High-level Radioactive Waste Disposal Site Research Articles

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.

A Study of Sr Sorption Behavior in Claystone from a Candidate High-Level Radioactive Waste Geological Disposal Site under the Action of FeOOH Colloids.

Colloids have a significant influence on the migration of nuclides in claystone, which is an important geological barrier. The sorption of strontium on claystone in the presence of FeOOH colloids was investigated in samples from the Suhongtu site, a candidate high-level radioactive waste disposal site in China. The effects of colloid amount, solid content, and pH were investigated by batch tests, and the sorption reaction mechanism was analyzed by kinetic modeling and microscopic characterization techniques. The results indicate that the sorption of Sr by claystone increased with the solids content, and the claystone had a stronger Sr sorption capacity under alkaline conditions. The Sr sorption kinetics were best described by the pseudo-first-order and pseudo-second-order models, which revealed that the progress is affected by physical diffusion and chemical sorption. Furthermore, the microscopic characterization results demonstrate that cation exchange reactions and surface complex reactions are the main sorption mechanisms for Sr sorption on claystone. Ca and Mg plasmas in claystone minerals can have cation replacement reactions with Sr, and functional groups such as -OH and [CO3]2− can have complexation reactions with Sr to adsorb Sr on the surface of the claystone. Additionally, the presence of the FeOOH colloid inhibited the sorption effect of claystone slightly. The FeOOH colloid could occupy sorption sites on the claystone surface, which reduces the activity of the functional groups and inhibits the sorption of Sr on claystone.

Influencing factors of 90Sr adsorption onto granite fracture filling material in a high-level radioactive waste disposal site

Influencing factors of 90Sr adsorption onto granite fracture filling material in a high-level radioactive waste disposal site

Interval Prediction of the Permeability of Granite Bodies in a High-Level Radioactive Waste Disposal Site Using LSTM-RNNs and Probability Distribution

During long-term geological tectonic processes, multiple fractures are often developed in the rock mass of high-level radioactive waste disposal sites, which provide channels for release of radioactive material or radionuclides. Studies on the permeability of fractured rock masses are essential for the selection and evaluation of geological disposal sites. With traditional methods, observation and operation of fractured rock mass penetration is time-consuming and costly. However, it is possible to improve the process using new methods. Based on the penetration characteristics of fractured rock mass, and using machine learning techniques, this study has created a prediction model of the fractured rock mass permeability based on select physical and mechanical parameters. Using the correlation coefficients developed by Pearson, Spearman, and Kendall, the proposed framework was first used to analyze the correlation between the physical and mechanical parameters and permeability and determine the model input parameters. Then, a comparison model was created for permeability prediction using four different machine-learning algorithms. The algorithm hyper-parameters are determined by a ten-fold cross-validation. Finally, the permeability interval prediction values are obtained by comparing and selecting the prediction results and probability distribution density function. Overall, the computational results indicate the framework proposed in this paper outperforms the other benchmarking machine learning algorithms through case studies in Beishan District, Gansu, China.

The Effectiveness and Limitations of the Veil of Ignorance in Prior Consent of Procedure toward Consensus Building in a NIMBY Issue: Development and Trial of “Consensus Building of High-Level Radioactive Waste Disposal Site Game”

The Effectiveness and Limitations of the Veil of Ignorance in Prior Consent of Procedure toward Consensus Building in a NIMBY Issue: Development and Trial of “Consensus Building of High-Level Radioactive Waste Disposal Site Game”

Geochemical and microtextural properties of veins in a potential high-level radioactive waste disposal site

In this study, geochemical and petrographic characteristics of veins from the Permian Boda Claystone Formation (Mecsek Mts., Hungary) are presented. Understanding the connection between these properties is vital in the reconstruction of paleofluid history and tectonic evolution of this potential high-level radioactive waste disposal site. Each of the observed four vein generations consists of several mineral phases and has complex evolution, which can be attributed to multiple diagenetic and tectonic processes. Syntaxial and antitaxial veins have been observed suggesting oscillatory advective and diffusive material transport mechanisms; however, veins associated with mobile hydrofractures have also been detected. The parent fluids with a predominant temperature of 100–150 °C and variable salinity (3.5–13.7% wNaCleq) originated potentially by mixing of connate brine with freshwater released by smectite-to-illite transition and isotope exchange with sedimentary minerals, which may have caused the observed δ18O values (−1.12 to 4.67‰, V-SMOW). In contrast to the most vein-filling mineral phases, a breccia cement phase precipitated from a low-temperature (<50 °C) and salinity (0.0–0.4% wNaCleq) meteoric fluid. In the pores of this breccia veins, late-stage fluid migration is verified. Therefore, these veins are of paramount importance for studying the isolation properties of the rock body.

