A fuel "hot" particle released during the accident at Chernobyl NPP in 1986 was collected in 2021 in a peat-bog soil 14.5 km to the north from the source. The particle was dissected by a focused ion beam, enabling observation of internal features. Scanning Electron microscopy reveals distinct morphological differences between external and internal pores, highlighting the influence of environmental conditions on surface degradation. X-ray absorption spectrum indicates that the particle maintains U(IV) oxidation state. TOF-SIMS investigation allowed precise determination of U isotopic ratio; calculated burn-up value is 15.2 MWd/kg(U). The measured U and Pu isotopic ratio are well correlated with the available literature data for Chernobyl-related samples and for RBMK fuel in general. The examined particle largely retained its structural integrity and U(IV) oxidation state after 35 years of environmental exposure, demonstrating considerable resistance against degradation.

Introduction The radioisotope Pb-212, which daughter isotope Bi-212 is an alpha emitter, is used in radiopharmaceuticals as an in vivo generator, allowing longer exposure time of tumor cells to radiation. Currently, molecules with Pb-212/Bi-212 have reached the stage of clinical trials using only chelator - TCMC. The complex with this chelator is obtained by heating, which limits its use with a number of temperature-sensitive biomolecules. In addition, part of the daughter radionuclide is released from the composition of the complex, causing irradiation of healthy tissues in the body. Radium is widely used in therapy in its chloride form. Targeted therapy based on vector molecules will greatly expand the use of this radionuclide if an effective chelator is found. Macropa has shown stability in vitro and in vivo, but has not yet been applied in radiopharmaceuticals. Therefore, the effective chelators for lead and radium are being researched. Objectives In our study complexes of lead and radium cations with new benzoazacrown ethers possessing varied number of chelating groups, including variation in azacrown cavity size. Complexation with these ligands occurred instantly at room temperature. Long-lived i Materials and Methods The long-lived lead isotope Pb-210 was obtained from the solution of parent Ra-226 with its daughters. Thin layer chromatography was used to control the bound fraction of radionuclide. The stability of the complexes was studied in biologically relevant media (solutions of microelements, isotonic solution of NaCl and a nine-fold excess of serum proteins). To analyze the stability of the most effective complexes in vivo, biodistribution studies in mice were performed and compared with cation blank solution. Results Lead and radium radionuclide complexes with a radiochemical purity >90% can be prepared at room temperature in ≤2 minutes, which is an advantage over currently used in radiopharmaceuticals macrocyclic chelators.Complexes of BA3Pic, BATA, and BADPA-18 chelators with lead isotopes are stable in vitro (2 days in a nine-fold excess of blood serum) and are also inert in vivo, being almost completely eliminated from mice body within 6 hours. Although complexes with the well-known chelator DOTA are stable with lead isotopes, when using the isotope Pb-212, approximately one-third of the bismuth (35%) is released from the complex, which was observed within 4 hours in our experiments. For BA3Pic, BATA, and BADPA-18 chelators, this value is significantly lower – 13, 6, and 12%, respectively.Complexes of chelators BADPA-21 and CADPA-18 with radium isotopes are stable in vitro (2 days in a nine-fold excess of blood serum). Conclusion All the studied ligands form stable complexes with lead and radium cations and are suitable for further studies with the Pb-212/Bi-212 and Ra-223 as potential components for radiopharmaceuticals for cancer therapy. Funding Acknowledgements This study is supported by Russian Science Foundation №25-73-00082.

Tetradentate phenanthroline-based ligands have demonstrated ability to efficiently extract uranium(VI) from nitric acid solutions. While their coordination with U(VI) has been extensively studied, their behavior toward tetravalent actinides under conditions relevant to spent nuclear fuel reprocessing remains poorly understood. Here, we investigated the extraction and coordination chemistry of Th(IV) in the presence of excess U(VI). Using a combination of solvent extraction, UV-Vis and Raman, we demonstrated that when the organic phase is pre-loaded with the uranyl ion pair [UO2L(NO3)]+[UO2(NO3)3]-, Th(IV) undergoes a selective anion-exchange reaction with the trinitratouranyl anion, forming the mixed ion pair [UO2L(NO3)]+[Th(H2O)2(NO3)5]-. Single-crystal X-ray diffraction further confirms the formation of heterometallic U-Th complexes, including ([UO2L(NO3)]+)2[Th(NO3)6]2-, providing direct structural evidence for mixed-metal ion pairing. These results revealed a previously unrecognized mechanism of Th(IV) uptake driven by anion exchange rather than direct ligand coordination.

