Radioactive Waste Research Articles

A mechanized assembly for erecting soil-cement barriers to protect agricultural lands from low-active waste during flood

The object of this study is the process of constructing a waterproof underground barrier from local soil using loess loam and medium-sized sand as an example. The values of waterproofing of soil cements on different types of soil and the norms of net labor consumption corresponding to them were obtained. The research solves the task of protecting agricultural lands in the areas of geological burials of low-level radioactive waste. Configuration of a mechanized drilling mixing assembly for installing a waterproof barrier in the field has been proposed. Waterproofness of soil cement on clay and sandy soils was determined experimentally. The corresponding norms of the net consumption of time for manufacturing the barrier in these soils have been determined. Units of the mechanized assembly are repairable, utilize widely available materials, parts, and mechanisms. As a result of studies on the labor intensity of the installation of soil cement, a net labor rate was established, which varies from 35 to 52 min/m3 depending on the type of soil. The corresponding values of waterproofness, which ranged from W6 to W14, were determined, which substantiates the possibility of effective functioning of soil-cement underground barriers. Options for the structural solution for impenetrable barriers have been offered. The values of the obtained net time rates are explained by the high degree of mechanization of the technological process and the use of local materials. A distinctive feature of the results is the emphasis on the data collection on the time consumption of machines and mechanisms, the characteristics of local soils under production conditions, and the use of local materials. The assembly implies using affordable and repairable units that can be serviced right in the field. Given this, the manufacturability of the proposed process was defined, confirmed by time-keeping studies. The realm of practical application of the reported results are sites within flat areas with sandy or loess bases. Barrier solutions are designed exclusively for geological waste storage facilities under the conditions of a high level of groundwater and the presence of a waterproof layer at the base

Insight into γ-Irradiation-Induced Structure Evolution of Uranium(IV) Germanates as Crystalline Nuclear Waste Forms.

New kinds of crystalline waste forms with improved structural stability are desirable for actinide immobilization. In this work, using a molten salt method, two uranium(IV) germanate compounds, namely, K2UGe3O9 (1) and K2UGe2O7 (2), were synthesized, whose compositions consisted of trimeric and dimeric units of germanate, as well as tetravalent uranium, as proved by bond valence calculation and X-ray absorption spectra. Radiation stability assessment is further performed by γ-irradiation to assess the potential of as-synthesized uranium germanate compounds as nuclear waste forms. Powder X-ray diffraction and single-crystal diffraction analyses reveal that 1 remains stable within 1 MGy dosage and undergoes a significant structural change with increasing dosage at 2 MGy, leading to a transformation of 1 to 1-ir analogous to 2 in chemical structure. The underlying mechanism was further studied through a combination of different characterization techniques, including Raman, UV-vis, and electron paramagnetic resonance spectroscopies. Density functional theory calculations of 1 and 2 were also conducted to probe the coordination interaction of germanium and uranium with oxygen atoms. This work reports new crystalline uranium germanates by flux growth and, most importantly, provides insights into the irradiation stability of these materials, which will be beneficial to developing waste forms for long-term immobilization of radionuclides.

Research on the implementation of integrated coastal management principles in Taiwan to mitigate disputes related to nuclear waste disposal

Taiwan's nuclear power plants are situated in coastal regions characterized by abundant socio-economic and ecological significance. In the context of managing high-level radioactive waste storage and disposal in the future, alongside technical considerations, there exist challenges related to public acceptance and communication. Radioactive waste management, including the siting of storage or disposal facilities, is a socially sensitive matter. The storage and disposal of radioactive waste represent a complex and multifaceted challenge that requires a comprehensive approach spanning multiple disciplines. One of the functions of Integrated Coastal Management (ICM) is to coordinate conflicts related to coastal use. The concept has been progressively embraced and implemented by nations globally. This study employs grounded theory to examine the perspectives of the interviewed stakeholders. It subsequently introduces the principles of integrated coastal management for conflict resolution post-compilation. The study utilizes the principles and mechanisms of integrated coastal management to address or alleviate the challenges related to radioactive waste management in our country. Issues concerning conflict in relation to storage and disposal.

Discerning Transuranic Sub-Concealments in Nuclear Waste Barrels Using γ-Ray Spectrometry: A Non-Invasive Assay Strategy To Combat the Threat of Nuclear Diversion.

