Radioactive Waste Disposal Site Research Articles

Permeability monitoring of underground concrete structures using elastic wave characteristics with modified Biot’s model

This study aims to develop a theoretical model for predicting the permeability of concrete in underground structures using compressive elastic waves. This research is motivated by the necessity of monitoring the permeability of concrete used in critical underground infrastructure, such as tunnels and radioactive waste disposal sites, to ensure their long-term safety. Increased permeability owing to crack generation can lead to groundwater inflow, undermining the structural integrity of these facilities. Traditional methods for permeability monitoring face challenges at depths of 500 m–1 km owing to high temperatures, high pressures, and limited space conditions. To address these issues, Biot’s model, which correlates the P-wave characteristics with the properties of porous media, was applied in this study. The P-wave velocity and attenuation were studied according to the permeability of concrete based on Biot’s model. Subsequently, concrete specimens were prepared to measure the permeability, P-wave velocity, and attenuation. The permeability results from the experiment were compared with those obtained from the model for validation. The findings indicate that the modified Biot’s model can effectively monitor permeability through elastic wave characteristics, offering a non-destructive and reliable method for assessing the condition of concrete structures in underground environments. This approach is expected to enhance the safety of underground infrastructure through accurate permeability monitoring.

Identifying a Self‐Sustaining Population, Spawning Site and Population Size of the Danube Salmon Hucho hucho Using the Citizen Science Approach

ABSTRACTThe last populations of Danube salmon (Hucho hucho) in Croatia are found in the Kupa and Una rivers. However, the size of the suitable area that could serve as the best spawning ground for the remnant Danube salmon population in these rivers is not known. This study aimed to leverage anglers' experiences to determine the sections of the Una and Kupa rivers where the last populations of Danube salmon (Hucho hucho) in Croatia are most abundant, identify potential spawning sites and assess threats that could impact the species' existence. The Kupica river emerged as a tributary of the Kupa river with a large Danube salmon population in Croatia. Experienced divers conducted three dives along a 350‐m transect in the Kupica river, estimating a total of 13 Danube salmon individuals ranging from 50 to 115 cm in total length, in pool and run mesohabitat types. In the Kupa and Kupica rivers, the survey identified 25 Danube salmon spawning sites. The primary local threats identified for the Danube salmon population include small hydropower plants, the construction of a radioactive waste disposal site, water abstraction, the removal of riparian vegetation, overfishing and climate change. Based on the results of this study, we strongly recommend the implementation of protective measures against these threats and the establishment of an ichthyological reserve specifically for Danube salmon in the Kupica river. This recommendation aligns with the EU Biodiversity Strategy, emphasizing the need to identify designated areas by 2030.

Evaluation of Hydrogeological Characteristic of Natural Barrier in Korea for Establishing Safety Guidelines of Deep Geological High-Level Radioactive Waste Disposal Site

Evaluation of Hydrogeological Characteristic of Natural Barrier in Korea for Establishing Safety Guidelines of Deep Geological High-Level Radioactive Waste Disposal Site

Improving the accuracy of density logging results considering mineral composition for evaluation of high-level radioactive waste disposal sites

ABSTRACT Site selection and characterisation are key factors influencing the safe, stable disposal of spent nuclear fuel. Site selection can be based on geophysical surveys, and geophysical well logging is performed at the detailed survey stage. Typically, gamma – gamma density logging is conducted to continuously obtain in situ density information regarding the well depth. However, gamma – gamma density logging is often influenced by the geological characteristics of the site. The ratio of atomic number to atomic weight is required to convert the electron density obtained through density logging counts into bulk density. Because it is difficult to calculate these ratios for the entire depth, an equation based on water-filled limestone is typically used for conversion. Therefore, as the difference in the ratio of the atomic number and atomic weight increases relative to that of limestone, the difference between the converted bulk density and the actual bulk density increases. In this study, equations were derived for various mineral compositions and applied to the density logging results. Matrix density was analyzed using a pycnometer, and the ratio between the atomic number and weight was calculated according to X-ray fluorescence analysis results. This approach improved the accuracy of the density logging data and reduced density errors. The proposed method is expected to be particularly useful for estimating in situ density at high-level radioactive waste disposal sites without complex geological formations.

