Search

We performed a series of hydraulic stimulations at 1.1 km depth in the Bedretto underground laboratory, Switzerland, as part of an overall research strategy attempting to understand induced seismicity on different scales. Using an ultra‐high frequency seismic network we detect seismic events as small as Mw < −4, revealing intricate details of a complex fracture network extending over 100 m from the injection sites. Here, we outline the experimental approach and present seismic catalogs as well as a comparative analysis of event number per injection, magnitudes, b‐values, seismogenic index and reactivation pressures. In our first‐order seismicity analysis, we could make the following observations: The rock volume impacted by the stimulations in different intervals differs significantly with a lateral extent from a few meters to more than 150 m. In most intervals multiple fractures were reactivated. The seismicity typically propagates upwards toward shallower depth on parallel oriented planes that are consistent with the stress field and seem to a large extent associated with preexisting open fractures. This experiment confirms the diversity in seismic behavior independent from the injection protocol. The overall seismicity patterns demonstrate that multi‐stage stimulations using zonal isolation allow developing an extended fracture network in a 3D rock volume, which is necessary for enhanced geothermal systems. Our stimulations covering two orders of magnitude in terms of injected volume will give insights into upscaling of induced seismicity from underground laboratory scale to field scale. Plain Language Summary: The Bedretto Underground Laboratory offers ideal conditions for studies focusing on the behavior of the deep underground. In this unique research facility, we built a geothermal test reservoir consisting of a set of injection/production boreholes with up to 400 m length drilled from the tunnel. In 2022 and 2023, we performed various stimulation experiments in packed off sections of this hectometer rock volume. The stimulations were monitored by a newly developed densely spaced multiparameter seismic and hydro‐mechanical monitoring system. The data show the activation of faults with linear dimensions approaching and passing 100 m, yielding a clear impression of a hectometer fractured reservoir. Key Points: The hectometer‐scale hydraulic stimulation experiments fill the gap between decameter experiments and the km scale of engineering projectsHydro‐geomechanical response of a complex 100 m+ fracture networks imaged by pico‐seismic eventsSeismicity occurs on preexisting fractures, activating dominantly the ones well‐oriented within the stress field for hydro‐shearing [ABSTRACT FROM AUTHOR]

In September 2022, Yemilab, a new underground laboratory, was finally completed in Jeongseon, Gangwon Province, South Korea. Situated at a depth of 1000 m, it boasts an exclusive experimental area of 3000 m2. Currently, preparations are in progress for the AMoRE-II experiment, which aims to investigate neutrinoless double beta decay, as well as for the COSINE-100 upgrade (COSINE-100U), a direct dark matter detection experiment. Both experiments are scheduled to commence in the second quarter of 2024 at Yemilab. Furthermore, the facility encompasses a cylindrical pit, approximately 6300 m3 in volume, designed to serve as a multipurpose laboratory. This laboratory will facilitate next-generation experiments focusing on neutrinos, dark matter, and related areas of research. This article presents a detailed overview of Yemilab's construction, infrastructure, and its pivotal physics programs. [ABSTRACT FROM AUTHOR]

In September 2022, Yemilab, a new underground laboratory, was finally completed in Jeongseon, Gangwon Province, South Korea. Situated at a depth of 1000 m, it boasts an exclusive experimental area of 3000 m2. Currently, preparations are in progress for the AMoRE-II experiment, which aims to investigate neutrinoless double beta decay, as well as for the COSINE-100 upgrade (COSINE-100U), a direct dark matter detection experiment. Both experiments are scheduled to commence in the second quarter of 2024 at Yemilab. Furthermore, the facility encompasses a cylindrical pit, approximately 6300 m3 in volume, designed to serve as a multipurpose laboratory. This laboratory will facilitate next-generation experiments focusing on neutrinos, dark matter, and related areas of research. This article presents a detailed overview of Yemilab's construction, infrastructure, and its pivotal physics programs. [ABSTRACT FROM AUTHOR]

In order to build a very-low-level γ ray radiation field and its magnitude transfer system，the scattering contribution caused by different mechanical device structure is researched based on the experimental conditions of the Jinping underground laboratory in China. In this research，the Monte Carlo model of the irradiation device，the magnitude transfer detector，and the internal transmission structure of the shielding box were built in the MCNP5 software. After that，the scattering contribution caused by three spatial variables: the emission angle of the irradiation device，the distance between the detector and the edge of the shielding box，and the distance between the source and the detector，was simulated，and the appropriate device design and layout scheme were obtained. The emission angle of 20°，30° and 40° were used in this research. The energy deposition in sensitive area (with/without the shielding box) was recorded under three different distances between the source and the detector. Three locations of the irradiation device were designed to analyze the change of energy deposition caused by the change of locations. The energy deposition in sensitive area was simulated under more distances between the source and the detector. According to the data，the increase in energy deposition with the emission angle of 20° is less than that caused by the emission angle of 30° and 40°，and the increase in energy deposition is less when the irradiation device is far from the edge of the shielding box. In this research，energy deposition caused by scattering radiation under various irradiation conditions were obtained and analyzed，the device design and layout in the radiation field were optimized，and the idea for establishing an extremely-low-background radiation field was provided.