Insufficient inventory control arising from inadequate monitoring procedures can lead to vulnerabilities in nuclear security. In addition, insider threats, by either malicious intent or negligence, can pose a substantial risk by exploiting such deficiencies to perform unlawful actions, such as theft or diversion, which may lead to compromised nuclear security. Interim storage barrels, intended for temporary containment of low-density nuclear waste, require special attention in this regard. In certain scenarios, the inadequacy of the existing waste barrel assay methodologies to identify and correctly measure any undesirable transuranic subconcealment present inside may pose a risk of nuclear diversion. The present work aims to establish an absolute waste barrel assay procedure to mitigate such risks by offering a robust method for the detection and assay of transuranic subconcealments in nuclear waste barrels using high-resolution γ-ray spectrometry. Challenges related to the varying amounts of attenuation experienced by the γ-rays within the subconcealments, low-density matrix, and the steel barrel wall have been addressed by an iterative photopeak efficiency transfer approach. The methodology has been verified for the assay of seven mock-up samples mimicking nuclear diversion attempts using waste barrels, for which conventional barrel scanning would be inadequate and tomographic scanning would be highly time-consuming. Using this methodology, Pu and 241Am isotopes have been assayed within <10% of the expected value for the majority, with the measurement uncertainty of <10%. The present method, which is simple and noninvasive, can identify inconsistencies with the labeled inventory and detect potential diversion attempts.

Laboratory assessment of real-time water infiltration measurement in SPV200 bentonite using TDR for high-level radioactive waste disposal design

The water content movement within compacted bentonite holds significance in appraising the thermo-hydro-mechanical (THM) performance of the engineered barrier system (EBS) for the disposal of high-level radioactive waste (HLRW), but it demands considerable time to monitor water infiltration in a representative model. Therefore, employing bentonite with varying water content is favored in the laboratory. A comprehensive 3-D phase diagram was established as a benchmark for dielectric constant, temperature, and volumetric water content (VWC) using Time Domain Reflectometry (TDR). SPV200 bentonite at different densities (1400, 1500, and 1600 kg/m3) and temperatures (25, 40, and 60 °C) were prepared with TDR, achieving real-time VWC measurements within a 6 % relative error. Furthermore, numerical outcomes exhibited trends like the TDR tests. Comparation between the simulation and test data is within a relative error ±10 %, which showcased the potential for efficient and effective estimations at a reduced cost for HLRW disposal design.

ERMƏNİSTANIN AZƏRBAYCANA QARŞI EKOLOJİ TERRORU

Since 1988, 20% of Azerbaijan's lands have been occupied as a result of the war waged by Armenia to pursue its territorial claims against Azerbaijan. After a long occupation, during the 44-day Patriotic War and 24-hour local anti-terrorist operations, our lands, which had been in the hands of the enemy for almost 30 years, were liberated by our brave Army. However, in the territories we liberated from occupation, the enemy left behind ruins and an environmental disaster. For almost 30 years, Armenia deliberately tried to destroy our nature, carried out environmental terrorism against Azerbaijan, spontaneously exploited natural resources, including our occupied territories, polluted drinking water reservoirs with industrial waste, and disrupted the ecological balance of the environment. During the occupation, the enemy committed the great¬est acts of vandalism on our lands; the occupying forces destroyed forests, national parks, nature reserves, valuable trees and other rare examples of biodiversity. The rivers that are the source of Azerbaijan's drinking water are contaminated with chemical, biologi¬cal and other radioactive waste flowing from the territory of Armenia. Over the past years, contamination of water sources flowing from the occupied territories has led to the death of valuable fish species and the depletion of fish stocks. 7 ecologically important relic lakes and 10 reservoirs in the liberated territories of Azerbaijan were subject to serious anthropogenic impact from the occupying Armenia.