Influence of colloidal Fe(OH)3 on the adsorption characteristics of strontium in porous media from a candidate high-level radioactive waste geological disposal site

Colloids in groundwater or geological barriers generally play a key role in the migration of special nuclides. Adsorption characteristics of strontium were investigated on porous media in the presence of colloidal Fe(OH)3 from the Beishan Site, the only high-level radioactive waste disposal site candidate in China. The effects of colloid amounts, solid contents, and pH were determined and studied by batch texts. The results revealed that the presence of colloidal Fe(OH)3 in porous media contributed to promotion of the sorption effect, and the influencing factors had a significant impact on the adsorption process. The sorption ability increased with increasing colloid amount when the equilibrium time was approximately 10 h under an optimal solid-liquid ratio of 20 g L−1. The sorption effect in alkaline conditions was better than that under acidic conditions. The sorption kinetics indicated that the strong chemical interaction and/or surface complexation contributed primarily to strontium sorption. The sorption isotherms and model fitting revealed that the sorption of strontium onto porous media in the presence of colloidal Fe(OH)3 was a monolayer adsorption, and the presence of colloidal Fe(OH)3 is an important factor that greatly influences the removal of strontium from aqueous solutions. These findings provide useful information for the treatment of strontium in radioactive waste disposal sites.

Sorption of selenite on Tamusu clay in simulated groundwater with high salinity under aerobic/anaerobic conditions

The sorption behavior of selenite onto the Tamusu clay from a preselected high-level radioactive waste disposal site in Inner Mongolia, China, was first investigated in simulated groundwater with high salinity by batch sorption experiments under aerobic/anaerobic conditions. The results demonstrated that the Kd values rapidly decreased and then remained steady in the pH range of 2.0–8.0. However, selenite sorption was promoted when pH exceeded 8.0, which might be attributed to the coprecipitation between Ca2+ and SeO32−. Besides, the change trend of the Kd values as functions of various parameters was not affected by oxygen. The sorption kinetics and isotherms could be well fitted by the pseudo-second-order kinetic model and the Freundlich model for both aerobic and anaerobic conditions, and the calculated thermodynamic parameters (△G and △H) suggested that the selenite sorption process was a spontaneous and endothermic process. Additionally, the XPS results revealed that Se(IV) could be reduced to Se (0) only in anaerobic conditions and that the different amounts of Fe on the clay surface led to the discrepancy of the Se(IV) Kd values under aerobic and anaerobic conditions even in high-salt simulated groundwater. Overall, our findings in this study are significant in regards to the retardation of selenite on the host rock under high salinity conditions.

Reconstructing Terrestrial Water Storage Variations from 1980 to 2015 in the Beishan Area of China

Terrestrial water storage (TWS) is a key element in the global and continental water cycle. Since 2002, the Gravity Recovery and Climate Experiment (GRACE) has provided a highly valuable dataset, which allows the study of TWS over larger river basins worldwide. However, the lifetime of GRACE is too short to demonstrate long-term variability in TWS. In the Beishan area of northwestern China, which is selected as the most prospective site for high-level radioactive waste (HLRW) disposal, the assessment of long-term TWS changes is crucial to understand disposal safety. Monthly and annual TWS changes during the past 35 years are reconstructed using GRACE data, other remote sensing products, and the water balance method. Hydrological flux outputs from multisource remote sensing products are analyzed and compared to select appropriate data sources. The results show that a decreasing trend is found for GRACE-filtered and Center for Space Research (CSR) mascon solutions from 2003 to 2015, with slopes of −2.30 ± 0.52 and −1.52 ± 0.24 mm/year, respectively. TWS variations independently computed from the water balance method also show a similar decreasing trend with the GRACE observations, with a slope of −0.94 mm/year over the same period. Overall, the TWS anomalies in the Beishan area change seasonally within 10 mm and have been decreasing since 1980, keeping a desirable dry condition as a HLRW disposal site.

Effects of thermal treatment on fracture characteristics of granite from Beishan, a possible high-level radioactive waste disposal site in China

In-situ experimental investigations on fracture behavior of Beishan granite under loading after 125–600°C thermal treatments have been carried out through high temperature Scanning Electron Microscope (SEM) testing system. Thermal microcracks and non-uniform expansion of grains, long and deep thermal cracks along the grain boundary were observed on the surface of Beishan granite with thermal treatments at different temperatures. The initial direction of microcracks and the main crack propagation path are affected by the shape of mineral grains and the distribution of thermal cracks. The effect of the distribution of thermal cracks becomes more dominant with the increasing temperatures. There are multiple mechanisms of thermal effects on strength and fracture toughness of Beishan granite, namely, thermal cracking, water evaporation, hot melting and phase transition of quartz. The main controlling mechanism changes with treatment temperatures. While elastic modulus slightly increases at 275°C because of hot melting, in general, it decreases with the increasing temperature due to increasing thermal cracks. Stress intensity factor for short-span (the ratio of span to height is 2) three-point bending specimen is determined using boundary collocation method. The relationship between fracture toughness and heat treatment temperature can be approximately described by linear decreasing function.