Abstract Nitrogen is widely used in various laboratories as a suppressive gas and a protective gas. Once nitrogen leaks and accumulates in a such confined space, it will bring serious threats to the experimental staff. Especially in underground tunnels or underground laboratories where there is no natural wind, the threat is more intense. In this work, the ventilation design factors and potential leakage factors are identified by taking the leakage and diffusion of a large liquid nitrogen tank in China Jinping Underground Laboratory (CJPL) as an example. Based on computational fluid dynamics (CFD) research, the effects of fresh air inlet position, fresh air velocity, exhaust outlet position, leakage hole position, leakage hole size, and leaked nitrogen mass flow rate on nitrogen diffusion behavior in specific environments are discussed in detail from the perspectives of nitrogen concentration field and nitrogen diffusion characteristics. The influencing factors are parameterized, and the Latin hypercube sampling (LHS) is used to uniformly sample within the specified range of each factor to obtain samples that can represent the whole sample space. The nitrogen concentration is measured by numerical value, and the nitrogen diffusion characteristics are measured by category. The GA-BP-ANN numerical regression and classification regression models for nitrogen concentration prediction and nitrogen diffusion characteristics prediction are established. By using various rating indicators to evaluate the performance of the trained model, it is found that models have high accuracy and recognition rate, indicating that it is effective in predicting and determining the concentration value and diffusion characteristics of nitrogen according to ventilation factors and potential leakage factors. The research results can provide a theoretical reference for the parametric design of the ventilation system.

Nitrogen is widely used in various laboratories as a suppressive gas and a protective gas. Once nitrogen leaks and accumulates in a such confined space, it will bring serious threats to the experimental staff. Especially in underground tunnels or underground laboratories where there is no natural wind, the threat is more intense. In this work, the ventilation design factors and potential leakage factors are identified by taking the leakage and diffusion of a large liquid nitrogen tank in China Jinping Underground Laboratory (CJPL) as an example. Based on computational fluid dynamics (CFD) research, the effects of fresh air inlet position, fresh air velocity, exhaust outlet position, leakage hole position, leakage hole size, and leaked nitrogen mass flow rate on nitrogen diffusion behavior in specific environments are discussed in detail from the perspectives of nitrogen concentration field and nitrogen diffusion characteristics. The influencing factors are parameterized, and the Latin hypercube sampling (LHS) is used to uniformly sample within the specified range of each factor to obtain samples that can represent the whole sample space. The nitrogen concentration is measured by numerical value, and the nitrogen diffusion characteristics are measured by category. The GA-BP-ANN numerical regression and classification regression models for nitrogen concentration prediction and nitrogen diffusion characteristics prediction are established. By using various rating indicators to evaluate the performance of the trained model, it is found that models have high accuracy and recognition rate, indicating that it is effective in predicting and determining the concentration value and diffusion characteristics of nitrogen according to ventilation factors and potential leakage factors. The research results can provide a theoretical reference for the parametric design of the ventilation system. [ABSTRACT FROM AUTHOR]

Deep underground laboratories offer advantages for conducting high-precision observations of weak geophysical signals, benefiting from a low background noise level. Enhancing strong, noisy ground electromagnetic (EM) field data using synchronously recorded underground EM signals, which typically exhibit a high signal-to-noise ratio, is both valuable and feasible. In this study, we propose an EM field reconstruction method employing a Long Short-Term Memory (LSTM) recurrent neural network with referenced deep underground EM observations. Initially, a deep learning model was developed to capture the time-varying features of underground multi-component EM fields using the LSTM recurrent neural network. Subsequently, this model was applied to process synchronously observed strong, noisy data from other conventional observation systems, such as those at the surface, to achieve noise suppression through signal reconstructions. Both the theoretical analysis and the practical observational data suggest that the proposed method effectively suppresses noise and reconstructs clean EM signals. This method is efficient and time-saving, representing an effective approach to fully utilizing the advantages of deep underground observation data. Furthermore, this method could be extended to the processing and analysis of other geophysical data. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Isotopes is the property of Journal of Isotopes Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Center for Underground Physics of the Institute for Basic Science (IBS) in Korea has been planning the construction of a deep underground laboratory since 2013 to search for extremely rare interactions such as dark matter and neutrinos. In September 2022, a new underground laboratory, Yemilab, was finally completed in Jeongseon, Gangwon Province, with a depth of 1,000 m and an exclusive experimental area spanning 3,000m³. The tunnel is encased in limestone and accommodates 17 independent experimental spaces. Over 2 years, from 2023 to 2024, the Yangyang Underground Laboratory facilities will be relocated to Yemilab. Preparations are underway for the AMoRE-II, a neutrinoless double beta decay experiment, scheduled to begin in Q2 2024 at Yemilab. Additionally, Yemilab includes a cylindrical pit with a volume of approximately 6,300m³, designed as a multipurpose laboratory for next-generation experiments involving neutrinos, dark matter, and related research. This article provides a focused overview of the construction and structure of Yemilab. [ABSTRACT FROM AUTHOR]

