Search Results (133)

Nuclear power is a low-emission and economically competitive energy source, yet the effective disposal and management of its associated radioactive waste can be challenging. Radioactive waste can be categorised as high-level waste (HLW), intermediate-level waste (ILW), and low-level waste (LLW). LLW primarily comprises materials contaminated during routine clean-up, such as mop heads, paper towels, and floor sweepings. While LLW is less radioactive compared to HLW and ILW, the management of LLW poses significant challenges due to the large volume that requires processing and disposal. The volume of LLW can be significantly reduced through sorting, which is typically performed manually in a labour-intensive way. Smart management techniques, such as computer vision (CV) and machine learning (ML), have great potential to help reduce the workload and human errors during LLW sorting. This paper provides a comprehensive review of previous research related to LLW sorting and a summative review of existing applications of CV in solid waste management. It also discusses state-of-the-art CV and ML algorithms and their potential for automating LLW sorting. This review lays a foundation for and helps facilitate the applications of CV and ML techniques in LLW sorting, paving the way for automated LLW sorting and sustainable LLW management. Full article

Some of nuclear power’s primary detractors are the unique environmental challenges and impacts of radioactive wastes generated during fuel cycle operations. Key benefits of spent fuel reprocessing (SFR) are reductions in primary high active waste (HAW) masses, volumes, and lengths of radiotoxicity at the expense of secondary waste generation and high capital and operational costs. By employing advanced waste management and resource recovery concepts in SFR beyond the existing standard PUREX process, such as minor actinide and fission product partitioning, these challenges could be mitigated, alongside further reductions in HAW volumes, masses, and duration of radiotoxicity. This work assesses various current and proposed SFR and fuel cycle options as base cases, with further options for fission product partitioning of the high heat radionuclides (HHRs), rare earths, and platinum group metals investigated. A focus on primary waste outputs and the additional energy that could be generated by the reprocessing of high-burnup PWR fuel from Gen III(+) reactors using a simple fuel cycle model is used; the effects of 5- and 10-year spent fuel cooling times before reprocessing are explored. We demonstrate that longer cooling times are preferable in all cases except where short-lived isotope recovery may be desired, and that the partitioning of high-heat fission products (Cs and Sr) could allow for the reclassification of traditional raffinates to intermediate level waste. Highly active waste volume reductions approaching 50% vs. PUREX raffinate could be achieved in single-target partitioning of the inactive and low-activity rare earth elements, and the need for geological disposal could potentially be mitigated completely if HHRs are separated and utilised. Full article

Nuclear energy can help stop climate change by generating large amounts of emission-free electricity. Nuclear reactor designs are continually being developed to be more fuel efficient, safer, easier to construct, and to produce less nuclear waste. The term advanced nuclear reactors refers either to Generation III+ and Generation IV or small modular reactors. Every reactor is associated with the nuclear fuel cycle that must be economically viable and competitive. An important matter is optimization of fissile materials used in reactor and/or reprocessing of spent fuel and reuse. Currently operating reactors use the open cycle or partially closed cycle. Generation IV reactors are intended to play a significant role in reaching a fully closed cycle. At the same time, we can observe the growing interest in development of small modular reactors worldwide. SMRs can adopt either fuel cycle; they can be flexible depending on their design and fuel type. Spent nuclear fuel management should be an integral part of the development of new reactors. The proper management methods of the radioactive waste and spent fuel should be considered at an early stage of construction. The aim of this paper is to highlight the challenges related to reprocessing of new forms of nuclear fuel. Full article