MONITORING OF GROUNDWATER CONTAMINATION WITH TRITIUM AFTER A RADIATION ACCIDENT AT A RADIOACTIVE WASTE DISPOSAL SITE

The article analyses the data of long-term monitoring of the level of tritium contamination of groundwater in the area of the radioactive waste disposal site. Tritium is a radioactive isotope of hydrogen, a soft beta emitter. The impressive effect of tritium is due to the biological significance of the molecules into which it incorporates. Radioactive waste storage facilities store a lot of tritium-rich radioactive waste of various origins, a potential tritium source entering the natural environment. Any tritium released appears as tritium water (water that contains tritium in its molecules). Nowadays, the problem of tritium contamination of water ecosystems in the radioactive waste storage facilities’ areas can be considered one of the main issues in radioecology. The study aims to assess the level of safety of underground water in the radioactive waste disposal site area by the level of tritium content based on long-term monitoring data. The object of the study was the content of tritium in the underground water of the first aquifer in the territory of the radioactive waste disposal site (strict regime zone, sanitary and protective zone, and in underground waters of wells outside and in surface water bodies of the natural environment). We tested the tritium activity in water samples using the Triathler 425-034 liquid scintillation radiometer. In 1997, a radiation accident occurred at the radioactive waste disposal site. It led to the penetration of tritium into the first aquifer. Work has been underway to eliminate the accident. Modernisation of the system of wells for monitoring the underground water tritium contamination level also took place. As a result of the performed works, the radiation situation in the accident area has stabilised, and contamination of the aquifer due to the inflow of surface contaminated water from radioactive waste storage facilities has completely stopped. The results of long-term monitoring of tritium content in water of boreholes and wells and natural objects (reservoirs) located outside the sanitary protection zone of the enterprise showed that 27 years after the radiation accident, the radiation situation in the studied area is stable. The total activity of tritium in the aquifer of the monitoring wells is decreasing and has now reached the regulatory level in all but three wells. The concentration of tritium in underground waters (wells) and surface waters (reservoirs) outside the sanitary and protective zone has never exceeded the environmentally safe level during the monitoring period. At present, 89% of the studied monitoring sites (boreholes, natural reservoirs, wells) have tritium content that is within the environmentally safe range. Keywords: radioactive waste disposal site, radiation accident, tritium, aquifers, monitoring, environmental safety.

Investigating advection–dispersion behavior for simulation of HTO and 238Pu transport in argillaceous shale with different varying degrees of weathering

Abstract Exploring the migration behavior of radioactive nuclides in the surrounding rock media of the disposal site is the basis for the safety evaluation of radioactive waste disposal sites. In this study, the column experiment was employed to evaluate the nuclide migration behavior in the surrounding rock medium of a near-surface disposal site in China and to investigate the advection–dispersion behavior of tritium (HTO) and plutonium-238 (238Pu) in highly weathered argillaceous shale with different degree of weathering. A reasonable numerical model was selected to fit the experimental breakthrough curves (BTCs) and obtain relevant migration parameters. The results showed that: (1) the breakthrough curves of HTO and 238Pu in fractured media with varying degrees of weathering exhibited clear “peak forward” and “tail dragging” phenomena; (2) the stream tube model can better fit the BTCs of the nuclides in the highly weathered fractures and obtain the average dispersion coefficient <D>, average distribution coefficient <K d>, and other parameters; (3) the two-region non-equilibrium model can better fit the BTCs of the nuclides in the penetrating fractures and weak weathering fractures and obtain the volumetric water content of the mobile liquid region (θ m), distribution coefficient (K d), and other parameters.

Distribution coefficients Kd of cobalt ions in soil samples of Anarak near-surface radioactive waste repository studied by batch and three different column methods

The selection of appropriate transport parameters of radionuclides is of utmost importance in the safety assessment of radioactive waste disposal sites. Both batch and column methods are widely performed to determine the transport parameters of radionuclides through soil layers. In this paper, the distribution coefficients Kd of Co ions in sandy mixtures containing soil samples taken from Anarak near-surface repository (Iran) were determined by batch and 3 different column methods namely, breakthrough curve, thin-section, and gamma spectroscopy methods. The distribution coefficients Kd of the mixture was obtained as 160 L kg−1 for the batch method, 23 L kg−1, 19 L kg−1, and 18 L kg−1 for the breakthrough curve, the thin-section, and the gamma spectroscopy methods, respectively. These results emphasize proper selection of transport data for using in the safety assessment programs.

