Repository Design Research Articles

PROPERTIES OF GRANULATED BENTONITE MIXTURES FOR RADIOACTIVE WASTE DISPOSAL: A REVIEW

Bentonite has long been considered as a potential sealing material in engineered barrier systems (EBS) for the geological disposal of radioactive waste due to its favorable physical and chemical properties. In some disposal concepts, the research evolution has led to the adaption of granulated bentonite mixtures (GBM) as a candidate buffer/backfill material owing to its high compaction properties, operational advantages, and ability to close gaps between the seal and host rock. A thorough understanding of the behavior of GBM is essential for proper design and construction of an efficient repository. As compared to compacted bentonite blocks, studies on GBM are somewhat limited. Thus, a review of former experimental studies conducted on GBM over the past two decades was performed. The topics included compaction properties, thermo-hydro-mechanical properties, gas transport, and microstructure. This work comprises a summary table listing material properties, sample scale, methodology, test conditions, and graphical representation of results. Based on the review, prospects for further investigations/studies have also been recommended to understand the behavior of GBM.

Indoor Airflow Distribution in Repository Design: Experimental and Numerical Microclimate Analysis of an Archive

The majority of cultural heritage is stored in archives, libraries and museum storage spaces. To reduce degradation risks, many archives adopt the use of archival boxes, among other means, to provide the necessary climate control and comply with strict legislation requirements regarding temperature and relative air humidity. A strict ambient indoor climate is assumed to provide adequate environmental conditions near objects. Guidelines and legislation provide requirements for ambient indoor climate parameters, but often do not consider other factors that influence the near-object environment, such as the use of archival boxes, airflow distribution and archival rack placement. This study aimed to provide more insight into the relation between the ambient indoor conditions in repositories and the hygrothermal conditions surrounding the collection. Comprehensive measurements were performed in a case study archive to collect ambient, local and near-object conditions. Both measurements and computational fluid dynamics (CFD) modeling were used to research temperature/relative humidity gradients and airflow distribution with a changing rack orientation, climate control strategy and supply as well as exhaust set-up in a repository. The following conclusions are presented: (i) supplying air from one air handling unit to multiple repositories on different floors leads to small temperature differences between them. Differences in ambient and local climates are noticed; (ii) archival boxes mute and delay variations in ambient conditions as expected—however, thermal radiation from the building envelope may have a large influence on the climate conditions in a box; (iii) adopting night reduction for energy conservation results in an increased influence of the external climate, with adequate insulation, this effect should be mitigated; and (iv) the specific locations of the supply air and extraction of air resulted in a vertical gradient of temperature and insufficient mixing of air, and adequate ventilation strategies should enhance sufficient air mixing in combination with the insulation of external walls, and gradient forming should be reduced.

Architecture design of the nusantara traditional Wastra digital repository

The Nusantara traditional wastra (NTW) is the Indonesian biodiversity product that has not been formally identified as the national referral and has yet been commercially oriented. The research objectives were to formulate the understanding of NTW dan to construct a valid architecture design of the Nusantara Traditional Wastra Digital Repository (NTWDR). It was described as implementing the digital inventory business in the form of a smart portal template that acted as an infinite window of the complete Indonesian traditional wastra and as a marketplace for the Indonesian traditional wastra value chain. The research used the Neuroresearch approach of exploratory research through literature studies and FGD with the Delphi Technique for the validity of the design. The NTW’s boundaries and the NTWDR’s design in the form of a portal-based website are set as the results.

IoT-based Knowledge Repository Design for Supporting Knowledge Integration within the Marine Information System Study Program

Knowledge repository is commonly used to store and manage explicit knowledge from knowledge worker. The development of internet of things (IoT) in Industry 4.0 enables the improvement of quality and quantity of knowledge repository. This study focuses on developing IoT-based knowledge repository as a means to support knowledge integration within The Marine Information System Study Program. The study provides architectural designs of a knowledge repository that consists of 5 knowledge domains of marine information system and the design of IoT-based knowledge repository, both of which are based on reviews on relevant literatures and focus group discussion. The solution offered by the current study allows knowledge integration through Community of Practice as the provider and the user of the knowledge.

