In order to research whether it is suitable to set a geological disposal repository for high-level radioactive nuclear waste into one target granite body,two active source seismic profles were arranged near a small to...In order to research whether it is suitable to set a geological disposal repository for high-level radioactive nuclear waste into one target granite body,two active source seismic profles were arranged near a small town named Tamusu,Western China.The study area is with complex surface conditions,thus the seismic exploration encountered a variettraveltimey of technical difculties such as crossing obstacles,de-noising harmful scattered waves,and building complex near-surface velocity models.In order to address those problems,techniques including cross-obstacle seismic geometry design,angle-domain harmful scattered noise removal,and an acoustic wave equation-based inversion method jointly utilizing both the and waveform of frst arrival waves were adopted.The fnal seismic images clearly exhibit the target rock’s unconformable contact boundary and its top interface beneath the sedimentary and weathered layers.On this basis,it could be confrmed that the target rock is not thin or has been transported by geological process from somewhere else,but a native and massive rock.There are a few small size fractures whose space distribution could be revealed by seismic images within the rock.The fractures should be kept away.Based on current research,it could be considered that active source seismic exploration is demanded during the sitting process of the geological disposal repository for nuclear waste.The seismic acquisition and processing techniques proposed in the present paper would ofer a good reference value for similar researches in the future.展开更多
The mission of nuclear safety authorities in national radioactive waste disposal programmes is to ensure that people and the environment are protected against the hazards of ionising radiations emitted by the waste.It...The mission of nuclear safety authorities in national radioactive waste disposal programmes is to ensure that people and the environment are protected against the hazards of ionising radiations emitted by the waste.It implies the establishment of safety requirements and the oversight of the activities of the waste management organisation in charge of implementing the programme.In Belgium,the safety requirements for geological disposal rest on the following principles:defence-in-depth,demonstrability and the radiation protection principles elaborated by the International Commission on Radiological Protection(ICRP).Applying these principles requires notably an appropriate identification and characterisation of the processes upon which the safety functions fulfilled by the disposal system rely and of the processes that may affect the system performance.Therefore,research and development(R&D)on safety-relevant thermo-hydro-mechanical-chemical(THMC)issues is important to build confidence in the safety assessment.This paper points out the key THMC processes that might influence radionuclide transport in a disposal system and its surrounding environment,considering the dynamic nature of these processes.Their nature and significance are expected to change according to prevailing internal and external conditions,which evolve from the repository construction phase to the whole heatingecooling cycle of decaying waste after closure.As these processes have a potential impact on safety,it is essential to identify and to understand them properly when developing a disposal concept to ensure compliance with relevant safety requirements.In particular,the investigation of THMC processes is needed to manage uncertainties.This includes the identification and characterisation of uncertainties as well as for the understanding of their safety-relevance.R&D may also be necessary to reduce uncertainties of which the magnitude does not allow demonstrating the safety of the disposal system.展开更多
With the rapid development of nuclear power in China, the disposal of high-level radioactive waste(HLW) has become an important issue for nuclear safety and environmental protection. Deep geological disposal is intern...With the rapid development of nuclear power in China, the disposal of high-level radioactive waste(HLW) has become an important issue for nuclear safety and environmental protection. Deep geological disposal is internationally accepted as a feasible and safe way to dispose of HLW, and underground research laboratories(URLs) play an important and multi-faceted role in the development of HLW repositories. This paper introduces the overall planning and the latest progress for China's URL. On the basis of the proposed strategy to build an area-specific URL in combination with a comprehensive evaluation of the site selection results obtained during the last 33 years, the Xinchang site in the Beishan area,located in Gansu Province of northwestern China, has been selected as the final site for China's first URL built in granite. In the process of characterizing the Xinchang URL site, a series of investigations,including borehole drilling,geological mapping, geophysical surveying,hydraulic testing and in situ stress measurements, has been conducted. The investigation results indicate that the geological,hydrogeological, engineering geological and geochemical conditions of the Xinchang site are very suitable for URL construction. Meanwhile, to validate and develop construction technologies for the Beishan URL, the Beishan exploration tunnel(BET), which is a 50-m-deep facility in the Jiujing sub-area, has been constructed and several in situ tests, such as drill-and-blast tests, characterization of the excavation damaged zone(EDZ), and long-term deformation monitoring of surrounding rocks, have been performed in the BET. The methodologies and technologies established in the BET will serve for URL construction.According to the achievements of the characterization of the URL site, a preliminary design of the URL with a maximum depth of 560 m is proposed and necessary in situ tests in the URL are planned.展开更多
Underground research laboratories(URLs),including "generic URLs" and "site-specific URLs",are underground facilities in which characterisation,testing,technology development,and/or demonstration ac...Underground research laboratories(URLs),including "generic URLs" and "site-specific URLs",are underground facilities in which characterisation,testing,technology development,and/or demonstration activities are carried out in support of the development of geological repositories for high-level radioactive waste(HLW) disposal.In addition to the generic URL and site-specific URL,a concept of "areaspecific URL",or the third type of URL,is proposed in this paper.It is referred to as the facility that is built at a site within an area that is considered as a potential area for HLW repository or built at a place near the future repository site,and may be regarded as a precursor to the development of a repository at the site.It acts as a "generic URL",but also acts as a "site-specific URL" to some extent.Considering the current situation in China,the most suitable option is to build an "area-specific URL" in Beishan area,the first priority region for China's high-level waste repository.With this strategy,the goal to build China's URL by 2020 may be achieved,but the time left is limited.展开更多
The geological disposal of high level radioactive waste is a challenging task facing the scientific and technical world.This paper introduces the latest progress of high level radioactive disposal programs in the worl...The geological disposal of high level radioactive waste is a challenging task facing the scientific and technical world.This paper introduces the latest progress of high level radioactive disposal programs in the world,and discusses the following key scientific challenges:(1)precise prediction of the evolution of a repository site;(2)characteristics of deep geological environment;(3)behaviour of deep rock mass,groundwater and engineering material under coupled conditions(intermediate to high temperature,geostress,hydraulic,chemical,biological and radiation process,etc);(4)geochemical behaviour of transuranic radionuclides with low concentration and its migration with groundwater;and(5)safety assessment of disposal system.Several large-scale research projects and several hot topics related with high-level waste disposal are also introduced.展开更多