Diffusion capability of Cs-137 in compacted soil and bentonite under groundwater-saturated condition

Several researches have been studied the diffusion coefficient (Da) of radionuclide in soil samples in varies location around the world; however, the effect of cations in groundwater as a medium of saturation for Cs-137 diffusion in soil and bentonite remains to be accomplished. Compacted soil and bentonite layers are utilized in the construction of radioactive waste disposal sites, which serve to prevent the release of Cs-137 from the repository to the unsaturated zone. The samples used were soil from the prospective disposal site in SP4—Serpong Nuclear Center (SNC) and bentonite taken from Santrijaya, Tasikmalaya. The diffusion coefficient (Da) is used as indicator of Cesium-137 diffusion in the samples. Experimental measurements were conducted on a diffusion column unit that varied in diffusion time and density conditions to determine diffusion coefficients. The samples were cut into slices and analyzed using Multichannel Analyzer (MCA) unit to measure Cs-137 radioactivity. The measurement results were then incorporated into Fick's Law equation to obtain the value of the diffusion coefficient (Da) of Cs-137 in soil and bentonite. The experimental results showed that the diffusion coefficients of samples with groundwater simulation are in the range of 10–12 m2 s−1 for the local soil and bentonite samples, respectively. Compare to the similar experiment that was conducted previously, the results indicated that the groundwater content could slightly impact the increase in the diffusion coefficient value of Cs-137.

Public service motivation and not-in-my-backyard: The case of high-level radioactive waste disposal sites in Japan

This study investigated the association between public service motivation (PSM) and the not-in-my-backyard (NIMBY) reaction by the public that often blocks important projects. A conjoint experiment was conducted using the scenario of hypothetical plans for the construction of a high-level radioactive waste disposal site, one of the most noxious NIMBY facilities. The results showed that overall PSM (the full scale) had no association with the public’s willingness to accept such facilities. Still, we observed significant positive correlations for the PSM dimensions of attraction to public service and self-sacrifice, and a significant negative correlation with the PSM dimension of compassion. As expected, some dimensions of PSM strengthened (moderated) the positive effect of policy attributes on acceptance. Contrary to our prediction that PSM attenuates the relationship between distance and acceptance, overall PSM, commitment to public values, and compassion amplified the relationship. Together, these findings suggest the need to promote research considering the multifaceted nature of PSM in NIMBY problems.

Рецензия на горно-геологическую часть обоснования строительства подземного хранилища радиоактивных отходов

The city district “Closed Administrative-territorial formation of the city of Zheleznogorsk” has appointed and organized public discussions on the materials of the justification of the license (including environmental impact assessment materials) for activities in the field of nuclear energy use “Creation of a second-class RW storage facility at FSUE GCK”. The mining and geological materials on the construction site of an underground repository of radioactive waste (RW) of the second hazard class in Zheleznogorsk of the Krasnoyarsk Territory are considered. The purpose of the construction of the storage facility is to ensure the storage of second-class radioactive waste at the site of the mining and chemical plant in volumes that meet the needs of the enterprise until the national operator is ready to handle radioactive waste. The review is a response to an offer to discuss supposedly public materials of open access. The subject of public discussions was conducted in the form of a survey. It is proposed to carry out the initial stage of the justification of the object on the basis of the Law “On Subsoil”. The following conclusion is made: the target horizon after the conservation of the object is likely to be flooded, primarily along vertical collector trunks; heterogeneous backfilling of the internal free space of trunks and horizontal workings with finished concrete lining with crushed/granular natural bentonite will not help; in reality, the volume of water in the burial zone will significantly determine the characteristics and the inexhaustible resource of the overlying water supply layers of rocks, rather than rocks of the target range, and even without recharge from other sources, the flooded PGZRO will quickly turn into a supplier of hot water and radiolytic gases. The opinion is expressed that it is unacceptable to turn a temporary storage facility into a permanent disposal site for radioactive waste.

Hydrogeochemistry and Statistical Analysis for Low and Intermediate Level Radioactive Waste Disposal Site in Gyeongju

Hydrogeochemistry and Statistical Analysis for Low and Intermediate Level Radioactive Waste Disposal Site in Gyeongju

Assessment of Radioecologically Relevant Radionuclides 14C, 99Tc, and 129I in Vitrified High-Level Nuclear Wastes from Spent Fuel Reprocessing

A method is proposed for quantifying the specific activities of radioecologically significant radionuclides, including 14C, 99Tc, and 129I, in vitrified high-level wastes. The conditions for the separation and purification of these radionuclides from potential interfering components are optimized and the yield coefficients and purification factors are determined. The quantification of 14C entails a three-fold distillation in CO2 followed by the measurement of the 14C counting rate in the purified solution by liquid scintillation spectrometry. 129I was determined by dissolving a sample in HNO3, five-fold extraction, and the subsequent measurement of the 129I counting rate in the purified solution using liquid scintillation spectrometry. The determination of 99Тс included dissolving a sample in the presence of ClO–, double extraction-chromatographic separation of 99Тс with an adsorbent impregnated with methyltrioctylammonium nitrate, followed by the determination of its activity by inductively coupled plasma–mass spectrometry. We have applied this approach to a simulator of vitrified high-level waste, labeled with radionuclides, and achieved satisfactory results. This approach will be instrumental in the analysis of the accumulated vitrified high-level wastes at the “Mayak” Production Association (Mayak PA). The results will be important for modeling the engineering safety barriers of a deep disposal site for radioactive wastes.