Resolving Dilemmas Arising during Design and Implementation of Digital Repository of Heterogenic Scientific Resources

The creation of digital repositories for archiving and disseminating scientific resources faces many challenges. These challenges relate not only to the modelling of the processes of preparing, depositing, sharing, maintaining, and curating resources. They also face the feasibility of the adopted assumptions and final implementation. Such kind of issues become particularly important in the case of processing of resources containing multimedia. The critical factor then becomes a properly designed architecture that supports efficient data processing and universal data presentation. This article aims to answer questions that may arise when approaching various designing and implementation dilemmas, such as how to handle processes in a digital repository, how to use cloud solutions in its construction, how to work with user interfaces, and how to process collected multimedia. The presented study explores their practical context based on the experiences gained during the AZON platform’s implementation. This platform stores tens of thousands of scientific resources: books, articles, magazines, teaching materials, presentations, photos, 3D scans, audio and video files, databases, and many more. It serves as a running example for all presented proposals.

HM and THM interactions in bentonite engineered barriers for nuclear waste disposal

Bentonite-based engineered barriers are a key component of many repository designs for the confinement of high-level radioactive waste and spent fuel. Given the complexity and interaction of the phenomena affecting the barrier, coupled hydro-mechanical (HM) and thermo-hydro-mechanical (THM) numerical analyses are a potentially useful tool for a better understanding of their behaviour. In this context, a Task (INBEB) was undertaken to study, using numerical analyses, the hydro-mechanical and thermo-hydro-mechanical Interactions in Bentonite Engineered Barriers within the international cooperative project DECOVALEX 2019. Two large scale tests, largely complementary, were selected for modelling: EB and FEBEX. The EB experiment was carried out under isothermal conditions and artificial hydration and it was dismantled after 10.7 years. The FEBEX test was a temperature-controlled non-isothermal test combined with natural hydration that underwent two dismantling operations, a partial one after 5 years of heating and a final one after a total of 18.4 years of heating. Direct observation of the state of the barriers was possible during the dismantling operations so that the evolution of barrier heterogeneity under transient conditions could be determined. Four teams performed the HM and THM numerical analyses using a variety of computer codes, formulations and constitutive laws. For each experiment, the basic features of the analyses are described and the comparison between calculations and field observations are presented and discussed. Comparisons involve measurements performed during the performance of the test and data gathered during dismantling. A final evaluation of the performance of the modelling closes the paper.

Safety Assessment on Long-term Radiological Impact of the Improved KAERI Reference Disposal System (the KRS+)

The Korea Atomic Energy Research Institute (KAERI) has developed geological repository systems for the disposal of high-level wastes and spent nuclear fuels (SNFs) in South Korea. The purpose of the most recently developed system, the improved KAERI Reference Disposal System Plus (KRS+), is to dispose of all SNFs in Korea with improved disposal area efficiency. In this paper, a system-level safety assessment model for the KRS+ is presented with long-term assessment results. A system-level model is used to evaluate the overall performance of the disposal system rather than simulating a single component. Because a repository site in Korea has yet to be selected, a conceptual model is used to describe the proposed disposal system. Some uncertain parameters are incorporated into the model for the future site selection process. These parameters include options for a fractured pathway in a geosphere, parameters for radionuclide migration, and repository design dimensions. Two types of SNF, PULS7 from a pressurized water reactor and Canada Deuterium Uranium from a heavy water reactor, were selected as a reference inventory considering the future cumulative stock of SNFs in Korea. The highest peak radiological dose to a representative public was estimated to be 8.19×10-4 mSv‧yr-1, primarily from 129I. The proposed KRS+ design is expected to have a high safety margin that is on the order of two times lower than the dose limit criterion of 0.1 mSv‧yr-1.

A study of thermal pressurization and potential for hydro-fracturing associated with nuclear waste disposal in argillaceous claystone

We present coupled Thermo–Hydro–Mechanical (THM) modeling of geologic nuclear waste disposal in argillaceous claystone, focusing on thermally-induced pressure changes and the potential for such pressure changes to induce hydro-fracturing. To investigate this possibility, we first conduct a three-dimensional repository scale model, with host rock properties, repository design, and nuclear waste decay heat functions derived from the French concept of geologic disposal in argillaceous claystone. The model simulations show that the highest potential for hydro-fracturing occurs between emplacement micro-tunnels (cells) at the center rather than at the edge of the repository. We further investigate the use of a two-dimensional single cell model as a simpler surrogate for a full three-dimensional model. Our results reveal that such geometric simplification is reasonably accurate for modeling coupled THM processes at the center of the repository, though it overestimates the likelihood for hydro-fracturing and substantially overpredicts ground surface uplift. A parameter study shows the importance of adjacent higher permeability geological layers that play a significant role in dissipating overpressure in the host rock layer. Finally, the study shows the importance of the spacing between emplacement tunnels, which if too short results in a higher fluid pressure and a strongly increased potential for hydro-fracturing. Overall, the study suggests, the limiting factor in the thermal management and design of a repository is not necessarily the maximum temperature in the engineered barrier system near the waste packages, but rather the more modest host rock temperature between emplacement tunnels, due to the potential for thermal damage.