A novel defect-rich Prussian blue analogue based on controlled doping strategy: Exceptional adsorption performance of platinum group metals and enhanced stability

The efficient separation of platinum group metals (PGMs, mainly Pd, Ru, and Rh) from high level liquid waste (HLLW) is of growing significance for resolving challenges in radioactive waste treatment and achieving sustainable development. Based on Prussian blue analogues (PBAs) with tunable compositions and morphologies, a defect-rich but also excellently stable cobalt-doped aluminum hexacyanoferrate (Co/KAlFC) was successfully synthesized for the separation of PGMs using defect engineering. Interestingly, the defects in Co/KAlFC induced an increase in active sites and vacancies, leading to a remarkable enhancement of PGM adsorption capacity compared to the undoped KAlFC. While maintaining the same excellent Pd(II) adsorption capacity, the convenient access provided by the defects led to a reduction of the Pd(II) adsorption equilibrium time to 30 min, as well as a 3-fold and 7-fold increase in the adsorption capacity for Ru(III) and Rh(III), respectively. The experimental and characterization results revealed that the adsorption mechanism of defect-rich Co/KAlFC on PGM was mainly a synergistic effect of ion-exchange and chemical complexation, and the enhanced electrostatic interaction promoted the adsorption process. The valence state of Fe shifted from divalent to trivalent during the adsorption process, which affected the strength of coordination interaction between PGMs and Fe-CN- at N-atom. Overall, this study not only demonstrated that Co/KAlFC is an excellent candidate for the removal of PGM from HLLW but also provided a new idea for the rational design and development of inorganic materials with exceptional properties and stability.

Modification of Portland cement matrix with diethyldithiocarbamate for technetium immobilization

The paper considers the effect of sodium diethyldithiocarbamate (SDDC) addition on the immobilization of technetium in a Portland cement matrix. The leaching process was evaluated in a model solution that simulated the conditions of the future radioactive waste (RW) storage site at the Yeniseisky site. The results demonstrated that the addition of 1.0 wt % SDDC to the cement composite increased the incorporation of immobilized technetium into the cement matrix by 35% in comparison to the blank sample. Furthermore, the retention of technetium in the cement matrix was observed to be enhanced, with a retention of up to 90% observed on the 200th day of the experiment. Resulting materials fulfill the necessary technical characteristics for use as a matrix and engineered safety barrier in the concept of deep RW disposal. The addition of SDDC into cement results in microbial respiratory activity decreasing. In order to evaluate the mechanisms of technetium immobilization, the structure of the technetium compound with diethyldithiocarbamate (DDC) [Tc(C5H10NS2)4]TcO4 is described for the first time. This compound contains a Tc(V) atom which coordinates four diethyldithiocarbamate C5H10NS2 moieties through eight sulfur atoms to form a complex cation. The addition of SDDC in cement is presumed to result in a cascade of disproportionation reactions and the formation of stable Tc(IV) compounds, as it was evidenced by XANES spectroscopy.

Biofilm Formation on Excavation Damaged Zone Fractures in Deep Neogene Sedimentary Rock.

Deep underground galleries are used to access the deep biosphere in addition to mining and other engineering applications, such as geological disposal of radioactive waste. Fracture networks developed in the excavation damaged zone (EDZ) are concerned with accelerating mass transport, where microbial colonization might be possible due to the availability of space and nutrients. In this study, microbial biofilms at EDZ fractures were investigated by drilling from a 350-m-deep gallery and subsequent borehole logging at the Horonobe Underground Research Laboratory (URL). By using microscopic and spectroscopic techniques, the dense colonization of microbial cells was demonstrated at the surfaces of the EDZ fractures with high hydraulic conductivity. 16S rRNA gene sequence analysis revealed the dominance of gammaproteobacterial lineages, the cultivated members of which are aerobic methanotrophs. The near-complete genomes from Horonobe groundwater, affiliated with the methanotrophic lineages, were fully equipped with genes involved in aerobic methanotrophy. Although the mediation of aerobic methanotrophy remains to be demonstrated, microbial O2 production was supported by the presence of genes in the near-complete genomes, such as catalase and superoxide dismutase that produce O2 from reactive oxygen species and a nitric oxide reductase gene with the substitutions of amino acids in motifs. It is concluded that the EDZ fractures provide energetically favorable subsurface habitats for microorganisms.