Residence time of deep groundwater is one of the most important parameters in safety and performance assessment for high-level radioactive waste geological disposal. In this study, we collected the deep groundwater sa...Residence time of deep groundwater is one of the most important parameters in safety and performance assessment for high-level radioactive waste geological disposal. In this study, we collected the deep groundwater samples of Jijicao in Gansu Beishan pre-selected region. The deep groundwater residence time at two depths estimated by Helium-4 accumulation method were 3.8 ka and 5.0 ka respectively upon measurement and calculation, which indicates that the deep groundwater is not derived from the deep crust circulation process. Hence, deep groundwater is featured with long residence time as well as slow circulation and update rate, and such features are conductive to the safe disposal of high-level radioactive waste.展开更多
One of the major concepts of the geological disposal of high level radioactive waste is to enclose a metallic container with bentonite buffer which is considered to be impermeable and chemically stable. Since the aver...One of the major concepts of the geological disposal of high level radioactive waste is to enclose a metallic container with bentonite buffer which is considered to be impermeable and chemically stable. Since the average density of the container is around 6 to 7 and very heavy compared to bentonite, the scenario of container sinking has been evaluated because excess sinking makes short the pathway of nuclide migration in the bentonite and is detrimental to the safety of the disposal system. Previous considerations on container sinking have been made from the viewpoint of mechanical deformation of the bentonite. In this paper, a chemical deformation process is presented as another mechanism of container sinking, which has not been previously considered for the container sinking in the field of radioactive waste disposal. The chemical deformation mentioned in this paper is the deformation through the process of pressure solution of minerals constituting the buffer, transportation by diffusion and precipitation. That such chemical deformation is a ubiquitous phenomenon occurring in various scales in the crust of the earth will be shown through the review of previous works. Then, some future research topics will be suggested which would be required in order to evaluate the container sinking in the safety case for radioactive waste disposal.展开更多
The China-mock-up test is to evaluate the performance of the compacted Gaomiaozi(GMZ) bentonite under coupled thermo-hydro-mechanical(THM) conditions in deep geological disposal.A numerical study of the test is conduc...The China-mock-up test is to evaluate the performance of the compacted Gaomiaozi(GMZ) bentonite under coupled thermo-hydro-mechanical(THM) conditions in deep geological disposal.A numerical study of the test is conducted in this paper.The principal THM characteristics of the bentonite are presented at first.A THM model is then presented to tackle the complex coupling behavior of the bentonite.The model of Alonso-Gens is incorporated to reproduce the mechanical behavior of the bentonite under unsaturated conditions.With the proposed model,numerical simulations of the China-mock-up test are carried out by using the code of LAGAMINE.The time variations associated with the temperature,degree of saturation,suction and swelling pressure of the compacted bentonite are studied.The results suggest that the proposed model is able to reproduce the mechanical behavior of the bentonite,and to predict moisture motion under coupled THM conditions.展开更多
One of the most suitable ways under study for the disposal of high-level radioactive waste (HLW) is isolation in deep geological repositories. It is very important to research the thermo-hydro- mechanical (THM) couple...One of the most suitable ways under study for the disposal of high-level radioactive waste (HLW) is isolation in deep geological repositories. It is very important to research the thermo-hydro- mechanical (THM) coupled processes associated with an HLW disposal repository. Non-linear coupled equations, which are used to describe the THM coupled process and are suited to saturated-unsaturated porous media, are presented in this paper. A numerical method to solve these equations is put forward, and a finite element code is developed. This code is suited to the plane strain or axis-symmetry problem. Then this code is used to simulate the THM coupled process in the near field of an ideal disposal repository. The temperature vs. time, hydraulic head vs. time and stress vs. time results show that, in this assumed condition, the impact of temperature is very long (over 10 000 a) and the impact of the water head is short (about 90 d). Since the stress is induced by temperature and hydraulic head in this condition, the impact time of stress is the same as that of temperature. The results show that THM coupled processes are very important in the safety analysis of an HLW deep geological disposal repository.展开更多
The mechanical behavior of host rock for a deep geological repository of high-level radioactive waste plays a key role in ensuring the isolation function of host rock as a natural barrier under the multi-field couplin...The mechanical behavior of host rock for a deep geological repository of high-level radioactive waste plays a key role in ensuring the isolation function of host rock as a natural barrier under the multi-field coupling environment.For a better understanding of granite in China's Beishan pre-selected area for geological disposal of high-level radioactive waste,a series of investigations were carried out on in-situ stress field of rock mass at depth,strength and deformation characteristics of rocks under different stress and temperature conditions,and rock boreability and adaptability to Tunnel Boring Machine(TBM)technology.The results indicate that Beishan granite shows typical characteristics as a hard and brittle rock with a quite low permeability,and it is favorable to geological disposal.Meanwhile,a new rock mass suitability evaluation system was proposed,and the rock mass mainly composed of Beishan granite was proven to be suitable for geological disposal.Besides,the constructability of Beishan granite at engineering scale was tested and verified through field tests in the Beishan Exploration Tunnel(BET).Here,we summarize the main outcomes of rock mechanics research on Beishan granite in the past years and introduced the current progress of Beishan underground research laboratory(URL)for geological disposal.展开更多
In Japan,high-level radioactive waste and specific low-level radioactive waste which includes long-lived radionuclides are planned to be disposed of in the geological formations at depths greater than 300 m.The dispos...In Japan,high-level radioactive waste and specific low-level radioactive waste which includes long-lived radionuclides are planned to be disposed of in the geological formations at depths greater than 300 m.The disposal site will be selected through a stepwise site investigation process that consists of a Literature Survey,Preliminary Investigation,and Detailed Investigation phases.In October 2020 a Literature Survey was launched in Japan at two municipalities in Hokkaido for the first time since NUMO initiated a nationwide call for volunteer municipalities in 2002,and the outcomes are currently being compiled.To enhance the public’s understanding of how to implement safe geological disposal in Japan based on the latest scientific knowledge and technology,NUMO,as the implementing organisation,developed and published a safety case for geological disposal at the pre-siting stage.This safety case provides multiple lines of arguments and evidence to demonstrate the feasibility of the geological disposal and a basic structure for a safety case that will be applicable to any potential sites in Japan.The safety case also presented some R&D challenges to enhance the technical confidence of the project,including the R&D topics related to rock mechanics.This report presents the current status of the geological disposal programme in Japan,together with the status of the Literature Survey phase and an overview of the NUMO safety case.展开更多
