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Huang H, Sun Q, Geng J, Hu J, Li P. Study of the influence of pore structure on the radon emission characteristics of terrestrial sedimentary shales after high temperature action. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2024; 31:13218-13229. [PMID: 38240968 DOI: 10.1007/s11356-024-31947-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Accepted: 01/05/2024] [Indexed: 02/23/2024]
Abstract
Heat-assisted development of shale oil and gas is recognized as a vital technique for the efficient extraction of shale gas; however, there is a need for comprehensive investigation regarding radon release during the extraction process. The aim of this study was to investigate the pore structure and radon release characteristics of heat-treated black shale using low-temperature nitrogen adsorption (LTNA) and radon (Rn-222) measurement equipment. The findings reveal that temperature initially enhances radon release, which subsequently decreases. The maximum radon release occurs at 500 °C, reaching 1.46 times the initial stage. The radon release rate is positively correlated with the volume of micropores (< 2 nm) in the shale. Organic pores within the shale serve as the primary storage spaces for radon, and the intricate pore structure of organic matter provides an optimal environment for radon gas retention. These results contribute to elucidating the mechanisms behind the impact of thermal treatment on shale's radon release rate, which is crucial for guiding radon radiation evaluation in thermal treatment processes.
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Affiliation(s)
- Hao Huang
- College of Geology and Environment, Xi'an University of Science and Technology, Xi'an, 710054, Shaanxi, China
| | - Qiang Sun
- College of Geology and Environment, Xi'an University of Science and Technology, Xi'an, 710054, Shaanxi, China
- Shaanxi Provincial Key Laboratory of Geological Support for Coal Green Exploitation, Xi'an, 710054, China
| | - Jishi Geng
- College of Geology and Environment, Xi'an University of Science and Technology, Xi'an, 710054, Shaanxi, China
| | - Jianjun Hu
- Jiangxi Key Laboratory of Solar Optoelectronic Materials, Nanchang Institute of Technology, Nanchang, 330044, China.
- State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering, Shenzhen University, Shenzhen, 518060, China.
| | - Pengfei Li
- College of Geology and Environment, Xi'an University of Science and Technology, Xi'an, 710054, Shaanxi, China
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Chan Z, Zhou B, Wang J, Lu Z, Yang Q, Dong Z, Dong K. Long-distance migration law of radon in overburden of abandoned goaf during coal spontaneous combustion. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2023; 270:107284. [PMID: 37634424 DOI: 10.1016/j.jenvrad.2023.107284] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2023] [Revised: 07/26/2023] [Accepted: 08/19/2023] [Indexed: 08/29/2023]
Abstract
The surface isotope radon measurement method (SIRMM) is widely used in fire source detection in abandoned mines. However, studies on the long-distance migration of radon during coal spontaneous combustion are lacking, which hinders the further popularization of this technology in coal fire prevention and control. For this reason, the migration law of radon in overlying strata in fire areas was studied through experiments and numerical simulation. The radon exhalation concentration of coal was found to increase at first and then decrease in the range of 30-350 °C through experiments. The radon concentration reaches the maximum value (557.1 Bq/m3) at 150 °C, which is 6.3 times higher than that at 30 °C. Based on the radon source term obtained by fitting the experimental data, the radon migration model of coal spontaneous combustion in abandoned goaf was constructed, and the dynamic distribution characteristics of the airflow, temperature, and radon concentration fields in the overlying strata area were analyzed. The internal relationship between surface radon and underground fire source was discussed. The simulation results revealed the sharp change in the porosity of the overlying rock causes radon concentration at the interface between the caving and fissure zones to increase continually with the process of spontaneous combustion, providing material and energy support for the long-distance radon migration. When the maximum temperature of the coal pile reaches 70 °C, the concentration of radon released from the coal pile increases rapidly to 13696 Bq/m3, and the radon from the underground space appears on the surface at this temperature. In the range of 70-150 °C, with rapid increase in radon released from coal piles, the surface concentration of radon also increased rapidly to 225 Bq/m3. At the high-temperature stage exceeding 150 °C, the concentration of radon released from coal piles exhibited a downward trend, resulting in a decrease in the rate of increase of radon concentration on the surface. A close relationship between the surface radon concentration and underground fire source temperature in the process of coal spontaneous combustion was observed. In the spatial position, the peak position of radon on the surface was highly consistent with that of the fire source longitudinally, which ensures the accuracy of the SIRMM to determine the location of the hidden fire source. This suggests that the SIRMM can accurately evaluate the fire source's temperature and fire area's development trend.