고준위폐기물 완충재로 사용되는 벤토나이트의 미생물의 존재 및 특성

There was a study for biological characteristics, except for physico-chemical and mineralogical properties, on the natural bentonite that is considered as a buffer material for the high-level radioactive waste disposal site. A bentonite slurry that was prepared from a local `Gyeongju bentonite` in Korea was incubated in a serum bottle with nutrient media over 1 week and its stepwise change was observed with time. From the activated bentonite in the nutrient media, we can find a certain change of both solid and liquid phases. Some dark and fine sulfides began to be generated from dissolved sulfate solution, and 4 species of sulfate-reducing bacteria (SRB) were identified as living cells in samples that were periodically taken and incubated. These results show that sulfate-reducing (or metal-reducing) bacteria are adhering and existing in the powder of bentonite, suggesting that there may be a potential occurrence of longterm biogeochemical effects in and around the bentonite buffer in underground anoxic environmental conditions.

Multi-geophysical Investigation of Geological Structures in a Pre-selected High-level Radioactive Waste Disposal Area in Northwestern China

A potential high-level radioactive waste (HLRW) disposal site in northwestern China was investigated to determine its suitability for such a use. The site is primarily covered with well-developed metamorphic granite rocks. The primary targets for geological repositories are three granite rock masses (I, II, and III). Only surface geological data were available from previous studies. The objective of this study was to evaluate the quality of the rock mass and identify any weak geological structures that could jeopardize this future underground repository. We used gravity and aeromagnetic data on a large scale to study the regional geological structures within and around the three rock masses. Subsequently, in 2009, a controlled source audio-frequency magnetotelluric (CSAMT) survey was conducted to study rock mass I in more detail. This paper introduces three-dimensional (3-D) tomography imaging of gravity and aeromagnetic data. 3-D tomography imaging was carried out on previously collected gravity and aeromagnetic data and, using the results of different depth slices, we evaluated the rock mass quality and interpreted the geology. The aeromagnetic depth slices show that at about 1-km deep in rock masses I and III there is a high magnetic susceptibility body, possibly caused by an early granite intrusion. The deep granite or metamorphic rocks appear as weak `magnetic anomalies in the magnetic slices. The results also indicate that rock mass II is more deeply buried and smaller than rock masses I and III. In the upper crust, inhomogeneous density variations have a strike direction consistent with that of the structure revealed in the aeromagnetic data. For rock mass I, we designed a CSAMT line to map small-scale outcropped faults to depth, and identify any hidden faults or weakened zones in the subsurface. Because of the highly resistive ground, we improved the electrode contact conditions by pouring salt water on both the transmitting and receiving electrodes. During data processing, we applied Hanning filtering to reduce static effects from lack of electrical homogeneity near the ground surface, and through experimentation found an optimum filter length to achieve maximum static effect reduction. Sounding data were inverted for geoelectrical cross sections using a two-dimensional smooth-model inversion method. Inversion artifacts were suppressed by imposing the model smoothness constraint. Several important results were revealed by the inversion: the inversion section correctly recognized two fractures at the surface, and also identified two new faults that were not observed during the previous geological survey. The inversion profile suggests that the narrow factures and deformation bands extend to a great depth. With further drilling confirmation, this interpretation will enhance understanding of the deep geological structures at the HLRW disposal site.

高レベル放射性廃棄物処分場の立地確保に向けた社会受容プロセスモデル

Generally speaking, a vast, advanced and unfamiliar science and technology are unacceptable to the public for fear of their unknown nature. Here, the social acceptance process model was examined on the basis of the analysis of the cause phenomenon and numerical grounds, by referring to the problems on the application of literature documentation for location examination of a high-level radioactive waste disposal site in Toyo town in Kochi Pref. in April 2007. In analyzing the Toyo town case, we have found a possibility that the majority of local residents knew very little about the object opposed by the fringe route processing. To ensure a healthy decision making by the public, it is vital to convey fundamental information using sufficient wide-area PR media before the issue becomes actual. After the issue becomes actual, dialog with residents through a careful technology assessment is indispensable. The authors focus attention on the decision-making process of human beings from the social and psychological viewpoints, and point out that it is desirable for promoting social acceptance by adopting two approaches: a direct approach aiming at better intelligibility for the different resident layers and a deductive approach in technological essence.

