Geological Disposal Of Radioactive Waste Research Articles

Changes of Temperature and Moisture Distribution over Time by Thermo-Hydro-Chemical (T-H-C)-Coupled Analysis in Buffer Material Focusing on Montmorillonite Content

Bentonite is used as a buffer material in engineered barriers for the geological disposal of high-level radioactive waste. The buffer material will be made of bentonite, a natural clay, mixed with silica sand. The buffer material is affected by decay heat from high-level radioactive waste, infiltration of groundwater, and swelling of the buffer material. The analysis of these factors requires coupled analysis of heat transfer, moisture transfer, and groundwater chemistry. The purpose of this study is to develop a model to evaluate bentonite types and silica sand content in a unified manner for thermo-hydro-chemical (T-H-C)-coupled analysis in buffer materials. We focused on the content of the clay mineral montmorillonite, which is the main component of bentonite, and developed a model to derive the moisture diffusion coefficient of liquid water and water vapor based on Philip and de Vries, and Kozeny–Carman. The evolutions of the temperature and moisture distribution in the buffer material were analyzed, and the validity of each distribution was confirmed by comparison with the measured data obtained from an in situ experiment at 350 m in depth at the Horonobe Underground Research Center, Hokkaido, Japan.

Three-Dimensional Modelling of a Large-Diameter Sealing Concept in a Deep Geological Radioactive Waste Disposal

AbstractThe French National Radioactive Waste Management Agency is leading the design of a deep geological radioactive waste disposal to be located in the Callovo-Oxfordian formation. At the disposal main level, large-diameter galleries will ensure access to the storage cells and connection between zones. After a long operational period, the disposal will be closed by sealing structures located at some key positions to ensure post-closure safety over the long term. The seals are intended to prevent the flow of water and the migration of radionuclides from the disposal to the biosphere throughout the entire storage life. Thus, the long-term safety of the disposal relies to a large extent on the performance of these structures. The paper presents the work carried out to assess and simulate the phenomena underlying the response and performance of a large-diameter sealing concept under real disposal conditions. The complexity of the problem is addressed by considering in the simulations large-scale 3D geometries, advanced constitutive models, complex coupled phenomena, key geometric details at decimetre scale, and all the phases from the excavation to the post-closure period (~ a few thousand years).

Gas-entry pressure impact on the evaluation of hydrogen migration at different scales of a deep geological disposal of radioactive waste

Although the importance of gas-entry pressure in simulating two-phase liquid–gas flow in porous media has been studied at the column and borehole scales, its impact on the simulation of transient hydraulic-gas at different scales of a deep geological repository of radioactive waste (DGR) in low permeability clay rock during the post-closure phase has not yet been studied. The purpose of this work is to show that neglecting this phenomenon can lead to underestimation of the maximum gas pressure and water–gas fluxes simulated within the host rock and backfilled drift network. This could impact the performance of the engineered barrier system of a DGR. Simulations performed for a high-level waste disposal cell and for a simplified repository composed of hundreds of disposal cells situated in a clay host rock, show that gas preferentially migrates through the DGR components with low capillary entry pressures, such as the excavation damaged zone (Refers to the zone where fractures develop due to failure of the rock mass around galleries after tunneling) (EDZ), the engineered barriers materials (backfill, bentonite-plug…) and interfaces between the EDZ and these materials. Such a result could have significant consequences on the performance of a repository, due to the accumulation of gas in the drift network and high increase of gas pressure, which could lead to the host rock hydraulic fracturing.

