Radioactive Waste Disposal Research Articles

Dual effect of Se(IV) and bentonite microbial community interactions on the corrosion of copper and Se speciation: Implication on repository safety assessment.

The Deep Geological Repository (DGR) design, the internationally safest option for the long-term disposal of high-level radioactive waste (HLW), features metal canisters encased in compacted bentonite clay and embedded deep within a host rock. Despite presenting a hostile environment for microorganisms, DGRs scenarios with favorable microbial-activity conditions must be considered for the safety assessment of this disposal. This study investigated the impact of Se(IV), as a natural analogue of 79Se present in the HLW, in anoxic microcosms of bentonite slurry spiked with a bacterial consortium and amended with lactate, acetate, and sulfate as electron donors/acceptor. The addition of the bacterial consortium promoted the rate of Se(IV) reduction to Se(0), while the tyndallization (heat-shock) of bentonite slowed this process. Se(IV) reduced the relative abundance of most genera of sulfate-reducing bacteria (SRB), while stimulating the abundance of Se-tolerant bacteria, which played an important role in Se(IV) reduction. Moreover, it was observed that lactate was the preferred electron donor, linking to the production and subsequent consumption of acetate. X-ray absorption spectroscopy (XAS) and high-resolution transmission electron microscopy (HRTEM) revealed the reduction of Se(IV) forming amorphous Se(0) nanospheres. In addition, HRTEM showed that the biogenic Se(0) undergo a biotransformation to more stable crystalline forms, contributing to the immobilization of Se in the case of HLW release. Additionally, the sulfide generated by the activity of SRB reacted with Cu producing corrosion products (CuxS) on the surface of the copper material.

Public perception and underlying values regarding final disposal of radioactively contaminated soil from a large nuclear accident.

Public understanding of the construction of radioactive waste disposal sites, including those for decontamination waste derived from a nuclear accident, is particularly difficult when the disposal site is far from the location in which the waste was generated. Radioactively contaminated soil from the 2011 Fukushima Daiichi Nuclear Power Plant accident is planned for final disposal outside of Fukushima Prefecture by 2045. The purpose of the current study was to identify underlying values influencing public perceptions regarding the final disposal. A total of 40 people were interviewed, including both supporters and opponents of the final disposal policy. The results of quantitative text analysis showed that the opinions of supporters were characterized by perspectives that reflected the Rawlsian maximin principle of sharing the burden of Fukushima and considering the most disadvantaged, while the opinions of opponents were characterized by distrust of the government. Statements of utilitarian perspectives on optimizing the safety and economic aspects of disposal were mentioned regardless of participants' opinions on the disposal policy. The study clarified the relationship between these underlying values and perception of the disposal policy. The results suggested several considerations for the government regarding final disposal: prioritizing public trust, valuing a fair process, and delivering messages that reflect burden of Fukushima. These findings provided valuable insights into public acceptance and stakeholder involvement in cases where a disposal site is far from the location in which the waste is generated.

The Future of Nuclear Energy: Key Chemical Aspects of Systems for Developing Generation III+, Generation IV, and Small Modular Reactors

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.

An Introduction to “Carbonate Reservoirs: Applying Current Knowledge to Future Energy Needs”

More than a century of exploitation of carbonate petroleum reservoirs has placed the geoscience subsurface community in a strong position to supply a wealth of knowledge and technology to our future energy needs. This special publication presents the latest learnings from carbonate oil and gas fields in key areas such as Brazil, the Middle East and North Africa, and demonstrates how the skills and workflows learnt in this industry can be directly applied to geothermal and radioactive waste disposal evaluations in carbonate successions. Particular reference is made to producing geothermal assets in Germany (Jurassic Malm reservoir), ultradeep geothermal exploration projects in The Netherlands (Carboniferous reservoirs), and feasibility studies of a deep geological repository for radioactive waste disposal in France (Jurassic). A common theme running through the special publication is the importance of recognising high-permeability zones which can have an enormous impact on producibility, whether in oil, gas or geothermal reservoirs. High permeability zones can result in high production rates, but can also be detrimental, whether due to early water breakthrough, resulting in bypassed oil, or H 2 S migration resulting in sour gas production. As we transition to alternative energy sources, this special publication looks back on the positive contributions of the oil and gas industry to our scientific knowledge and understanding, and discusses the ways in which carbonate and associated evaporite successions will play a critical role in our future energy needs.