China is home to shales of three facies:Marine shale,continental shale,and marine-continental transitional shale.Different types of shale gas are associated with significantly different formation conditions and major ...China is home to shales of three facies:Marine shale,continental shale,and marine-continental transitional shale.Different types of shale gas are associated with significantly different formation conditions and major controlling factors.This study compared the geological characteristics of various shales and analyzed the influences of different parameters on the formation and accumulation of shale gas.In general,shales in China’s several regions exhibit high total organic carbon(TOC)contents,which lays a sound material basis for shale gas generation.Marine strata generally show high degrees of thermal evolution.In contrast,continental shales manifest low degrees of thermal evolution,necessitating focusing on areas with relatively high degrees of thermal evolution in the process of shale gas surveys for these shales.The shales of the Wufeng and Silurian formations constitute the most favorable shale gas reservoirs since they exhibit the highest porosity among the three types of shales.These shales are followed by those in the Niutitang and Longtan formations.In contrast,the shales of the Doushantuo,Yanchang,and Qingshankou formations manifest low porosities.Furthermore,the shales of the Wufeng and Longmaxi formations exhibit high brittle mineral contents.Despite a low siliceous mineral content,the shales of the Doushantuo Formation feature a high carbonate mineral content,which can increase the shales’brittleness to some extent.For marine-continental transitional shales,where thin interbeds of tight sandstone with unequal thicknesses are generally found,it is recommended that fracturing combined with drainage of multiple sets of lithologic strata should be employed to enhance their shale gas production.展开更多
Introduction: Not all medicines that pass-through consumers’ hands are used, and some often expire in households. These health products can be sources of accidental risks and pollution when they are not properly disp...Introduction: Not all medicines that pass-through consumers’ hands are used, and some often expire in households. These health products can be sources of accidental risks and pollution when they are not properly disposed of. In Burkina Faso, there are as yet no guidelines for the disposal of unused medicines in households. The aim of this study was to estimate the extent of household possession of unused or expired medicines, and to describe attitudes and disposal practices. Methods: This was a descriptive cross-sectional study covering households in the Ouagadougou commune conducted from June to August 2021. Two-stage stratified sampling was used: selection of Enumeration Zones (EZs) and selection of households, with each EZ comprising several households. Data collection was based on direct interviews using a structured questionnaire. Data were processed using Epi Info software version 7.2.4.0. Results: In total, 417 household residents were surveyed out of the planned 423 households, corresponding to a completion rate of 98.58% compared with the initial sample. Among the respondents, 79.62% had unused and/or expired medicines in their household. A total of 2562 drug packaging units were counted, for a total weight of 121.90 kg. Nearly 75% were aware that improper disposal was a danger to the environment. Some respondents kept their unused medicines at home until they expired (43.41%), and disposed of them mainly by throwing them in the household garbage (75.58%). The majority (79%) were in favor of the government setting up a take-back program for these medicines. Conclusion: The introduction of a take-back program for unused or out-of-date medicines will ensure safer disposal of medicines, and better protection for households and the environment.展开更多
Background: Handling of medicines is a day-to-day activity by patients and many health care providers. However, multiple studies have brought to light inappropriate disposal methods for expired and unused medication (...Background: Handling of medicines is a day-to-day activity by patients and many health care providers. However, multiple studies have brought to light inappropriate disposal methods for expired and unused medication (EUM). Improper disposal of expired and unused medicines is hazardous both to humans and the environment. Objective: This sought to measure patients’ knowledge, attitude, and practices on disposal methods of EUM. Methods: A cross-sectional study was carried out among 384 patients at three outpatient pharmacies at the University Teaching Hospitals (UTHs). The structured questionnaire was used to collect data and STAT version 15.1 was used to analyse the data. Results: 384 respondents participated in this study and, at some point, had EUM. In this study, 356 (92.7%) of the participants reported that they had never heard of a drug take-back system. Most of the participants 285 (74.2%) and 239 (62.2%) kept and donated their unused medicine, respectively. Additionally, 244 (63.5%), 212 (55.2%), and 176 (44.8%) of the participants disposed of expired medicines in the bin or garbage, flushed them in toilets or sinks, or burned them, respectively. Occupation was significantly associated with unsafe disposal of unused medicine [P-value = 0.019]. Conclusion and Relevance: Knowledge of safe disposal methods for EUM was good amongst most participants. However, used unsafe disposal methods. The majority of the participants exhibited positive attitude concerning safe disposal methods. This study highlights the need for drug-take-back program creation in Zambia.展开更多
Geological discontinuity(GD)plays a pivotal role in determining the catastrophic mechanical failure of jointed rock masses.Accurate and efficient acquisition of GD networks is essential for characterizing and understa...Geological discontinuity(GD)plays a pivotal role in determining the catastrophic mechanical failure of jointed rock masses.Accurate and efficient acquisition of GD networks is essential for characterizing and understanding the progressive damage mechanisms of slopes based on monitoring image data.Inspired by recent advances in computer vision,deep learning(DL)models have been widely utilized for image-based fracture identification.The multi-scale characteristics,image resolution and annotation quality of images will cause a scale-space effect(SSE)that makes features indistinguishable from noise,directly affecting the accuracy.However,this effect has not received adequate attention.Herein,we try to address this gap by collecting slope images at various proportional scales and constructing multi-scale datasets using image processing techniques.Next,we quantify the intensity of feature signals using metrics such as peak signal-to-noise ratio(PSNR)and structural similarity(SSIM).Combining these metrics with the scale-space theory,we investigate the influence of the SSE on the differentiation of multi-scale features and the accuracy of recognition.It is found that augmenting the image's detail capacity does not always yield benefits for vision-based recognition models.In light of these observations,we propose a scale hybridization approach based on the diffusion mechanism of scale-space representation.The results show that scale hybridization strengthens the tolerance of multi-scale feature recognition under complex environmental noise interference and significantly enhances the recognition accuracy of GD.It also facilitates the objective understanding,description and analysis of the rock behavior and stability of slopes from the perspective of image data.展开更多