Swelling and gas transport characteristics of saturated compacted bentonite/sand samples considering the scale effect

The generation and migration of gas is an unavoidable process that should be considered in the safety evaluation of nuclear waste geological repositories. The first aim of this study is to determine whether the gas will affect the swelling and sealing properties of the bentonite-based barrier. The results show that the gas/water can significantly affect the pore pressure of the material, which can further affect the total pressure of the compacted bentonite/sand sample. There exists a mathematical relationship between the gas pressure, total pressure, and effective swelling pressure. Furthermore, the influence of the size effect on the swelling properties and gas breakthrough properties of compacted bentonite/sand mixture was also investigated. The change in the sample’s size has a limited impact on the swelling pressure of the sample, but delays the water saturation process. Concerning the gas breakthrough properties, the influence of the sample’s size is also not apparent. Finally, the results of laboratory experiments are compared with the results of in situ experiments. The results show that the laboratory experiments have a good reference value based upon the key indicators, such as swelling pressure, water/gas permeability, and gas breakthrough pressure. This means that the results obtained from the small-scale laboratory experiments are reliable and can be referenced for the in situ design of the nuclear waste geological repository.

Creep and swelling of bentonite for the safety of disposal pit in high-level radioactive waste repository

Displacement of the canisters with high-level radioactive waste (HLW) could be induced by creep and swelling of buffer material bentonite in the disposal pit of HLW geological repository. The displacement of the canisters could lead to the safety of HLW repository decrease. Several large scale experiments with bentonite and heater which was only regarded as components that would simulate the reference canister with respect to dimensions, weight and thermal emission were conducted in situ and laboratory respectively. The evolution of displacement of the heater, RH and stress in the bentonite indicate that the displacements of the heater are controlled by consolidation and volumetric/deviatoric creep of the bentonite under the heater induced by weight of heater, thermal expansion of heater and bentonite with heating, as well as swelling process of bentonite with the hydration. The canisters could move upward slightly in disposal pit during the early phase of HLW disposal. With the saturation of bentonite and stress redistribution in bentonite, the canisters could remain steady and minor fluctuation. After the bentonite in the disposal pit saturated fully, the canisters might move downward due to the weight of canisters. The thickness of buffer material around HLW canister and long-term stability of HLW canister should be considered in the design of the HLW repository.The parameters and evaluation of THM processes taking place in the compacted bentonite-buffer during the early phase of HLW disposal can provide a reliable database for numerical modeling and further investigations of EBS, and the design of HLW repository.

Design and Analysis of the E-Journal Repository for Final Projects and Student Practices in the D3 Computer Engineering

Higher education institutions are the main institutions in creating young people who can be ready to enter the world of work and industry, and one of the educational programs that take part in vocational education. Vocational education is higher education that is directed at focusing certain applied skills. Harapan Bersama of Polytechnic is one of the vocational education institutions that provides Human Resources (HR) to become the younger generation as practitioners in industry, companies, or other stoke holders. In the D3 Computer Engineering Study Program, each batch can graduate approximately 300 graduates, where each graduate will produce one scientific work from the final project research conducted. Likewise, with students who do practical work (KP), every student who does KP will produce scientific papers. But all the results of this scientific work, namely the research report of the Final Project and the Job Training Report are still being submitted to the Study Program in one compact disk (CD). This turned out to be a problem for the Study Program because from each batch, around 300 compact disks (CDs) were collected from the results of scientific work from the practical work and 300 compact disks (CDs) from the final project research outputs. Physical data in the form of a compact disk (CD) requires a large space for its placement. Meanwhile, the condition of the D3 Computer Engineering study program room makes it impossible to place the physical form. And along with technological developments, this physical form can be replaced by soft files in the form of e-journals or e-reports. This needs to be done in line with the paradigm shift from conventional libraries to e-libraries. With the existence of SIPESTA or the information system for the completion of this Final Project, the results of writing scientific papers are uploaded and become a digital trace of all scientific papers that have been carried out by all D3 Computer Engineering students. And so if this data is needed it will be easy to find because the database has been well managed.