Mineralogical Evolution of High-pH/Low-pH Cement Pastes in Contact with Seawater

In facilities for the geological disposal of radioactive waste in coastal areas, the long-term alteration of cementitious materials in engineered barriers is expected to occur due to the ingress of groundwater derived from seawater. Although the reaction between cement and seawater has been studied, the alteration behavior caused by the reaction between seawater and low-pH cement, which is expected to be used in a disposal facility, has not yet been clarified. In this study, the effects of cement type on cement–seawater interactions were investigated, and the chemical stability and mineral evolution of cement pastes caused by reactions with seawater were determined. The dissolution of cement hydrates occurred upon increased contact with seawater, and the formation of secondary minerals, including carbonate and Mg-containing minerals, was observed. The progress of dissolution depended on the mineral composition of the initially formed cement hydrates, and low-pH cement containing pozzolanic materials showed less resistance to seawater. Differences in pH and Si concentration that are due to the type of cement used had a strong influence on the evolution of minerals (especially Mg-containing minerals), implying that the formed mineral species possibly affect the migration characteristics of radionuclide.

Modelling of failure and fracture development of the Callovo-Oxfordian claystone during an in-situ heating experiment associated with geological disposal of high-level radioactive waste

To ensure the safety of geological disposal of high-level radioactive waste, in-situ experiments have been carried out to examine the behavior of rocks in underground research laboratories (URLs). At the Meuse/Haute-Marne URL in France, the French National Radioactive Waste Management Agency (Andra) has been assessing the Callovo-Oxfordian claystone (COx) as potential host rock of geological disposal by subjecting the COx to in-situ heating mimicking exothermic radioactive waste. Results of the in-situ experiments are used to validate and bolster the numerical simulators for predicting the thermo-hydromechanically (THM) coupled behavior of the COx. The numerical simulators are, however, yet to be tested for predicting the failure and fracture development of the COx during heating, which is of paramount importance to the safety of the geological disposal. In this research, we modelled a recently carried out in-situ experiment at the Meuse/Haute-Marne URL using the TOUGH-FLAC simulator to predict the failure and fracture development of the COx during heating. The objectives are to examine the effects of (i) the weak bedding planes, (ii) the softening rate of matrix/weak plane strengths, and (iii) the stiffness anisotropy of the COx on the development of shear and tensile fractures during heating. Results show that considering failure along the weak planes enabled accurate predictions of fracture development. Also, fracture development intensified at a softening rate beyond a threshold level and the geometry of fractures was significantly affected by the stiffness anisotropy. These results will help boost the reliability of the safety and performance assessment of geological disposal in claystone.

Enhanced Identification of Fracture Smectites and Other Alteration Minerals Via Short-Wave Infrared Reflectance at Two Finnish Crystalline Sites, Olkiluoto and Hyrkkölä

AbstractFracture filling minerals and the smectite-group clay minerals in particular play a significant role in the geotechnical stability of the fractured rock mass. Smectites have multiple uses as geomaterials in waste management solutions, of which the most technically demanding is the geological disposal of radioactive waste. Here, the stability and occurrence of smectites as fracture filling minerals were studied with two main objectives: 1) to test the capability of short-wave infrared spectroscopy as a tool to streamline the site assessment where clay mineralogy needs to be characterised in detail, and 2) to provide a first assessment of naturally occurring smectites in various sample types collected from two Finnish sites (Olkiluoto and Hyrkkölä) and their potential as natural analogues of smectite stability for bentonite used in the engineered barrier systems of geological disposal repositories. The short-wave infrared (SWIR) method has been validated to be a useful tool in fracture mineral characterisation, specifically due to its fast acquisition and interpretation time compared to the conventional methods. The study confirms the in situ occurrence of smectites at both sites studied showing that, especially in Hyrkkölä, the smectite-group member is close to montmorillonite, the main constituent of bentonite. At Olkiluoto, the smectites studied show more interstratified features. The differences in the mode of occurrence are related to the history of their formation, especially hydrothermal alteration, and parent rock composition.