This overview provides a comprehensive insight into Callio Lab, a versatile multidisciplinary research platform, by describing the events and actions that have led to the development of the project-based, pay-by-service approach to organizing and economically running the research activities, a mandatory approach for a platform operating without governmental funding. The research platform has a maximum depth of 1.4 km underground, equivalent to approximately 4,100 m of water equivalent (m.w.e.). The flat-overburden mine configuration of Callio Lab minimizes cosmic-ray background interference, making it an ideal setting for low-background experiments, particularly in neutrino and dark matter research. The main-level galleries, with dimensions up to 12 m wide, 30-40 m long, and 8 m tall, provide ample space for research activities, with the potential for even more extensive galleries based on Laguna design studies. Callio Lab has a history with several small and medium-scale cosmic ray and low-background experiments. This overview highlights the site's inherent characteristics, revealing promising opportunities for high-energy and applied physics research and applications across various scientific domains. [ABSTRACT FROM AUTHOR]

The Center for Underground Physics of the Institute for Basic Science (IBS) in Korea has been planning the construction of a deep underground laboratory since 2013 to search for extremely rare interactions such as dark matter and neutrinos. In September 2022, a new underground laboratory, Yemilab, was finally completed in Jeongseon, Gangwon Province, with a depth of 1,000 m and an exclusive experimental area spanning 3,000 m3. The tunnel is encased in limestone and accommodates 17 independent experimental spaces. Over 2 years, from 2023 to 2024, the Yangyang Underground Laboratory facilities will be relocated to Yemilab. Preparations are underway for the AMoRE-II, a neutrinoless double beta decay experiment, scheduled to begin in Q2 2024 at Yemilab. Additionally, Yemilab includes a cylindrical pit with a volume of approximately 6,300 m3, designed as a multipurpose laboratory for next-generation experiments involving neutrinos, dark matter, and related research. This article provides a focused overview of the construction and structure of Yemilab.

Nuclear astrophysics is an interdisciplinary subject of nuclear physics and astrophysics. As the forefront of fundamental research, it has played an important role in the process of deepening understanding of the universe and stellar evolution. One of the primary tasks of nuclear astrophysics is the precise measurement of the cross-sections of the thermonuclear reactions which are responsible for stellar evolution and the synthesis of the chemical elements. Deep underground laboratory, where the flux of cosmic muons is reduced by several orders of magnitude, provides a great opportunity of conducting the measurements of the crucial reaction cross section directly within their Gamow energy regions. At present, there are three ongoing underground nuclear astrophysics experiments, including LUNA in National Laboratory of Gran Sasso (LNGS), CASPER in Sanford Underground Research Facility (SURF), and Jinping Underground Nuclear Astrophysics (JUNA) in China Jinping Underground Laboratory (CJPL). As a pioneer, LUNA has carried out experimental research on several key reactions in the last three decades. LUNA’s result deepens our understanding of the properties of the neutrino, of the sun, and of the universe itself. Recently, with the development of CASPAR and JUNA, the underground experiment has breathed new life. JUNA project is carried out in the second phase of CJPL (CJPL-Ⅱ). CJPL was built under Jinping Mountain with 2 400 m of rock overburden (6 720 m of water equivalent, m.w.e.) leading to the muon flux, the most penetrating component of the cosmic rays, is about 100 times lower compared with LNGS and SURF. More importantly, JUNA has developed a 400 kV intense current accelerator, the beam intensity is more than 10 times that of LUNA. Corresponding underground measurement techniques have also been developed. With the advantage of the ultra-low background of CJPL-Ⅱ and intense beam current at mA level, JUNA’s experimental platform becomes the underground accelerator facility with the highest measurement accuracy in the world. In 2021, JUNA started its first campaign of experimental measurements. Within the 4-month of operation, JUNA measured several important reaction cross sections for the studies of hydrostatic hydrogen and helium burnings, including 25Mg(p, γ)26Al, 19F(p, αγ)16O, 19F(p, γ)16O, 13C(α, n)16O, 18O(α, γ)22Ne and 12C(α, γ)16O reactions. JUNA’s experiments achieved the lowest energy and the highest accuracy in all the above measurements, bringing the underground nuclear astrophysics experiment into a new stage. After nearly a century of development, people have a deeper understanding of stellar evolution and the synthesis of chemical elements. In particular, the deep underground experiment has brought nuclear astrophysics into a new stage of accurate measurement. However, there are still many mysteries to be resolved in nuclear astrophysics. For example, the most important reaction 12C(α, γ)16O, known as the “Holy Grail”, still has no accurate cross-section data in its Gamow window. Looking to the future, measurements over a wider energy range and with higher beam current intensity will be the development direction of underground nuclear astrophysics experiments. Now CASPAR has temporarily withdrawn from SURF due to laboratory construction, and improving the accelerator beam intensity will be its primary task for future restarts. LUNA-MV accelerator is in the commissioning phase at LNGS, and its high voltage reaches 3.5 MV. JUNA also proposed a new plan, which will be focused on improving beam intensity and developing new underground techniques to maintain the advantage of measurement accuracy. With the new plan, JUNA will continue to occupy a dominant position in underground nuclear astrophysics experiments. The future of underground nuclear astrophysics experiments can be expected.

