Search Results (66)

In the context of the disposal of spent radioactive fuel, heat-emitting radionuclides such as Cs and Sr are of utmost concern, as they have a major influence on the distance at which disposal galleries should be spaced apart and, thus, the cost of a disposal facility. Therefore, certain scenarios investigate the partitioning and transmutation of spent fuel to optimize the disposability of both Cs- and Sr-rich waste streams and the remaining fractions. In this study, the Cs- and Sr-rich waste stream, a nitrate-based solution, was immobilized in metakaolin and blast furnace slag-based alkali-activated matrices. These matrices were chosen for immobilization because they are known to offer advantages in terms of durability and/or heat resistance compared with traditional cementitious materials. The goal of this study is to develop an optimal recipe for the retention of Cs and Sr. For this purpose, recipes were developed following a design-of-experiments approach by varying the water-to-binder ratio, precursor, and waste loading while respecting matrix constraints. Leaching tests in deionized water showed that the metakaolin-based matrix was superior for the combined retention of both Cs and Sr. The optimal recipe was further tested under accelerated leaching conditions in an ammonium nitrate solution, which revealed that the leaching of Cs and Sr remained within reasonable limits. These results confirm that alkali-activated materials can be effectively used for the immobilization and long-term retention of heat-emitting radionuclides. Full article

State-of-the-art hydrogeological investigations use transient calibrated numerical flow and transport models for multiple scenario analyses. However, the transient calibration of numerical flow and transport models still requires consistent long-term groundwater time series, which are often not available or contain data gaps, thus reducing the robustness and confidence of the numerical model. This study presents a data-driven approach for the reconstruction and prediction of gaps in a discontinuous groundwater level time series at a monitoring station in the Allertal (Saxony-Anhalt, Germany). Deep Learning and classical machine learning (ML) approaches (artificial neural networks (TensorFlow, PyTorch), the ensemble method (Random Forest), boosting method (eXtreme gradient boosting (XGBoost)), and Multiple Linear Regression) are used. Precipitation and groundwater level time series from two neighboring monitoring stations serve as input data for the prediction and reconstruction. A comparative analysis shows that the input data from one measuring station enable the reconstruction and prediction of the missing groundwater levels with good to satisfactory accuracy. Due to a higher correlation between this station and the station to be predicted, its input data lead to better adapted models than those of the second station. If the time series of the second station are used as model inputs, the results show slightly lower correlations for training, testing and, prediction. All machine learning models show a similar qualitative behavior with lower fluctuations during the hydrological summer months. The successfully reconstructed and predicted time series can be used for transient calibration of numerical flow and transport models in the Allertal (e.g., for the overlying rocks of the Morsleben Nuclear Waste Repository). This could lead to greater acceptance, reliability, and confidence in further numerical studies, potentially addressing the influence of the overburden acting as a barrier to radioactive substances. Full article

The radiological impact of radionuclide transport via groundwater pathways at the Wolsong Low- and Intermediate-Level Waste (LILW) Disposal Center was estimated by considering site-specific characteristics, including hydrogeology, geochemistry, and land use. Human intrusion scenarios, such as groundwater well development, were analyzed to evaluate potential pumping volumes and radionuclide migration pathways. Particular attention was given to the hydrological and geochemical aspects of radionuclide transport, with a focus on local aquifer heterogeneity, flow dynamics, and interactions with engineered barriers and surrounding rock formations that delay radionuclide migration through sorption and other retention mechanisms. Sorption coefficients (K_d), calibrated using site-specific geochemical data, were incorporated to ensure realistic modeling of radionuclide behavior. A hierarchical approach integrating scenario screening, particle tracking techniques, and mass transfer modeling was employed. Numerical simulations using FEFLOW ver. 7.3 and GoldSim ver. 14.0 software provided insights into near-field and far-field transport phenomena under well pumping conditions. The results revealed distinct spatial flux behaviors, where carbon-14 (¹⁴C) dominated near-field flux due to its high inventory, while technetium-99 (⁹⁹Tc) emerged as the primary dose contributor in the far-field flux, owing to its anionic nature and limited sorption capacity. Additionally, under high-pH conditions near concrete barriers, cellulose degradation into isosaccharinic acid was identified, enhancing radionuclide mobility through complex formation. These findings underscore the importance of site-specific sorption and speciation parameters in safety assessment and highlight the need for accurate geochemical modeling to optimize waste placement and ensure long-term disposal safety. The outcomes provide valuable insights for optimizing waste placement and contribute to the development of evidence-based safety strategies for long-term performance assessment. Full article