Influence of the Al Content on the Electrochemical Behavior of Zn-Al Cold-Sprayed Coatings in the Context of the Deep Geological Disposal of Radioactive Waste

For high-level radioactive waste, the French National Radioactive Waste Management Agency is currently developing a 500 m deep geological disposal facility called Cigéo. Carbon steel containers will be used to contain the wastes in the specific conditions of the disposal. The use of a sacrificial coating was studied as an additional protection for the containers against corrosion. A previous work had shown the possibility to use Zn-Al coatings in this specific medium. To optimize the coatings’ performance, the cold-spraying process was considered instead of the previously used wire arc spraying because it can increase the cohesion between the particles in the coating. Moreover, three aluminum contents, i.e., 5, 15 and 25 wt.%, were considered. The characterization of the obtained coatings revealed a strongly heterogeneous composition for the lower Al content (5 wt.%), with local Al contents from 1.3 wt.% Al to 44.5 wt.% Al. The corrosion study was carried out in a specific solution mimicking the pore solution of the surrounding cementitious material designed for disposal at a temperature of 50 °C. First, the polarization curves acquired with coated steel electrodes revealed the pseudo-passive behavior of the 25 wt.% Al coating, while for the other compositions, the coating remained active. Moreover, the higher aluminum content (25 wt.%) induced an important decrease in potential, with a possible risk of hydrogen embrittlement for the protected steel. Secondly, the sacrificial properties were investigated through 6 months of experiments using coated electrodes with cross-like defects and coated electrodes coupled with bare steel electrodes. Whatever the composition of the coating, the protection was maintained, with the 15 wt.% Al coating giving the best performance.

Enhancement of U(VI) sorption in natural soils at prospective high-level radioactive waste geological disposal sites with Fe(OH)3-humic acid composite colloids

Enhancement of U(VI) sorption in natural soils at prospective high-level radioactive waste geological disposal sites with Fe(OH)3-humic acid composite colloids

Scenario development for safety assessment in deep geologic disposal of high-level radioactive waste and spent nuclear fuel: A review.

Radiation and radioactive substances result in the production of radioactive wastes which require safe management and disposal to avoid risks to human health and the environment. To ensure permanent safe disposal, the performance of a deep geological repository for radioactive waste is assessed against internationally agreed risk-based standards. Assessing postclosure safety of the future system's evolution includes screening of features, events, and processes (FEPs) relevant to the situation, their subsequent development into scenarios, and finally the development and execution of safety assessment (SA) models. Global FEP catalogs describe important natural and man-made repository system features and identify events and processes that may affect these features into the future. By combining FEPs, many of which are uncertain, different possible future system evolution scenarios are derived. Repository licensing should consider both the reference or "base" evolution as well as alternative futures that may lead to radiation release, pollution, or exposures. Scenarios are used to derive and consider both base and alternative evolutions, often through production of scenario-specific SA models and the recombination of their results into an assessment of the risk of harm. While the FEP-based scenario development process outlined here has evolved somewhat since its development in the 1980s, the fundamental ideas remain unchanged. A spectrum of common approaches is given here (e.g., bottom-up vs. top-down scenario development, probabilistic vs. bounding handling of uncertainty), related to how individual numerical models for possible futures are converted into a determination as to whether the system is safe (i.e., how aleatoric uncertainty and scenarios are integrated through bounding or Monte Carlo approaches).

The role of bentonite in the repository concepts for radioactive waste in Germany: a review