With an extension of the geological entropy concept in porous media,the approach called directional entrogram is applied to link hydraulic behavior to the anisotropy of the 3D fracture networks.A metric called directi...With an extension of the geological entropy concept in porous media,the approach called directional entrogram is applied to link hydraulic behavior to the anisotropy of the 3D fracture networks.A metric called directional entropic scale is used to measure the anisotropy of spatial order in different directions.Compared with the traditional connectivity indexes based on the statistics of fracture geometry,the directional entropic scale is capable to quantify the anisotropy of connectivity and hydraulic conductivity in heterogeneous 3D fracture networks.According to the numerical analysis of directional entrogram and fluid flow in a number of the 3D fracture networks,the hydraulic conductivities and entropic scales in different directions both increase with spatial order(i.e.,trace length decreasing and spacing increasing)and are independent of the dip angle.As a result,the nonlinear correlation between the hydraulic conductivities and entropic scales from different directions can be unified as quadratic polynomial function,which can shed light on the anisotropic effect of spatial order and global entropy on the heterogeneous hydraulic behaviors.展开更多
The surrounding geological conditions and supporting structures of underground engineering are often updated during construction,and these updates require repeated numerical modeling.To improve the numerical modeling ...The surrounding geological conditions and supporting structures of underground engineering are often updated during construction,and these updates require repeated numerical modeling.To improve the numerical modeling efficiency of underground engineering,a modularized and parametric modeling cloud server is developed by using Python codes.The basic framework of the cloud server is as follows:input the modeling parameters into the web platform,implement Rhino software and FLAC3D software to model and run simulations in the cloud server,and return the simulation results to the web platform.The modeling program can automatically generate instructions that can run the modeling process in Rhino based on the input modeling parameters.The main modules of the modeling program include modeling the 3D geological structures,the underground engineering structures,and the supporting structures as well as meshing the geometric models.In particular,various cross-sections of underground caverns are crafted as parametricmodules in themodeling program.Themodularized and parametric modeling program is used for a finite element simulation of the underground powerhouse of the Shuangjiangkou Hydropower Station.This complicatedmodel is rapidly generated for the simulation,and the simulation results are reasonable.Thus,this modularized and parametric modeling program is applicable for three-dimensional finite element simulations and analyses.展开更多
The well-developed coal electricity generation and coal chemical industries have led to huge carbon dioxide(CO_(2))emissions in the northeastern Ordos Basin.The geological storage of CO_(2) in saline aquifers is an ef...The well-developed coal electricity generation and coal chemical industries have led to huge carbon dioxide(CO_(2))emissions in the northeastern Ordos Basin.The geological storage of CO_(2) in saline aquifers is an effective backup way to achieve carbon neutrality.In this case,the potential of saline aquifers for CO_(2) storage serves as a critical basis for subsequent geological storage project.This study calculated the technical control capacities of CO_(2) of the saline aquifers in the fifth member of the Shiqianfeng Formation(the Qian-5 member)based on the statistical analysis of the logging and the drilling and core data from more than 200 wells in the northeastern Ordos Basin,as well as the sedimentary facies,formation lithology,and saline aquifer development patterns of the Qian-5 member.The results show that(1)the reservoirs of saline aquifers in the Qian-5 member,which comprise distributary channel sand bodies of deltaic plains,feature low porosities and permeabilities;(2)The study area hosts three NNE-directed saline aquifer zones,where saline aquifers generally have a single-layer thickness of 3‒8 m and a cumulative thickness of 8‒24 m;(3)The saline aquifers of the Qian-5 member have a total technical control capacity of CO_(2) of 119.25×10^(6) t.With the largest scale and the highest technical control capacity(accounting for 61%of the total technical control capacity),the Jinjie-Yulin saline aquifer zone is an important prospect area for the geological storage of CO_(2) in the saline aquifers of the Qian-5 member in the study area.展开更多
Spent UO2 fuel will rapidly be altered to U6+ phases in nuclear waste repositories. Be-cause most uranyl phases are based on sheet or chain structures and usually contain several mo-lecular water groups, site-mixing, ...Spent UO2 fuel will rapidly be altered to U6+ phases in nuclear waste repositories. Be-cause most uranyl phases are based on sheet or chain structures and usually contain several mo-lecular water groups, site-mixing, vacancies, as well as disorder in the orientation of hydrogen bonds may occur. A systematic survey of the published crystallographic data for uranates, uranyl oxide hydrates, phosphates, silicates, carbonates, and sulfates demonstrates that site-mixing ap-parently occurs in the structures of at least 31 uranyl phases. Calculations of the ideal site-mixing entropy indicate that the residual contribution that arises from substitution and vacancies to the third-law entropies of some uranyl phases is large. A brief examination of the crystal chemistry of water molecules in uranyl phases suggests that considerable residual entropy may be caused by the disorder of hydrogen bonds associated with interstitial H2O groups. In the geochemical envi-ronment that expected to occur in the near-field of nuclear waste repositories, the existence of structure-configurational entropy may reduce the uranium concentration of several log units in so-lutions equilibrated with some uranyl phases. Therefore, compositional analysis and structural de-terminations must be made on the samples used in calorimetric measurements, and the calorimet-ric data must be combined with solubility data to evaluate the thermodynamic stability of the inter-ested phases.展开更多
On October 26,2022,the International Union of Geological Sciences(IUGS)unveiled the First 100 IUGS Geological Heritage Sites in Spain.These sites are located in56 countries,including 34 in the Americas,28 in Europe,15...On October 26,2022,the International Union of Geological Sciences(IUGS)unveiled the First 100 IUGS Geological Heritage Sites in Spain.These sites are located in56 countries,including 34 in the Americas,28 in Europe,15 in Africa and 23 in the Asia-Pacific-Middle East region(Table 1).The seven selected sites of China are introduced as follows(black font in Table 1).展开更多
基金This research was supported by the National Key R&D Program of China(No.2018YFC1503200)the Nuclear Waste Geological Disposal Project([2013]727)+2 种基金the National Natural Science Foundation of China(Grant Nos.41790463 and 41730425)the Spark Program of Earthquake Sciences of CEA(XH18063Y)the Special Fund of GEC of CEA(YFGEC2017003,SFGEC2014006).
