High-level nuclear waste containing long-lived radionuclides must be reliably contained in a deep underground storage facility. Its safety will be ensured by a system of artificial engineered barriers and the surrounding geological environment. Backfill is one of the least studied barriers, and it is often considered in conjunction with a bentonite buffer. However, it has its own tasks: fixing the position of the buffer and waste container, stabilizing tunnels and galleries, decreasing their permeability and thermal conductivity, maintaining groundwater Eh and pH to reduce the solubility and enhance the sorption of radionuclides, and preventing their migration as colloids on bentonite particles derived from the buffer erosion. Clays, bentonite, zeolites, cement, and a mixture of bentonite and crushed rock were proposed previously as potential backfill materials. One of the requirements to the backfill is its compatibility with the geological environment, which is met by the crushed rocks around the repository. High sorption properties of such rocks for radionuclides significantly reduce the radionuclide washout by water from the repository into the biosphere.
Recent advances in the fundamental chemistry of technetium carbonyl compounds on the macroscopic and tracer levels and in the field of search for and development of new radiopharmaceuticals based on 99mTc carbonyl compounds are summarized. A comparative analysis of the results is made, and the scientific approaches used in the basic and nuclear medical research are compared. The directions that seem promising are outlined.
The possibility of replacing potentially hazardous perfluorooctanoic acid (PFOA) by nonfluorinated analogs in the technology of low-water decontamination using liquefied Freon HFC-134a was demonstrated. The efficiency of the radionuclide extraction from the fabric surface with formulations based on PFOA and on alkylbenzenesulfonic acid (ABSA) was compared. The emulsion formation in the PFOA–water–Freon and ABSA–water–Freon systems was detected; it favors the radionuclide extraction from the fabric surface. The optimum reactant concentrations in the system were determined.
The extraction of U(VI), Th(IV), and lanthanides(III) from nitric acid solutions using solutions of a complex of diphenyl(dibutylcarbamoylmethyl)phosphine oxide (L) with hydrogen di(2-ethylhexyl) sulfosuccinate (HSSu) in organic solvents was studied. Actinide and lanthanide(III) ions are extracted from nitric acid solutions with solutions of this complex via a cation-exchange mechanism. The stoichiometry of the extracted complexes was determined, and the effect of the organic diluent on the extraction of metal ions into the organic phase was examined. The conversion of CMPO to a complex with HSSu leads to a significant increase in the degree of extraction of U(VI), Th(IV), and Ln(III) ions from nitric acid solutions.
Intermolecular interactions in the known mono-, bi-, tri-, and tetranuclear manganese, technetium, and rhenium carbonyl halides were analyzed using the method of molecular Voronoi–Dirichlet polyhedra. The topology of transition metal (M) sublattices in dimeric carbonyl halides [MХ(CO)4]2 was examined in terms of the Voronoi–Dirichlet polyhedra. This analysis has proved that such complexes with X = Cl or Вr are isostructural but differ from the related iodides, which, in turn, are isostructural to each other irrespective of the kind of M. Similar pattern is observed for mononuclear complexes [MХ(CO)5]. The size effect is considered as the main cause of the change in the crystal structure in going from X = Cl and Br to X = I. No convincing evidences of specific intermolecular interactions involving halide ligands (halogen bonds) have been found.
Spectrophotometric monitoring of the photolysis of 1–3 mM uranyl solutions containing 0.4 mM terbium(III) perchlorate or 0.1 mM silver(I) perchlorate and 1 mM unsaturated phosphotungstate K10P2W17O61 at pH 2 and below has not revealed the formation of terbium(IV) and silver(II). Because the TbIVL2/TbIIIL (L is unsaturated phosphotungstate anion) and Ag(II)/Ag(I) oxidation potentials are about 2 V, it follows from the experimental data that the *UO22+/UO2+ potential is lower than 2 V. The water oxidation to the ОН radical has not been confirmed. However, it is known from the published data that the photolysis yields Н2О2. Therefore, it can be stated that the potential of the excited uranyl ion is higher than the potential of the Н2О2, Н+/Н2О system, i.e., higher than Е0(H2O2, Н+/H2O (liq.) = 1.763 V.
