Search Results (32)

This article systematizes research data on the natural radioactivity of fossil coals and of ash and slag waste from coal power engineering in the context of radioecological safety. The relatively low energy efficiency of the operating thermal power plants in Kazakhstan has a significant impact on the environment. In addition to natural radioactive elements (U²³⁸ and its decay products, Th²³² and its decay products, and K⁴⁰), coal combustion waste also contains a significant amount of trace elements that have a negative impact on the atmosphere and the environment. In Kazakhstan, about 67% of electricity is generated by coal power engineering. However, in the process of burning coals, radioactive nuclides are concentrated in ash and slag waste. In the fuel power industry of Kazakhstan, high-ash coals with low concentrations of radionuclides are mainly used. The average contents of uranium and thorium are close to the clarke values. The natural radioactivity of coal and of ash and slag waste from Karaganda GRES-1, which consumes Ekibastuz coals with an ash content of 32–39%, was studied. The average values of the specific activities of U²³⁸, Th²³², and K⁴⁰ in 25 coal samples were 27.9 Bq/kg, 19.5 Bq/kg, and 81.0 Bq/kg, respectively. In ash and slag waste, the concentrations of these radionuclides were several times higher. The concentration coefficients of the studied radionuclides varied within the ranges of 4.7–5.5 for U, 3.8–5.7 for Th, and 4.2–8.6 for K⁴⁰. It was established that during coal combustion in thermal power plants, due to carbon combustion and the removal of volatile compounds, not only natural radionuclides but also many microelements, including toxic ones (Mn, Cd, Ni, Co, Zn, etc.), are concentrated in the ash. Full article

Isotopes at the limits of nuclear existence are of great interest for their critical role in nuclear astrophysical reactions and their exotic structure. Experimentally, exotic nuclides are challenging to address due to their low production cross-sections, overwhelming amounts of contamination, and lifetimes of typically less than a second. To this end, a Multiple-Reflection Time-of-Flight mass spectrometer at the TITAN-TRIUMF facility was built to determine atomic masses. This device is the preferred tool to work with exotic nuclides due to its ability to resolve the species of interest from contamination and short measurement cycle times, enabling mass measurements of isotopes with millisecond half-lives. With a relative precision of the order 10⁻⁷, we demonstrate why the TITAN MR-TOF MS is the tool of choice for precision mass surveys for nuclear structure and astrophysics. The capabilities of the device are showcased in this work, including new mass measurements of short-lived tin isotopes (^104–107Sn) approaching the proton dripline as well as ⁸⁹Zr, ⁹⁰Y, and ⁹¹Y. The last three illustrate how the broadband surveys of MR-TOF MS reach beyond the species of immediate interest. Full article

(1) Background: Targeted alpha therapy is an emerging field in nuclear medicine driven by two advantages: overcoming resistance in cancer-suffering patients to beta therapies and the practical application of lower activities of ²¹²Pb- and ²²⁵Ac-labelled peptides to achieve the same doses compared to beta therapy due to the highly cytotoxic nature of alpha particles. However, quality control of the ²¹²Pb/²²⁵Ac-radiopharmaceuticals remains a challenge due to the low activity levels used for therapy (100 kBq/kg) and the formation of several free daughter nuclides immediately after the formulation of patient doses; (2) Methods: The routine alpha detection on thin-layer chromatograms (TLC) of ²¹²Pb- and ²²⁵Ac-labelled peptides using a MiniScanPRO+ scanner combined with an alpha detector head was compared with detection using an AR-2000 scanner equipped with an open proportional counter tube. Measurement time, resolution and validity were compared for both scanners; (3) Results: For ²²⁵Ac, the quality control values of the radiochemical purity (RCP) were within the acceptance criteria 2 h after TLC development, regardless of when the TLC probe was taken. That is, if the TLC probe was taken 24 h after radiosynthesis, the true value of the RCP was not measured until 5 h after TLC development. For ²¹²Pb-labelled peptides, the probe sampling did not have a high impact on the value of the RCP for the MiniScanPRO+ and AR-2000. A difference was observed when measuring TLC with the AR-2000 in different modes; (4) Conclusions: The MiniScanPRO+ is fast, does not require additional equipment and can also measure the gamma spectrum, which may be important for some radiopharmaceutical production sites and regulatory authorities. The AR-2000 has a better signal-to-noise ratio, and this eliminates the need for additional waiting time after TLC development. Full article