Uranium migration lengths in Opalinus Clay depend on geochemical gradients, radionuclide source term concentration and pore water composition

Abstract. Safety assessments of highly radioactive waste disposal sites are done based on simulation of radionuclide migration lengths through the containment providing rock zone. For a close to real case situation, the present model concept established for uranium is derived from the hydrogeological evolution and geochemical and mineralogical data measured at the deep geothermal borehole Schlattingen including the effect of geo-engineered barriers on the source term. In the Schlattingen area, the Opalinus Clay is tectonically undeformed compared to the Mont Terri anticline and represents the geochemical and temperature conditions at the favoured disposal depth. The geochemical conditions are more or less constant with slightly decreasing concentrations of pore water components towards the footwall aquifer. Uranium migrates less compared to the Opalinus Clay system at Mont Terri, where gradients of pore water geochemistry towards the embedding aquifers are more pronounced. This means, stable geochemical conditions with no or low concentration gradients are to be favoured for a safe disposal since migration lengths strongly depend on spatial and temporal variation of the hydrogeological and geochemical conditions within the host formation. The engineered barriers reduce the source term concentration what, in turn, is associated with a decrease in uranium migration. Stable geochemical conditions further enable the application of the Kd approach to estimate the impact of the barriers. The hydrogeological system must always be considered when quantifying radionuclide migration.

Does the Fukushima nuclear accident still matter? Analysis of its mediated effects on five dimensions of nuclear power acceptance by using the parallel multiple mediator model

Although 10 years have passed since the Fukushima nuclear accident, it continues to greatly impact global energy policy and the acceptance of nuclear power. This study aims to empirically analyze the Fukushima accident's effects on five dimensions of nuclear power acceptance and the interactions of these effects with various determinants of nuclear power acceptance. We analyze survey data from 1020 Korean respondents and find that they remain highly worried about the Fukushima accident 10 years later. The Fukushima accident has negative impacts on the general acceptance of nuclear power, acceptance of nuclear power's contributions to addressing climate change, acceptance of high-level radioactive waste disposal sites, and acceptance of extensions of old nuclear power plants. However, the accident has a positive impact on the acceptance of denuclearization policies. Our parallel multiple mediator model shows that the Fukushima accident has only an indirect effect on general acceptance; this effect is negative and significant. The accident has a positive direct and indirect effect on acceptance of denuclearization policies but negative direct and indirect effects on the acceptability of high-level nuclear waste disposal and extensions of old nuclear power plants. Finally, we find a positive direct effect and a negative indirect effect of the accident on acceptance of nuclear power's contributions to addressing climate change. The latter is greater than the former, meaning that acceptance of nuclear power in the context of addressing climate change fell in response to the accident. In short, the Fukushima accident has different direct and indirect effects across different dimensions of nuclear power acceptance.

Sorption behavior and mechanism of U(VI) on Tamusu clay in the presence of U(VI)-CO3 complexes

The sorption behavior of U(VI) on Tamusu clay sampled from a pre-selected high-level radioactive waste (HLW) disposal site in Inner Mongolia (China) was studied systematically in the U(VI)–CO3 solution at pH 7.8 by batch experiments. The results demonstrated that the distribution coefficients (Kd) decreased with the increasing values of pHinitial, [U(VI)]initial, and ionic strength, but increased with the extended time and the rising temperature. The sorption was a pH-dependent, heterogeneous, spontaneous, and endothermic chemical process, which could be better described by Freundlich isothermal model and pseudo-second-order kinetic model. The presence of humic acid (HA) or fulvic acid (FA) significantly inhibited the U(VI) sorption, due to the enhanced electrostatic repulsion between the negatively charged HA/FA adsorbed on the clay surface and the negative U(VI) species, as well as the well dispersed HA/FA aggregates in solution wrapping the U(VI) species. The FTIR and XPS spectra indicated that the HCO3− groups on the surface of Tamusu clay after hydroxylation and the ‒OH groups in HA/FA were involved in the U(VI) sorption. The results reported here provide valuable insights into the further understanding of U(VI) migration in geological media.