Physical-geographical characteristics of the Una river basin – contribution to the analysis of the state and possibilities of radioactive waste disposal in the border zone

Physical-geographical characteristics of the Una river basin – contribution to the analysis of the state and possibilities of radioactive waste disposal in the border zone

Final thoughts: The fragile connection of safety and science in the geological disposal of radioactive waste

ABSTRACT While research on the safety of geological disposal of radioactive waste has been ongoing for more than 50 years, the research community has not achieved a clear understanding of repository safety. Repository safety is often considered a concept developed by safety engineers, putting ever-growing knowledge in the overall context of a safety case, with scientists providing building blocks for it, some of which might not contribute to safety. This article argues that scientists need to increase their overall understanding of repository safety and in particular of the redundancy of various barriers assuring the isolation capacity of a repository over an unprecedented long time.

Molecular simulation on Cs, Rb retention in Na/K-montmorillonite interlayer coupling clay swelling/collapse

A key issue about radioactive waste disposal and nuclear accident contamination control is the retention of radionuclides in clay minerals. The cation (Cs+, Rb+, Na+, K+) selectivity in montmorillonite (Mt) interlayers have not been quantitatively studied. This work employs classical molecular dynamics (CMD) to systematically investigate the interlayer structure, swelling properties, diffusion dynamics, and cation exchange processes. The selectivity of alkali ions within the interlayer space coupled with clay swelling/collapse under different water activity (aw) and cation activity, has been quantified. Both Cs-, Rb-Mt demonstrate a monolayer hydrate configuration as the most stable state. The mobility of intercalated species, as indicated by self-diffusion coefficients, exhibits a stepwise trend with increasing water content. The cationic selectivity within the interlayer follows the order Cs+ > Rb+ > K+ > Na+ at aw = 1.0. The logarithm values of the selectivity coefficients for Cs/Rb relative to Na/K are as follows: logKc(Cs/K) = 0.73, logKc(Cs/Na) = 1.62, logKc(Rb/K) = 0.62, and logKc(Rb/Na) = 1.57 at aw = 1.0. A model correlating selectivity coefficients with water activity has been proposed. It is noted that Cs+ and Rb+ ions tend to accumulate within the interlayer as water activity decreases, and interlayer Rb+ competes with Cs+ for exchange positions at low water activity. These results can be used to quantify cationic partitioning during the remediation of radiocesium contamination in soil and weathering processes of sediments.

Latest revisions to AESJ Standards for safe disposal of low-level radioactive waste (1)

Latest revisions to AESJ Standards for safe disposal of low-level radioactive waste (1)

Latest revisions to AESJ Standards for safe disposal of low-level radioactive waste (3)

Latest revisions to AESJ Standards for safe disposal of low-level radioactive waste (3)

Latest revisions to AESJ Standards for safe disposal of low-level radioactive waste (4)

Latest revisions to AESJ Standards for safe disposal of low-level radioactive waste (4)

Latest revisions to AESJ Standards for safe disposal of low-level radioactive waste (2)

Latest revisions to AESJ Standards for safe disposal of low-level radioactive waste (2)

On the Development of a Self-Sealing Experimental Setup for Natural Claystones Considered as Potential Host Rocks for Radioactive Waste Disposal: Application to the Sandy Opalinus Clay

On the Development of a Self-Sealing Experimental Setup for Natural Claystones Considered as Potential Host Rocks for Radioactive Waste Disposal: Application to the Sandy Opalinus Clay

Applying multiple processes nonequilibrium model to investigate cesium transport in crushed granite

Abstract Understanding the movement of radionuclides (RN) in the subsurface environment is of paramount importance, particularly when it comes to the planning and assessment of facilities devoted to the disposal of radioactive waste. Comprehensive mathematical models serve as indispensable tools in this regard, demanding a profound and thorough understanding of the intricate mechanisms underlying radionuclide transport. The effective application of these models is contingent upon accurately determining the required input parameters. This is a critical aspect to consider given the inherent physical and chemical variations exhibited by the subsurface environment. These variations can induce significant effects on the movement of RNs below ground, potentially altering the predicted outcomes of radionuclide transport. This paper presents the findings of a comprehensive investigation that was conducted utilizing both advective-dispersive experiments (ADE) and multiple processes nonequilibrium (MPNE) inversion. These methodologies were employed using the advanced HYDRUS code, which is highly regarded in the field. The research specifically focuses on the transportation mechanisms of Cesium (Cs), a common radionuclide, in a medium of crushed granite. The study considers varying conditions, including different flow rates and column lengths, to provide a broad understanding of the behavior of Cs. The findings reveal that the transport behavior of Cs is not only influenced by the different flow rates and column lengths but is also significantly affected by the diffusive mass transfer and nonequilibrium sorption. These factors collectively contribute to our understanding of the complex processes involved in radionuclide transport.