The safety of a radioactive waste deep geological repository (DGR) depends on the retaining ability of crystalline rocks, which act as a key natural barrier preventing the radionuclide release into the environment. Therefore, one of important factors is that heat-releasing radionuclides present in radioactive waste (RW) can cause the temperature elevation in the near zone of the repository, which, in turn, can affect the sorption behavior of radionuclides. The cesium and strontium sorption onto a diabase sample taken from the R-7 well at a depth of 418 m on the Yeniseisky site was studied. The diabase sample was characterized by scanning electron microscopy with X-ray microanalysis, X-ray fluorescence analysis, and X-ray diffraction analysis. The data on the cesium and strontium sorption onto the diabase sample at 25, 37.5, and 50°C were obtained. The sorption isotherms were constructed and approximated by the Freundlich and Langmuir models. The Gibbs energy (ΔG), enthalpy (ΔH), and entropy (ΔS) of the process were determined.
Modified polymer matrices based on methacrylic acid (MA) cross-linked with triethylene glycol dimethacrylate (TGM-3) or divinylbenzene (DVB) were synthesized. Diethyl allylphosphonate (DEAP), dibutyl allylphosphonate (DBAP), and diethyl vinylphosphonate (DEVP) were synthesized and used as matrix modifiers. To obtain sorbents based on the matrices prepared, two methods of introducing the extractant, tetraoctyldiglycolamide (TODGA), were chosen: impregnation and in situ method. The second method proved to be worse because of lower mobility of the extractants inside the matrix. In addition, the kinetics of f-element cation sorption also correlated with the water sorption rate. The presence of active binding sites on the surface of the polymer matrix affects the complexation of the Eu(III) ion, but the extractant applied to its surface makes the major contribution to the sorption of the ions under study.
A process was developed for the treatment of decontamination solutions (DSs) from nuclear power plants (NPPs) equipped with VVER-1200 reactors, Novovoronezh NPP-2 (NVNPP-2) and Leningrad NPP-2 (LNPP-2), to remove the main radionuclides using sorption, precipitation, destructive, and membrane methods. The NVNPP-2 DS contains such radionuclides as 124,125Sb, 137,134Cs, 60Co, 54Mn, etc. The specific activity of the major radionuclides, 125Sb, 60Co, and 54Mn, is n × 103 Bq/dm3, рН is 2–12, and the concentration of salts is 5–12 g/dm3 (major components: sodium nitrate, oxalates, and carbonates). In LNPP-2 DS, the major radionuclide is 110mAg (1.6 × 105 Bq/dm3). The suggested flowsheet for the decontamination of NVNPP-2 and LNPP-2 DSs to remove radionuclides involves pH adjustment, filtration to separate the precipitate, ozonation, filtration, repeated pH adjustment, and sorption onto T-35. The resulting filtrate after the evaporation to dry salts has the total specific α-activity of <120 Bq/kg and the β-activity of 1000–10000 Bq/kg, mainly due to the presence of natural 40K.
High radiochemical purity (RCP) is a crucial requirement to radiopharmaceuticals for positron emission tomography (PET). Semipreparative reversed-phase HPLC with UV and radioactivity detection is an efficient method for purifying radiopharmaceuticals. In separation of highly lipophilic molecules, most of the product remains on the chromatographic column owing to nonspecific sorption. We encountered this problem recently when developing a procedure for purifying [18F]anle138b, a candidate radiotracer for Parkinson’s disease diagnostics. In this study, we tested standard С18 columns, Supelco Ascentis RP-AMIDE, ACE 5 C18, and Macherey-Nagel Nucleosil, in the step gradient mode; however, the required RCP (>95
The effects of soil organic matter, moisture content, and soil texture on the retention of the fallout radionuclide 137Cs in soils from several mountains were studied. A high-resolution gamma-ray measurement system based on a high-purity germanium detector was used to measure the activity concentration of 137Cs in soils collected from Bawajy, Haibatsultan, Bnabawe, Keshke, and Awagird mountains, which are located in the Koya district of the Kurdistan region, northeast of Iraq. The activity concentration levels of 137Cs ranged from 0.0 to 102.9 Bq kg–1 with a mean value of 37.2 Bq kg–1. The mean values of absorbed dose rate and annual effective dose rate were found to be 1.12 nGy h–1 and 1.37 µSv year–1, respectively. The results obtained tend to exhibit a linear correlation between the altitudes of the sampling sites and the 137Cs concentration levels.