This overview provides a comprehensive insight into Callio Lab, a versatile multidisciplinary research platform, by describing the events and actions that have led to the development of the project-based, pay-by-service approach to organizing and economically running the research activities, a mandatory approach for a platform operating without governmental funding. The research platform has a maximum depth of 1.4 km underground, equivalent to approximately 4,100 m of water equivalent (m.w.e.). The flat-overburden mine configuration of Callio Lab minimizes cosmic-ray background interference, making it an ideal setting for low-background experiments, particularly in neutrino and dark matter research. The main-level galleries, with dimensions up to 12 m wide, 30–40 m long, and 8 m tall, provide ample space for research activities, with the potential for even more extensive galleries based on Laguna design studies. Callio Lab has a history with several small and medium-scale cosmic ray and low-background experiments. This overview highlights the site’s inherent characteristics, revealing promising opportunities for high-energy and applied physics research and applications across various scientific domains.

Deep underground laboratories offer advantages for conducting high-precision observations of weak geophysical signals, benefiting from a low background noise level. Enhancing strong, noisy ground electromagnetic (EM) field data using synchronously recorded underground EM signals, which typically exhibit a high signal-to-noise ratio, is both valuable and feasible. In this study, we propose an EM field reconstruction method employing a Long Short-Term Memory (LSTM) recurrent neural network with referenced deep underground EM observations. Initially, a deep learning model was developed to capture the time-varying features of underground multi-component EM fields using the LSTM recurrent neural network. Subsequently, this model was applied to process synchronously observed strong, noisy data from other conventional observation systems, such as those at the surface, to achieve noise suppression through signal reconstructions. Both the theoretical analysis and the practical observational data suggest that the proposed method effectively suppresses noise and reconstructs clean EM signals. This method is efficient and time-saving, representing an effective approach to fully utilizing the advantages of deep underground observation data. Furthermore, this method could be extended to the processing and analysis of other geophysical data.

For more than three decades, accelerators are in use in the underground laboratories of the Laboratori Nazionali del Gran Sasso (LNGS), located in central Italy. The LUNA Collaboration has exploited the potential of the site’s low cosmic ray background to achieve important and often groundbreaking results in the field of nuclear astrophysics. This long success story stimulated the installation of accelerators in deep underground laboratories also in other countries, including the USA and China. Recently, LNGS took a major step forward with the activation of the Bellotti Ion Beam Facility, which will provide ion beams to the scientific community for research not only in nuclear astrophysics, but in all fields that can benefit from the low cosmic ray background conditions of the underground site.

Copyright of Atomic Energy Science & Technology is the property of Editorial Board of Atomic Energy Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Tunnel Construction / Suidao Jianshe (Zhong-Yingwen Ban) is the property of Tunnel Construction Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Taking the Beishan underground laboratory in Gansu Province as the research object, an exploratory study on the stability analysis of the surrounding rock of granite underground chambers was carried out using the discrete fracture network-discrete element (DFN-DEM) coupling method. The representative survey borehole and surface outcrop fracture data within the engineering survey scope of the underground laboratory were selected for statistical analysis. The discrete fracture network (DFN) and equivalent rock mass model were constructed by using the three-dimensional discrete element software 3DEC. The stability of the chamber of the underground laboratory -560 m horizontal test roadway was simulated and analyzed. The results show that the excavation of the chamber causes the redistribution of stress in the surrounding rock of the chamber. Stress concentration occurs at the intersection of the crack and the excavation surface of the chamber. The surrounding rock of the chamber has displacement and deformation. Under the existing conditions, the deformation of the surrounding rock of the chamber is small, the stress concentration is low, and the underground chamber has good stability [ABSTRACT FROM AUTHOR]

In 1991, a 14C ß-counting installation with four proportional CO2 gas counters was tested at the Modane underground laboratory, 1700 m below the summit of Pointe du Fréjus, reducing the muon flux to 4 muons per square meter and per day. With cosmic radiation attenuated by a factor of 2.106, the background level of the counters was reduced by 65 to 85% while its variability was reduced by a factor of 30–80 depending on the type of counter. The dating limit of these counters extends to well beyond 60,000 years. [ABSTRACT FROM AUTHOR]