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Affiliation(s)
- Zhikang Chan
- College of Mining Engineering, Taiyuan University of Technology, Taiyuan, 030024, Shanxi, China
| | - Bin Zhou
- College of Safety and Emergency Management Engineering, Taiyuan University of Technology, Jinzhong, 030600, Shanxi, China.
| | - Junfeng Wang
- College of Mining Engineering, Taiyuan University of Technology, Taiyuan, 030024, Shanxi, China.
| | - Zhifan Lu
- College of Mining Engineering, Taiyuan University of Technology, Taiyuan, 030024, Shanxi, China
| | - Qifan Yang
- College of Mining Engineering, Taiyuan University of Technology, Taiyuan, 030024, Shanxi, China
| | - Zhiyu Dong
- College of Mining Engineering, Taiyuan University of Technology, Taiyuan, 030024, Shanxi, China
| | - Kaili Dong
- College of Mining Engineering, Taiyuan University of Technology, Taiyuan, 030024, Shanxi, China
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Zheng X, Sun Q, Jing X, Yang D, Jia H. Evolution of pore structure and radon exhalation characterization of porous media grouting. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 865:161352. [PMID: 36596422 DOI: 10.1016/j.scitotenv.2022.161352] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Revised: 12/24/2022] [Accepted: 12/29/2022] [Indexed: 06/17/2023]
Abstract
Cracks and pores are considered as major sources of radon. Cement is widely used as a grouting material in mines, tunnels, and other projects for reinforcement, seepage prevention, and water plugging. This paper mainly experimentally studied the correlation between the radon exhalation rate of the porous medium after grouting and the sand grain diameter, grouting pressure, and slurry water-cement ratio. The pore characteristics of the samples before and after grouting were also studied based on the low field nuclear magnetic resonance (LF-NMR). The findings of the study show that the porosity of samples increases after the superfine cement solidification with an increase in the water-cement ratio, and the radon exhalation rate is proportional to porosity, the radon exhalation rate increases by 0.0005 Bq·m-2/s at W/C = 1.5, and by 0.0017 Bq·m-2/s at W/C = 2 increases, in comparison to the W/C = 1.The radon exhalation rate of porous media gradually increased after grouting in response to an increase in grouting pressure and the water-cement ratio. The radon exhalation rate of the porous media with larger pores was relatively higher and exhibited a positive correlation with the volume of micropores in porous media,the correlations of coarse, medium and fine media are 0.815, 0.826, and 0.859. The change in pore structure has an influence on radon exhalation. Although grouting changes the pore structure and reduces the connectivity between internal pores, the micropores generated after cement slurry solidification improves the radon exhalation rate by providing new channels, When the water-cement ratio is 1.5 and the grouting pressure is 1.5 MPa, the radon exhalation rate of porous media is 0.00273 Bq·m-2/s. The research results serve as a reference basis for the evaluation of the impact of rock masses on grouting reinforcement and pore sealing.
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Affiliation(s)
- Xinchao Zheng
- College of Geology and Environment, Xi'an University of Science and Technology, Xi'an, Shaanxi 710054, China.
| | - Qiang Sun
- College of Geology and Environment, Xi'an University of Science and Technology, Xi'an, Shaanxi 710054, China; Shaanxi Provincial Key Laboratory of Geological Support for Coal Green Exploitation, 710054, China; Key Laboratory of Coal Resources Exploration and Comprehensive Utilization, Ministry of Land and Resources, China.
| | - Xudong Jing
- College of Geology and Environment, Xi'an University of Science and Technology, Xi'an, Shaanxi 710054, China.
| | - Duoxing Yang
- National Institute of Natural Hazards, Ministry of Emergency Management of China, Beijing 100085, China.
| | - Hailiang Jia
- College of Architecture and Civil Engineering, Xi'an University of Science and Technology, Xi'an, Shaanxi 710054, China.
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Hao Y, Jiang F, Tan B, Zhang C, Zhang M, Li H, Yang X, Mo Y, Hu T, Li S, He H. Study on damage evolution and radon exhalation of uranium-bearing granite under high temperature. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2023; 30:35223-35237. [PMID: 36527562 DOI: 10.1007/s11356-022-24740-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Accepted: 12/08/2022] [Indexed: 06/17/2023]
Abstract
Deep geological disposal of high-level radioactive waste is a feasible method for solving the problem of spent fuel storage in China. High-level radioactive waste releases heat during the decay process, which increases the temperature of the surrounding rock in the repository, resulting in a significant increase in radon concentration. In this study, the surrounding rock (granite) of a high-level radioactive waste repository was taken as the research object and, based on the similarity principle, an orthogonal test designed. Similar materials of uranium-containing granite were prepared in the laboratory and the physical and mechanical properties and cumulative radon concentration of granite samples assessed under different temperatures (25, 50, 100, 150, and 200 °C). The results showed that, with increased temperature, the compressive and tensile strengths of samples gradually increased and their pore volume gradually decreased. After heat treatment, the longitudinal wave velocity and thermal conductivity of samples decreased linearly with increased temperature. The radon exhalation rate first increased and then decreased, with the rate reaching a maximum at 100 °C. The radon exhalation rate of single-sided and double-sided samples was 0.00914 and 0.00460 Bq·m-2·s-1, respectively. When the temperature was 25-100 °C, the dominant stage was pore water. The radon exhalation rates of samples were positively correlated with compressive and tensile strengths and negatively correlated with pore volume, longitudinal wave velocity, and thermal conductivity. The temperature of 100-200 °C was range of the dominant stage of pore structure. The conclusions obtained in this study can provide theoretical support for radon reduction and radon control of granite in high temperature environments.