A Multimodel Framework for Quantifying Flow and Advective Transport Controlled by Earthquake-Induced Canister Failures in a Reference Case for Radioactive Waste Geological Disposal

Characterizing flow and transport for earthquake-induced shear canister failure is critical for the performance and safety assessment of radioactive waste geological disposal. The study presents a modeling framework that integrates multiple models to account for fractures produced by shear displacements, evaluate canister failures, and simulate flow and advective transport in a conceptual repository site based on a selected reference case in an offshore island in western Taiwan. The typical KBS-3 disposal concept associated with 500 realizations of the shear-induced fracture properties is employed to quantify the uncertainty of flow and advective transport in the geological disposal site. The radionuclides in canisters are assumed to migrate through the shear-induced fractures surrounding the deposition holes. The results from 500 realizations show that two types of fractures produce a high potential to destroy canisters induced by the shear displacements. The earliest canister failure time influenced by possible shear movements is 0.23 million years for the reference case. The modeling framework identifies five canisters and the associated shear-induced fractures for flow and advective transport simulations. Based on the results of the density-dependent flow fields, the particle tracking algorithm enables the calculations of flow and transport parameters, including equivalent initial flux, equivalent flow rate, path length, travel time, and flow-related transport resistance for the identified five canisters. These parameters are critical for the performance and safety assessments of buffer erosion and canister corrosion near the disposal repository and the far field of the radioactive waste disposal site.

Back-Analysis of Rock Mass Strength at a Radioactive Waste Disposal Site Using Acoustic Emission Monitoring Data and 3D Numerical Modelling

In this study, a new method was examined that used acoustic emission (AE) monitoring data, in combination with a primary Boundary Element stress analysis, to back-calculate rock mass strength. The presented AE data came from the National Radioactive Waste Repository (NRWR) for low- and intermediate-level waste (LLW/ILW). AE monitoring is able to detect the pre-peak, peak, and post-peak stress changes in rock mass. The presented method used AE monitoring data to back-calculate parameters, such as uniaxial compressive strength and the rock mass deformation modulus. The AE initiation threshold was used to develop an objective function that considered the stress in the rock mass and the rock mass strength. The findings of this research propose that most AE events can be related to the crack initiation threshold, and in space, most of them are located at points away from the excavated walls. In the vicinity of the excavation damage zones around the cavities, the stress conditions beyond the crack damage boundary of the rock mass occur in many areas, leading to significant irreversible deformations. This novel method was demonstrated to aid in the prediction of rock mass strength and is a valuable, non-invasive method for improving the spatial prediction of rock mass parameters, which will lead to safer underground storage facilities.

Radionuclide Transport Simulations Supporting Proposed Borehole Waste Disposal in Israel

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.

Enhanced borehole stability analysis for geological waste disposal under conditions of in-situ stress uncertainty: The case of Yamin Plain, Israel

This work presents a comprehensive parametric study of unsupported and supported vertical boreholes in deep geological deposits. The parametric study is demonstrated for the case of Yamin Plain area, which is the designated site for radioactive waste disposal in Israel, where uncertainty exists regarding the in-situ stresses. The Yamin case is suitable for this study as the target rock layers are of marginal stability under the applied stresses, and therefore a detailed analysis is called for. A parametric factor of safety analysis is utilized for the evaluation of the borehole stability, with and without structural support. To this aim, the estimated stress field is evaluated using both analytical calculations and advanced numerical analyses, incorporating a new spring-boundary condition that yields far greater accuracy than with the commonly used boundary conditions. The parametric study for the borehole stability problem is examined with respect to the in-situ stresses and the structural support. We find that a steel liner is safe under any in-situ stress scenario; HDPE liner is found to be insensitive to liner thickness for the stress scenarios examined, because of the compatibility between the stiffnesses of the rock mass and the liner material; because of the relatively high difference between compressive and tensile strengths of concrete, we find that beyond a certain liner thickness the stability of a concrete liner in fact decreases.

Application Analysis on Past Cases of Radioactive Waste Disposal Site Selection based on Geo-electric and Electromagnetic Surveys

As nuclear power generation has been under operation for a long time, a deep geological repository of spent nuclear fuel, which is a high-level radioactive waste, has become an important issue for nuclear safety and environmental protection. Since improper site selection can lead to radionuclide leaks, which negatively affect the environment, appropriate sites should be selected by comprehensive consideration of various factors, such as the geological and hydrogeological setting. Electrical and electromagnetic surveys can be used to delineate the deep subsurface structure of a target area by detecting physical properties, such as electrical conductivity or resistivity. This paper briefly introduces the proper characteristics of environmentally safe deep disposal sites, identifies electrical and electronic surveys that can be applied in site selection, and analyzes overseas cases applied to the actual site selection process.