Radioactive iodine (¹³¹I) with a short half-life of ~8.02 days is one of the most commonly used nuclides in nuclear medicine. However, ¹³¹I easily poses a significant risk to human health and ecological environment. Therefore, there is an urgent need to develop a secure and efficient strategy to capture and store radioactive iodine. Metal–organic frameworks (MOFs) are a new generation of sorbents with outstanding physical and chemical properties, rendering them attractive candidates for the adsorption and immobilization of iodine. This review focuses on recent research advancements in mechanisms underlying iodine adsorption over MOFs and their derivatives, including van der Waals interactions, complexing interactions, and chemical precipitation. Furthermore, this review concludes by outlining the challenges and opportunities for the safe disposal of radioactive iodine from the perspective of the material design and system evaluation based on our knowledge. Thus, this paper aims to offer necessary information regarding the large-scale production of MOFs for iodine adsorption. Full article

Heavy nuclides like uranium and their decay products are commonly found in nuclear industries and can pose a significant health risk to humans due to their alpha-emitting properties. Traditional alpha detectors require close contact with the contaminated surface, which can be time-consuming, labour-intensive, and put personnel at risk. Remote detection is urgently needed but very challenging. To this end, a candidate detection mechanism is alpha-induced radio-luminescence. This approach uses the emission of photons from radio-ionised excited nitrogen molecules to imply the presence of alpha emitters from a distance. Herein, the use of this phenomenon to remotely image various alpha emitters with unparalleled levels of sensitivity and spatial accuracy is demonstrated. Notably, the system detected a 29 kBq Am-241 source at a distance of 3 m within 10 min. Furthermore, it demonstrated the capability to discern a 29 kBq source positioned 7 cm away from a 3 MBq source at a 2 m distance. Additionally, a ‘sandwich’ filter structure is described that incorporates an absorptive filter between two interference filters to enhance the ambient light rejection. The testing of the system is described in different lighting environments, including room light and inside a glovebox. This method promises safer and more efficient alpha monitoring, with applications in nuclear forensics, waste management and decommissioning. Full article

Throughout the nuclear power production process, the disposal of radioactive waste has consistently raised concerns about environmental safety. When the metal tanks used for waste disposal are corroded, radionuclides seep into the groundwater environment and eventually into the biosphere, causing significant damage to the environment. Hence, investigating the adsorption behavior of radionuclides on the corrosion products of metal tanks used for waste disposal is an essential component of safety and evaluation protocols at disposal sites. In order to understand the adsorption behavior of important radionuclides ⁶⁰Co, ⁵⁹Ni, ⁹⁰Sr, ¹³⁵Cs and ¹²⁹I on α-FeOOH, the influences of different pH values, contact time, temperature and ion concentration on the adsorption rate were studied. The adsorption mechanism was also discussed. It was revealed that the adsorption of key nuclides onto α-FeOOH is significantly influenced by both pH and temperature. This change in surface charge corresponds to alterations in the morphology of nuclide ions within the system, subsequently impacting the adsorption efficiency. Sodium ions (Na⁺) and chlorate ions (ClO₃⁻) compete for coordination with nuclide ions, thereby exerting an additional influence on the adsorption process. The XPS analysis results demonstrate the formation of an internal coordination bond (Ni–O bond) between Ni²⁺ and iron oxide, which is adsorbed onto α-FeOOH. Full article