The possibility of using carboxymethylcellulose as a platform for transporting ruthenium or bismuth ions in the body along with a medicinal preparation (a thiourea-derived NO synthase activator) was examined. Carboxymethylcellulose microgels were obtained by cross-linking with ruthenium or bismuth ions in a biological environment, and differences in their physicochemical parameters were identified. Furthermore, it was found that the size and aggregation stability of the microgels depend on the amount of the introduced organic ligand-drug.

This paper presents the results of a comprehensive study of neptunium oxides in oxidation states +4 to +7 using X-ray absorption near-edge spectroscopy (XANES) and theoretical modeling. Based on laboratory measurements of the L3-edge absorption, a systematic edge shift and changes in the spectral characteristics with increasing oxidation state were observed, reflecting changes in the local environment of neptunium atoms. Spectral XANES modeling using the FDMNES code and an analysis of the electron density of states (DOS) allowed us to interpret the contributions of the 6d states of neptunium to the formation of the absorption spectra, as well as their hybridization with the 2p states of oxygen. Particular attention is paid to CsNpVIIO4, which exhibits characteristic splitting features on the main absorption edge. The results demonstrate the high information content of XANES, especially in combination with theoretical analysis, for studying the electronic structure of actinide compounds.

Introduction The most in-demand direction in nuclear medicine today is targeted alpha therapy (TAT). It applies alpha emitters with high linear energy transfer (LET), such as Ac-225, together with Bi-213, which is formed from Ac-225 decay. Alpha particles induce higher cytotoxicity compared to beta particles. Hence, alpha particles can overcome the resistance of certain tumors. Moreover, due to their shorter range, their use in metastatic therapy results in lower dose rates for healthy tissues. Together with the high specificity of monoclonal antibodies, radioimmunotherapy with alpha-emitters is a very selective and effective way of treatment. However, monoclonal antibodies are heat-sensitive. Hence, it is necessary to use chelating agents that bind the radionuclide like Ac-225 at room temperature with high speed and yield. Objectives A series of new 18- and 21-membered macrocyclic ligands containing either benzene, pyridine, or cyclohexane were studied. Their complexing ability with Ac(III) was investigated. The stability of the resulting complexes with Ac-225 in vitro was evaluated Materials and Methods Thin layer chromatography was used to control the radiochemical purity of the studied complexes. The stability of the complexes was studied in vitro (fetal bovine serum with 1:10 dilution). The radioactivity measurements were performed by measuring Bi-213 activity after equilibrium had been reached. Results Complexes of Ac-225 with the studied series of ligands were formed within minutes at room temperature, which is an advantage compared with the macrocyclic chelators currently used in radiopharmaceuticals.All chelators were labeled under identical conditions (1 mM ligand, pH 8), and their in vitro stability was then assessed. The weakest Ac-225 binding was observed for the 18- and 21-membered macrocycles carrying diacetate pendant arms and a benzyl ring in the macrocyclic framework. Replacing the acetate groups with picolinate groups led to a modest increase in stability, more noticeable for the 18-membered macrocycle. Within this 18-membered group of chelators, we also examined diacetate and dipicolinate derivatives in which the benzyl ring was substituted with a pyridine ring. As before, picolinate groups provided better Ac(III) binding, and the switch from a benzene to a pyridine ring did not significantly affect stability.The 18-crown-6 scaffold generally showed a more favorable interaction with Ac(III). A similar improvement was seen when the benzyl ring in the dipicolinate derivative was replaced with a cyclohexane moiety, giving the most stable complex among the ligands with two pendant arms. This ligand, CADPA-18, together with the 18-azacrown-6 chelator bearing four acetate groups, BATA, showed outstanding stability of their Ac-225 complexes in fetal bovine serum (1:10 dilution), remaining intact even after 17 days. Conclusion Among all the chelators studied, the highest in vitro stability of the complex with Ac-225 was observed with chelators CADPA-18 and BATA (at least 17 days). Funding Acknowledgements The study was supported by state assignment of Lomonosov Moscow State University "Obtaining and application of radionuclides and labeled compounds for the purposes of nuclear medicine, the study of biologically significant processes and the interaction of living organisms with ionizing radiation" (Project Reg. No. 122012600116-4)