Downhole kick is one of the most severe safety hazards in deep and ultra-deep well drilling operations. Traditional monitoring methods, which rely on surface flow rate and fluid level changes, are limited by their delayed response and insufficient sensitivity, making them inadequate for early warning. This study proposes a real-time monitoring technique for gas content in drilling fluid based on the attenuation principle of Ba-133 γ-rays. By integrating laboratory static/dynamic experiments and Geant4-11.2 Monte Carlo simulations, the influence mechanism of gas–liquid two-phase media on γ-ray transmission characteristics is systematically elucidated. Firstly, through a comparative analysis of radioactive source parameters such as Am-241 and Cs-137, Ba-133 (main peak at 356 keV, half-life of 10.6 years) is identified as the optimal downhole nuclear measurement source based on a comparative analysis of penetration capability, detection efficiency, and regulatory compliance. Compared to alternative sources, Ba-133 provides an optimal energy range for detecting drilling fluid density variations, while also meeting exemption activity limits (1 × 10⁶ Bq) for field deployment. Subsequently, an experimental setup with drilling fluids of varying densities (1.2–1.8 g/cm³) is constructed to quantify the inverse square attenuation relationship between source-to-detector distance and counting rate, and to acquire counting data over the full gas content range (0–100%). The Monte Carlo simulation results exhibit a mean relative error of 5.01% compared to the experimental data, validating the physical correctness of the model. On this basis, a nonlinear inversion model coupling a first-order density term with a cubic gas content term is proposed, achieving a mean absolute percentage error of 2.3% across the full range and R² = 0.999. Geant4-based simulation validation demonstrates that this technique can achieve a measurement accuracy of ±2.5% for gas content within the range of 0–100% (at a 95% confidence interval). The anticipated field accuracy of ±5% is estimated by accounting for additional uncertainties due to temperature effects, vibration, and mud composition variations under downhole conditions, significantly outperforming current surface monitoring methods. This enables the high-frequency, high-precision early detection of kick events during the shut-in period. The present study provides both theoretical and technical support for the engineering application of nuclear measurement techniques in well control safety. Full article

In the decommissioning of nuclear facilities, activated steel often contains radionuclides such as ⁵⁵Fe and ⁶³Ni, which are categorized as hard-to-measure due to their emission of only low-energy beta particles or X-rays. In samples exhibiting very low radioactivity, close to background levels, a large quantity of steel must undergo extensive physical and chemical processing to achieve the Minimum Detectable Activity Concentration (MDC) necessary for clearance, recycling, or reuse. Italian regulations set particularly stringent clearance levels for these radionuclides (1 Bq/g for both ⁵⁵Fe and ⁶³Ni), significantly lower than those specified in the EU Directive 2013/59 (1000 Bq/g for ⁵⁵Fe and 100 Bq/g for ⁶³Ni). Additionally, Italian authorities may enforce even stricter limits depending on specific circumstances. The analytical challenge is compounded by the presence of large amounts of non-radioactive Fe and Ni, which can cause color quenching, further extending analysis times. This study presents a reliable and optimized method for the quantitative determination of ⁵⁵Fe and ⁶³Ni in steel samples with activity levels approaching regulatory thresholds. The methodology was specifically developed and applied to steel from the Frascati Tokamak Upgrade (FTU) facility, under decommissioning by ENEA. The optimization process demonstrated that achieving the required MDCs necessitates acquisition times of approximately 5 days for ⁵⁵Fe and 6 h for ⁶³Ni, ensuring compliance with stringent regulatory requirements and supporting efficient laboratory workflows. Full article

This study examines methods to improve the energy efficiency of radiofrequency inductively coupled plasma (RF-ICP) torches for radioactive waste treatment, with a focus on surpassing the typical energy efficiency limit of approximately 70%. To improve energy efficiency and plasma performance, this research investigates the transition from axial gas flow to vortex gas flow patterns using COMSOL Multiphysics software v6.2. Key plasma parameters, including energy efficiency, number of gas vortices, heat transfer, and temperature distribution, were analyzed to evaluate the improvements. The results indicate that adopting a vortex flow pattern increases energy conversion efficiency, increases heat flux, and reduces charge losses. Furthermore, optimizing the torch body design, particularly the nozzle, chamber volume, and gas entry angle, significantly improves plasma properties and energy efficiency by up to 90%. Improvements to RF-ICP torches positively impact waste decomposition by creating better thermal conditions that support resource recovery and potential material recycling. In addition, these improvements contribute to reducing secondary waste, mitigating environmental risks, and fostering long-term public support for nuclear technology, thereby promoting a more sustainable approach to waste management. Simulation results demonstrate the potential of RF-ICP flares as a cost-effective and sustainable solution for the thermal treatment of low- to intermediate-level radioactive waste. Full article