Can CO2 sequestration in basalt efficiently reduce greenhouse gas emission?

ABSTRACT The research on the Columbia River Basalt is a unique combination of projects that minimise CO2 emissions to the atmosphere. Both are underground waste disposal projects: CO2 waste versus nuclear waste. The recent Wallula CO2 project and the previous nuclear-waste project in the Columbia River Basalt (CRB), USA, provide the database for a high-capacity CO2 sequestration model. Due to geomechanical constraints, the injection rate of CO2 sequestration must be limited in order not to jeopardise the integrity of the reservoir and cap rock. The interbed in the continental flood basalt tested in the Wallula project only allows injection at a rate in the range of 9–19 kg CO2/s, depending on permeability (4 × 10−14–10−13 m2) and porosity (0.1–0.15). At the end of a 50-year injection period, the fraction of CO2 converted to carbonate minerals is 37.1–67.1%. Underground space for waste disposal is a rare asset. The Columbia River Basalt occupies an area of 200,000 km2. Fifty years of CO2 sequestration from a single well would require about the same fraction of the area as that of a nuclear waste repository (0.025%). The repository design is for a capacity of 70,000 MTHM (metric tons heavy metal). If all the waste is spent nuclear fuel, it originates from 1.2 × 104–8.4 × 104 TWh electric power production, depending on reactor type. The CO2 injection well operating at maximum capacity (19 kg CO2/s) represents 50 TWh generated in a gas power station minus the energy consumed for CO2 separation, i.e. less than 0.4% of the nuclear option.

Influence of Geological and Environmental Factors on the Reconsolidation Behavior of Fine Granular Salt

Understanding the consolidation behavior of granular salt is of great significance for salt cavern repository design and the corresponding long-term safety assessments. To evaluate the influence of environmental and geological factors on the reconsolidation behavior of fine granular salt, a series of orthogonal array design experiments were performed. The experimental results showed that temperature, compressive stress, moisture content and compression time had significant impacts on the compaction properties of granular salt. The compressive stress exerted the greatest impact on porosity of the granular salt, which decreased the porosity. An increase in moisture content (within 3%) in the granular salt sample substantially reduced the porosity of the sample, whereas this effect was limited when moisture exceeded 3%. In the process of granular salt compaction, all of the deformation mechanisms were temperature dependent. The correlation between porosity and permeability of the dried compacted salt samples was independent of the environmental and geological factors during the compaction of the granular salt. The use of granular salt with a smaller particle size in the compacted salt backfill can improve its sealing performance. In the transient loading stage of granular salt compaction, the porosity decreased rapidly under stress to form a denser layer, which was mainly accomplished by particle rearrangement and cataclastic flow. However, in the constant-load creep stage, the additional porosity reduction was dominated by grain boundary processes and crystal plasticity mechanisms, including dislocation creep, pressure-solution creep and recrystallization.

Stability of plutonium oxide nanoparticles in the presence of montmorillonite and implications for colloid facilitated transport

The physical and chemical stability of PuO2 nanoparticles (intrinsic colloids) in groundwater will control their transport and may affect the performance of high-level radioactive waste repositories. We examined the chemical stability of two types of PuO2 nanoparticles at both 25 and 80 °C. The “alkaline” PuO2 nanoparticles were prepared by neutralizing an acidic Pu(IV) solution with dilute NaOH to pH ~9.5. The “acidic” PuO2 nanoparticles were precipitated from 0.1 M nitric acid by heating a Pu(IV) solution at 60–80 °C for 30 min. The chemical stability of these PuO2 nanoparticles was tested in the presence of montmorillonite, a common mineral in the environment and potentially relevant backfill material in some nuclear waste repository designs. The “alkaline” PuO2 nanoparticles were found to be unstable over a timescale of months at both 25 and 80 °C, with elevated temperature enhancing their dissolution rates and sorption to montmorillonite. PuO2 nanoparticle dissolution rates decreased with increasing Pu concentration, consistent with solution saturation. The “acidic” PuO2 nanoparticles appeared to remain stable for much longer than the “alkaline” PuO2 nanoparticles. The “alkaline” PuO2 nanoparticle dissolution rate constants were as high as 10−11.9±0.4 mol m−2 s−1 and 10−11.2±0.2 mol m−2 s−1 at 25 and 80 °C, respectively, while the “acidic” PuO2 nanoparticle dissolution rate at 80 °C was 10−13.5 mol m−2 s−1. Based on transmission electron microscopy, the “alkaline” and “acidic” PuO2 nanoparticles were of similar size (2.5–4.5 and 2–3 nm nanoparticles, respectively). However, the “acidic” PuO2 nanoparticles formed more ordered nanoparticle aggregates. Our results suggest that the specific conditions experienced during PuO2 nanoparticle formation could significantly affect the stability of PuO2 in the presence of competing sorption processes and, in turn, the relative importance of intrinsic versus pseudocolloid transport in the environment.

