A luminescence line-narrowing spectroscopic study of the uranium(VI) interaction with cementitious materials and titanium dioxide

Non-selective luminescence spectroscopy and luminescence line-narrowing spectroscopy were used to study the retention of UO22+ on titanium dioxide (TiO2), synthetic calcium silicate hydrate (C-S-H) phases and hardened cement paste (HCP). Non-selective luminescence spectra showed strong inhomogeneous line broadening resulting from a strongly disordered UO22+ bonding environment. This problem was largely overcome by using luminescence line-narrowing spectroscopy. This technique allowed unambiguous identification of three different types of UO22+ sorbed species on C-S-H phases and HCP. Comparison with spectra of UO22+ sorbed onto TiO2 further allowed these species to be assigned to a surface complex, an incorporated species and an uranate-like surface precipitate. This information provides the basis for mechanistic models describing the UO22+ sorption onto C-S-H phases and HCP and the assessment of the mobility of this radionuclide in a deep geological repository for low and intermediate level radioactive waste (L/ILW) as this kind of waste is often solidified with cement prior to storage.Swiss National Cooperative for the Disposal of Radioactive Wast

Annual Report 2016 Institute of Resource Ecology

The Institute of Resource Ecology (IRE) is one of the eight institutes of the Helmholtz-Zentrum Dresden – Rossendorf (HZDR). The research activities are mainly integrated into the program “Nuclear Waste Management, Safety and Radiation Research (NUSAFE)” of the Helmholtz Association (HGF) and focused on the topics “Safety of Nuclear Waste Disposal” and “Safety Research for Nuclear Reactors”..

Annual Report 2018 - Institute of Resource Ecology

Annual Report 2018 of the scientific activities of the Institute of Resource Ecology of the Helmholtz-Zentrum Dresden-Rossendor

Annual Report 2015 Institute of Resource Ecology

The Institute of REsource Ecology (IRE) is one of the eight institutes of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The research activities are mainly integrated into the program “Nuclear Waste Management, Safety and Radiation Research (NUSAFE)” of the Helmholtz Association (HGF) and focused on the topics “Safety of Nuclear Waste Disposal” and “Safety Research for Nuclear Reactors”. Additionally, various activities have been started investigating chemical and environmental aspects of processing and recycling of strategic metals, namely rare earth elements. These activities are located in the HGF program “Energy Efficiency, Materials and Resources (EMR)”. Thus, all scientific work of the IRE belongs to the research field “Energy” of the HGF. The research objective is the protection of humans and the environment from hazards caused by pollutants resulting from technical processes that produce energy and raw materials. Treating technology and ecology as a unity is the major scientific challenge in assuring the safety of technical processes and gaining their public acceptance. We investigate the ecological risks ensued by radioactive and non-radioactive metals in the context of nuclear waste disposal, the production of energy in nuclear power plants and in processes along the value chain of metalliferous raw materials. A common goal is to generate better understanding about the dominating processes essential for metal mobilization and immobilization on the molecular level by using advanced spectroscopic methods. This in turn enables us to assess the macroscopic phenomena, including models, codes and data for predictive calculations, which determine the transport and distribution of contaminants in the environment

Interaction of Actinides with the Predominant Indigenous Bacteria in Äspö Aquifer - Interactions of Selected Actinides U(VI), Cm(III), Np(V) and Pu(VI) with Desulfovibrio äspöensis