Irrespective of the host rock and the repository concept, bentonite plays a central role in the geological disposal of radioactive waste by serving as the main sealing element in most repository concepts. Due to its favourable chemical, hydraulic and mechanical properties, bentonite is of paramount importance in the overall safety of a repository for radioactive waste. This work gives an overview of the use of bentonite in the German repository concepts in different host rocks. Starting with the current repository safety regulations in force in Germany, the principles for the design of the engineered barrier system are described. Among them, the principle of diverse redundancy has been established as the main design principle to fulfil the requirements of the Repository Safety Ordinance. This principle allows the arrangement of different geomaterials in the design of the geotechnical barriers where bentonite plays a key role. Bentonite is used in the German repository concepts in different host rocks as either buffer, backfill and/or sealing material. In clay and in crystalline rock, highly compacted bentonite blocks are considered for the sealing of disposal boreholes and for the construction of drift seals. Processed excavated material is mixed with bentonite to backfill the remaining voids inside the repository. For the closure of shafts, bentonite as binary mixture of briquettes and powder or as equipotential sand-bentonite-segments are considered. The present work also brings to light how bentonite is used in German repository concepts. We also discuss the differences between German and international geological disposal programmes in regards to the applications of bentonite. The innovative aspect of the German approach is demonstrated through the adoption of a dual bentonite/asphalt sealing system and the implementation of equipotential segments comprising layers of sand and bentonite. Thematic collection: This article is part of the Sustainable geological disposal and containment of radioactive waste collection available at: https://www.lyellcollection.org/topic/collections/radioactive

Evaluation of Thermodynamic Model of Pd(II) Complex Formation with Isosaccharinic Acid

AbstractPalladium-107 is one of the selected radionuclides in the safety assessment of geological disposal of radioactive waste. Although isosaccharinic acid (ISA) forms strong complexes with many elements and enhances element solubility, the thermodynamic evaluation of the complex of Pd with ISA has not been conducted. In this study, the solubility of Pd(OH)2 at pH 8.5–12.5 in the presence of ISA was investigated under inert gas (N2) atmosphere. Furthermore, the coordination state of aqueous Pd and ISA was investigated by X-ray absorption and Fourier transform infrared spectroscopy, respectively. According to experimental results, the number of OH ligands in the mixed complex depends on pH. The thermodynamic model and conditional equilibrium constants of the Pd-ISA complex were estimated by slope analyses of solubility experiments at different pH levels and ionic strengths based on the specific ion interaction theory. Hence, the impact of complexation with ISA on Pd(II) solubility under disposal conditions could be quantified using the proposed thermodynamic models in this study.

Influence of radiation on borosilicate glass leaching behaviors

Vitrification is widely recognized as a promising method for the geological disposal of high-level radioactive waste (HLW) worldwide. To ensure the safe disposal of radioactive waste, the borosilicate glass that vitrifies HLW must exhibit exceptional water resistance to prevent the possibility of groundwater corrosion and subsequent radioactive leaks. Radiation might change the water resistance of borosilicate glass. A series of zirconium-containing borosilicate glass with an irradiation dose of 0.3 dpa were utilized to examine the radiation effect on glass-water interaction. Scanning electron microscopy (SEM), Time-of-Flight Secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron spectroscopy (XPS), Inductively Coupled Plasma Optical Emission spectroscopy (ICP-OES) and Fourier transform infrared spectroscopy (FTIR) were used to investigate the leaching behavior of the non- and irradiated samples. The depth profile of the leached samples implied the interdiffusion dominated glass-water interaction. The results from FTIR and ICP-OES indicated that, after irradiation, the initial leaching rate increased by threefold. Additionally, the impact of different zirconium contents on the water resistance of borosilicate glass was also presented.

Stress field disruption allows gas-driven microdeformation in bentonite to be quantified

Geological disposal of radioactive waste is being planned by many countries. Bentonite clay is often included in facility design, providing a barrier to radionuclide migration. Gas, generated by the waste or corrosion of waste canisters, may disrupt the properties of the bentonite. Robust prediction of this interaction is, therefore, necessary to demonstrate safe facility evolution. In some cases, gas may deform the clay, resulting in localised flow; however, the nature of this deformation has been widely debated. Accurate numerical representation of this behaviour has been limited by a shortage of information on the degree/distribution of deformation. Using experimental data from gas injection tests in bentonite, we show that first order fluctuations in the stress field can provide this information. We show that hundreds of microdeformation events can be detected, with similar characteristics to established fracturing phenomena, including earthquakes and acoustic emissions. We also demonstrate that stress field disruption (i) is spatially localised and (ii) has characteristics consistent with gas pathway ‘opening’ and ‘closure’ as gas enters and exits the clay, respectively. This new methodology offers fundamental insight and a new opportunity to parameterise and constrain gas advection models in clays and shales, substantially improving our capacity for safe facility design.