[Display omitted] The 25Mg(p , γ)26Al reaction plays an important role in the study of cosmic 1.809 MeV γ -ray as a signature of ongoing nucleosynthesis in the Galaxy. At astrophysical temperature around 0.1 GK, the 25Mg(p , γ)26Al reaction rates are dominated by the 92 keV resonance capture process. We report a precise measurement of the 92 keV 25Mg(p , γ)26Al resonance in the day-one experiment at Jinping Underground Nuclear Astrophysics experiment (JUNA) facility in the China Jinping Underground Laboratory (CJPL). The resonance strength and ground state feeding factor are determined to be 3.8 ± 0.3 ×10−10 eV and 0.66 ± 0.04 , respectively. The results are in agreement with those reported in the previous direct underground measurement within uncertainty, but with significantly reduced uncertainties. Consequently, we recommend new 25Mg(p , γ)26Al reaction rates which are by a factor of 2.4 larger than those adopted in REACLIB database at the temperature around 0.1 GK. The new results indicate higher production rates of 26gAl and the cosmic 1.809 MeV γ -ray. The implication of the new rates for the understanding of other astrophysical situations is also discussed. [ABSTRACT FROM AUTHOR]

Aim of a low radon cleanroom technology is to minimize at the same time radon, radon decay products concentration and aerosol concentration and to minimize deposition of radon decay products on the surfaces. The technology placed in a deep underground laboratory such as LSM Modane with suppressed muon flux and shielded against external gamma radiation and neutrons provides “Zero dose” space for basic research in radiobiology (validity of the LNT hypothesis for very low doses) and for the fabrication of nanoelectronic circuits to avoid undesirable “single event effects.” Two prototypes of a low radon cleanroom were built with the aim to achieve radon concentration lower than 100 mBq·m3 in an interior space where only radon-free air is delivered into the cleanroom technology from a radon trapping facility. The first prototype, built in the laboratory of SÚRO Prague, is equipped with a standard filter-ventilation system on the top of the cleanroom with improved leakproofness. In an experiment, radon concentration of some 50 mBq·m−3 was achieved with the filter-ventilation system switched out. However, it was not possible to seal the system of pipes and fans against negative-pressure air leakage into the cleanroom during a high volume ventilation with the rate of 3,500 m3·h−1. From that reason more sophisticated second prototype of the cleanroom designed in the LSM Modane uses the filter-ventilation system which is completely covered in a further improved leakproof sealed metal box placed on the top of the cleanroom. Preliminary experiments carried out in the SÚRO cleanroom with a high radon activity injection and intensive filter-ventilation (corresponding to room filtration rate every 13 s) showed extremely low radon decay products equilibrium factor of 0.002, the majority of activity being in the form of an “unattached fraction” (nanoparticles) of 218Po and a surface deposition rate of some 0.05 mBq·m−2·s−1 per Bq·m−3. Radon exhalation from persons may affect the radon concentration in a low radon interior space. Balance and time course of the radon exhalation from the human body is therefore discussed for persons that are about to enter the cleanroom.

With the increasing application of nuclear energy in power industry, China has accumulated a large amount of high‐level radioactive nuclear waste, which are characterized by high toxicity, high radioactivity, and long half‐life. Improper disposal will cause great harm to human life and property. China has decided to establish an underground laboratory for geological disposal of high‐level radioactive waste (HLW) in Beishan, Gansu Province, to study the scientific issues related to geological disposal of HLW. In this paper, an online monitoring system including two kinds of integrated inductance probe for the corrosion monitoring of metallic materials used in atmospheric or bentonite environment in Beishan underground laboratory was developed, and the reliability and accuracy of the system were studied. The results show that the system can satisfy the requirement of online monitoring of the corrosion rate of metallic materials, ambient temperature, resistivity, and humidity of bentonite in the underground laboratory for geological disposal of HLW in different environments. [ABSTRACT FROM AUTHOR]

Geological disposal at deep burial depths is a widely accepted method for the treatment of high-level radioactive waste, in which an underground laboratory is regarded as an essential facility to connect various aspects of the process. To evaluate the excavation-induced stability of the rock mass surrounding the underground laboratory for deep geological disposal of high-level radioactive waste in Beishan, Gansu Province, true three-dimensional geomechanical model tests are carried out for the first time. A model test loading system is developed with an intelligent numerical control function and automatic excavation apparatuses. The variations in the displacement and stress surrounding the caverns are revealed. The test results indicate that after excavation, (1) the surrounding rock deforms toward the cavern with small displacements less than 3 mm; (2) the radial stress is lower, and the tangential stress is higher; tensile stress is induced in certain parts near the intersection of caverns but at a magnitude lower than the tensile strength of the rock; (3) the excavation-induced perturbation reaches approximately 1.5–2.0 times the cave diameter; and (4) the surrounding rock shows stability after excavation due to the favorable geological conditions and the overall high strength of the surrounding rock. Nevertheless, enhanced support via combined bolting and shotcrete are recommended at the crossing sections. The research results verify the rationality of the design scheme and provide important guidance for the construction of underground laboratories for deep underground disposal of high-level radioactive waste. [ABSTRACT FROM AUTHOR]