Differentiated thyroid cancer (DTC), comprising papillary and follicular thyroid carcinoma, is the most common thyroid malignancy and typically has a favourable prognosis when detected early. Positron emission tomography/computed tomography (PET/CT) has emerged as a valuable imaging modality, integrating metabolic and anatomical data. Although PET/CT is not usually part of the initial diagnostic process due to DTC’s indolent nature and low metabolic activity, it plays an essential role in selected clinical scenarios. This includes identifying recurrence in patients with elevated thyroglobulin (Tg) levels and negative radioactive iodine (RAI) scans, evaluating metastatic disease, and guiding treatment in advanced cases. As the use of PET/CT evolves in oncology, this review explores its application in regard to staging, detection of recurrence, and follow-up in terms of managing DTC while also evaluating potential challenges that may occur in the future. The review also considers emerging radiotracers and the theragnostic potential of PET/CT. Full article

Four severe nuclear accident scenarios have been identified for operating nuclear power plants (ONPPs). However, there is a research gap in predicting the mid–long-term radiation doses for these scenarios. This study aims to address this gap by proposing a novel approach for predicting the mid–long-term radiation dose in the case of a hypothetical short-term station blackout (STSBO) scenario, one of the aforementioned scenarios. Firstly, the Weather Research and Forecasting (WRF) model was coupled with the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) (WRF-HYSPLIT) model to establish an atmospheric transport and diffusion model for airborne radionuclides, and the regularity of the atmospheric transport and diffusion for the airborne radionuclides was determined. Subsequently, the Residual Radioactive Material Guidelines (RESRAD) OFFSITE (RESRAD-OFFSITE) code was utilized to establish a radiation dose model for predicting the mid–long-term radiation dose resulting from the airborne radionuclides, and the evolution of the mid–long-term radiation dose was analyzed. Finally, the proposed approach was applied to an ONPP, and the results were used to predict the mid–long-term public radiation dose. The results indicated that the total radiation dose would be lower than the dose limit recommended by the International Commission on Radiological Protection (1 mSv/yr) from the second month to the 100th year after the hypothetical STSBO nuclear accident, and the total radiation dose would decrease slowly over time. Recommendations are made for offsite emergency response measures. These research findings can assist ONPPs in analyzing their environmental impacts in the event of an STSBO scenario. Full article

Due to the higher susceptibility of children to ionizing radiation, it is imperative to evaluate the radon activity concentration (RAC) in educational buildings, conduct additional investigations to identify radon entry routes, and implement remedial measures to minimize exposure to this radioactive gas. In Romania, educational buildings are a category of public buildings where it is mandatory to perform RAC measurements. The present study examines data obtained from 41 Romanian educational buildings, where initial and additional radon investigations were performed. The first objective was to identify the factors influencing the variability of the RAC inside the buildings. The second objective was to emphasize the importance of short-term (a few days), continuous measurements in identifying buildings with RAC exceeding the reference level. High RAC values were associated with the classrooms located on the ground floor of the building compared to the administrative ones. The multiple linear regression led to a coefficient of determination of 0.11, the relative humidity and the amount of precipitation being the main variables with a significant impact, kept in the model, the lack of a significant association between the indoor RAC and the radon potential in the soil being obtained. Comparison of the radon long-term integrated measurements with continuous, short-term, led to the suggestion of three different scenarios for the measurement work protocol. By following the suggested modifications, it is possible to accelerate the procedure in situations where the time needed to plan renovations and radon remedial measures is shorter than the time needed to conduct integrated measurements. Full article