Modelling of the Corrosion-Induced Gas Impact on Hydraulic and Radionuclide Transport Properties of Geological Repository Barriers

The geological disposal of high-level radioactive waste is the final step in the nuclear fuel cycle. It is realized via isolating the high-level radioactive waste in the geological environment with an appropriate system of engineered barriers. Radionuclides-containing materials must be isolated from the biosphere until the radioactivity contained in them has diminished to a safe level. In the case of high-level radioactive waste, it could take hundreds of thousands of years. Within such a long timescale, a number of physical and chemical processes will take part in the geological repository. For the assessment of radionuclide migration from a geological repository, it is necessary to predict the repository’s behavior once placed in the host rock as well as the host-rock response to disturbances due to construction. In this study, the analysis of repository barriers (backfill, concrete, inner excavation disturbed zone (EDZ), outer EDZ, host rock) thermo–hydraulic–mechanical (THM) evolution was performed, and the scope of gas-induced desaturation was analyzed with COMSOL Multiphysics. The analysis was based on modelling of a two-phase flow of miscible fluid (water and H2) considering important phenomena such as gas dissolution and diffusion, advective–diffusive transport in the gaseous phase, and mechanical deformations due to thermal expansion of water and porous media. The importance of proper consideration of temperature-dependent thermodynamic properties of water and THM couplings in the analysis of near-field processes was also discussed. The modelling demonstrated that such activities as 50 years’ ventilation of the waste disposal tunnel in initially saturated porous media, and such processes as gas generation due to corrosion of waste package or heat load from the waste, also led to desaturation of barriers. H2 gas generation led to the desaturation in engineered barriers and in a part of the EDZ close to the gas generation place vanishing soon after finish of gas generation, while the host rock remained saturated during the gas generation phase (50–100,000 years). Radionuclide transport properties in porous media such as effective diffusivity are highly dependent on the water content in the barriers determined by their porosity and saturation.

A Multiphysics Model for the Near-Field Evolution of a Geological Repository of Radioactive Waste

The safety and robustness of Deep Geological Repositories (DGRs) are of paramount importance for the long-term management of spent nuclear fuel from electricity generation. The introduction of a multi-barrier system, which includes the host rock formation and an engineered barrier system (including the bentonite buffer), has been a widely used approach to ensure the safety of DGRs. The assessment of the long-term safety of DGRs involves the mathematical modeling of the coupled thermal–hydraulic–mechanical–chemical (THMC) processes that occur in the near-field of the DGRs and their impact on the behaviour and engineering properties of the bentonite buffer. This paper presents a review of the THMC-coupled processes that arise in the bentonite buffer as well as a mathematical model governing such coupled processes. The model is verified against existing analytical solutions and validated against measured data of a thermal diffusion experiment in a sand bentonite column. Also, scoping analyses were performed to assess the influence of coupled THM processes on solute transport in clayrocks. The results of the numerical model closely matched those of the analytical solutions and experimental data demonstrating the capability of the provided mathematical model as well as the numerical approach in enhancing our comprehension of DGR behaviour. This enhanced comprehension will be valuable for safety prediction and assessment in the context of DGRs. The work presented in this paper is part of the Canadian Nuclear Safety Commission’s (CNSC) regulatory research to gain independent knowledge on the safety of the geological disposal of radioactive waste.