A critical analysis of the role of artificial intelligence and machine learning in enhancing nuclear waste management

Abstract Controlling and managing nuclear waste is a significant challenge due to the harmful effects of radioactive materials on human health. To address this, long-term storage solutions are essential. Artificial Intelligence (AI) and Machine Learning (ML) are being utilized to make nuclear waste management safer, more effective, and efficient. This paper evaluates various applications of AI and ML in the field of nuclear waste, covering aspects such as predictive maintenance, waste sorting, and classification. AI and ML enhance real-time monitoring of storage conditions and optimize waste handling procedures through advanced data processing capabilities. Implementing cutting-edge solutions is crucial to protect public health and the environment from radioactive waste. The purpose of this evaluation is to examine how AI and ML improve nuclear waste management processes. These technologies can reduce human exposure to harmful materials and increase the safety and efficiency of managing nuclear waste through advanced predictive capabilities. The introduction of AI and ML in nuclear waste management is driving significant changes and innovations, addressing current issues, and establishing new guidelines for future policies.

Assessment of radiological risk to workers and members of the public from the operation of a groundwater treatment plant in Jordan

ABSTRACT The study aimed to evaluate the radiation doses received by workers at a pilot water treatment plant (WTP) in Jordan. It also examined the concentrations of gross alpha, gross beta, and radium activities in both groundwater and treated water, along with a radiological risk assessment for the waste generated by the treatment process. The radioactivity levels of gross alpha and gross beta in the groundwater were found to exceed the established drinking water limits. In the pilot WTP, two methods were applied for water treatment, namely, ceramic ultra-filtration (CUF) and reverse osmosis (RO), both of which produced treated water that met drinking water quality standards. The annual effective dose from external radiation exposure to the WTP workers was found to be less than 0.007 mSv y−1 (during the filters backwash operation). However, the average annual dose from internal radiation due to inhalation of radon released from groundwater reached 3.2 mSv y−1, exceeding the 1 mSv y−1 limit. Therefore, monitoring radon levels in workplaces is recommended. Radioisotope concentrations in the waste (sludge) stockpiles exceeded clearance levels, requiring them to be treated as radioactive waste. Overall, the WTP successfully produced drinking water that met quality standards, and the methods used could be replicated in other locations.

A computational framework to support probabilistic criticality modelling for the geological disposal of radioactive waste

Nuclear Waste Services is tasked with disposal of the UK’s higher-activity radioactive waste in a Geological Disposal Facility. The disposal of fissile nuclides requires a demonstration that there is no significant concern from criticality, i.e. a fission chain reaction. While waste packages will initially be emplaced in a subcritical configuration, over the long timescales following closure there is potential for waste packages to degrade and for nuclides to be dispersed in the subsurface by groundwater, leading to the potential for a critical system forming. To facilitate modelling, a codebase has been developed which interfaces a probabilistic simulation tool (GoldSim) with a neutron transport code (MONK/MCNP). This allows large ensemble simulations to be run iteratively to determine limiting fissile masses which satisfy a criticality safety criterion. This paper documents the main algorithms and methodologies implemented within this framework, and provides background and example results illustrating the application to post-closure criticality modelling.

Influence of Chemical Weathering and Microcracks on Permeability Variations in Crystalline Rocks

Rock permeability, an important factor in subsurface fluid migration, can be influenced by microcracks and chemical weathering due to water–rock interactions. Understanding the relationship between permeability, chemical weathering, and microcracks is crucial for assessing fluid flow in rocks. This study focuses on the hydrogeological characteristics of granite and gneiss, potential host rocks for high-level radioactive waste disposal in South Korea. Samples were analyzed for permeability, porosity, P-wave velocity, and chemical weathering indices. Regression analysis revealed a weak correlation between permeability and both porosity and rock density, while an inverse correlation was observed between permeability and chemical weathering indices. Interestingly, some samples showed low permeability (10−21 to 10−22 m2) despite high weathering, while others showed high permeability (10−18 to 10−19 m2) despite low weathering. SEM-EDS analysis indicated the presence of microcracks within the rocks or the filling of these cracks with secondary minerals. The findings suggest that chemical weathering generally increases pore size and porosity, but actual permeability can vary depending on the presence and connectivity of microcracks and the extent to which they are filled with secondary minerals. Therefore, both chemical weathering and microcrack connectivity must be considered when evaluating the hydrogeological characteristics of crystalline rocks.