The kinetic isotope effect (KIE) is essential in various chemical applications from reaction mechanism studies to tritium removal from water, however, its evaluation is associated with computational difficulties, mainly related to the correct determination of the geometry of the transition state. Traditional KIE evaluation relies on experimental measurements or computational approaches like density functional theory (DFT), which are often costly and whose accuracy strongly depends on the level of theory used. Here, we present a novel semi-empirical method for rapid and precise KIE estimation in proton-exchange reactions. By refining transition state identification through an iterative surface scan, our approach significantly improves accuracy while maintaining computational efficiency. Benchmarking against experimental data demonstrates superior performance compared to both DFT and conventional semi-empirical methods. Additionally, validation with tritium exchange reactions confirms its robustness. The computational implementation is freely available, facilitating its integration into future research.

Sorption properties of clays play a crucial role in the long-term safety of radioactive waste disposal. In this study, the sorption behavior of cesium on 11 different clay samples from various geological deposits was investigated under a broad range of experimental conditions, including varying cesium concentrations and pH levels. While smectite is the predominant mineral in all samples, sorption isotherms exhibit at least two types of sorption sites with different affinities. Experimental data were analyzed using previously published thermodynamic models and their modifications, with an automated heuristic optimization approach applied to adjust model parameters. The two-site ion-exchange model demonstrated a good fit to the experimental data, yet no clear correlation was observed between the number of exchange sites and sample properties such as mineral composition, specific surface area, cation exchange capacity determined by the Cu-trien method, or layer charge. Even highly smectitic bentonites required the introduction of highly selective sorption sites to adequately describe cesium sorption behavior. These findings highlight the complexity of cesium sorption mechanisms in clays and the necessity for further studies to refine predictive models for nuclear waste management applications.

Technetium pentacarbonyl hydride 99TcH(CO)5 was studied using X-ray absorption spectroscopy at the Tc K-edge, complemented by a series of 99TcX(CO)5 (X = Cl, Br, I, 99Tc(CO)5) as the references. Experimental Tc K-edge XANES and EXAFS data were interpreted with the aid of density functional theory and advanced spectral modeling. EXAFS analysis of liquid pentacarbonyl hydride showed that the Tc-C and Tc-O interatomic distances in the molecule of this complex were close to those in 99Tc2(CO)10. The Tc K-edge XANES fingerprint and the first-shell EXAFS responses are largely controlled by the carbonyl coordination, whereas the nature of the X ligands in a series of 99TcX(CO)5 (X = Cl, Br, I, 99Tc(CO)5) exerts only a secondary role. The combined experimental and computational results further elucidate the factors underlying the enhanced stability of 99TcH(CO)5 toward carbonyl substitution.

Porous carbons based on activated reduced graphene oxide (rGO) have been demonstrated as excellent sorbents for U(vi), with their sorption capacity correlating with the degree of their oxidation. Herein, we demonstrate an extraordinarily high U(vi) sorption of similar to 7050 mu mol g-1 for super-oxidized porous carbon (SOPC) with a specific surface area (SSA) of similar to 970 m2 g-1 and an extremely high degree of oxidation (C/O = 2.1), similar to graphene oxide. The SOPC materials were prepared using an oxidation treatment applied to activated carbon produced from spruce cones. The extremely high SSA of the precursor activated carbon (similar to 3400 m2 g-1) as well as its microporous structure and mild oxidation treatment allowed for the preservation of a significant part of the surface area, providing materials with rather narrow pore size distribution (similar to 7.5 & Aring;). The SOPC prepared from spruce cone biochar is similar to defective graphene oxide but with a significantly higher surface area, resulting in superior U(vi) sorption. Analysis of EXAFS and XPS data shows that U(vi) likely binds to carboxylic groups on the opposite sides of the micropores. The small size of the micropores and irregular pore wall structure are the main factors affecting pore sorption. The spruce-cone biochar has a strong advantage compared with earlier used rGO as a precursor for the preparation of SOPC.