Understanding K‐12 teachers’ intention to adopt open educational resources: A mixed methods inquiry

AbstractTeachers in K‐12 settings often teach out of textbooks in order to provide differentiated instruction. Open educational resources (OER) might be an effective alternative to traditional textbooks for K‐12 teachers because of a free access to a rich collection of open‐licensed educational materials. Understanding how to encourage teachers to accept OER is thus critical. However, existing evidence mainly concerns the advantage of OER in cost reduction but overlooks the merit of openness. To fill this gap, this mixed methods inquiry, implementing the technology acceptance model, integrated qualitative and quantitative findings to obtain a comprehensive understanding of teachers’ intentions of adopting OER in K‐12 settings. This study found that perceived ease of use and perceived usefulness predicted K‐12 teachers’ intention to adopt OER with attitudes toward OER as a mediating variable. Perceived ease of use also determined perceived usefulness. Teachers’ perceptions of OER adoption were also examined for additional insight into the quantitative findings. Practical implications of adopting OER in K‐12 curriculum were discussed. Practitioner NotesWhat is already known about this topic K‐12 teachers need to teach out of textbooks to provide differentiated instruction but publishers usually charge teachers high subscription fees without giving them permission to customize the resources. Open educational resources (OER) allow teachers to retain, reuse, revise, remix and redistribute free open‐licensed resources. Teachers’ intention to use technology predicts their actual technology use, but evidence regarding reinforcing teachers’ intention to adopt OER is limited. What this paper adds This paper demonstrates the perceived ease of use of OER is a primary factor in how useful teachers consider them to be, how teachers feel about them in general, and how likely they are to use OER. This paper shows perceived usefulness of OER determines teachers’ attitudes toward and intention to use OER. This paper shows teachers’ attitudes toward OER mediate the effect of perceived ease of use and perceived usefulness on their intention to adopt OER. Implications for practice and/or policy Simplifying the search process by improving the design of OER repositories to reinforce teachers’ perception that OER are easy to use. Establishing quality assurance of OER to strengthen teachers’ perception that OER are useful. Advocating open educational practices in K‐12 settings to engage students and teachers in the creation and curation of open content. Initiating nationwide campaigns (eg, #GoOpen) to engage school districts and teachers in producing and publishing high‐quality OER.

Variation of swelling pressure, consolidation characteristics and hydraulic conductivity of two Indian bentonites due to electrolyte concentration

The hydro-mechanical properties of the buffer material play an important role in the design of deep geological repositories. This paper presents the effect of various electrolyte concentrations on swelling pressure, consolidation characteristics and hydraulic conductivity of two different Indian bentonites. Constant volume swelling pressure tests on compacted bentonite specimens as well as consolidation tests on saturated bentonite specimens were carried out by supplying 0, 0.1, 0.5 and 1.0 N NaCl and CaCl2 solutions. The change in morphology and microstructure of bentonite specimens were examined by Scanning Electron Microscope (SEM) and XRD analysis. The hydraulic conductivity was calculated based on consolidation test results. At a dry density of 1.4 Mg/m3 both swelling pressure and hydraulic conductivity of divalent bentonite were found to be approximately 2.9 and 7.3 times higher than that of monovalent bentonite when saturated with deionized water. The electrolyte solutions altered the morphology, microstructure and hydro-mechanical properties of the monovalent bentonite significantly; however, the effect was found to be negligible for divalent bentonite. An empirical equation is proposed to predict the hydraulic conductivity of the bentonites. A good correlation between experimental and predicted hydraulic conductivity of bentonites is obtained. The divalent bentonite was found to be better suitable engineered barrier material in the electrolyte environment, whereas monovalent bentonite was found preferable at low salinity conditions.