Currently, targeted alpha therapy (TAT) is a new therapy involving the administration of a therapeutic drug that combines a substance of α-emitting nuclides that kill cancer cells and a drug that selectively accumulates in cancer cells. It is known to be effective against cancers that are difficult to treat with existing methods, such as cancer cells that are widely spread throughout the whole body, and there are high expectations for its early clinical implementation. The nuclides for TAT, including ¹⁴⁹Tb, ²¹¹At, ^212/213Bi, ²¹²Pb (for ²¹²Bi), ²²³Ra, ²²⁵Ac, ^226/227Th, and ²³⁰U, are known. However, some nuclides encounter problems with labeling methods and lack sufficient preclinical and clinical data. We labeled the compounds targeting prostate specific membrane antigen (PSMA) with ²¹¹At and ²²⁵Ac. PSMA is a molecule that has attracted attention as a theranostic target for prostate cancer, and several targeted radioligands have already shown therapeutic effects in patients. The results showed that ²¹¹At, which has a much shorter half-life, is no less cytotoxic than ²²⁵Ac. In ²¹¹At labeling, our group has also developed an original method (Shirakami Reaction). We have succeeded in obtaining a highly purified labeled product in a short timeframe using this method. Full article

Alpha particle-emitting radiopharmaceuticals are in high demand for use in targeted alpha therapy. Ac-225 is currently produced using Th-229, but its annual production remains low, approximately 63 GBq. Previously, we produced a large amount of Ac-225 via the (n,2n) reaction in fast reactors; however, it required repetitive irradiation. In this work, we investigated a method to produce Th-229 via the (3n,x) reaction through long-term irradiation using neutrons from Pressurized Water Reactors. As target nuclides, Ra-226, which is commonly used for Ac-225 production, and Th-230, which is not widely used but is abundant, were selected. The evaluation was conducted under mixed conditions of Th-230 and Th-232. Ra-226 and Th-230 produce Th-229 (T1/2 = 7920 years) after long-term neutron irradiation. Th-229, which has a long half-life, the α-decays to produce Ra-225, and the β-decays of Ra-225 to produce Ac-225. These processes are semi-permanent owing to the long half-life of Th-229. Further, an irradiation method that does not require major changes in the upper part of the PWR fuel assembly geometry was employed by replacing the plugging device attached to the control rod guide tube with a target pin. The PWR loaded with abundant natural thorium target and irradiated with thermal neutrons for as long as approximately 5 years can produce more than twice the current world supply of Ac-225 annually and permanently. Full article

The high energy of α emitters, and the strong linear energy transfer that goes along with it, lead to very efficient cell killing through DNA damage. Moreover, the degree of oxygenation and the cell cycle state have no impact on these effects. Therefore, α radioisotopes can offer a treatment choice to individuals who are not responding to β− or gamma-radiation therapy or chemotherapy drugs. Only a few α-particle emitters are suitable for targeted alpha therapy (TAT) and clinical applications. The majority of available clinical research involves ²²⁵Ac and its daughter nuclide ²¹³Bi. Additionally, the ²²⁵Ac disintegration cascade generates γ decays that can be used in single-photon emission computed tomography (SPECT) imaging, expanding the potential theranostic applications in nuclear medicine. Despite the growing interest in applying ²²⁵Ac, the restricted global accessibility of this radioisotope makes it difficult to conduct extensive clinical trials for many radiopharmaceutical candidates. To boost the availability of ²²⁵Ac, along with its clinical and potential theranostic applications, this review attempts to highlight the fundamental physical properties of this α-particle-emitting isotope, as well as its existing and possible production methods. Full article