Borehole disposal of spent fuel and other high-level wastes: the case for deep, vertical, fully cased holes in saturated “hard” rock

Driven by major advances in deep drilling technology and the geological understanding of the deep continental crust over the past 70 years, disposal in deep boreholes has moved from being technically unachievable to the point that it now offers a viable solution for the most hazardous nuclear wastes that could effectively be implemented “tomorrow”—i.e., within a few years. Moreover, disposal in deep boreholes is arguably superior in almost every respect to the mined and engineered repositories being pursued for high level waste by most countries. During the first 50 years of their evolution, almost all deep borehole disposal concepts shared five key aspects: (i) the hole was as deep as possible, (ii) it was vertical, (iii) it was fully cased, and (iv) it was in “hard” basement rock (v) saturated with aqueous fluid (groundwater). Technical advances in drilling over the last 20 years have encouraged proposed versions of the concept which depart from one or more of these aspects, but it is our contention that all five fundamental aspects should be retained. This paper summarises the more important arguments supporting this view. In order to meet the necessary post-closure (radiological) safety requirements, engineer out possible operational problems during construction and waste-package deployment, and capitalise on the main benefits of borehole disposal, the hole itself must be over 3 km deep, vertical, fully cased, and in suitably hard (ideally granitic) host rock saturated with aqueous fluid.

Incorporation of trace metals in Hanford waste boehmite mineral phases and dissolution rate impacts

AbstractData from radioactive Hanford tank waste samples was analyzed to assess whether trace metals present were incorporated into the bulk boehmite matrix or were simply intermingled with the bulk material and subsequent impacts to the boehmite dissolution rate. Results suggest that chromium is primarily blended into the bulk boehmite, with a small fraction present on the surface of the solids. However, increasing the level of chromium incorporation 30‐fold decreased the dissolution rate of boehmite by only 8%, suggesting incorporation of chromium into these samples had a minimal impact on the dissolution rate. Iron was also found to be incorporated in the boehmite solids. Silicon appears to be simply intermingled and not blended into the boehmite crystals.

Synthesis of La2Ti2O7 nanoscale powder and ceramics based on it by sol-gel and spark plasma sintering

The application of ceramics as matrices for the immobilization of radionuclides for the purpose of their safe long-term disposal or beneficial use is being studied with an emphasis on phase stability, structural integrity, hydrolytic stability, etc. In this work, a combined approach was investigated, based on the sol-gel citrate synthesis of nanosized La2Ti2O7 powder and its subsequent spark plasma sintering to produce dense ceramics. The phase composition and structure of the nanosized La2Ti2O7 powder and ceramic samples based on it, obtained in the temperature range of 900–1300 °C, were studied by XRD and SEM. It has been shown that the powder synthesis conditions ensure the formation of nanosized crystalline La2Ti2O7 grains, whose consolidation under spark plasma heating conditions proceeds with a change in the phase composition from single-phase La2Ti2O7 of monoclinic structure to orthorhombic with an admixture of LaTiO3 at temperatures above 1200 °C. It was revealed that the change in the ceramic structure is accompanied by the formation of non-porous and defect-free monolithic samples. It was determined that such a change leads to an increase in relative density (81.3–95.7%) and compressive strength (78–566 MPa) of the ceramic samples. However, the hydrolytic stability of the ceramics decreases, as indicated by an increase in the leaching rate of La3+ from 10–7 to 10–5 g/cm2·day. The obtained results are useful for the systematic study of materials suitable for immobilization technologies of radioactive waste in ceramics.

The Upshots of Dufour and Soret in Stretching Porous Flow of Convective Maxwell Nanofluid with Nonlinear Thermal Emission

In this paper, the combined upshot of Soret and Dufoue of a convective Maxwell nanofluid on a porous perpendicular surface with nonlinear thermal emission was investigated. In the present work, the impact of permeable stretching sheet, nonlinear thermal emission, heat sour sink, Dufour and Soret effect, chemical reaction, Brownian motion and thermophoresis in a convective Maxwell nanofluid flow is widely discussed. The governing equations derived for the problem are highly nonlinear coupled partial differential equations. The governing equations were transformed into ordinary differential equations using Lie symmetry group alterations. The BVP4C MATLAB solver was employed to solve the ordinary differential equations numerically after validating the convergence of the method with existing results in the literature. The numerical results were established and discussed using tables and graphs. It was found that variations in porosity parameter (K), Dufour (Du) and Soret (Sr) improves velocity, temperature and concentration profiles respectively and the present of nonlinear thermal radiation and heat source emit more heat for the flow. Also, it is exciting to report that both porosity (K) and Dufour (Du) parameters has a strong impact on the flow of skin frictions, Nusselt number and Sherwood number. However, the current results may present applications in the areas of petroleum reservoir, heat exchangers, steel industries, cooling applications, nuclear waste disposal and so on.