Underground laboratories provide a unique environment for various industries and are the perfect place for developing new technologies for mining, geophysical surveys, radiation detection as well as many other studies and measurements. Unfortunately working in underground excavations is associated with exposure to many hazards not encountered in the laboratories located on the surface. Water inflow, gas burst, roof fall and even seismic hazards translate into high accident rates in the underground mining industry across the globe. Therefore, to minimise the risk of serious accidents, a lot of research investigations related to the development of effective risk assessment procedures are being carried out. One of the initiatives aimed at improving the work safety in underground laboratories in the Baltic Sea Innovation Network project implemented under the Interreg Baltic Sea Region Programme. This study presents the process of compiling a database on hazards within underground laboratories. Finally, a proposal of unification of the procedure for risk assessment, including methods for determining the likelihood and potential impact of unwanted events has been developed. [ABSTRACT FROM AUTHOR]

Current EU policy will force a significant reduction of hard coal mines in the near future due to environmental restrictions. There are also numerous non-coal underground mines that will be excavated in the next few years. Taking the above into consideration, it is worth starting to plan further steps in terms of reclamation of these facilities. Within this manuscript, both recently used and novel approaches to underground space reclamation have been reviewed. Selected methods of reclamation were analyzed in terms of their strengths and weaknesses, and the results were compared with the effect of a commonly used approaches (i.e., filling or flooding of underground space after mine termination). The analysis has been performed in the scope of sustainable development. Taking into account the opinion of many stakeholder groups and underground facilities, reuse was considered as an action aimed at fulfilling sustainable development goals and the circular economy concept. Based on numerous surveys, the challenges and opportunities have been determined as well. Finally, most perspectives concerning underground mine reclamation, including environmental impact, social acceptance, and profitability have been proposed and described.

Natural radioactivity in underground locations is the main parameter for the safety of work (occupational hazards) and for the success of experiments in physics or biology requiring unique conditions. The characterization of natural prominence was carried out in the Conceptual Lab development in one of KGHM deep copper mines co-ordinated by KGHM Cuprum R&D. Natural radioactivity studies were performed and included in situ gamma spectrometry, neutron flux measurements, radon concentration, and alpha and gamma laboratory spectrometry measurements of rock samples. At a depth of 1014.4 m (2941.8 m w.e.) within the anhydrite layer, a neutron flux of 2.0 ± 0.2 × 10−6 cm−2 s−1, a gamma-ray dose of 0.008 ± 0.001 μSv/h, a photon flux density of 0.64 ± 0.20 cm−2 s−1, and a radon concentration of 6.6 Bq/m3 were determined. Laboratory analyses of 226,228Ra, 40K, and 238,234U concentrations in collected rock samples showed low values. The exceptionally low level of natural radioactivity in the Polkowice-Sieroszowice mine makes this location a unique place for scientific research.

The most sensitive technologies for ultra-low-level analyses of long-lived radionuclides have been accelerator mass spectrometry and inductively coupled plasma mass spectrometry, reaching detection limits about 1 nBq/g. Together with underground operation of large volume HPGe detectors they have had great impact on underground physics experiments, approaching new frontiers in radioanalytics—a single atom counting. [ABSTRACT FROM AUTHOR]

In a tunnel, instabilities in the surrounding rock mostly occur within the sidewalls and crown. After acquiring the rock mass structure, a combination of laboratory experiments, numerical simulations, and in situ monitoring data can permit a more reasonable stability analysis of the surrounding rock and engineering support design to ensure a safer engineering project. To overcome the shortcomings (e.g., inefficiency, high labor costs, and safety risks) of traditional methods for mapping the rock mass structures of the sidewalls and crowns of tunnels, this study proposes a safe, rapid, and efficient method that can acquire a 3D digital elevation model (DEM) of the sidewalls and crown of a tunnel and the corresponding rock mass structures by using digital photogrammetry (DP). The proposed method was then tested in an engineering tunnel. Error analysis of check points and discontinuity orientations showed that the errors were within a reasonable range. The method was further applied to traffic tunnel #1 of the China Jinping Underground Laboratory Phase II (CJPL-II), and the spatial coordinates and orientations of the joints were obtained. A 3D quasi-deterministic discrete model was subsequently established by converting the coordinates and orientations of the joints from a geological coordinate system to a local coordinate system in discrete element software. The quasi-deterministic model was then used to confirm that the joint persistence has an important influence on the stability of the surrounding rock of a tunnel and, thus, affects the support installation. Finally, the joint persistence value was determined by the size of the onsite unstable block. The results of this study provide a reference for the design, construction, and support of similar deep-buried jointed hard rock tunnels. [ABSTRACT FROM AUTHOR]

