Search Results (7)

The efficient separation and removal of key nuclides is important for the nuclear fuel cycle from the aspects of radioactivity reduction and potential resource recycling. The urgent objective is to design and develop functional materials for the separation and removal of important nuclides. Porous silicon-based adsorbents are considered highly advantageous materials for separating and removing radioactive nuclides in complex environments due to their excellent mechanical properties, high porosity, and functionalization ability. In this review, we compiled the applications of porous silica-based materials in recent years in the separation and removal of key nuclides, such as actinides, lanthanides, strontium, cesium, iodine, and platinum group metals; discussed their separation and removal performances; analyzed the constitutive relationship between key radionuclides and porous silica-based adsorbents; and systematically described the properties and mechanisms of different types of porous silica-based adsorbents. This article aims to provide some ideas for the design of an advanced separation process in the nuclear fuel cycle. Full article

Previously, proof-of-concept studies have demonstrated that rare-earth elements (REEs) can be preferentially extracted from coal fly ash (CFA) solids using a recyclable ionic liquid (IL), betainium bis(trifluoromethylsulfonyl)imide ([Hbet][Tf₂N]). When the suspension of aqueous solution—IL-CFA—is heated above 65 °C, the majority of REEs will separate from the bulk elements in the solids and partition to the IL phase. Acid stripping of the IL removes REEs and regenerates the IL for reuse in additional extraction cycles. The objective of this study is to showcase the applicability and effectiveness of the optimized method to recover REEs from various CFAs. Six CFA samples with different characteristics (feed coal basins, coal beds, and ash collecting points) and classifications (Class C and Class F) were examined. The process performance was evaluated for a broad range of elements (33 total), including 15 REEs, two actinides, six bulk elements, and 10 trace metals. Results confirmed good recovery of total REEs (ranging from 44% to 66% among the CFA samples) and the recovery process’ high selectivity of REEs over other bulk and trace elements. Sc, Y, Nd, Sm, Gd, Dy, and Yb consistently showed high leaching and partitioning into the IL phase, with an average recovery efficiency ranging from 53.8% to 66.2%, while the other REEs showed greater variability among the different CFA samples. Some amounts of Al and Th were co-extracted into the IL phase, while Fe co-extraction was successfully limited by chloride complexation and ascorbic acid reduction. These results indicated that the IL-based REE-CFA recovery method can maintain a high REE recovery efficiency across various types of CFA, therefore providing a promising sustainable REE recovery strategy for various coal ash wastes. Full article

NpO₂(NO₃)₂ units are connected by bis(2-pyrrolidone) linker molecules with the trans-1,4-cyclohexyl bridging part (L1) to form a one-dimensional coordination polymer, [NpO₂(NO₃)₂(L1)]_n. Molecular and crystal structures of this compound are nearly identical to that of the UO₂²⁺ analogue, while its aqueous solubility is greatly enhanced, probably owing to weaker thermodynamic stability of the complexation in NpO₂²⁺ compared with that in UO₂²⁺. Full article

Nuclear fuel is both the densest form of energy in its virgin state and, once used, one of the most hazardous materials known to humankind. Though commonly viewed as a waste—with over 300,000 tons stored worldwide and an additional 7–11,000 tons accumulating annually—spent nuclear fuel (SNF) represents a significant potential source of scarce, valuable strategic materials. Beyond the major (U and Pu) and minor (Np, Am, and Cm) actinides, which can be used to generate further energy, resources including the rare earth elements (Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, and Tb), platinum group metals, (Ru, Rh, Pd, and Ag), noble gases (He, Kr, and Xe), and a range of isotopes useful for medical and energy generation purposes are also produced during fission. One reason for the accumulation of so much SNF is the low uptake of SNF recycle (or reprocessing), primarily due to the high capital and operational costs alongside concerns regarding proliferation and wastes generated. This study will highlight the predominantly overlooked potential for the recovery of strategic materials from SNF, which may offset costs and facilitate advanced waste management techniques for minimised waste volumes, thus increasing the sustainability of the nuclear fuel cycle on the path towards Net Zero. Potential challenges in the implementation of this concept will also be identified. Full article