In recent works, many industrial by-products were employed as solid precursors for the synthesis of alkali-activated binders and as alternatives to Portland cement for the immobilization of hazardous, toxic and nuclear wastes. Among industrial wastes, alkali-activated brick was found to be an interesting porous composite for removing very toxic heavy metals (Pb²⁺, Cd²⁺, Co²⁺) and radio-nuclides (Sr²⁺, Cs⁺, Rb⁺) from aqueous solutions. The starting material is very attractive due to the presence of metakaolinite as a geo-polymer precursor and silica for increasing material permeability and facilitating water filtration. The alkaline reaction gave rise to geo-polymerization followed by partial zeolitization. Elemental surface micro-analysis was performed by Scanning Electron Microscopy (SEM) equipped with an Energy-Dispersive X-ray Spectrometer (EDS). The formation of crystalline phases was corroborated by X-ray diffraction (XRD) analysis. Information about ²⁹Si, ²⁷Al and ¹H nuclei environments in crystallized and amorphous aluminosilicates was obtained by ²⁹Si, ²⁷Al and ¹H MAS NMR. ²⁷Al–¹H dipolar-mediated correlations were investigated by employing dipolar hetero-nuclear multiple quantum coherence (D-HMQC) NMR, highlighting Al–O–H bonds in bridging hydroxyl groups (Si–OH–Al) that are at the origin of adsorptive properties. Aqueous structural stability and cationic immobilization characteristics before and after material calcination were investigated from acid-leaching experiments. Full article

We explore the effect of neutron lifetime and its uncertainty on standard big bang nucleosynthesis (BBN). BBN describes the cosmic production of the light nuclides, ${}^1\mathrm{H}$, D, ${}^3\mathrm{H}$+${}^3\mathrm{He}$, ${}^4\mathrm{He}$, and ${}^7\mathrm{Li}$+${}^7\mathrm{Be}$, in the first minutes of cosmic time. The neutron mean life ${\tau }_n$ has two roles in modern BBN calculations: (1) it normalizes the matrix element for weak $n\leftrightarrow p$ interconversions, and (2) it sets the rate of free neutron decay after the weak interactions freeze-out. We review the history of the interplay between ${\tau }_n$ measurements and BBN, and present a study of the sensitivity of the light element abundances to the modern neutron lifetime measurements. We find that ${\tau }_n$ uncertainties dominate the predicted ${}^4\mathrm{He}$ error budget, but these theory errors remain smaller than the uncertainties in ${}^4\mathrm{He}$ observations, even with the dispersion in recent neutron lifetime measurements. For the other light element predictions, ${\tau }_n$ contributes negligibly to their error budget. Turning the problem around, we combine present BBN and cosmic microwave background (CMB) determinations of the cosmic baryon density to predict a “cosmologically preferred” mean life of ${\tau }_n\left(\mathrm{BBN}+\mathrm{CMB}\right)=870\pm 16\mathrm{s}$, which is consistent with experimental mean life determinations. We show that if future astronomical and cosmological helium observations can reach an uncertainty of ${\sigma }_{\mathrm{obs}}\left(Y_p\right)=0.001$ in the ${}^4\mathrm{He}$ mass fraction $Y_p$, this could begin to discriminate between the mean life determinations. Full article

Many ongoing studies for predicting the production rates of cosmogenic nuclides, forecasting changes of atmospheric compositions and climate, assessing the cosmic-radiation exposure of aircraft crew, and the effects on precise electronic devices use numerical models that estimate cosmic-radiation intensities in the atmosphere. Periodic verifications of those models are desirable to be performed for assuring the reliability of the study outcomes. Here, we investigated an application of a portable neutron-monitoring system composed of an extended-energy-range neutron monitor and a small data logger for monitoring of cosmic-neutron intensities in a polar region. As a result of measurements in the east Antarctica region covering a wide range of altitudes (from 30 m to 3762 m) and comparisons with the model calculations performed with an analytical model based on comprehensive Monte Carlo simulations (PARMA), it was demonstrated that the portable neutron-monitoring system could be effectively applied for periodic verification of cosmic-neutron intensities that would improve the reliability of related studies. Full article