Cassandra-based data repository design for food supply chain traceability

PurposeThe purpose of this paper is to design a supply chain database schema for Cassandra to store real-time data generated by Radio Frequency IDentification technology in a traceability system.Design/methodology/approachThe real-time data generated in such traceability systems are of high frequency and volume, making it difficult to handle by traditional relational database technologies. To overcome this difficulty, a NoSQL database repository based on Casandra is proposed. The efficacy of the proposed schema is compared with two such databases, document-based MongoDB and column family-based Cassandra, which are suitable for storing traceability data.FindingsThe proposed Cassandra-based data repository outperforms the traditional Structured Query Language-based and MongoDB system from the literature in terms of concurrent reading, and works at par with respect to writing and updating of tracing queries.Originality/valueThe proposed schema is able to store the real-time data generated in a supply chain with low latency. To test the performance of the Cassandra-based data repository, a test-bed is designed in the lab and supply chain operations of Indian Public Distribution System are simulated to generate data.

Experimental Study on Characteristics and Mechanism of Macrography and Mesoscopic Failure of Deep Granite from Beishan

Because of its good stability, high strength and low permeability, granite is considered as an ideal surrounding rock for geological disposal of high-level radioactive waste, which is also the main candidate surrounding rock for high-level radioactive waste disposal project in China. Rock mechanics is one of the important problems for site selection, design, construction and operation of geological repository. It is of great theoretical and practical value to study the failure law of rock from the microcosmic aspect, to link the microcosmic failure morphology characteristics with the mechanical mechanism of rock macro fracture failure, and finally to establish a bridge between microcosmic failure mechanism and macro fracture analysis of rock. We carried out uniaxial compression test, triaxial compression test under different confining pressures, Brazilian splitting test and direct tensile test for the deep granite from the core of No. BS28 hole in Beishan area with depth of 560–680 m. SEM and EDS was carried out for the fracture surface under different test conditions. The macro and micro failure characteristics of granite under different test conditions are analyzed: It is basically the splitting failure phenomenon dominated by tensile failure after the uniaxial compression test, while the failure of the triaxial test specimen are basically all form a large inclined failure surface which show the shear failure phenomenon. It shows obvious brittle tensile failure under direct tensile test, while not simply tensile failure under Brazil split test. The micro structure and mineral composition of rocks are closely related to their macro mechanical properties. Due to the existence of other impurities, Beishan granite has a certain degree of discreteness, and because of the different composition, its fracture presents different forms. These studies provide the necessary basis for the design and construction of the geological disposal of high-level radioactive waste.

Removal of Cesium from Simulated Spent Fuel Dissolver Liquor

With a resurgence of the nuclear industry’s fortunes, waste management will be an even greater consideration; reducing wastes, better segregation and treatment that lower the impact on waste storage facilities and repositories, in particular geological repositories will help the sustainability of the industry. We at the University of Central Lancashire (UCLan) proposed in a previous publication a sequential chromatographic separation process, Alternative Reprocessing Technology (ART) for Fission Products (FPs) and Minor Actinides (MAs) separation from spent fuel dissolver liquor, as an improvement to/replacement for PUREX (Plutonium Uranium Redox Extraction). This publication addresses the removal of one particular fission product, cesium, and its impact on waste management, and down-stream PUREX operations. Although our proposed process is still in its infancy, its impact on the PUREX process could be significant, with major gains in the separation circuit, waste management of High Level Waste (HLW) and subsequently waste disposal to and design of a geological repository. This paper briefly describes; our concept, some preliminary experimental data and why re-classification of the bulk of HLW (High Level Waste) to Intermediate Level Waste (ILW) would be possible.

Investigating the contribution of claystone to the swelling pressure of its mixture with bentonite

Compacted MX80 bentonite/Callovo-Oxfordian (COx) claystone mixture has been considered as a possible sealing/backfilling material in the French deep geological radioactive waste disposal. The swelling pressure of such mixture is an important factor in the design and long-term safety assessment of deep geological repositories. In this study, constant-volume swelling pressure tests were performed on the mixtures with different claystone fractions and dry densities. The test results show that the swelling pressure of the mixtures decreased with the increasing claystone fraction and decreasing dry density. According to the experimental results, the contribution of claystone to the global swelling pressure was further investigated. It was found that the deformation of claystone and its contribution to swelling pressure was highly dependent on the claystone fraction. As the claystone fraction was larger than 30%, the claystone in the mixture swelled, contributing to the global swelling pressure; On the contrary, as the claystone fraction was less than 30%, the swelling of claystone was inhibited by the bentonite and it worked an inert material without any contribution to the swelling pressure.