This paper presents an optimized design approach using nonlinear dynamic analysis and finite element methods to ensure the structural integrity of square-shaped containers made from ductile cast iron for intermediate- and low-level radioactive waste packaging. Ductile cast iron, with its spherical graphite structure, effectively distributes stress throughout the material, leading to a storage capacity increase of approximately 18%. Considering the critical need for containers that maintain integrity under extreme conditions like earthquakes, the design focuses on mitigating stress concentrations at the corners of square structures. Nonlinear dynamic analyses were conducted in five drop directions: three specified by ASTM-D5276 standards and two additional directions to account for different load patterns. Fractures were observed in four out of the five scenarios. For each direction where fractures occurred, equivalent loads causing similar displacement fields were applied to linear static models, which were then used for multi-load topology optimization. Three optimized models were derived, each increasing the volume by 1.4% to 1.6% compared to the original model, and the design that best met the structural integrity requirements during drop scenarios was selected. To further enhance the optimization process, weights were assigned to different load conditions based on numerical analysis results, balancing the impact of maximum stress, average stress, and plastic deformation energy. The final model, with its increased storage capacity and enhanced structural integrity, offers a practical solution for radioactive waste management, overcoming limitations in previous designs by effectively addressing complex load conditions. Full article

The current scenario of radioactive waste management requires innovative and automated solutions to ensure its effectiveness and safety. In response to this need, the Proximity Imaging System for Sort and Segregate Operations (PI3SO) project was proposed. It is a gamma radiation proximity scanner system for radioactive waste with the primary goal of speeding up some aspects of the waste management cycle while reducing direct human operations. The system will provide proximity imaging for hot-spot finding and spectral analysis for radiological characterization, enabling semiautomatic recognition, sorting and separation of radioactive waste. The core of the proposed scanning system consists of an array of 128 CsI(Tl) scintillators, 1 cm³ size, coupled with silicon photomultipliers (SiPMs), installed on a motorized bridge sliding along a suitable table in order to scan the materials under investigation. Full article

Earthworms are a resilient group of species thriving in varied habitats through feeding on decaying organic matter, and are therefore predicted to survive an abrupt sunlight reduction scenario, e.g., a nuclear winter. In this study, the feasibility and cost-effectiveness of foraging earthworms to reduce global famine in such a scenario with or without global catastrophic infrastructure loss was considered. Previously reported earthworm extraction methods (digging and sorting, vermifuge application, worm grunting, and electroshocking) were analysed, along with scalability, climate-related barriers to foraging, and pre-consumption processing requirements. Estimations of the global wild earthworm resource suggest it could provide three years of the protein needs of the current world human population, at a median cost of USD 353·kg⁻¹ dry carbohydrate equivalent or a mean cost of USD 1200 (90% confidence interval: 32–8500)·kg⁻¹ dry carbohydrate equivalent. At this price, foraging would cost a median of USD 185 to meet one person’s daily caloric requirement, or USD 32 if targeted to high-earthworm-biomass and low-labour-cost regions; both are more expensive than most existing resilient food solutions. While short-term targeted foraging could still be beneficial in select areas given its quick ramp-up, earthworms may bioaccumulate heavy metals, radioactive material, and other contaminants, presenting a significant health risk. Overall, earthworm foraging cannot be recommended as a scalable resilient food solution unless further research addresses uncertainties regarding cost-effectiveness and food safety. Full article