This study presents a comparative analysis of natural radioactivity and radiological hazard parameters in core samples from the Titas and Rashidpur gas fields, Bangladesh, determined using a high-purity germanium (HPGe) detector. Six core samples from Titas (depths: 2713–2784 m) and four from Rashidpur (depths: 1454–2896 m) were analyzed for the activity concentrations of 226Ra, 232Th, and 40K. The radionuclide concentrations in Titas range from 17 ± 2 to 64 ± 4 Bq/kg for 226Ra, 43 ± 3 to 109 ± 4 Bq/kg for 232Th, and 787 ± 47 to 2701 ± 70 Bq/kg for 40K; while in Rashidpur, the concentrations of ²²⁶Ra range from 32 ± 3 to 52 ± 3 Bq/kg; those of 232Th, from 48 ± 3 to 88 ± 4 Bq/kg; and those of 40K, from 660 ± 33 to 1737 ± 63 Bq/kg, both surpassing the global average significantly. Assessment of radiological hazard parameters indicates that some values in the Titas samples and a few in the Rashidpur samples exceed internationally recommended reference levels. These findings highlight the importance of continued monitoring and suggest that caution should be exercised when handling or utilizing materials from these gas fields for any purpose.
This study explores the distribution and radiological impact of transporting naturally occurring radioactive materials (NORMs) in soils collected from the vicinity of the Mymensingh 210 MW Combined (heavy fuel oil/gas) Cycle Power Plant in Bangladesh. Twenty-five soil samples were systematically collected at radial distances of 250, 500, and 1000 m from the power plant to assess the spatial variation in radioactivity levels. The measured activity concentrations of 226Ra, 232Th, and 40K ranged from 18 ± 1 to 34 ± 3, from 23 ± 2 to 60 ± 5, and from 340 ± 29 to 550 ± 35 Bq/kg, respectively. Although the 226Ra level did not exceed global average values, high levels of 232Th and 40K, exceeding world average values, were revealed. Contrary to expectations of a gradual decrease in the radionuclide concentrations with increasing distance from the power station, their levels actually varied nonmonotonically. The results obtained can be explained by high variability of geological background conditions, mobility of radionuclides, and human impact on the environment. While radium equivalent activity and general hazard index were within international safety standards, some samples exceeded these values, which could lead to a potential threat to public health. Multivariate statistics analysis showed that 226Ra and 232Th were the main factors causing radiological hazard in the research area, whereas 40K showed completely different behavior and formed a special cluster due to the presence of other geochemical processes related to its formation.
The equilibrium mechanism of sorption interaction of CrO42–, MoO42–, SeO32–, and ReO4– ions with surface functional centers of the graphene–oxide composite TiO2||C was established. The anion sorption isotherms are described by the Langmuir model for a monoenergetic sorbent with the Henry region at concentrations below 1 μM. The pH dependences of the anion distribution coefficient Kd are dome-shaped with a maximum at pH in the range 3–4. At pH in the range 2–6, the composite exhibits the properties of a collective action sorbent for the oxo anions studied with logKd [mL/g] ≈ 2–5. A mechanism of oxo anion sorption based on the 2-pK model of surface complexation of anions by the sorption sites of the composite is proposed. The sorption mechanism suggests that the affinity of the nonprotonated anion for sorption sites in the pH range studied significantly exceeds that of the protonated species. As a result, the parameters of the surface complexation of anions KM(0,1,2) are independent of the protonation constants of anions in the solution and remain constant, but different for the sorption sites Ti–OH2+, Ti–OН, and Ti-O– of the composite. Based on the modeling results, a predictive calculation of the sorption isotherm of the Sb(OH)6– anion by the composite as a function of pH was performed. Qualitative agreement of the calculation results with published data was demonstrated.
T-cell immunoreceptor with Ig and ITIM domains (TIGIT) is a newly identified immune checkpoint involved in tumor immune evasion; it represents a promising target for cancer immunotherapy. Noninvasive in vivo imaging of TIGIT expression may provide valuable insights into the tumor immune microenvironment and facilitate the evaluation of TIGIT-targeted therapies. In this study, tiragolumab (anti-TIGIT monoclonal antibody) was conjugated with HYNIC and radiolabeled with 99mTc using an EDDA/tricine coligand system under optimized mild conditions. Radiochemical purity and stability were assessed by ITLC and SEC-HPLC, while the chelator-to-antibody ratio (CAR) was determined using MALDI-TOF. In vitro binding was evaluated using saturation binding assays in TIGIT-expressing Jurkat cells, and the immunoreactivity was evaluated by Lindmo analysis. Biodistribution and small-animal SPECT imaging were conducted in a Jurkat tumor-bearing mouse model. The radioconjugate was obtained with a radiochemical yield of 64.2 ± 1.7
This study presents an assessment of gross alpha and beta radioactivity levels in groundwater samples collected from the Al-Gwaa region in central Saudi Arabia and evaluates the associated radiological health risks. A total of 19 groundwater samples were collected from wells and analyzed using a low-background gas proportional alpha/beta counting system. The measured gross alpha activity concentrations ranged from 0.12 to 1.68 Bq/L with an average value of 0.55 Bq/L, while gross beta activities varied from 0.16 to 2.70 Bq/L with a mean value of 0.86 Bq/L. Several groundwater samples exceeded the World Health Organization (WHO) recommended screening levels of 0.1 Bq/L for gross alpha and 1.0 Bq/L for gross beta activities. Total dissolved solids (TDS) ranged between 312 and 3350 mg/L with an average value of 817 mg/L, indicating elevated mineralization in some groundwater sources. The calculated annual effective dose (AED) and excess lifetime cancer risk (ELCR) values revealed that some sampling locations may pose potential radiological health risks due to long-term groundwater consumption. The elevated radioactivity levels are mainly attributed to naturally occurring radionuclides associated with the geological formations of the aquifer system studied. Continuous radiological monitoring and detailed radionuclide investigations are therefore recommended to ensure groundwater safety in the region.