Lake sediment is continuously formed by gradually atmospheric deposition of air particles and the riverine input, it records information of environmental changes in the past year. Accumulated history of human industrial activities, especially since the 1950s, was reconstructed through analysis of sediment cores collected in Lake Khanka (Xingkai) located in the East Asia. Sediment cores collected from different locations in Lake Khanka (Xingkai), as well as surface soil surrounding the lake and sediment of the Spasovka River flowing into Lake Khanka (Xingkai) were analyzed for artificial (137Cs, 239,240Pu, 241Am, 237Np) and natural (238U, 232Th, 40K) radionuclides. Varied sedimentation rate across sections of Lake Khanka (Xingkai) was observed, which is mainly influenced by particles load in the inflowing rivers and the distance to the mouth of the inflowing rivers. The level, distribution of temporal variation of anthropogenic radionuclides 137Cs, plutonium isotopes, 237Np and 241Am in the sediments and soil indicate that this area only received global fallout without local sources of contamination. Intensive leaching of 40K from the catchment area of Lake Khanka (Xingkai) was detected, which might attribute to the soil features of this area. We demonstrate the preponderance of sediment runoff for radionuclide migration in the sediment column over diffusion and chemical processes.Anthropogenic pressure on Lake Khanka (Xingkai) is reflected in sedimentation rates linked to land use, while artificial radionuclides serve as precise tracers of radioactive contamination linked to the global fallout, providing a chronological archive of human impact without local contamination signals.

We investigated crystal structures and the mechanism of thermal expansion of weeksite and its synthetic analogues (K-, Rb-, Cs-) using a combination of geometrical-topological analysis and empirical methods (powder X-ray diffraction, infrared spectroscopy, scanning electron microscopy, single-crystal and powder X-ray variable-temperature diffraction). The weeksite sample studied herein was collected at the Anderson mine, Yavapai County, Arizona, USA. Its synthetic analogues were prepared using high-temperature approaches in sealed silica tubes. Natural weeksite is stable up to 860 +/- 10 degrees C; it dehydrates between 100-200 degrees C. Its synthetic analogues with Rb and Cs are stable at least until 1000 degrees C. Their thermal expansion is strongly anisotropic due to shear deformations of the crystal structure. The framework in the structure of weeksite can be regarded as a sequence of uranyl silicate layers linked by SiO4 tetrahedra. With increasing temperature, the angles at the Si-O-Si 'hinges' change, which causes the shear deformations. The differences in the thermal behaviour, including expansion anisotropy, are probably due to the nature (size) of the alkali cations occupying the cavities in the framework. The partial or complete replacement of Rb+ by Cs+ illustrates the zeolite-like nature of the uranyl silicate framework in weeksite. Therefore, its structure can be considered a possible candidate for the selective immobilization of 137Cs+ upon storing nuclear waste with little interference from the more abundant Na+ and K+.

In this work, double conjugate-microgels of Bi-CMC with different content of bismuth natural isotope were obtained and physicochemically characterized. The aggregative stability was demonstrated and the hydrodynamic and electrokinetic characteristics of Bi-CMC microgels under physiological conditions were quantitatively studied. The cytotoxicity of the obtained microgels was studied with respect to both tumor and healthy cells. The approach used to prepare microgels with stable bismuth ions was applied to obtain microgels cross-linked with radionuclide 207Bi with following parameters of decay: T1/2= 31.55 years, EC 99.962 %, beta+ 0.038 %. The obtained microgels labeled by 207Bi[Bi]3+ ions allowed a comparative analysis of the accumulation and organ distribution of radioactive ions within the microgel and free 207Bi3+ ions using a mouse model.

In this study, neptunium(V) double carbonate with magnesium was synthesized by the cation exchange synthesis method. Synchrotron powder X-ray diffraction, X-ray absorption spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy were employed for comprehensive solid-phase analysis. Solubility experiments were carried out in 0.01 M and 0.05 M NaClO4 solutions in the pH range 6-10 for the evaluation of the thermodynamic stability of solid magnesium-neptunium(V) double carbonate. Based on these data, the solubility product constant was estimated from the experimental data and established to be log Ksp = -15.9. During the solubility experiments, the initial Np(V)-Mg double carbonate underwent a phase transformation. This transformation led to the formation of a Np(V)-K double carbonate, caused by increasing potassium concentrations in solution primarily from the KCl-filled pH electrode. The solubility constant for the Np(V) double carbonate with potassium was determined to be log Ksp = -16.53 ± 0.10, which is significantly lower than that reported in the literature, confirming the high thermodynamic stability of the KNpO2CO3 solid phase.