Pulmonary monitoring is crucial for the diagnosis and management of respiratory conditions, especially after the epidemic of coronavirus disease. Electrical impedance tomography (EIT) is an alternative non-radioactive tomographic imaging tool for monitoring pulmonary conditions. This review proffers the current EIT technical principles and applications on pulmonary monitoring, which gives a comprehensive summary of EIT applied on the chest and encourages its extensive usage to clinical physicians. The technical principles involving EIT instrumentations and image reconstruction algorithms are explained in detail, and the conditional selection is recommended based on clinical application scenarios. For applications, specifically, the monitoring of ventilation/perfusion (V/Q) is one of the most developed EIT applications. The matching correlation of V/Q could indicate many pulmonary diseases, e.g., the acute respiratory distress syndrome, pneumothorax, pulmonary embolism, and pulmonary edema. Several recently emerging applications like lung transplantation are also briefly introduced as supplementary applications that have potential and are about to be developed in the future. In addition, the limitations, disadvantages, and developing trends of EIT are discussed, indicating that EIT will still be in a long-term development stage before large-scale clinical applications. Full article

Theranostics utilize ligands that chelate radionuclides and selectively bind with cancer-specific membrane antigens. In the case of prostate cancer (PCa), the state-of-the-art lutetium-177-PSMA combines the radioactive β-emitter ¹⁷⁷Lu with Vipivotide Tetraxetan, a prostate-specific membrane antigen (PSMA)-binding ligand. Several studies have been conducted, and the therapy is not without adverse effects (e.g., xerostomia, nausea, and fatigue); however, few events are reported as severe. The available evidence supports the use of ¹⁷⁷Lu-PSMA in selected metastatic castration-resistant prostate cancer patients, and the treatment is considered a standard of care in several clinical scenarios. Emerging research shows promising results in the setting of hormone-sensitive prostate cancer; however, evidence from high-quality controlled trials is still missing. In this review, we discuss the available evidence for the application of ¹⁷⁷Lu-PSMA in the management of PCa patients. Full article

Safety in nuclear energy utilization is crucial. In the event of a radioactive release incident, coupled with meteorological uncertainties, a radioactive plume can impact personnel evacuation. This paper presents an integrated solution for radionuclide release accident assessment and emergency evacuation decision making. The solution consists of three processes: atmospheric dispersion calculation, dose calculation, and path planning. The individual processes are connected through data exchange, thus allowing users to choose specific models based on experience. The proposed scheme combination is the Gaussian plume model, the dose conversion factor method, and an improved Dijkstra’s path planning algorithm. This algorithm, combined with dispersion and dose results, weighs nodes using the moving expected dose, facilitating the path with minimum dose risk. A program for Atmospheric Diffusion and Dose Calculation (ADDC) is developed based on the recommended scheme. Advantages include ease of use, minimal data requirements, data accessibility, and efficient evacuation. Dose estimates and optimal evacuation routes can be obtained quickly and at very low cost in response to rapidly changing environmental conditions. In a case study at a Chinese planned nuclear plant, we consider a spent fuel pool water loss scenario, assessing dose risks from 2020 to 2022 meteorological statistics. In dose calculation, results reveal that during an SFP drying accident, the radiation dose in the core area (100 m away) can reach 30–150 mSv within 2 h, and at 500 m away, it can reach 5–15 mSv. The dose in all downwind directions can drop below 250 mSv within 60 m. In path planning, results reveal the program is capable of accurately and efficiently calculating the minimum dose evacuation route. The program’s path reduces the effective dose by up to 67.3% compared to the shortest route, enhancino safety, and guiding post-accident decision making and planning. Full article

Gamma-ray spectroscopy is an effective technique for radioactive material characterization, routine inventory verification, nuclear safeguards, health physics, and source search scenarios. Gamma-ray spectrometers typically cannot be operated in the immediate vicinity of nuclear reactors due to their high flux fields and their resulting inability to resolve individual pulses. Low-power reactor facilities offer the possibility to study reactor gamma-ray fields, a domain of experiments hitherto poorly explored. In this work, we present gamma-ray spectroscopy experiments performed with various detectors in two reactors: The EPFL zero-power research reactor CROCUS, and the neutron beam facility at the Ohio State University Research Reactor (OSURR). We employed inorganic scintillators (CeBr₃), organic scintillators (trans-stilbene and organic glass), and high-purity germanium semiconductors (HPGe) to cover a range of typical—and new—instruments used in gamma-ray spectroscopy. The aim of this study is to provide a guideline for reactor users regarding detector performance, observed responses, and therefore available information in the reactor photon fields up to 2 MeV. The results indicate several future prospects, such as the online (at criticality) monitoring of fission products (like Xe, I, and La), dual-particle sensitive experiments, and code validation opportunities. Full article