Effect of sodium occupancy and solute concentration on the swelling pressure and hydraulic conductivity of Boom Clay

The poorly indurated Boom Clay (BC) has been studied as a potential host formation for the geological disposal of radioactive waste including the intermediate-level long-lived bituminized radioactive waste called Eurobitum. In case of leaching of Eurobitum, fluids with altered chemical compositions would be expected to infiltrate locally into the BC. To evaluate the effect of salinity on the Boom Clay hydromechanical behaviour, a series of one-dimensional constant-volume swelling tests were conducted on intact BC samples that were first percolated with mixed sodium-calcium-nitrate solutions ((Na,Ca)NO3) with varying sodium concentrations, resulting in varying Na+ occupancies in the clay. Results showed that the swelling pressure of BC decreased with an increase in the solute concentration and sodium occupancy. Additionally, higher Na+ concentrations led to a faster stabilization of the swelling pressure. The hydraulic conductivity of BC increased with increasing solute concentration and sodium occupancy. Moreover, the sodium occupancy and concentration affected the swelling pressure and hydraulic conductivity in a similar way. This phenomenon could be elucidated by two primary mechanisms: i) the influence of solute concentration on the Diffuse Double Layer (DDL), and ii) the effect of cation type and hydrated radius within the interbasal space of montmorillonite sheets, especially concerning sodium occupancy.

South African Nuclear Necropolitics in Helmut Starcke’s Study for “Vaalputs Madonna”

Art provides a meaningful instrument with which to understand, reflect, and communicate history, humanity, scientific progress, and societal threats. Nuclear art is a particular and critical art form that deals with the duality of the nuclear chain reaction which is either used for peaceful purposes such as nuclear medicine and food irradiation, or for weapons of mass destruction such as nuclear bombs. Despite South Africa’s long nuclear history and unprecedented voluntary nuclear weapons disarmament, nuclear art as a visual practice is underdeveloped in the country. This article considers German-born South African artist Helmut Starcke’s Study for “Vaalputs Madonna” (2007) as a visual expression of South African nuclear art, and the nuclear necropolitics related to the Vaalputs National Radioactive Waste Disposal Facility in South Africa’s Northern Cape province. Starcke’s use of Marian iconography and his juxtaposition of European and African art symbolises the violence of nuclear colonialism, while he also confirms the realities of the nuclear necropolitics of apartheid and post-apartheid South Africa.

Analysis of Long-Term Thermo–Hydro–Mechanical Behavior in the Near-Field of a Deep Geological Repository System

The deep geological repository (DGR) system has been selected by most of the world’s nuclear waste management organizations for the long-term disposal of radioactive wastes. The DGR mainly consists of a multi-barrier system—comprising the natural host rock and an engineered barrier system—to contain and isolate high-level radioactive waste, including used fuel containers (UFCs), to protect humans and the environment. Bentonite materials and host rock are the main components of the DGR’s engineered and natural barrier system, respectively. It is crucial to understand the coupled behavior of bentonite and rock materials under various in situ conditions over long-term durations, as it supports safety assessments and enhances the overall safety level of DGR systems. This study presents a methodology for the numerical modeling of a hypothetical DGR using developed coupled models. The developed model was used to investigate the hydromechanical (HM) and thermomechanical (TM) response within the near-field (the area within a radius of 50 m near the UFC and multiple-barrier system) of a simplified hypothetical DGR, based on the proposed design concept of the Nuclear Waste Management Organization (NWMO) of Canada. The analysis results included the evolution of temperature, thermal stresses, saturation, and swelling pressure at different stages of the DGR system’s lifetime. The results indicated that it could take up to 10,000 years to fully saturate the bentonite materials with a corresponding swelling pressure of 2.7 MPa associated with a decrease in the rock’s strength/stress ratio near the placement room; however, the ratio did not indicate a significant system failure. Sensitivity analysis was also conducted to assess the impact of various parameters on the saturation time and the strength/stress ratio in a DGR. The results highlighted that saturation time was highly influenced by the permeability of both the rock formation and the bentonite, resulting in saturation times ranging from 500 to 20,000 years. Moreover, the strength/stress ratio was found to be sensitive to the model’s parameters, particularly the maximum swelling pressure. The results of the TM analysis show that temperature development around the placement of rooms in a DGR is highly influenced by room spacing, with a lower factor of safety (FOS) as time and temperature progressed due to elevated temperature, while the rock remained stable over the 150-year analysis period. The inclusion of temperature-dependent mechanical properties produced negligible changes to the overall stability of the rock around the placement rooms of the DGR.