This study proposes a decision-making model based on the economic assessment of phased decommissioning of energy facilities, specifically focusing on a nuclear power plant (NPP). The objective of the research is to develop and validate an economic assessment methodology for comparing immediate and deferred dismantling strategies for a 1000 MW NPP unit. For economic justification, a comparison of the economic expenses is proposed based on the accumulation of radioactive waste, safety activities, and labour costs for the two options. The methods employed include a multifactorial analysis based on expert assessments, considering economic expenses related to radioactive waste accumulation, safety activities, and labour costs. Criteria with differences exceeding 10% for quantitative indicators and fundamental differences for qualitative indicators were deemed significant; each criterion’s acceptability was weighted accordingly. The key results show that deferred dismantling is economically preferable; the total score for deferred dismantling exceeds that of immediate dismantling by approximately 10% (14.16 points vs. 15.86 points). A comparison of block schedules for decommissioning, dynamics of labour costs, and annual volumes of reprocessed radioactive waste for the baseline and optimised deferred dismantling options shows that both options meet the continuity condition of the ‘active’ stages. At the same time, the optimised option demonstrates significant advantages in the uniformity of labour costs and workload of radioactive waste treatment plants during dismantling. The activities at the stage of power unit decommissioning are proposed to be carried out within the licence framework for its operation by the organisational and technical solutions to ensure safety during operation. The deterministic consequences and risks will align with the safety assessment, which will be determined based on the latest analysis results, taking into account sustainable operation. Full article

Low carbon dioxide (CO₂) emissions make nuclear energy crucial in decarbonizing the economy. In this context, nuclear safety, and especially the operation of nuclear power plants, remains a critical issue. This article presents a new fractal cluster method of control that improves the quality of assessing fuel element cladding integrity, which is critical for nuclear and environmental safety. The proposed non-destructive testing method allows for detecting defects on the inner and outer cladding surfaces without removing the elements from the nuclear reactor, which ensures prompt response and prevention of radiation leakage. Studies have shown that the fractal dimension of the cladding surface, which varies from 2.1 to 2.5, indicates significant heterogeneity caused by mechanical damage or corrosion, which can affect its integrity. The density analysis of defect clusters allows quantifying their concentration per unit area, which is an important indicator for assessing the risks associated with the operation of nuclear facilities. The data obtained are used to assess the impact of defects on the vessel’s integrity and, in turn, on nuclear safety. The monitoring results are transmitted in real time to the operator’s automated workstation, allowing for timely decision making to prevent radioactive releases and improve environmental safety. The proposed method is a promising tool for ensuring reliable quality control of the fuel element cladding condition and improving nuclear and environmental safety. While the study is based on VVER-1000 reactor data, the flexibility of the proposed methodology suggests its potential applicability to other reactor types, opening avenues for broader implementation in diverse nuclear systems. Full article