文摘In order to research whether it is suitable to set a geological disposal repository for high-level radioactive nuclear waste into one target granite body,two active source seismic profles were arranged near a small town named Tamusu,Western China.The study area is with complex surface conditions,thus the seismic exploration encountered a variettraveltimey of technical difculties such as crossing obstacles,de-noising harmful scattered waves,and building complex near-surface velocity models.In order to address those problems,techniques including cross-obstacle seismic geometry design,angle-domain harmful scattered noise removal,and an acoustic wave equation-based inversion method jointly utilizing both the and waveform of frst arrival waves were adopted.The fnal seismic images clearly exhibit the target rock’s unconformable contact boundary and its top interface beneath the sedimentary and weathered layers.On this basis,it could be confrmed that the target rock is not thin or has been transported by geological process from somewhere else,but a native and massive rock.There are a few small size fractures whose space distribution could be revealed by seismic images within the rock.The fractures should be kept away.Based on current research,it could be considered that active source seismic exploration is demanded during the sitting process of the geological disposal repository for nuclear waste.The seismic acquisition and processing techniques proposed in the present paper would ofer a good reference value for similar researches in the future.
文摘The mission of nuclear safety authorities in national radioactive waste disposal programmes is to ensure that people and the environment are protected against the hazards of ionising radiations emitted by the waste.It implies the establishment of safety requirements and the oversight of the activities of the waste management organisation in charge of implementing the programme.In Belgium,the safety requirements for geological disposal rest on the following principles:defence-in-depth,demonstrability and the radiation protection principles elaborated by the International Commission on Radiological Protection(ICRP).Applying these principles requires notably an appropriate identification and characterisation of the processes upon which the safety functions fulfilled by the disposal system rely and of the processes that may affect the system performance.Therefore,research and development(R&D)on safety-relevant thermo-hydro-mechanical-chemical(THMC)issues is important to build confidence in the safety assessment.This paper points out the key THMC processes that might influence radionuclide transport in a disposal system and its surrounding environment,considering the dynamic nature of these processes.Their nature and significance are expected to change according to prevailing internal and external conditions,which evolve from the repository construction phase to the whole heatingecooling cycle of decaying waste after closure.As these processes have a potential impact on safety,it is essential to identify and to understand them properly when developing a disposal concept to ensure compliance with relevant safety requirements.In particular,the investigation of THMC processes is needed to manage uncertainties.This includes the identification and characterisation of uncertainties as well as for the understanding of their safety-relevance.R&D may also be necessary to reduce uncertainties of which the magnitude does not allow demonstrating the safety of the disposal system.
基金support from the China Atomic Energy Authority (CAEA) for China's URL Development Program and the Geological Disposal ProgramThe International Atomic Energy Agency is specially thanked for its support for China's geological disposal program through its Technical Cooperation Projects
文摘With the rapid development of nuclear power in China, the disposal of high-level radioactive waste(HLW) has become an important issue for nuclear safety and environmental protection. Deep geological disposal is internationally accepted as a feasible and safe way to dispose of HLW, and underground research laboratories(URLs) play an important and multi-faceted role in the development of HLW repositories. This paper introduces the overall planning and the latest progress for China's URL. On the basis of the proposed strategy to build an area-specific URL in combination with a comprehensive evaluation of the site selection results obtained during the last 33 years, the Xinchang site in the Beishan area,located in Gansu Province of northwestern China, has been selected as the final site for China's first URL built in granite. In the process of characterizing the Xinchang URL site, a series of investigations,including borehole drilling,geological mapping, geophysical surveying,hydraulic testing and in situ stress measurements, has been conducted. The investigation results indicate that the geological,hydrogeological, engineering geological and geochemical conditions of the Xinchang site are very suitable for URL construction. Meanwhile, to validate and develop construction technologies for the Beishan URL, the Beishan exploration tunnel(BET), which is a 50-m-deep facility in the Jiujing sub-area, has been constructed and several in situ tests, such as drill-and-blast tests, characterization of the excavation damaged zone(EDZ), and long-term deformation monitoring of surrounding rocks, have been performed in the BET. The methodologies and technologies established in the BET will serve for URL construction.According to the achievements of the characterization of the URL site, a preliminary design of the URL with a maximum depth of 560 m is proposed and necessary in situ tests in the URL are planned.
文摘Underground research laboratories(URLs),including "generic URLs" and "site-specific URLs",are underground facilities in which characterisation,testing,technology development,and/or demonstration activities are carried out in support of the development of geological repositories for high-level radioactive waste(HLW) disposal.In addition to the generic URL and site-specific URL,a concept of "areaspecific URL",or the third type of URL,is proposed in this paper.It is referred to as the facility that is built at a site within an area that is considered as a potential area for HLW repository or built at a place near the future repository site,and may be regarded as a precursor to the development of a repository at the site.It acts as a "generic URL",but also acts as a "site-specific URL" to some extent.Considering the current situation in China,the most suitable option is to build an "area-specific URL" in Beishan area,the first priority region for China's high-level waste repository.With this strategy,the goal to build China's URL by 2020 may be achieved,but the time left is limited.