A more sustainable management of natural resources and the establishment of processes allowing a joint management of nuclear materials to avoid their diversion from their civilian use are two issues for the nuclear industry. Short alternatives to existing processes have therefore been proposed based on known systems available, tributylphosphate (TBP), for the separation of actinides by liquid/liquid extraction. Proof of concept of such alternative has been established on the uranium(VI)/thorium(IV) system. From an organic phase consisting of a mixture of TBP/n-dodecane loaded with uranium and thorium, two fluxes have been obtained: the first contains almost all of the thorium in the presence of uranium in a controlled ratio, the second contains surplus uranium. Two levers were selected to control the spontaneous separation of the organic phase: the addition of concentrated nitric acid, or the temperature variation. Best results have been obtained using a temperature drop in the liquid/liquid extraction process, and variations in process conditions have been studied. Final metal recovery and solvent recycling have also been demonstrated, opening the door for further process development. Full article

In this early 21st century, our societies have to face a tremendous and increasing energy need while mitigating the global climate change and preserving the environment. Addressing this challenge requires an energy transition from the current fossil energy-based system to a carbon-free energy production system, based on a relevant energy mix combining renewables and nuclear energy. However, such an energy transition will only occur if it is accepted by the population. Powerful and reliable tools, such as life cycle assessments (LCA), aiming at assessing the respective merits of the different energy mix for most of the environmental impact indicators are therefore mandatory for supporting a risk-informed decision-process at the societal level. Before studying the deployment of a given energy mix, a prerequisite is to perform LCAs on each of the components of the mix. This paper addresses two potential nuclear energy components: a nuclear fuel cycle based on the Generation III European Pressurized Reactors (EPR) and a nuclear fuel cycle based on the Generation IV Sodium Fast Reactors (SFR). The basis of this study relies on the previous work done on the current French nuclear fuel cycle using the bespoke NELCAS tool specifically developed for studying nuclear fuel cycle environmental impacts. Our study highlights that the EPR already brings a limited improvement to the current fuel cycle thanks to a higher efficiency of the energy transformation and a higher burn-up of the nuclear fuel (−20% on most of the chosen indicators) whereas the introduction of the GEN IV fast reactors will bring a significant breakthrough by suppressing the current front-end of the fuel cycle thanks to the use of depleted uranium instead of natural enriched uranium (this leads to a decrease of the impact from 17% on water consumption and withdrawal and up to 96% on SO_x emissions). The specific case of the radioactive waste is also studied, showing that only the partitioning and transmutation of the americium in the blanket fuel of the SFR can reduce the footprint of the geological disposal (saving up to a factor of 7 on the total repository volume). Having now at disposition five models (open fuel cycle, current French twice through fuel cycle, EPR twice through fuel cycle, multi-recycling SFR fuel cycle and at a longer term, multi-recycling SFR fuel cycle including americium transmutation), it is possible to model the environmental impact of any fuel cycle combining these technologies. In the next step, these models will be combined with those of other carbon-free energies (wind, solar, biomass…) in order to estimate the environmental impact of future energy mixes and also to analyze the impact on the way these scenarios are deployed (transition pathways). Full article

Recent advances (during the 2007–2014 period) in the coordination and organometallic chemistry of compounds containing natural and artificially prepared radionuclides (actinides and technetium), are reviewed. Radioactive isotopes of naturally stable elements are not included for discussion in this work. Actinide and technetium complexes with O-, N-, N,O, N,S-, P-containing ligands, as well π-organometallics are discussed from the view point of their synthesis, properties, and main applications. On the basis of their properties, several mono-, bi-, tri-, tetra- or polydentate ligands have been designed for specific recognition of some particular radionuclides, and can be used in the processes of nuclear waste remediation, i.e., recycling of nuclear fuel and the separation of actinides and fission products from waste solutions or for analytical determination of actinides in solutions; actinide metal complexes are also usefulas catalysts forcoupling gaseous carbon monoxide,as well as antimicrobial and anti-fungi agents due to their biological activity. Radioactive labeling based on the short-lived metastable nuclide technetium-99m (^99mTc) for biomedical use as heart, lung, kidney, bone, brain, liver or cancer imaging agents is also discussed. Finally, the promising applications of technetium labeling of nanomaterials, with potential applications as drug transport and delivery vehicles, radiotherapeutic agents or radiotracers for monitoring metabolic pathways, are also described. Full article