The efficiency of the treatment of liquid radioactive media, mainly with pH 4.0–10.5, containing boric acid in combination with iron(III) hydroxo species, as well as complexing agents such as oxalic acid and EDTA, to remove ruthenium radionuclides by sorption onto a composite sorbent based on Zr, Ca, and Mg phosphates was determined. The highest distribution coefficients (Kd = 1.68 × 105 cm3/g) and decontamination factor (Kdec = 360) were obtained in solutions containing 5 g/dm3 boric acid and 1 mg/dm3 Fe(III) at pH ≥ 9.0. The presence of EDTA, as well as an increase in the boric acid concentration to 10 g/dm3, leads to a decrease in the treatment performance of the sorbent. Increasing the aging time of model solutions leads to a significant decrease in the efficiency of solution decontamination from ruthenium radionuclides with the sorbent at pH ≥ 9.0. The sorbent was applied to the treatment of real boron-containing liquid radioactive waste at the Joint Institute for Power and Nuclear Research—Sosny complex for liquid radioactive waste reprocessing. The required purification criterion (106Ru volume activity ˂100 Bq/dm3) is achieved after 2–3 purification stages at the main Fe(III) concentration in the purified liquid radioactive waste of 1 mg/dm3 and pH ≥ 9.
The effect of acetic acid on the thermal stability of a nitric acid solution of acetohydroxamic acid with hydrazine nitrate was studied. Acetic acid intensifies the exothermic reaction occurring in the solution, thereby increasing the start temperature of the exothermic reaction. The dependence of the exothermic reaction parameters on the preliminary exposure time of the solution was established. The kinetic parameters of the reaction were determined.
As a part of implementation of the closed nuclear fuel cycle concept, approaches to the recovery and use of valuable fission products from high-level waste resulting from spent nuclear fuel reprocessing at the Mayak Production Association were examined. The results of the development and trials of the extraction and sorption technologies for the concentration and purification of cesium and strontium radionuclides, rare earth elements, and platinum group metals are presented. Effectiveness of the crown ether based extraction systems for the simultaneous recovery of strontium and cesium was demonstrated during both rig and industrial trials. Methods of the combined alkaline and oxalate precipitation were developed for the concentration and purification of rare earth elements, including 144Ce. Experimental data on the combined sorption and electrochemical recovery of platinum group metals from nitric acid solutions resulting from spent nuclear fuel reprocessing are provided. Procedures for reprocessing accumulated salt-rich high-level waste, for example, using ferrocyanide sorbents in a tangential flow filtration system, are considered. The results obtained show that the recovery of valuable radionuclides can be integrated into the general scheme of high-level waste reprocessing to increase the resource efficiency of the nuclear fuel cycle and reduce the radioactive waste volume.
The formation conditions and existence borders for 63Ni ionic and nonionic species in aqueous solutions containing anions with different complexing abilities (NO3–, NH4+, SO42–, C2O42–, EDTA, boric acid) were determined using ultrafiltration, centrifugation, and pH-metric titration. 63Ni forms pseudocolloids and Ni(OH)+ hydroxo complexes in a medium of weak complexing ions at pH > 6. The behavior of 63Ni in the electrolyte solution for electrolyte–plasma treatment method is similar to its behavior in H2SO4 solution: At pH 8.0, 63Ni(II) forms ammonium sulfate complexes that are retained by the membrane but do not undergo sedimentation during centrifugation. The presence of hydrolyzed Fe(III) species in solution leads to an increase in the retention of 63Ni by the semipermeable membrane to 90
