New Rapid Evaluation for Long-Term Behavior in Deep Geological Repository by Geotechnical Centrifuge—Part 2: Numerical Simulation of Model Tests in Isothermal Condition

2016 ◽  
Vol 50 (1) ◽  
pp. 159-169 ◽  
Author(s):  
Masataka Sawada ◽  
Soshi Nishimoto ◽  
Tetsuji Okada
2011 ◽  
Vol 322 ◽  
pp. 353-356
Author(s):  
Qing Chun Yang

Safety assessment of nuclear waste disposal in a deep geological repository requires understanding and quantifying radionuclide transport through the hosting geological formation. Determining diffusion parameters under real conditions is necessary for the performance assessment of a deep geological repository where high level wastes are placed for safety disposal. The in situ diffusion and retention (DR) experiments are designed to study the transport and retention properties of the Opalinus clay formation. In this paper, a scoping numerical simulation is performed in Opalinus Clay, The simulated results for all the traces illustrate that the maximum transport distance perpendicular to the bedding is larger in the isotropic case and those along the bedding is larger in the anisotropic case. Tracer depletion in the isotropic case is a little larger than in the anisotropic case. Deuterium and iodide can be detected in the other interval but strontium can’t. Since the length of injection interval is shorter than the transport distance, the anisotropy effect is clearly measurable. This numerical simulation of diffusion experiment aims at contributing to the optimum design of the experiment. The results of this experiment will provide additional insight into the role of diffusion anisotropy and sorption parameters for radionuclides in clays.


2019 ◽  
Vol 133 ◽  
pp. 02005
Author(s):  
Markéta Camfrlová

Nuclear energy accounts for a significant part of the total energy production in the Czech Republic, which is currently facing a problem dealing with the high-level radioactive waste (HLW) and the spent nuclear fuel (SNF). Deep repository is the safest option for storage of HLW. Rock environment of the area must guarantee the stability of the deep geological repository for at least 100,000 years. The aim of the research is a long-term evaluation of the climatic changes of the hypothetical area of interest, which corresponds to the candidate sites for deep geological repository in the Czech Republic. The occurrences of endogenous and exogenous phenomena, which could affect site stability, were evaluated. Concerning exogenous processes, research focuses mainly on the assessment of climatic effects. The climate scenarios for the Central Europe were examined – global climate change, glaciation, and the depth of permafrost as well as CO2 increase.


2020 ◽  
Vol 225 ◽  
pp. 06012
Author(s):  
Dorota Flamíková ◽  
Vladimír Nečas

The deep geological repository system provides long-term protection against the undesirable effects of ionizing radiation on the population and the environment. An important part of the long-term safety strategy is development of a monitoring program that collects information about the behaviour of the deep geological repository throughout its whole lifetime. A simplified model of the disposal system, geosphere, and biosphere was developed using the GoldSim simulation tool to demonstrate the behaviour of the hypothetical deep geological repository located in crystalline rocks. Also an initial model of the reference biosphere was created based on the scenario of an agricultural habitation (normal evolution scenario) and it was developed based on the recommendations provided in the BIOMASS methodology. After a significant period of time, disposal containers will be degraded and evolution changes in the repository system will occur. Several important parameters appear in the annual effective dose calculation for an individual from critical exposure group within the reference biosphere model. One of them are, for example, distribution coefficients and so-called translocation factors that define the transported rate of released radionuclides into the environment. This paper provides a view into the selected part of the deep geological repository through the data obtained by monitoring during the selected period of time. Simulations describing changes in the repository system. The aim of this contribution is to evaluate the impact of selected changes on the annual effective dose for an adult individual from a critical exposure group while it is assumed, that the respondent consumes contaminated crops and animal products. This model includes various biosphere components and multiple exposure pathways such as inhalation, ingestion and external exposure.


Author(s):  
Leif G. Eriksson

Abstract Retrieval (and various permutations of this term) of long-lived radioactive wastes/materials (LLRMs) from deep geological repositories is a “concept” currently believed to increase public confidence in, and acceptance of, national LLRM-repository programs. If the “retrievability concept” provides the missing link to increased public acceptance, which is imperative in a democratic society for the siting and development of a deep LLRM repository, then the understanding and expectations of the terms used must be clearly defined, and the associated benefits and shortcomings clearly explained, to the public. To quote the Danish mathematician and philosopher Piet Hein: Knowing what you knowest not is in a sense omniscience. Based on more than 20 years of involvement in the development of deep geological repositories for LLRMs in the United Sates of America and abroad, it is the preliminary conclusion of this author that retrievability conveys a false positive because it: 1. Does not add any appreciable post-closure physical safety to current and future generations and environments. 2. Could compromise (but does not necessarily have to) the long-term integrity of the disposal system. 3. Conveys the erroneous message that this generation does not have confidence in its ability to design, construct, decommission, and close a deep geological repository for LLRMs, in a manner that provides long-term containment and isolation of the emplaced LLRMs.


