Analysis of the Secondary Phases Formed by Corrosion of U₃Si₂-Al Research Reactor Fuel Elements in the Presence of Chloride Rich Brines.

Corrosion experiments with non-irradiated U₃Si₂-Al research reactor fuel samples were carried out in synthetic MgCl₂-rich brine to identify and quantify the secondary phases because depending on their composition and on their amount, such compounds can act as a sink for the radionuclide release in final repositories. Within the experimental period of 100 days at 90 °C and anoxic conditions the U₃Si₂-Al fuel sample was completely disintegrated. The obtained solids were subdivided into different grain size fractions and non-ambient X-ray diffraction (XRD) was applied for their qualitative and quantitative phase analysis.

Thermodynamics of formation of coffinite, USiO4.

Coffinite, USiO4, is an important U(IV) mineral, but its thermodynamic properties are not well-constrained. In this work, two different coffinite samples were synthesized under hydrothermal conditions and purified from a mixture of products. The enthalpy of formation was obtained by high-temperature oxide melt solution calorimetry.

Energetics of metastudtite and implications for nuclear waste alteration.

Metastudtite, (UO2)O2(H2O)2, is one of two known natural peroxide minerals, but little is established about its thermodynamic stability. In this work, its standard enthalpy of formation, -1,779.6 ± 1.

Synthesis of coffinite, USiO4, and structural investigations of UxTh(1-x)SiO4 solid solutions.

The miscibility behavior of the USiO4-ThSiO4 system was investigated. The end members and 10 solid solutions UxTh(1-x)SiO4 with x = 0.12-0.

Incorporation of Eu(III) into hydrotalcite: a TRLFS and EXAFS study.

The behavior of radionuclides in the environment (geo-, hydro-, and biosphere) is determined by interface reactions like adsorption, ion exchange, and incorporation processes. Presently, operational gross parameters for the distribution between solution and minerals are available. For predictive modeling of the radionuclide mobility in such systems, however, individual reactions and processes need to be localized, characterized, and quantified.