234U/ 238U evidence for local recharge and patterns of ground-water flow in the vicinity of Yucca Mountain, Nevada, USA

Uranium concentrations and 234U/ 238U ratios in saturated-zone and perched ground water were used to investigate hydrologic flow and downgradient dilution and dispersion in the vicinity of Yucca Mountain, a potential high-level radioactive waste disposal site. The U data were obtained by thermal ionization mass spectrometry on more than 280 samples from the Death Valley regional flow system. Large variations in both U concentrations (commonly 0.6–10 μg l −1) and 234U/ 238U activity ratios (commonly 1.5–6) are present on both local and regional scales; however, ground water with 234U/ 238U activity ratios from 7 up to 8.06 is restricted largely to samples from Yucca Mountain. Data from ground water in the Tertiary volcanic and Quaternary alluvial aquifers at and adjacent to Yucca Mountain plot in 3 distinct fields of reciprocal U concentration versus 234U/ 238U activity ratio correlated to different geographic areas. Ground water to the west of Yucca Mountain has large U concentrations and moderate 234U/ 238U whereas ground water to the east in the Fortymile flow system has similar 234U/ 238U, but distinctly smaller U concentrations. Ground water beneath the central part of Yucca Mountain has intermediate U concentrations but distinctive 234U/ 238U activity ratios of about 7–8. Perched water from the lower part of the unsaturated zone at Yucca Mountain has similarly large values of 234U/ 238U. These U data imply that the Tertiary volcanic aquifer beneath the central part of Yucca Mountain is isolated from north-south regional flow. The similarity of 234U/ 238U in both saturated- and unsaturated-zone ground water at Yucca Mountain further indicates that saturated-zone ground water beneath Yucca Mountain is dominated by local recharge rather than regional flow. The distinctive 234U/ 238U signatures also provide a natural tracer of downgradient flow. Elevated 234U/ 238U in ground water from two water-supply wells east of Yucca Mountain are interpreted as the result of induced flow from 40 a of ground-water withdrawal. Elevated 234U/ 238U in a borehole south of Yucca Mountain is interpreted as evidence that natural downgradient flow is more likely to follow southerly paths in the structurally anisotropic Tertiary volcanic aquifer where it becomes diluted by regional flow in the Fortymile system.

Simulation of Gas Dipole Tests in Fractures at the Intermediate Scale Using a New Upscaling Method

A high-level radioactive waste disposal site may lead to gas generation by different physical mechanisms. As these sites are to be located in areas with low water flow, any small amount of gas can lead to relative high gas pressures, so that multiphase flow analysis becomes relevant. The movement of gas and water through the system has two important implications. Firstly, water flow takes place in unsaturated conditions, and thus travel times of the radioactive particles transported are affected; and secondly, gas can also carry radioactive particles. Therefore, one of the key points in such studies is the time when gas would break through the biosphere under a number of different flow conditions. In fractured zones, gas would flow preferentially through the most conductive features. We consider a two-dimensional system representing an isolated fracture. In each point we assign a local porosity and permeability and a local pressure-saturation relationship. A dipole (injector-producer) gas flow system is generated and the variation in water saturation is studied. A simple method is proposed for obtaining upscaled values for several parameters involved in two-phase flow. It is based on numerical simulation on a block scale assuming steady-state conditions and absence of capillary pressure gradients. The proposed method of upscaling is applied to simulate a dipole test using a coarser grid than that of the reference field. The comparison between the results in both scales shows an encouraging agreement.

Long-Term Performance Assessment for a Proposed High-Level Radioactive Waste Disposal Site at Yucca Mountain - Explanation of the Shape of Release Curves

The Nuclear Regulatory Commission (NRC) Total-system Performance Assessment (TPA) code is a tool to independently evaluate the long-term performance of the proposed Yucca Mountain (YM) high-level radioactive waste (HLW) repository by modeling processes such as the dissolution of the spentnuclear fuel (SNF) and the subsequent transport through unsaturated and saturated highly heterogeneous fractured porous media to a hypothetical release into the biosphere. The release rates of radionuclides into the biosphere corresponding to some of the SNF dissolution models show a sinusoidal trend with an overall decrease in the rate with time; for other models the sinusoidal behavior is nonexistent. This study identifies two key mechanisms contributing to these trends: the spatial discretization of the repository into subareas and radionuclide-specific sorption properties in the saturated zone alluvium. Other mechanisms which might affect the release rates, such as solubility limits, radioactive decay and ingrowth, inventory depletion, and transport properties of the unsaturated zone (UZ), do not significantly contribute to these trends.