文摘The geological disposal of high level radioactive waste is a challenging task facing the scientific and technical world.This paper introduces the latest progress of high level radioactive disposal programs in the world,and discusses the following key scientific challenges:(1)precise prediction of the evolution of a repository site;(2)characteristics of deep geological environment;(3)behaviour of deep rock mass,groundwater and engineering material under coupled conditions(intermediate to high temperature,geostress,hydraulic,chemical,biological and radiation process,etc);(4)geochemical behaviour of transuranic radionuclides with low concentration and its migration with groundwater;and(5)safety assessment of disposal system.Several large-scale research projects and several hot topics related with high-level waste disposal are also introduced.
基金sponsored by decommissioning of nuclear installations and radioactive waste treatment special project (K.G.E.S, No.(2014)305)
文摘Residence time of deep groundwater is one of the most important parameters in safety and performance assessment for high-level radioactive waste geological disposal. In this study, we collected the deep groundwater samples of Jijicao in Gansu Beishan pre-selected region. The deep groundwater residence time at two depths estimated by Helium-4 accumulation method were 3.8 ka and 5.0 ka respectively upon measurement and calculation, which indicates that the deep groundwater is not derived from the deep crust circulation process. Hence, deep groundwater is featured with long residence time as well as slow circulation and update rate, and such features are conductive to the safe disposal of high-level radioactive waste.
文摘One of the major concepts of the geological disposal of high level radioactive waste is to enclose a metallic container with bentonite buffer which is considered to be impermeable and chemically stable. Since the average density of the container is around 6 to 7 and very heavy compared to bentonite, the scenario of container sinking has been evaluated because excess sinking makes short the pathway of nuclide migration in the bentonite and is detrimental to the safety of the disposal system. Previous considerations on container sinking have been made from the viewpoint of mechanical deformation of the bentonite. In this paper, a chemical deformation process is presented as another mechanism of container sinking, which has not been previously considered for the container sinking in the field of radioactive waste disposal. The chemical deformation mentioned in this paper is the deformation through the process of pressure solution of minerals constituting the buffer, transportation by diffusion and precipitation. That such chemical deformation is a ubiquitous phenomenon occurring in various scales in the crust of the earth will be shown through the review of previous works. Then, some future research topics will be suggested which would be required in order to evaluate the container sinking in the safety case for radioactive waste disposal.
文摘The China-mock-up test is to evaluate the performance of the compacted Gaomiaozi(GMZ) bentonite under coupled thermo-hydro-mechanical(THM) conditions in deep geological disposal.A numerical study of the test is conducted in this paper.The principal THM characteristics of the bentonite are presented at first.A THM model is then presented to tackle the complex coupling behavior of the bentonite.The model of Alonso-Gens is incorporated to reproduce the mechanical behavior of the bentonite under unsaturated conditions.With the proposed model,numerical simulations of the China-mock-up test are carried out by using the code of LAGAMINE.The time variations associated with the temperature,degree of saturation,suction and swelling pressure of the compacted bentonite are studied.The results suggest that the proposed model is able to reproduce the mechanical behavior of the bentonite,and to predict moisture motion under coupled THM conditions.
文摘One of the most suitable ways under study for the disposal of high-level radioactive waste (HLW) is isolation in deep geological repositories. It is very important to research the thermo-hydro- mechanical (THM) coupled processes associated with an HLW disposal repository. Non-linear coupled equations, which are used to describe the THM coupled process and are suited to saturated-unsaturated porous media, are presented in this paper. A numerical method to solve these equations is put forward, and a finite element code is developed. This code is suited to the plane strain or axis-symmetry problem. Then this code is used to simulate the THM coupled process in the near field of an ideal disposal repository. The temperature vs. time, hydraulic head vs. time and stress vs. time results show that, in this assumed condition, the impact of temperature is very long (over 10 000 a) and the impact of the water head is short (about 90 d). Since the stress is induced by temperature and hydraulic head in this condition, the impact time of stress is the same as that of temperature. The results show that THM coupled processes are very important in the safety analysis of an HLW deep geological disposal repository.
基金supported by the China Atomic Energy Authority(CAEA)through the Geological Disposal Program and the National Natural Science Foundation of China(Grant No.11972149).
文摘The mechanical behavior of host rock for a deep geological repository of high-level radioactive waste plays a key role in ensuring the isolation function of host rock as a natural barrier under the multi-field coupling environment.For a better understanding of granite in China's Beishan pre-selected area for geological disposal of high-level radioactive waste,a series of investigations were carried out on in-situ stress field of rock mass at depth,strength and deformation characteristics of rocks under different stress and temperature conditions,and rock boreability and adaptability to Tunnel Boring Machine(TBM)technology.The results indicate that Beishan granite shows typical characteristics as a hard and brittle rock with a quite low permeability,and it is favorable to geological disposal.Meanwhile,a new rock mass suitability evaluation system was proposed,and the rock mass mainly composed of Beishan granite was proven to be suitable for geological disposal.Besides,the constructability of Beishan granite at engineering scale was tested and verified through field tests in the Beishan Exploration Tunnel(BET).Here,we summarize the main outcomes of rock mechanics research on Beishan granite in the past years and introduced the current progress of Beishan underground research laboratory(URL)for geological disposal.
文摘In Japan,high-level radioactive waste and specific low-level radioactive waste which includes long-lived radionuclides are planned to be disposed of in the geological formations at depths greater than 300 m.The disposal site will be selected through a stepwise site investigation process that consists of a Literature Survey,Preliminary Investigation,and Detailed Investigation phases.In October 2020 a Literature Survey was launched in Japan at two municipalities in Hokkaido for the first time since NUMO initiated a nationwide call for volunteer municipalities in 2002,and the outcomes are currently being compiled.To enhance the public’s understanding of how to implement safe geological disposal in Japan based on the latest scientific knowledge and technology,NUMO,as the implementing organisation,developed and published a safety case for geological disposal at the pre-siting stage.This safety case provides multiple lines of arguments and evidence to demonstrate the feasibility of the geological disposal and a basic structure for a safety case that will be applicable to any potential sites in Japan.The safety case also presented some R&D challenges to enhance the technical confidence of the project,including the R&D topics related to rock mechanics.This report presents the current status of the geological disposal programme in Japan,together with the status of the Literature Survey phase and an overview of the NUMO safety case.