Underground Nuclear Astrophysics in China (JUNA) will take the advantage of the ultra-low background in Jinping underground lab. High current accelerator with an ECR source and detectors were commissioned. JUNA plans to study directly a number of nuclear reactions important to hydrostatic stellar evolution at their relevant stellar energies. At the first period, JUNA aims at the direct measurements of 25Mg(p,γ)26 Al, 19F(p,α) 16 O, 13C(α, n) 16O and 12C(α,γ) 16O near the Gamow window. The current progress of JUNA will be given. [ABSTRACT FROM AUTHOR]

Abstract We performed measurements of thermal and non-thermal neutron flux in underground laboratories in Gran Sasso, Italy and in Slanic Prahova, Romania. The measurements were made with a set of helium counters: bare for thermal neutrons and covered by blocks of moderator for higher energy neutrons. We found that thermal neutron flux in Slanic is four times smaller than in Gran Sasso, probably due to lack of alpha-radioactive sources in the surrounding rocks. In contrast, the flux of higher energy neutrons in Slanic proved to be 1.4 times higher than in Gran Sasso, which can be explained by higher cosmic muon flux in Slanic. Our result for thermal neutron flux is lower than results of most of the previous measurements carried out in LNGS laboratory but thanks to a different method of analysis the reliability of our results is very high. The result for higher energy neutrons agrees with average energy spectrum resulting from previous measurements. Our measurements in Slanic were the first ones ever performed in this laboratory, and can be used as a reference by future experiments. [ABSTRACT FROM AUTHOR]

The overlying rock of underground laboratories provides excellent radiation shielding necessary for many experiments searching for extremely rare nuclear and astroparticle events. Monte Carlo simulations of HPGe detector background and attenuation of gamma-ray fluxes with different shielding configurations were carried out for an underground laboratory. It has been found that even a small radioactive contamination of the shielding material may increase gamma-ray fluxes in underground laboratory by several orders of magnitude. [ABSTRACT FROM AUTHOR]

We present a retrospective on the foundation, evolution, contributions and future prospects of the TEXONO Collaboration and its research programs on neutrino physics and dark matter searches at the Kuo-Sheng Reactor Neutrino Laboratory in Taiwan and, as a founding partner of the CDEX program, at the China Jinping Underground Laboratory in China. aThis retrospective paper is an expansion and update of one that appeared in “The Universe” newsletter of the Asia Pacific Organization for Cosmology and Particle Astrophysics (APCosPA Org).1 [ABSTRACT FROM AUTHOR]

Recent developments in radiometric and mass spectrometry technologies have been associated in the radiometric sector mainly with underground operations of large volume Ge detectors, while the mass-spectrometry sector, represented mainly by accelerator mass spectrometry and inductively coupled plasma mass spectrometry has become the most sensitive technique for ultra-low-level analyses of long-lived radionuclides. These new developments have had great impact on investigations of rare nuclear processes and applications of radionuclides in environmental, life and space sciences. New scientific investigations have been carried out therefore which have not been possible before either because of lack of sensitivity or required large sample size. [ABSTRACT FROM AUTHOR]

We report on the measurements of the fluxes and spectra of the environmental fast neutron background at the China Jinping Underground Laboratory (CJPL) with a rock overburden of about 6700 meters water equivalent, using a liquid scintillator detector doped with 0.5% gadolinium. The signature of a prompt nuclear recoil followed by a delayed high energy γ -ray cascade is used to identify neutron events. The large energy deposition of the delayed γ -rays from the ( n , γ ) reaction on gadolinium, together with the excellent n- γ discrimination capability provides a powerful background suppression which allows the measurement of a low intensity neutron flux. The neutron flux of ( 1 . 51 ± 0 . 03 ( s t a t . ) ± 0 . 10 ( s y s t . ) ) × 1 0 − 7 cm − 2 s − 1 in the energy range of 1–10 MeV in the Hall A of CJPL was measured based on 356 days of data. In the same energy region, measurement with the same detector placed in a room surrounding with one meter thick polyethylene shielding gives a significantly lower flux of ( 4 . 9 ± 0 . 9 ( s t a t . ) ± 0 . 5 ( s y s t . ) ) × 1 0 − 9 cm − 2 s − 1 with 174 days of data. This represents a measurement of the lowest environmental fast neutron background among the underground laboratories in the world, prior to additional experiment-specific attenuation. Additionally, the fast neutron spectra both in the Hall A and the polyethylene room were reconstructed with the help of GEANT4 simulations. [ABSTRACT FROM AUTHOR]