Comparison of feature importance measures and variance-based indices for sensitivity analysis: case study of radioactive waste disposal flow and transport model

Comparison of feature importance measures and variance-based indices for sensitivity analysis: case study of radioactive waste disposal flow and transport model

Operational Excellence by Implementation of 5S Concepts and Lean Management Practices in Vivarium

Modern vivarium operation requires collective efforts by cross-functional teams especially within the collaborative research organizations for the successful outcomes of comprehensive laboratory animal care program. The drug discovery with rapid screening turnovers and innovative approaches demands infrastructure expansion by increasing several other capabilities in vivarium. The strategic portfolio changes and therapeutic areas closure retained several high-end equipment’s left unused that eventually occupied space in the barrier system which intricate daily operations and space management became challenging over the period. The vivarium facility was under continuous improvement by the quality assurance program based on monthly independent audit reports and compiled the compliance including animal welfare standards of at least 5 years period. Corporate initiatives such as Kaizen events, 5S concepts, Gemba walk and green labs certifications were implemented systematically at various phases across the organization including vivarium. The leadership team was a driving force behind the lean management practices and its implementation. The quality assurance program was able to bring out several improved operational processes notably by creating an additional quarantine space; repurposing high-end equipment for other investigators to support their ongoing programs; effective space utilization by creating in-house diagnostic laboratory; donating low-density animal racks for academic institutions as part of educational outreach efforts; containment of solid radioactive waste disposal by compaction process for longer half-life radioisotopes. In conclusion, lean management practices collectively demonstrated a measurable outcome in terms of continuous process improvement, effective vivarium management by ensuring compliance based on periodical observations without compromising animal welfare, conservation of energy and resources, effective space utilization and systematic implementation of 5S concepts by repurposing of equipment to other laboratories. Overall, the system-driven process has improved the standards with better performance that eventually enhanced the quality and productivity at the laboratory animal facility

Numerical Analysis of Gas Generation and Migration in a Radioactive Waste Disposal Cell of a Deep Geological Repository

Abstract In a deep geological repository (DGR) for the long-term disposal of radioactive waste, gases (e.g., hydrogen (H2), carbon dioxide (CO2) and methane (CH4)) can be generated through a number of processes, such as corrosion of various metals and alloys and degradation of organic materials. If gas induced pressure exceeds the containment capacity of the engineered barrier systems (EBS) or the host rock, the gases could migrate through these barriers and potentially expose people and the environment to radiation. Therefore, a good understanding on the long-term performance of these barriers against gas migration is an important component in DGR design and safety assessment. In the present work, a numerical model has been developed to simulate the diffusion of CO2 (one of the gas species) in the near field of a DGR with the generation from related chemical reactions. The generation of CO2 was investigated to determine if it is a critical factor to impact the DGR safety under Canadian geological formations. A commercial computational fluid dynamics (CFD) code, ANSYS Fluent was used for the calculations. The model considered pH and temperature effects on CO2 migration under Canadian DGR geochemistry conditions.

A Numerical Simulation Study on the Migration of the 90Sr Nuclide of Buffer Material Under the Coupling Effect of Multiple Factors

With the development of nuclear energy in China, the geological disposal of high-level radioactive waste (HLW) is increasingly receiving national attention. Among them, the study of nuclide migration is an important and complex technical system, which requires continuous in-depth research. Under the decay heat, radiation, and groundwater effects of HLW, buffer materials generate complex coupled thermo-hydro-mechanical-chemical (THMC) processes. The migration and diffusion of nuclides in buffer materials are controlled by the coupling effect of THMC. It is of great significance for the long-term safety of a HLW repository to study the long-term retarding effect of buffer material on nuclide strontium under the coupling effect of multiple factors. This study leverages the solving advantages of COMSOL Multiphysics 5.6, using a combination of the self-developed Mock-up experimental device as a geometric model and numerical simulations to study the multi-field coupling performance and radionuclide migration evolution characteristics of THMC buffer materials, which overcomes the difficulties due to the limitations of the experimental time and spatial scale. The simulation results can predict the migration range and distance variation of strontium in buffer materials at different time scales. In the initial stage, the migration and diffusion of nuclide in buffer materials are relatively slow, and the migration distance increases by about 0.03 m with time. In the mid-to-late stage, the migration distance increases by about 0.05 m over time; to ensure that, in 1000 years, core strontium does not penetrate the buffer material and migrate into the surrounding rock groundwater of the disposal facility, a buffer material thickness of 0.3 m needs to be set. The construction of THMC control equations for the migration and diffusion of nuclides in buffer materials under multi-field coupling conditions has been revealed, providing an important reference for a deeper understanding of the risk analysis of radionuclide contamination in disposal environments.