基金supported by the project of the China Geological Survey for shale gas in Southern China(DD20221852)the National Natural Science Foundation of China(42242010,U2244208)。
文摘China is home to shales of three facies:Marine shale,continental shale,and marine-continental transitional shale.Different types of shale gas are associated with significantly different formation conditions and major controlling factors.This study compared the geological characteristics of various shales and analyzed the influences of different parameters on the formation and accumulation of shale gas.In general,shales in China’s several regions exhibit high total organic carbon(TOC)contents,which lays a sound material basis for shale gas generation.Marine strata generally show high degrees of thermal evolution.In contrast,continental shales manifest low degrees of thermal evolution,necessitating focusing on areas with relatively high degrees of thermal evolution in the process of shale gas surveys for these shales.The shales of the Wufeng and Silurian formations constitute the most favorable shale gas reservoirs since they exhibit the highest porosity among the three types of shales.These shales are followed by those in the Niutitang and Longtan formations.In contrast,the shales of the Doushantuo,Yanchang,and Qingshankou formations manifest low porosities.Furthermore,the shales of the Wufeng and Longmaxi formations exhibit high brittle mineral contents.Despite a low siliceous mineral content,the shales of the Doushantuo Formation feature a high carbonate mineral content,which can increase the shales’brittleness to some extent.For marine-continental transitional shales,where thin interbeds of tight sandstone with unequal thicknesses are generally found,it is recommended that fracturing combined with drainage of multiple sets of lithologic strata should be employed to enhance their shale gas production.
文摘Introduction: Not all medicines that pass-through consumers’ hands are used, and some often expire in households. These health products can be sources of accidental risks and pollution when they are not properly disposed of. In Burkina Faso, there are as yet no guidelines for the disposal of unused medicines in households. The aim of this study was to estimate the extent of household possession of unused or expired medicines, and to describe attitudes and disposal practices. Methods: This was a descriptive cross-sectional study covering households in the Ouagadougou commune conducted from June to August 2021. Two-stage stratified sampling was used: selection of Enumeration Zones (EZs) and selection of households, with each EZ comprising several households. Data collection was based on direct interviews using a structured questionnaire. Data were processed using Epi Info software version 7.2.4.0. Results: In total, 417 household residents were surveyed out of the planned 423 households, corresponding to a completion rate of 98.58% compared with the initial sample. Among the respondents, 79.62% had unused and/or expired medicines in their household. A total of 2562 drug packaging units were counted, for a total weight of 121.90 kg. Nearly 75% were aware that improper disposal was a danger to the environment. Some respondents kept their unused medicines at home until they expired (43.41%), and disposed of them mainly by throwing them in the household garbage (75.58%). The majority (79%) were in favor of the government setting up a take-back program for these medicines. Conclusion: The introduction of a take-back program for unused or out-of-date medicines will ensure safer disposal of medicines, and better protection for households and the environment.
文摘Background: Handling of medicines is a day-to-day activity by patients and many health care providers. However, multiple studies have brought to light inappropriate disposal methods for expired and unused medication (EUM). Improper disposal of expired and unused medicines is hazardous both to humans and the environment. Objective: This sought to measure patients’ knowledge, attitude, and practices on disposal methods of EUM. Methods: A cross-sectional study was carried out among 384 patients at three outpatient pharmacies at the University Teaching Hospitals (UTHs). The structured questionnaire was used to collect data and STAT version 15.1 was used to analyse the data. Results: 384 respondents participated in this study and, at some point, had EUM. In this study, 356 (92.7%) of the participants reported that they had never heard of a drug take-back system. Most of the participants 285 (74.2%) and 239 (62.2%) kept and donated their unused medicine, respectively. Additionally, 244 (63.5%), 212 (55.2%), and 176 (44.8%) of the participants disposed of expired medicines in the bin or garbage, flushed them in toilets or sinks, or burned them, respectively. Occupation was significantly associated with unsafe disposal of unused medicine [P-value = 0.019]. Conclusion and Relevance: Knowledge of safe disposal methods for EUM was good amongst most participants. However, used unsafe disposal methods. The majority of the participants exhibited positive attitude concerning safe disposal methods. This study highlights the need for drug-take-back program creation in Zambia.
基金supported by the National Natural Science Foundation of China(Grant No.52090081)the State Key Laboratory of Hydro-science and Hydraulic Engineering(Grant No.2021-KY-04).
文摘Geological discontinuity(GD)plays a pivotal role in determining the catastrophic mechanical failure of jointed rock masses.Accurate and efficient acquisition of GD networks is essential for characterizing and understanding the progressive damage mechanisms of slopes based on monitoring image data.Inspired by recent advances in computer vision,deep learning(DL)models have been widely utilized for image-based fracture identification.The multi-scale characteristics,image resolution and annotation quality of images will cause a scale-space effect(SSE)that makes features indistinguishable from noise,directly affecting the accuracy.However,this effect has not received adequate attention.Herein,we try to address this gap by collecting slope images at various proportional scales and constructing multi-scale datasets using image processing techniques.Next,we quantify the intensity of feature signals using metrics such as peak signal-to-noise ratio(PSNR)and structural similarity(SSIM).Combining these metrics with the scale-space theory,we investigate the influence of the SSE on the differentiation of multi-scale features and the accuracy of recognition.It is found that augmenting the image's detail capacity does not always yield benefits for vision-based recognition models.In light of these observations,we propose a scale hybridization approach based on the diffusion mechanism of scale-space representation.The results show that scale hybridization strengthens the tolerance of multi-scale feature recognition under complex environmental noise interference and significantly enhances the recognition accuracy of GD.It also facilitates the objective understanding,description and analysis of the rock behavior and stability of slopes from the perspective of image data.