Searching for new compounds and synthetic routes for medical applications is a great challenge for modern chemistry. Porphyrins, natural macrocycles able to tightly bind metal ions, can serve as complexing and delivering agents in nuclear medicine diagnostic imaging utilizing radioactive nuclides of copper with particular emphasis on ⁶⁴Cu. This nuclide can, due to multiple decay modes, serve also as a therapeutic agent. As the complexation reaction of porphyrins suffers from relatively poor kinetics, the aim of this study was to optimize the reaction of copper ions with various water-soluble porphyrins in terms of time and chemical conditions, that would meet pharmaceutical requirements and to develop a method that can be applied for various water-soluble porphyrins. In the first method, reactions were conducted in a presence of a reducing agent (ascorbic acid). Optimal conditions, in which the reaction time was 1 min, comprised borate buffer at pH 9 with a 10-fold excess of ascorbic acid over Cu²⁺. The second approach involved a microwave-assisted synthesis at 140 °C for 1–2 min. The proposed method with ascorbic acid was applied for radiolabeling of porphyrin with ⁶⁴Cu. The complex was then subjected to a purification procedure and the final product was identified using high-performance liquid chromatography with radiometric detection. Full article

The article presents a model for simulating changes in the activity concentration of radon and thoron as well as their progeny in closed or poorly ventilated systems. A system can be considered closed when a stream of radon and thoron flows into a space, but nothing comes out. It was also assumed that there may be devices or installations with a filtering system that would reduce the concentration of radon and thoron decay products. These assumptions may, therefore, correspond to a situation in which, in an isolated chamber, the calibration of radon hazard-monitoring devices is carried out, and nuclides are supplied from an emanation or flow through sources or well-isolated spaces in an environment where the source of nuclides is, for example, radon and thoron exhalation. The differential equations were formulated on the basis of the assumption that the activity concentration of radionuclides of concern in the space is uniform. The equations do not consider possible losses due to diffusion or the inertial or gravitational deposition of aerosols. If these phenomena have a limited impact on changes in the activity concentration of nuclides, the solutions provided may be used to simulate the activity concentration of radon and thoron and their decay products in any confined space assuming different boundary conditions. Full article

Quantifying fission product yield uncertainty contribution to reactor burnup calculation is an important aspect of pebble-bed High Temperature Gas-cooled Reactor (pebble-bed HTGR) uncertainty analysis. In this work, uncertainty propagation of fission product yield to pebble-bed HTGR burnup calculation is conducted. Uncertainty of fission product yields from four fissile isotopes, namely ²³³U, ²³⁵U, ²³⁹Pu and ²⁴¹Pu, are considered. The stochastic sampling-based uncertainty analysis method is adopted and fission product yield covariance matrices are estimated from ENDF/B-VII.1. The covariance matrix for each fissile actinide is estimated based on the Bayesian method and fission product yields are assigned with log-normal distribution in the sampling process with the Latin Hypercube Sampling (LHS) method. Since the fission fraction from ²³⁹Pu plays an important role in fissions of fuels with high burnup value in pebble-bed HTGR, the fission product yield uncertainty contribution from ²³⁹Pu is highlighted in this work. The result shows that, in the burnup equilibrium state of pebble-bed HTGR, fission product yield uncertainty contributions from ²³⁵U and ²³⁹Pu to relative uncertainty of k_eff are 0.027% and 0.026%, respectively. The overall uncertainty contribution from four fissile isotopes (²³³U, ²³⁵U, ²³⁹Pu and ²⁴¹Pu) to relative uncertainty of equilibrium core k_eff is 0.038%. Furthermore, fission product yield uncertainty has an important contribution to the nuclide density uncertainty of fission products. The most relative uncertainty, 10.82%, is observed in ¹⁰⁹Ag contributed from the fission product yield uncertainty of ²³⁹Pu at the burnup equilibrium state. This indicates the uncertainty contribution from the fission product yield of ²³⁹Pu cannot be neglected in pebble-bed HTGR burnup uncertainty analysis. Full article