Prediction of Decay Heat from PWR Spent Nuclear Fuel Using Fuel Parameters

In the context of a geological repository for nuclear waste, fast and accurate predictions of decay heat are needed for different applications ranging from canister loading optimization to comparing decay heat predictions from state-of-the-art codes with experimental measurements. This work uses a large database of simulated pressurized water reactor (PWR) spent nuclear fuel (SNF) with an extensive range of fuel parameters to demonstrate that by using only the burnup, initial enrichment, and cooling time of the SNF, it is possible to predict the decay heat of a PWR SNF. A linear interpolation model has been developed using the simulated data and tested on data from decay heat measurements using a calorimeter. The model code was also made publicly available [V. Solans, “Python Script for the Prediction of Decay Heat from PWR Spent Nuclear Fuel Using Fuel Parameters,” Zenodo (2024)]. The results show that the decay heat can be well predicted, with the relative error between measurements and predictions ranging between 4% and 8%. After correcting for a systematic deviation between predictions and experimental results using the limited set of experimental measurement data available, the relative error can be further reduced to 2% to 3%.

Long term durability of Tc-bulk and Tc-coatings in various environmental conditions

Technetium metal is renowned for its inertness in environmental conditions, rendering it an optimal candidate for use as a container material for high-level radioactive waste. Alternatively, thin technetium electroplated coatings can be employed to prevent corrosion of steel containers and the subsequent biofouling that may result. The utilization of metallic technetium in the design of containers for radioactive waste in deep burial may be promising from two perspectives: firstly, in terms of increasing their stability, and secondly, in terms of the utilization of technetium, which is a macrocomponent of radioactive waste. In this study, the resilience of the metal technetium and its two derivative coatings (amorphous and crystalline) was assessed under various conditions, including exposure to fresh groundwater and seawater. The multifunctional strain Shewanella xiamenensis DCB-2-1, known for its ability to enzymatically reduce pertechnetate ions, was used to investigate the possibility of microbial biofouling of metallic technetium. Laboratory experiments have demonstrated that amorphous electrodeposited technetium is more susceptible to oxidation processes compared to its crystalline counterpart. Ultimately, the most durable form of technetium was metal foil. The potential for biofouling on Tc surfaces is largely attributed to the diverse nature of the specimens’ surface. Research conducted in the Barents Sea has revealed that the accumulation of iron, calcium, and magnesium mineral phases within the microbial biofilm may shield beta radiation, resulting in the establishment of macro-fouling (Balanus and Mutilus).

Study on the coupled hydro-mechanical model of gas-induced dilation effects in bentonite

IntroductionGas migration in low-permeability buffer materials is a crucial aspect of nuclear waste disposal. This study focuses on Gaomiaozi bentonite to investigate its behavior under various conditions.MethodsWe developed a coupled hydro-mechanical model that incorporates damage mechanisms in bentonite under flexible boundary conditions. Utilizing the elastic theory of porous media, gas pressure was integrated into the soil's constitutive equation. The model accounted for damage effects on the elastic modulus and permeability, with damage variables defined by the Galileo and Coulomb–Mohr criteria. We conducted numerical simulations of the seepage and stress fields using COMSOL and MATLAB. Gas breakthrough tests were also performed on bentonite samples under controlled conditions.ResultsThe permeability obtained from gas breakthrough tests and numerical simulations was within a 10% error margin. The experimentally measured gas breakthrough pressure aligned closely with the predicted values, validating the model's applicability.DiscussionAnalysis revealed that increased dry density under flexible boundaries reduced the damage area and influenced gas breakthrough pressure. Specifically, at dry densities of 1.4 g/cm³, 1.6 g/cm³, and 1.7 g/cm³, the corresponding gas breakthrough pressures were 5.0 MPa, 6.0 MPa, and 6.5 MPa, respectively. At a dry density of 1.8 g/cm³ and an injection pressure of 10.0 MPa, no continuous seepage channels formed, indicating no gas breakthrough. This phenomenon is attributed to the greater tensile and compressive strengths associated with higher dry densities, which render the material less susceptible to damage from external forces.