Sulfate-reducing bacteria (SRB) frequently occur in the deep granitic rock aquifers at the Äspö Hard Rock Laboratory (Äspö HRL), Sweden. The new SRB strain Desulfovibrio äspöensis could be iso-lated. The objective of this project was to explore the basic interaction mechanisms of uranium, curium, neptunium and plutonium with cells of D. äspöensis DSM 10631T. The cells of D. äspöensis were successfully cultivated under anaerobic conditions as well in an optimized bicarbonate-buffered mineral medium as on solid medium at 22 °C. To study the interaction of D. äspöensis with the actinides, the cells were grown to the mid-exponential phase (four days). The collected biomass was usually 1.0±0.2 gdry weight/L. The purity of the used bacterial cultures was verified using microscopic techniques and by applying the Amplified Ribosomal DNA Restriction Enzyme Analysis (ARDREA). The interaction experiments with the actinides showed that the cells are able to remove all four actinides from the surrounding solution. The amount of removed actinide and the interaction mechanism varied among the different actinides. The main U(VI) removal occurred after the first 24 h. The contact time, pH and [U(VI)]initial influence the U removal efficiency. The presence of uranium caused a damaging of the cell membranes. TEM revealed an accumulation of U inside the bacterial cell. D. äspöensis are able to form U(IV). A complex interaction mechanism takes place consisting of biosorption, bioreduction and bioaccumulation. Neptunium interacts in a similar way. The experimental findings are indicating a stronger interaction with uranium compared to neptunium. The results obtained with 242Pu indicate the ability of the cells of D. äspöensis to accumulate and to reduce Pu(VI) from a solution containing Pu(VI) and Pu(IV)-polymers. In the case of curium at a much lower metal concentration of 3x10-7 M, a pure biosorption of Cm(III) on the cell envelope forming an inner-sphere surface complex most likely with organic phosphate groups was detected. To summarize, the strength of the interaction of D. äspöensis with the selected actinides at pH 5 and actinide concentrations ≥10 mg/L ([Cm] 0.07 mg/L) follows the pattern: Cm > U > Pu >> Np

Annual Report 2014 - Institute of Resource Ecology

The Institute of Resource Ecology (IRE) is one of the eight institutes of the Helmholtz-Zentrum Dresden – Rossendorf (HZDR). The research activities are mainly integrated into the program “Nuclear Waste Management, Safety and Radiation Research (NUSAFE)” of the Helmholtz Association (HGF) and focused on the topics “Safety of Nuclear Waste Disposal” and “Safety Research for Nuclear Reactors”. Additionally, various activities have been started investigating chemical and environmental aspects of processing and recycling of strategic metals, namely rare earth elements. These activities are located in the HGF program “Energy Efficiency, Materials and Resources (EMR)”. Both programs, and therefore all work which is done at IRE, belong to the research sector “Energy” of the HGF. The research objectives are the protection of humans and the environment from hazards caused by pollutants resulting from technical processes that produce energy and raw materials. Treating technology and ecology as a unity is the major scientific challenge in assuring the safety of technical processes and gaining their public acceptance. We investigate the ecological risks exerted by radioactive and nonradioactive metals in the context of nuclear waste disposal, the production of energy in nuclear power plants, and in processes along the value chain of metalliferous raw materials. A common goal is to generate better understanding about the dominating processes essential for metal mobilization and immobilization on the molecular level by using advanced spectroscopic methods. This in turn enables us to assess the macroscopic phenomena, including models, codes, and data for predictive calculations, which determine the transport and distribution of contaminants in the environment

Enantiomerically Pure Tetravalent Neptunium Amidinates: Synthesis and Characterization

The synthesis of a tetravalent neptunium amidinate [NpCl((S )‐PEBA)$_{3}$] (1 ) ((S )‐PEBA=(S ,S )‐N ,N′‐bis‐(1‐phenylethyl)‐benzamidinate) is reported. This complex represents the first structurally characterized enantiopure transuranic compound. Reactivity studies with halide/pseudohalides yielding [NpX((S )‐PEBA)$_{3}$] (X=F (2 ), Br (3 ), N3 (4 )) have shown that the chirality‐at‐metal is preserved for all compounds in the solid state. Furthermore, they represent an unprecedented example of a structurally characterized metal–organic Np complex featuring a Np−Br (3 ) bond. In addition, 4 is the only reported tetravalent transuranic azide. All compounds were additionally characterized in solution using para‐magnetic NMR spectroscopy showing an expected C$_{3}$‐symmetry at low temperatures