Energy Technology Platform (SNE-TP), a SET Plan industrial initiative named ESNII (European Sustainable Nuclear Energy Industrial Initiative) gather the main research industry players in the field. The Euratom Treaty provides a framework for all civil nuclear activities and the Euratom Framework Programmes provides financial support to several European research projects, amongst them fast reactor programme initiatives. Investigations cover the fields of advanced fuel concepts, their safety relevant properties and irradiation behaviour, as well as separation strategies for closing the fuel cycle and training and education programmes. The results are integrated, at the international level, within the Generation IV International Forum activities.JRC.E-Institute for Transuranium Elements (Karlsruhe

Solubility of Plutonium Hydroxides/Hydrous Oxides under Reducing Conditions and in the Presence of Oxygen

The present paper analyzes solubility data reported for plutonium hydroxides or hydrous oxides under different redox conditions (in the presence of reducing chemicals, in solutions without reducing or oxidising agents under Ar atmosphere and under air). Special attention is dedicated to the solubility controlling solid phases, total Pu concentrations, oxidation-state distributions and simultaneously measured redox potentials. Thermodynamic calculations and experimental data show that Pu(OH)3(s) is not stable. Under reducing conditions in the stability field of water it converts into PuO2(s,hyd). The solubility is given by the equilibrium concentrations of aqueous Pu(III) and Pu(IV) species. In the absence of reducing and oxidising agents but in the presence of traces of O2(g), the total Pu concentration at pH > 3 is dominated by Pu(V) and the solubility is controlled by PuO2þx(s,hyd), mixed valent (PuV)2x(PuIV)12xO2þx(s,hyd). Small Pu(IV) colloids/polymers present in neutral to alkaline solutions at a constant level of log[Pu(IV)]coll¼8.3 1.0 play an important role for the redox potentials in these systems. Including these species, the experimental results in the system Pu/e/Hþ/OH/NaClO4 or NaCl/H2O (25 C) can be described in terms of equilibrium thermodynamics. To cite this article: V. Neck et al., C. R. Chimie 10 (2007)..JRC.E.5-Nuclear chemistr

Redoc Reactions of Plutonium with Hydroquinone and Humic Substances

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Recent Advances in Aqueous Actinide Chemistry and Thermodynamics

This review presents an overview of recent advances in aqueous actinide chemistry and thermodynamics. It addresses actinides from thorium to curium and covers three main areas of interest which are discussed in separate sub-chapters: Actinide solubility and complexation with inorganic ligands at low and intermediate ionic strength conditions; Actinide solubility and speciation in concentrated salt brine systems; Actinide chemistry at elevated temperatures.JRC.E-Institute for Transuranium Elements (Karlsruhe

Nuclear Forensic Science - From Cradle to Maturity

Since the beginning of the 1990s, when the first seizures of nuclear material were reported, the IAEA recorded more than 800 cases of illicit trafficking of nuclear or other radioactive materials. Despite the decreasing frequency of seizures involving nuclear materials (i.e. uranium or plutonium), the issue continues to attract public attention and is a reason for concern due to the hazard associated with such materials. Once illicitly trafficked nuclear material has been intercepted, the questions of its intended use and origin are to be addressed. Especially the origin is of prime importance in order to close the gaps and improve the physical protection at the sites where the theft or diversion occurred. To answer the questions, a dedicated nuclear forensics methodology has been developed. In this paper, an overview is given on the methodologies used, the measurement techniques that are applies and on the characteristic parameters that help in the identification of the origin of the material. Some selected examples shall illustrate the challenges and the complexity associated with this work. In particular the past and on-going developments in this new area of science will be highlighted and special attention is attributed to the challenges ahead.JRC.E.5-Nuclear chemistr

Complexation and thermodynamics of Cm(III) at high temperatures: the formation of [Cm(SO4)n]3-2n (n=1,2,3) complexes at T=25 to 200°C

The formation of [Cm(SO4)n]3-2n (n=1,2,3) complexes in an aquatic solution is studies by time resolved laser fluorescence spectroscopy as a function of the ligand concentration, the ionic strength (NaCIO4) and the temperature (25 to 200 °C).JRC.E-Institute for Transuranium Elements (Karlsruhe

Direct nano ESI time-of-flight Mass Spectrometric Investigations on Lanthanide BTP Complexes in the Extraction-relevant Diluent 1-octanol

The present work focuses on investigations of a highly selective ligand for Am(III)/Ln(III) separation: bis-triazinyl-pyridine (BTP). By means of nano-electrospray mass spectrometry, complex formation of BTP with selected elements of the lanthanide series is investigated. We show that the diluent drastically influences complex speciation. Measurements obtained in the extraction-relevant diluent 1-octanol show the occurrence of Ln(BTP)i (i = 1¿3) species in different relative abundances, depending on the lanthanide used. Here, the relative abundances of the Ln(BTP)3 complexes correlate with the distribution ratios for extraction to the organic phase of the respective lanthanide.JRC.E-Institute for Transuranium Elements (Karlsruhe