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Affiliation(s)
- Yuying Hao
- School of Resource & Environment and Safety Engineering, University of South China, Hengyang, 421001, China
| | - Fuliang Jiang
- School of Resource & Environment and Safety Engineering, University of South China, Hengyang, 421001, China.
- School of Safety and Management Engineering, Hunan Institute of Technology, Hengyang, 421002, China.
- School of Physics and Electronic Engineering, Hengyang Normal University, Hengyang, 421001, China.
- Hunan Provincial Engineering Research Center for Uranium Mineral Exploration Technology, Hengyang, 421001, China.
| | - Biao Tan
- School of Resource & Environment and Safety Engineering, University of South China, Hengyang, 421001, China
| | - Chao Zhang
- School of Resource & Environment and Safety Engineering, University of South China, Hengyang, 421001, China
| | - Mian Zhang
- School of Resource & Environment and Safety Engineering, University of South China, Hengyang, 421001, China
| | - Haoyu Li
- School of Resource & Environment and Safety Engineering, University of South China, Hengyang, 421001, China
| | - Xiaotong Yang
- School of Resource & Environment and Safety Engineering, University of South China, Hengyang, 421001, China
| | - Yixiang Mo
- School of Physics and Electronic Engineering, Hengyang Normal University, Hengyang, 421001, China
- Hunan Provincial Engineering Research Center for Uranium Mineral Exploration Technology, Hengyang, 421001, China
| | - Tao Hu
- School of Physics and Electronic Engineering, Hengyang Normal University, Hengyang, 421001, China
- Hunan Provincial Engineering Research Center for Uranium Mineral Exploration Technology, Hengyang, 421001, China
| | - Shiyan Li
- School of Safety and Management Engineering, Hunan Institute of Technology, Hengyang, 421002, China
| | - Huiting He
- School of Safety and Management Engineering, Hunan Institute of Technology, Hengyang, 421002, China
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Experimental Study on Unsteady Radon Exhalation from the Overburden Layer of the Uranium Mill Tailings Pond under Rainfall. SCIENCE AND TECHNOLOGY OF NUCLEAR INSTALLATIONS 2022. [DOI: 10.1155/2022/9366056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In order to find out radon reduction performance of the overburden layer on uranium mill tailings (UMTs) pond beach surface after rainfall, the rainfall simulation experiment of the overburden layer was carried out with the self-developed equipment. Based on the radon migration model of the overburden layer on the UMTs pond beach surface, the change rule of radon exhalation in four types of compactness of the overburden layer within 120 hours after rainfall was studied, and the corresponding moisture content was also analyzed. The results show that the radon concentration in the overburden layer of UMTs increases nonlinearly; the dynamic change in moisture content of the overburden layer on the beach surface leads to the unsteady radon exhalation. The variation of radon exhalation shows three stages: increase, linear decrease, and stability tendency. After rainfall, radon exhalation rate increases due to water vapor and there is free radon seepage in pores. With the decrease of free radon production rate, radon exhalation rate gradually decreases until it reaches stability again. When the thickness of the overburden layer reduces, the porosity decreases with the increase in compactness of the overburden layer. While the decrease in radon reduction is more obvious, the less time it takes for radon exhalation to vary from unstable to stable overburden after rainfall.