基金supported by the National Natural Science Foundation of China(Nos.42077243,52209148,and 52079062).
文摘With an extension of the geological entropy concept in porous media,the approach called directional entrogram is applied to link hydraulic behavior to the anisotropy of the 3D fracture networks.A metric called directional entropic scale is used to measure the anisotropy of spatial order in different directions.Compared with the traditional connectivity indexes based on the statistics of fracture geometry,the directional entropic scale is capable to quantify the anisotropy of connectivity and hydraulic conductivity in heterogeneous 3D fracture networks.According to the numerical analysis of directional entrogram and fluid flow in a number of the 3D fracture networks,the hydraulic conductivities and entropic scales in different directions both increase with spatial order(i.e.,trace length decreasing and spacing increasing)and are independent of the dip angle.As a result,the nonlinear correlation between the hydraulic conductivities and entropic scales from different directions can be unified as quadratic polynomial function,which can shed light on the anisotropic effect of spatial order and global entropy on the heterogeneous hydraulic behaviors.
基金The Construction S&T Project of the Department of Transportation of Sichuan Province(Grant No.2023A02)the National Natural Science Foundation of China(No.52109135).
文摘The surrounding geological conditions and supporting structures of underground engineering are often updated during construction,and these updates require repeated numerical modeling.To improve the numerical modeling efficiency of underground engineering,a modularized and parametric modeling cloud server is developed by using Python codes.The basic framework of the cloud server is as follows:input the modeling parameters into the web platform,implement Rhino software and FLAC3D software to model and run simulations in the cloud server,and return the simulation results to the web platform.The modeling program can automatically generate instructions that can run the modeling process in Rhino based on the input modeling parameters.The main modules of the modeling program include modeling the 3D geological structures,the underground engineering structures,and the supporting structures as well as meshing the geometric models.In particular,various cross-sections of underground caverns are crafted as parametricmodules in themodeling program.Themodularized and parametric modeling program is used for a finite element simulation of the underground powerhouse of the Shuangjiangkou Hydropower Station.This complicatedmodel is rapidly generated for the simulation,and the simulation results are reasonable.Thus,this modularized and parametric modeling program is applicable for three-dimensional finite element simulations and analyses.
基金funded by the Top 10 key scientific and technological projects of CHN Energy in 2021 entitled Research and Demonstration of Technology for Carbon Dioxide Capture and Energy Recycling Utilization(GJNYKJ[2021]No.128,No.:GJNY-21-51)the Carbon Neutrality College(Yulin)Northwest University project entitled Design and research of large-scale CCUS cluster construction in Yulin area,Shaanxi Province(YL2022-38-01).
文摘The well-developed coal electricity generation and coal chemical industries have led to huge carbon dioxide(CO_(2))emissions in the northeastern Ordos Basin.The geological storage of CO_(2) in saline aquifers is an effective backup way to achieve carbon neutrality.In this case,the potential of saline aquifers for CO_(2) storage serves as a critical basis for subsequent geological storage project.This study calculated the technical control capacities of CO_(2) of the saline aquifers in the fifth member of the Shiqianfeng Formation(the Qian-5 member)based on the statistical analysis of the logging and the drilling and core data from more than 200 wells in the northeastern Ordos Basin,as well as the sedimentary facies,formation lithology,and saline aquifer development patterns of the Qian-5 member.The results show that(1)the reservoirs of saline aquifers in the Qian-5 member,which comprise distributary channel sand bodies of deltaic plains,feature low porosities and permeabilities;(2)The study area hosts three NNE-directed saline aquifer zones,where saline aquifers generally have a single-layer thickness of 3‒8 m and a cumulative thickness of 8‒24 m;(3)The saline aquifers of the Qian-5 member have a total technical control capacity of CO_(2) of 119.25×10^(6) t.With the largest scale and the highest technical control capacity(accounting for 61%of the total technical control capacity),the Jinjie-Yulin saline aquifer zone is an important prospect area for the geological storage of CO_(2) in the saline aquifers of the Qian-5 member in the study area.
基金This work was supported by the National Natural Science Foundation of China(Grant No.40072095)the DOE/EMSP grant of USA(DE-FG07-97ER-14816,RCE).
文摘Spent UO2 fuel will rapidly be altered to U6+ phases in nuclear waste repositories. Be-cause most uranyl phases are based on sheet or chain structures and usually contain several mo-lecular water groups, site-mixing, vacancies, as well as disorder in the orientation of hydrogen bonds may occur. A systematic survey of the published crystallographic data for uranates, uranyl oxide hydrates, phosphates, silicates, carbonates, and sulfates demonstrates that site-mixing ap-parently occurs in the structures of at least 31 uranyl phases. Calculations of the ideal site-mixing entropy indicate that the residual contribution that arises from substitution and vacancies to the third-law entropies of some uranyl phases is large. A brief examination of the crystal chemistry of water molecules in uranyl phases suggests that considerable residual entropy may be caused by the disorder of hydrogen bonds associated with interstitial H2O groups. In the geochemical envi-ronment that expected to occur in the near-field of nuclear waste repositories, the existence of structure-configurational entropy may reduce the uranium concentration of several log units in so-lutions equilibrated with some uranyl phases. Therefore, compositional analysis and structural de-terminations must be made on the samples used in calorimetric measurements, and the calorimet-ric data must be combined with solubility data to evaluate the thermodynamic stability of the inter-ested phases.
文摘On October 26,2022,the International Union of Geological Sciences(IUGS)unveiled the First 100 IUGS Geological Heritage Sites in Spain.These sites are located in56 countries,including 34 in the Americas,28 in Europe,15 in Africa and 23 in the Asia-Pacific-Middle East region(Table 1).The seven selected sites of China are introduced as follows(black font in Table 1).