Survivability and proliferation of microorganisms in bentonite with implication to radioactive waste geological disposal: strong effect of temperature and negligible effect of pressure

As bentonite hosts a diverse spectrum of indigenous microorganisms with the potential to influence the long-term stability of deep geological repositories, it is essential to understand the factors influencing microbial activity under repository conditions. Here, we focus on two factors, i.e., temperature and swelling pressure, using a suspension of Cerny Vrch bentonite to boost microbial activity and evaluate microbial response. Suspensions were exposed either to different pressures (10, 12 and 15 MPa; to simulate the effect of swelling pressure) or elevated temperatures (60, 70, 80 and 90 °C; to simulate the effect of cannister heating) for four weeks. Each treatment was followed by a period of anaerobic incubation at atmospheric pressure/laboratory temperature to assess microbial recovery after treatment. Microbial load and community structure were then estimated using molecular-genetic methods, with presence of living cells confirmed through microscopic analysis. Our study demonstrated that discrete application of pressure did not influence on overall microbial activity or proliferation, implying that pressure evolution during bentonite swelling is not the critical factor responsible for microbial suppression in saturated bentonites. However, pressure treatment caused significant shifts in microbial community structure. We also demonstrated that microbial activity decreased with increasing temperature, and that heat treatment strongly influenced bentonite microbial community structure, with several thermophilic taxa identified. A temperature of 90 °C proved to be limiting for microbial activity and proliferation in all bentonite suspensions. Our study emphasizes the crucial role of a deep understanding of microbial activity under repository-relevant conditions in identifying possible strategies to mitigate the microbial potential within the deep geological repository and increase its long-term stability and safety.

Phyllite/bentonite mixture—an alternative effective buffer material for a geological disposal of radioactive waste

The use of phyllite (Phy) instead of quartz in mixtures with bentonite (B) is recommended as a buffer material for engineering barriers in a geological repository of nuclear waste. The recommendation is based on experimentally determined sorption properties of various Phy/B mixtures. The adsorption capacity of Phy/B mixtures (Phy/B: 75/25, 50/50, and 25/75), the removal efficacy of Eu(III) ions (an analog for fissiongenic lanthanides and actinides), and the rate of their binding reaction were studied using the batch adsorption equilibrium and kinetic experiments at different Eu(III) initial concentrations, solution pH, and solution to adsorbent (L/S) ratio. The adsorption capacity of the Phy/B mixtures increased with the increased bentonite content in the mixture depending on the L/S ratio and solution pH. The highest increase in the adsorption capacity of the Phy/B mixtures compared to phyllite was observed for the Phy/B proportions of 25/75 and 50/50. The rate of the Eu(III) adsorption was the best fitted by the pseudo-second-order kinetic model indicating that the adsorption rate was controlled by chemisorption. The Sips model provided the best correlation of the adsorption experimental data, indicative of more than one adsorption site. The results of this study show the advantage of the Phy/B mixtures in immobilizing Eu and certain fission products by combining adsorption properties of the materials.

Using multiple isotopes to determine groundwater source, age, and renewal rate in the Beishan preselected area for geological disposal of high-level radioactive waste in China

Understanding hydrogeological conditions is crucial for selecting and assessing the long-term safety performance of a high-level radioactive waste (HLW) disposal repository. Utilizing environmental isotopes as effective markers for analysing groundwater movement, this study investigates groundwater recharge sources, age, and renewal rates using multiple isotopes in China's potential HLW repository site, the Beishan area. The results indicated deep bedrock groundwater primarily derives from ancient precipitation infiltration under cold climatic conditions. A noteworthy distinction is that loose sedimentary groundwater exhibits higher tritium content (>10 TU) compared to bedrock groundwater (<3.2 TU). Groundwater within the recharge area, especially within gullies and piedmont slope deposits, is relatively youthful, with an age of less than 30 years and an annual renewal rate exceeding 5 %. In contrast, the shallow groundwater age in the intermountain basins and depressions of the discharge area generally exceeds 50 years, with an annual renewal rate often falling below 0.5 %. At the Beishan underground research laboratory site, deep groundwater at the disposal repository depth displays a corrected 14C age exceeding 8,000 years, indicating an extremely slow movement and alteration rate. As a result, the hydrogeological conditions in the Beishan area are expected to be relatively beneficial for ensuring the safety of HLW repository.