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Li S, Zhang M, Wang H. Simulation of gas sensing mechanism of porous metal oxide semiconductor sensor based on finite element analysis. Sci Rep 2021; 11:17158. [PMID: 34433870 PMCID: PMC8387441 DOI: 10.1038/s41598-021-96591-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 08/11/2021] [Indexed: 11/09/2022] Open
Abstract
In recent years, finite element analysis is increasingly adopted to simulate the mechanism of metal oxide semiconductor (MOS) resistive gas sensors. In this article, the chemical reaction engineering module in the COMSOL Multiphysics tool is used to describe the dynamic equilibrium process of oxygen ions in the sensor. The boundary conditions of temperature transfer, conductivity model, and mass transfer are applied to simulate the convection, diffusion, and penetration processes. The response of the sensor at different temperatures (445 K-521 K) and different target gas concentrations (1-500 ppm) is simulated. In this paper, the dynamic model of oxygen ions is used creatively as a bridge between gas concentration and sensor response instead of the traditional direct parameter fitting method. The simulated result of the surface oxygen ion control and permeability control model of the MOS gas sensor shows a good agreement with the real sensor. For explaining the principle of metal oxide semiconductor gas sensors simulations has been performed on COMSOL Multiphysics software. The proposed method in this paper is based on the underlying transfer logic of the sensor signal, it is expected to predict the sensor signal and assist the sensor design.
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Affiliation(s)
- Songlin Li
- School of Aerospace Science and Technology, Xidian University, 2 Taibai South Road, Xi'an, 710000, China
| | - Min Zhang
- School of Aerospace Science and Technology, Xidian University, 2 Taibai South Road, Xi'an, 710000, China
| | - Hai Wang
- School of Aerospace Science and Technology, Xidian University, 2 Taibai South Road, Xi'an, 710000, China.
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Feng S, Wu Y, Liu Y, Li X, Wang X, Chen P. A fractal analysis of radon migration in discrete fracture network model. CHEMOSPHERE 2021; 266:129010. [PMID: 33279241 DOI: 10.1016/j.chemosphere.2020.129010] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 11/14/2020] [Accepted: 11/15/2020] [Indexed: 06/12/2023]
Abstract
A novel model is proposed to simulate radon migration by combining the fractal theory and the discrete fracture network (DFN) model. In the model, a power-law distribution based on fractal theory is applied to fracture length and aperture and the fracture locations and orientations are modeled with the Poisson distribution and von Mises-Fisher distribution, respectively. The model was applied to produce a computer code that can calculate the radon concentration, flux, and diffusivity of the fractured media. The key issues related to the model were analyzed and the results reveal that: (1) the threshold value of the ratio of the minimum fracture length to the maximum decreases as the fractal dimension of the fracture lengths and the relation between them follows an exponential law; (2) As the fractal dimension of the fracture lengths increases, more connected fractures are generated, resulting in a linear increase of the mean efficient radon diffusivity. (3) The dip angle is the parameter that has the greatest influence on radon migration in determining fracture orientations. (4) The radon exhalation rate increases exponentially with increasing advection velocity. (5) Models with larger fractal dimension for fracture lengths have larger representative elementary volume (REV) size and follow an exponential law.
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Affiliation(s)
- Shengyang Feng
- School of Resource Environment and Safety Engineering, University of South China, Hengyang, 421001, Hunan, China; School of Civil and Architectural Engineering, Guangxi University of Science and Technology, Liuzhou, 545006, China.
| | - Yurong Wu
- School of Resource Environment and Safety Engineering, University of South China, Hengyang, 421001, Hunan, China
| | - Yong Liu
- School of Resource Environment and Safety Engineering, University of South China, Hengyang, 421001, Hunan, China; Hunan Province Engineering Technology Research Center of Uranium Tailings Treatment, Hengyang, 421001, China
| | - Xiangyang Li
- School of Resource Environment and Safety Engineering, University of South China, Hengyang, 421001, Hunan, China; Hunan Province Engineering Technology Research Center of Uranium Tailings Treatment, Hengyang, 421001, China
| | - Xiaodong Wang
- School of Nuclear Science and Technology, University of South China, Hengyang, 421001, Hunan, China.
| | - Puxin Chen
- School of Resource Environment and Safety Engineering, University of South China, Hengyang, 421001, Hunan, China
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Novel method for measuring temperature-dependent diffusion coefficient of radon in porous media. Appl Radiat Isot 2020; 169:109506. [PMID: 33340786 DOI: 10.1016/j.apradiso.2020.109506] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Revised: 09/21/2020] [Accepted: 10/29/2020] [Indexed: 11/21/2022]
Abstract
The temperature-dependent diffusion coefficient of radon is one of the most important parameters for predicting radon migration in porous media. In order to measure this parameter more effectively and accurately, theoretical formulas were derived by the steady-state one-dimensional equation of radon migration in porous media for designing the corresponding experimental device, which was used to measure the diffusion coefficients of radon in uranium mill tailings. The results show that the diffusion coefficient of radon in porous media increases with increasing the temperature, which is in agreement with existing researches, verifying the method effectiveness. The changes of the diffusion coefficient of radon with the absolute temperature follow a power law.
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