Between the years 2013 and 2017, the Bukov Underground Research Facility (Bukov URF) was under construction on the 12th floor of the Rožná uranium minee (at a depth of approx. 520 m). This high-quality laboratory funded by the Czech Radioactive Waste Repository Authority (CRWRA) was established to assess the behavior of rock environment in the neighborhood of a potential deep-seated radioactive waste repository in process of the preparatory stage of its construction. A parallel hydrogeological research was focused on the flow regime and the chemistry of both shallow and deep groundwater. Rukavičková et al. (2016) earlier reported results of the first stage of hydrogeological investigation carried out at this site. The aim of the current study was to evaluate the chemistry of groundwater and its temporal and spatial development in the recently built URF Bukov, and for comparison also in other parts of the Rožná mine. The groundwater of Ca-HCO3 type usually occurs at depths of up to 520 m (the 12th floor of the mine, the site of URF Bukov) below surface. The content of Na+ was found to be rising with increasing depth, and the groundwater of Na-HCO3 type is typical of deep parts of the Rožná mine. A stagnant water of Na-Cl type was identified in the deepest parts of the Rožná mine (the 24th floor, approx. 1150 m below surface). Natural vertical hydrochemical zonation of groundwater is affected by anthropogenic intervention of underground mine ventilation system. The change of the redox potential in the environment of crystalline rocks containing sulfides resulted in the change of Na-HCO3 and Ca-HCO3 groundwater types towards Na-SO4 and Ca-SO4 types. As a result of this process, the groundwater of Ca-HCO3 type is completely absent in the long‑opened drifts of the Rožná mine, while the anthropogenic Ca-SO4 type of higher mineralization is widespread from the 3rd down to the 12th floor of the mine. The groundwater of Na-SO4 type (a result of sulfides oxidation due to ventilation of mine drifts) occurs in deeper parts of the mine along with Na-HCO3 and Na-Cl types. Gradual increase of total dissolved solids (TDS) and change of ion content (decrease of HCO3 -, increase of SO4 2-, Cl- and cations) have been observed in groundwater of inflows into URF Bukov since January 2014. It can be assumed that the groundwater of URF Bukov, which was primarily of the Ca-HCO3 type, will eventually attain the same chemistry as groundwater in the Rožná mine. [ABSTRACT FROM AUTHOR]

The Josef adit was driven during a mineral exploration project in search for gold in the Psí hory gold district in Central Bohemia in the 1980s. Two gold deposits were discovered in this area named after nearby villages of Čelina and Mokrsko. This area is built of two main geological units - the Jílové Zone consisting of a volcano-sedimentary complex of Neoproterozoic age, mainly composed of acid and intermediate volcanic rocks, tuffaceous shales and greywackes, and an amphibole-biotite granodiorite body of Variscan age belonging to the Central Bohemian Plutonic Complex. The low grade gold mineralization is disseminated in densely spaced quartz veins together with low amount of sulfides (pyrite, arsenopyrite, pyrrhotite). Recently, the Centre of Experimental Geotechnics of Faculty of Civil Engineering of the Czech Technical University in Prague established in the Josef adit an underground laboratory to carry out a range of experiments oriented on in-situ tests and measurements of underground structures or geotechnics in general including possible nuclear waste disposal site in relation to migration of groundwater or use of bentonite barriers and other tests. The groundwater chemistry is one of the main parameters which can strongly influence this kind of experiments, but no general groundwater chemistry was studied in this area as yet. One-year lasting groundwater monitoring, split into three quarterly sampling campaigns, was based on eleven monitoring and sampling sites. Six of them were in granodiorite, and the remaining five were located in the Jílové Zone. Some parameters such as pH, electric conductivity (EC), total dissolved solids (TDS) and temperature (T) were measured on site, while concentrations of Ca2+, Mg2+, K+, and SO4 2- were determined in the laboratory shortly after collection of samples. The results showed that the host rocks played the major role in chemical composition of groundwater. There is no direct evidence that ground waters are affected by experiments and ongoing activities (salt solution influx, water pumping, construction works, etc). The only exception is the DOPAS experiment during which the grouting mixture was used in the construction which devaluated the measurements of potassium concentration. Based on chemical composition, two main types of groundwater can be distinguished. Both of them are classified as moderately mineralized waters. The first type is represented by water collected in the Jílové Zone showing pH close to neutral (7.85), higher TDS (369 mg/l), almost identical calcium and magnesium concentrations (43.5 and 51.5 mg/l), and higher content of sulfates (128 mg/l), which is likely to be due the oxidation of sulfides. The second type is a water from granodiorite which is slightly alkaline with pH corresponding to 8.18, with lower TDS content (307 mg/l), and showing significantly higher content of calcium relative to magnesium (59.9 and 24.7 mg/l, respectively), and lower concentration of sulfates (97.8 mg/l). [ABSTRACT FROM AUTHOR]