Glass/steel/clay interactions in a simulated radioactive waste geological disposal system

Deep geological storage is the accepted solution for the final disposal of high-level radioactive waste therefore, it is necessary to study the host rock of the planned Hungarian waste repository and the materials involved in the engineered barriers. The main goal was to understand the characteristics and stability of the glass/steel/claystone system, from the structural properties of the vitrified waste (borosilicate glasses) to the clay response in the repository. Repository conditions were applied during the experiments to understand the chemical evolution of the system. A triplicate setup was kept at 80 °C for 3, 7 and 12 months and post-mortem characterization was performed. No alteration products were observed with scanning electron microscopy energy dispersive X-ray spectroscopy measurements on the surface of the glass and Fe or in the clay after the end of the experimental period. Based on the elemental analysis of the liquid phase, the released amount of B, K, Si and Na increased, while that of Ca and Mg decreased compared to the baseline. The concentrations of Cl− and SO42− did not change significantly. Ca- and Mg-silicate precipitation was observed by X-ray photoelectron spectroscopy at the surface range of the borosilicate glasses because of the synthetic porewater treatment.

Identification of modern meteoric water, glacial meteoric water, and fossil seawater in a deep borehole at the coastal area of Horonobe, north Japan, using groundwater dating and paleoclimatic proxy methods

Groundwater flow in deep areas of coastal regions has attracted significant attention for geological radioactive waste disposal or geological CO2 storage. To investigate groundwater flow in coastal areas, groundwater dating methods with the potential to assess slow groundwater flow were used at depths of up to 1200 m at Hamasato, Horonobe, northern Japan. Multiple groundwater dating methods were applied using pore water in drilling core and pumping groundwater. This study shows that modern meteoric water, glacial meteoric water, and fossil seawater are distributed in sand and silt layers at 300–360 and 90–300 m in depth and in silt and mud layers below 800 m in depth, respectively. Modern meteoric water infiltrated after and glacial meteoric water infiltrated during the latest glacial period were identified using δD and δ18O values, estimated recharge temperature from noble gas concentrations, and 14C concentrations. The estimated recharge temperatures of modern and glacial meteoric waters were 8.1 ± 2.0 and 2.1 ± 2.0 °C, respectively, whereas the δD and δ18O values were −68 ± 3‰ and −10.3 ± 0.2‰, −81 ± 2‰ and −11.4 ± 0.3‰, respectively. The 14C age of modern meteoric water was 10–16 ka. However, the 14C age of glacial meteoric water could not be estimated because it was highly diluted by 14C-free CO2 from methanogenesis and marine carbonate dissolution. Fossil seawater was identified using δD, δ18O, 36Cl, and 4He. δD and δ18O values underwent water-rock interaction and approached inland fossil seawater with increasing depth. 36Cl/Cl values did not reach secular equilibrium in situ in the Yuchi Formation due to its relatively short geological age and consolidation-induced porosity changes. However, the Yuchi Formation seawater is considered extremely old because its 36Cl/Cl ratio is higher than that of modern seawater as a result of 36Cl production, which also explains the observed 36Cl/Cl increases with depth toward the secular equilibrium ratio (36Cl/Clse). 4He concentrations were in the order of 10−6 ccSTP/gw, corresponding to an in situ accumulation age of 1–2 Ma, neglecting the external flux. The contribution of external flux could be negligible for the short geological age and rapid sedimentation rates. 4He ages were equivalent to the geological age of the Yuchi Formation. Core investigations can interpolate groundwater investigations because cores, particularly those from low-hydraulic conductivity layers, can be collected continuously. In addition, stable and radioactive isotopes and noble gases can help identify modern meteoric water, glacial meteoric water, and fossil seawater, assisting in understanding the groundwater flow velocity.