Given the pressing demand for efficient uranium (U(VI)) enrichment and its elimination from wastewater to curtail the risks of radioactive contamination inherent in nuclear energy applications, it is crucial to design materials with high removal efficiency and straightforward separation processes. In the current study, we incorporated konjac gum (KGM) into MgAl-double oxide (MgAl-LDO) and synthesized an innovative, economical, and environmentally friendly LDO-KGM material by using the freeze-drying-calcination (FDC) method, which provided a solution for U(VI) concentration from aqueous solutions. The nanoflower structures LDO-KGM with abundant pore structure and high specific surface area exhibited an optimal U(VI) adsorptive capacity (3019.56 mg·g⁻¹) at pH = 6.0 and 293 K, which was 2.3 times greater than that of MgAl-LDO (1296.39 mg·g⁻¹). LDO-KGM also showed great adaptability for the immobilization of U(VI) over a broad pH range (4.0 to 9.0) and coexisting ions. U(VI) adsorption onto LDO-KGM adhered to the pseudo-second-order kinetic model (R² ≥ 0.99) and the Langmuir isotherm model (R² ≥ 0.99). The analysis of thermodynamic parameters derived from isotherms at varying temperatures revealed that U(VI) adsorption onto LDO-KGM was an endothermic and spontaneous process. The mechanism underlying U(VI) adsorption by LDO-KGM was mainly complexation, carbonate co-precipitation, and electrostatic adsorption. Furthermore, the adsorption efficiency of LDO-KGM for U(VI) could still retain more than 84.5% after five cycles. The findings indicate that the synthesized LDO-KGM exhibits potential as an exceptionally potent adsorbent for the purification of wastewater contaminated with U(VI). Full article

Nuclear energy has a great impact on the global energy mix. In Spain, it supplies over 20% of current energy requirements, demonstrating the relevance of nuclear power plants. These plants generate different types of waste (apart from radioactive) that should be managed. For instance, the activated carbon included in filters (which neutralize isotopes in a possible radioactive leakage) should be periodically replaced. Nevertheless, these activated carbons might present long service lives, as they have not undergone any adsorption processes. Consequently, a considerable amount of activated carbon can be reused in alternative processes, even in the same nuclear power plant. The aim of this work was to assess the use of activated carbons (previously included in filters to prevent possible radioactive releases in primary circuits) for water treatment derived from the steam cycle of a nuclear power plant. A regeneration process (boron removal) was carried out (with differences between untreated carbon and after treatments, from S_BET = 684 m² g⁻¹ up to 934 m² g⁻¹), measuring the adsorption efficiency for ethanolamine and triton X-100. There were no significative results that support the adsorption effectiveness of the activated carbon tested for ethanolamine adsorption, whereas a high adsorption capacity was found for triton X-100 (q_L1 = 281 mg·g⁻¹), proving that factors such as porosity play an important role in the specific usage of activated carbons. Full article

Coal mining and combustion have the potential to increase exposure to radon, a form of radioactive gas recognized as one of the major contributors to lung cancer incidents. In South Africa, coal is used as the primary energy source for producing electricity and for heating, predominantly in informal settlements and township communities. Most of the existing coal-fired power plants are found in the Mpumalanga province. This paper presents long-term radon (²²²Rn) measurements in dwellings surrounding coal mining centres in the Mpumalanga province and evaluates their contributions to indoor radon exposures. The indoor radon measurements were conducted using solid-state nuclear track detectors and were performed during warm and cold seasons. It was found that the overall indoor radon activity concentrations ranged between 21 Bq/m³ and 145 Bq/m³, with a mean value of 40 Bq/m³. In all the measured dwellings, the levels were below the WHO reference level of 100 Bq/m³ and 300 Bq/m³ reference level recommended by the IAEA and ICRP, with the exception of one dwelling that was poorly ventilated. The results reveal that individuals residing in the surveyed homes are not exposed to radon levels higher than the WHO, ICRP, and IAEA reference levels. The main source influencing indoor radon activity concentrations was found to be primarily the concentration of uranium found in the geological formations in the area, with ventilation being an additional contributing factor of radon levels in dwellings. To maintain good air quality in homes, it is recommended that household occupants should keep their dwellings well ventilated to keep indoor radon levels as low as possible. Full article