Neptunium is a minor actinide with diverse redox chemistry and high tendency to form unique structures with cation-cation interactions. As a result, the fate of neptunium during nuclear fuel reprocessing remains underexplored. In this work, we aim to understand neptunium chemistry in organic solutions with a tetradentate N,O-donor ligand that is pre-organized to stabilize 5f-elements in contact with concentrated nitric acid solutions. Crystal structures of neptunium(v) and (vi) complexes with ligands revealed the formation of three types of species: [LNpVIO2NO3][NpVIO2(NO3)3], [LNpVIO2NO3]2[NpVIO2(NO3)4] ion pairs, and [LNpVO2NO3]2NpVIO2(NO3)2. The latter one is a mixed-valence NpV-NpVI complex with ligand-coordinated neptunium(v), which stabilizes poorly extractable neptunium(v) in organic solution. Neptunium speciation in organic phase after extraction from neptunium(v) and (vi) aqueous solutions was investigated using a combination of XAS and 1H-NMR spectroscopies, supported by thermodynamic calculations. The results demonstrate that neptunium(v) is extracted as LNpVO2NO3 and then oxidized to form [LNpVIO2NO3]NO3. Extraction of neptunium(vi) leads to the formation of ion pairs. The formation of mixed-valence NpV-NpVI complexes was not observed in solvent extraction systems, but they were found to be stable in acetonitrile. This study provides valuable insights into the chemical processes behind the extraction of neptunium(v) and (vi) under conditions relevant to spent nuclear fuel reprocessing.

Pu behavior under conditions of injection of acidic liquid radioactive waste into a deep permeable disposal was laboratory simulated. Rapid Pu sorption in the nearest zone, slow leaching and resorption on fresh disposal sand were demonstrated.

Brachytherapy, or internal radiation therapy, is a highly effective treatment option for localized tumors. Herein, injectable and biodegradable metal-organic frameworks (MOFs) were engineered to deliver the therapeutic radioisotope yttrium-90 (90Y). Particles of bimetallic MIL-100(Fe,Y) and Y-BTC, doped with 90Y and 88Y, were synthesized in a single step and retained radioyttrium in various buffer solutions. Tumor injectability and radioisotope retention were evaluated using tumor-bearing mice. In vivo analysis and calculations showed that radiolabeled MIL-100(Fe,Y) emitted more than 38% of its radioactivity, while Y-BTC emitted greater than 75% of its radioactivity, for 7 days at the tumor site upon intratumoral injection, without significant yttrium accumulation in off-target tissues. The anticancer effects of MIL-100(Fe,Y,90Y) and 90Y,Y-BTC particles were assessed using 3D multicellular tumor spheroids and a tumor-bearing mouse model, respectively. 90Y-doped MIL-100(Fe,Y) particles penetrated A549 tumor spheroids and caused superior cytotoxic effects compared to non-radioactive particles or 90YCl3, added at the same dose. Brachytherapy with 90Y-doped Y-BTC MOFs induced inhibition of B16F1 melanoma tumor growth and resulted in an increased median survival of 8.5 days compared to 4.5 days in untreated mice. This study shows the feasibility of preparing radioactive 90Y-containing biodegradable non-toxic MOF particles that are advantageous for low-dose rate internal radiotherapy.

Nowadays, PSMA ligands are widely used for radiotheragnostic purposes in prostate cancer. The synthesis of a PSMA-Bisp conjugate was developed and realized with good yield (overall yield ~58% for the last two steps). All newly synthesized compounds were characterized by physicochemical methods: 1H and 13C NMR, HRMS, and LCMS (for biologically tested samples). Subsequently, Bisp1 (diacetate bispidine ligand), Bisp-alkyne (bifunctional derivative of Bisp1), and its conjugate PSMA-Bisp were labeled by 64Cu in mild conditions. In vitro studies of the labeled conjugate [64Cu]Cu-PSMA-Bisp have shown great stability in model solutions. Finally, [64Cu]Cu-PSMA-Bisp was compared to the well-known PSMA-617 conjugate labeled with 64Cu and they showed similar stability in excess bovine serum (BVS), and at the same time, labeling PSMA-Bisp with 64Cu is characterized by extremely high kinetics in mild conditions, while labeling PSMA-617 with 64Cu requires heating (90 °C). Thus, this conjugate can be incredibly promising for nuclear medicine.