The Large Aperture Ultrasound System (LAUS) developed at BAM is known for its ability to penetrate thick objects, especially concrete structures commonly used in nuclear waste storage and other applications in civil engineering. Although the current system effectively penetrates up to ~9 m, further optimization is imperative to enhance the safety and integrity of disposal structures for radioactive or toxic waste. This study focuses on enhancing the system’s efficiency by optimizing the transducer spacing, ensuring that resolution is not compromised. An array of twelve horizontal shear wave transducers was used to find a balance between penetration depth and resolution. Systematic adjustments of the spacing between transmitter and receiver units were undertaken based on target depth ranges of known reflectors at depth ranges from 5 m to 10 m. The trade-offs between resolution and artifact generation were meticulously assessed. This comprehensive study employs a dual approach using both simulations and measurements to investigate the performance of transducer units spaced at 10 cm, 20 cm, 30 cm, and 40 cm. We found that for depths up to 5 m, a spacing of 10 cm for LAUS transducer units provided the best resolution as confirmed by both simulations and measurements. This optimal distance is particularly effective in achieving clear reflections and a satisfactory signal-to-noise ratio (SNR) in imaging scenarios with materials such as thick concrete structures. However, when targeting depths greater than 10 m, we recommend increasing the distance between the transducers to 20 cm. This increased spacing improves the SNR in comparison to other spacings, as seen in the simulation of a 10 m deep backwall. Our results emphasize the critical role of transducer spacing in achieving the desired SNR and resolution, especially in the context of depth imaging requirements for LAUS applications. In addition to the transducer spacing, different distances between individual sets of measurement positions were tested. Overall, keeping the minimal possible distance between measurement position offsets provides the best imaging results at greater depths. The proposed optimizations for the LAUS in this study are primarily relevant to applications on massive nuclear structures for nuclear waste management. This research highlights the need for better LAUS efficiency in applications such as sealing structures, laying the foundation for future technological advances in this field. Full article

A scientific collaboration between the U.S. and Israel is underway to assess the suitability of a potential site for subsurface radioactive waste disposal in the Negev Desert, Israel. The Negev Desert has several favorable attributes for geologic disposal, including an arid climate, a deep vadose zone, interlayered low-permeability lithologies, and carbonate rocks with high uranium-sorption potential. These features may provide a robust natural barrier to radionuclide migration. Geologic and laboratory characterization data from the Negev Desert are incorporated into multiphase flow and transport models, solved using PFLOTRAN, to aid in site characterization and risk analysis that will support decision-making for waste disposal in an intermediate-depth borehole design. The lithology with the greatest uranium sorption potential at the site is phosphorite. We use modeling to evaluate the ability of this layer to impact uranium transport around a proposed disposal borehole. The current objective of the simulations is focused on characterizing hypothetical leakage from waste canisters and subsequent uranium migration under three infiltration scenarios. Here, we describe a hydrogeologic model based on data from a local exploratory borehole and present results for uranium flow and transport simulations under varying infiltration scenarios. We find that under the current climate conditions, it is likely that uranium will remain in the near-field of the borehole for thousands of years. However, under a hypothesized extreme climate scenario representing an increase in infiltration by a factor of 300x above present-day values, uranium may break through the phosphorite layer and exit the base of the model domain (~200 m above the water table) within 1000 years. Simulation results have direct implications for the planning of nuclear waste disposal in the Negev Desert, and specifically in intermediate-depth boreholes. Full article