Gamma-ray spectroscopy is essential in nuclear science, enabling the identification of radioactive materials through energy spectrum analysis. However, high count rates lead to pile-up effects, resulting in spectral distortions that hinder accurate isotope identification and activity estimation. This phenomenon highlights the need for automated and precise approaches to pile-up correction. We propose a novel deep learning (DL) framework plugging count rate information of pile-up signals with a 2D attention U-Net for energy spectrum recovery. The input to the model is an Energy–Duration matrix constructed from preprocessed pulse signals. Temporal and spatial features are jointly extracted, with count rate information embedded to enhance robustness under high count rate conditions. Training data were generated using an open-source simulator based on a public gamma spectrum database. The model’s performance was evaluated using Kullback–Leibler (KL) divergence, Mean Squared Error (MSE) Energy Resolution (ER), and Full Width at Half Maximum (FWHM). Results indicate that the proposed framework effectively predicts accurate spectra, minimizing errors even under severe pile-up effects. This work provides a robust framework for addressing pile-up effects in gamma-ray spectroscopy, presenting a practical solution for automated, high-accuracy spectrum estimation. The integration of temporal and spatial learning techniques offers promising prospects for advancing high-activity nuclear analysis applications. Full article

Nuclear power plants have the lowest life-cycle greenhouse gas emissions intensity and produce more electricity with less land use compared to any other low-carbon-emission-based energy source. There is growing global interest in Generation IV reactors and, at the same time, there is great interest in using small modular reactors. However, the development of new reactors introduces new engineering and chemical challenges critical to advancing nuclear energy safety, efficiency, and sustainability. For Generation III+ reactors, water chemistry control is essential to mitigate corrosion processes and manage radiolysis in the reactor’s primary circuit. Generation IV reactors, such as molten salt reactors (MSRs), face the challenge of handling and processing chemically aggressive coolants. Small modular reactor (SMR) technologies will have to address several drawbacks before the technology can reach technology readiness level 9 (TRL9). Issues related to the management of irradiated graphite from high-temperature reactors (HTR) must be addressed. Additionally, spent fuel processing, along with the disposal and storage of radioactive waste, should be integral to the development of new reactors. This paper presents the key chemical and engineering aspects related to the development of next-generation nuclear reactors and SMRs along with the challenges associated with them. Full article

Following the 1987 referendums, the Italian government stopped its nuclear energy production. Radioactive waste produced by existing nuclear facilities and the very-low- and low-level radioactive waste due to other activities (e.g., healthcare) require the construction of a National Repository. To this end, the National Map of Suitable Areas (CNAI), through which the optimal site to host the National Repository would be identified, was published on 23 December 2023. Over the years, the possible location of the National Repository has been repeatedly contested by the citizens of the territories concerned. However, the need to identify a site and build the National Repository is unavoidable. This study proposes an approach based on multi-criteria analysis. The approach represents an alternative model useful for enriching the public debate with additional information and criteria and is also consistent with the local needs of the communities involved. The proposed approach compares the sites proposed in the CNAI by analyzing their main short- and long-term risks, namely their seismic, transport-related and socio-economic risks. The obtained results show a possible different priority order of the CNAI sites. They highlight the possibility of identifying the optimal site mainly via using site safety criteria assessed throughout the entire service life of the infrastructures to be built and also consider the possible short-term economic advantages deriving from the construction of the National Repository. Full article

Uranium mining for the production of nuclear technologies has left visible scars across the United States and perpetuated legacies of extraction that extend beyond material consumption to the exploitation of people and the environment. Influenced by important ongoing conversations in the environmental and energy humanities, posthumanism, and decolonial studies, I analyze how uranium extraction has been conceived of as an “event” within a colonial temporal framework. A critical examination of how religious worldviews have informed the ways that time is conceptualized and understood shifts thinking about extraction away from colonial temporalities and helps reimagine extraction through a decolonial perspective as temporally distributed, enmeshed, and complex. This reframing is imperative to foster an understanding that the radioactive byproducts of uranium created through the nuclear production process are globally dispersed, will persist across generations, and will have transgenerational implications for human and non-human organisms and the health and viability of ecologic systems. Full article