2021 ◽  
Vol 1 ◽  
pp. 271-273
Author(s):  
Johann Arne Othmer ◽  
Karl-Heinz Lux ◽  
Ralf Wolters ◽  
Jörg Feierabend

Abstract. Within the framework of disposal of radioactive waste in Germany, the question arises how trust in the safety of a future deep geological repository and therefore the acceptability can be increased. One aspect that could contribute to this is the option of long-term monitoring of a deep geological repository by participation of the civil society. Whether and exactly how long-term monitoring of a deep geological repository leads to more trust, is being researched in the transdisciplinary work package TRUST within the research project TRANSENS in cooperation with members of the civil society. For the transdisciplinary processing of specific repository topics, a group of 16 persons from the civil society were recruited, none of which were stakeholders with respect to the topic of repositories. This group is designated as the Working Group Civil Society (AGBe). With the help of 12 members of the AGBe a first workshop on the topic “Monitoring and trust” was carried out on 13 March 2021, supported by partners of the LUH-IRS, the TUBS-IGG and the ETH-TdLab. This article is concerned with the preparation work, the course itself and the knowledge gained from the workshop. It deals with the preparation work in the form of a website and a report on information of the AGBe suitable for those who have been addressed, which has meant a challenge in view of the complexity of the topic of monitoring of a deep geological repository and prior knowledge of the AGBe. Furthermore, the course of the workshop, which was carried out online due to the coronavirus pandemic, is discussed, in which the 12 members of the AGBe and 10 scientists came together. The workshop began with a brainstorming on the topic of monitoring. This was followed by two specialist lectures, in which information on deep geological disposal and monitoring as well as the possibilities and limits of monitoring and monitoring conceptions was presented. The members of the AGBe were then divided into three groups, in which the central research questions of the workshop were discussed: Does a long-term near-field monitoring contribute to trust in the safety of deep geological disposal of radioactive waste? Which aspects of monitoring conceptions could increase trust in the implementation of near-field monitoring and which do not? After the presentation of the results from the group discussion a common discussion was first carried out in the plenum, in which a picture of the sentiments within the AGBe was finally formulated. Furthermore, the knowledge from the three discussion formats of the workshop is presented in this article. This includes the characterization of information and communication with the civil society as a central aspect in relationship with monitoring and trust. Furthermore, it showed that the AGBe views the long-term monitoring of a repository as a suitable measure for gaining trust. However, which aspects of monitoring conceptions contribute significantly to trust in the safe storage of radioactive waste is less clear after this first workshop and could not be conclusively answered. The results of this workshop with the AGBe reflect a first impression in the discussion on monitoring and trust. As monitoring is a complex topic with many interfaces on repository storage and sealing concepts, repository processes and multiple physical simulations as well as on societal topics, the discussion with the AGBe on the topic of monitoring should be continued during the course of the project. Thereby, it must be taken into consideration if the first positive assesments as well as the first AGBe specific requirements regarding long-term near-field monitoring activities will change with increasing knowledge.


2021 ◽  
Author(s):  
Lukas Vondrovic ◽  
Jaromir Augusta ◽  
Antonin Vokal ◽  
Katerina Konopacova ◽  
Eva Popelova ◽  
...  

<p>The future deep geological repository for radioactive waste in the Czech Republic will be constructed in a suitable crystalline rock mass around 500 metres below the earth’s surface. The commencement of operation is planned for 2065. The current DGR development phase is devoted principally to the determination of the optimum disposal concept and the selection of the most suitable site. A total of nine potential sites have been assessed with the aim of reducing their number to four.</p><p>The data set subjected to assessment included site descriptions from the geological point of view (3D geological and hydrogeological model), and long-term site stability (seismotectonic, climate and erosion) and geomechanical data. A further assessed dataset included information on construction issues and on the evaluation of both environmental characteristics and the presence of groundwater resources. All the assessed characteristics were derived from surface-based exploration without the need for borehole drilling.</p><p>The key criteria reflected the three main areas of concern i.e. long-term and operational safety (including geological and hydrogeological indicators), technical feasibility and environmental impacts. The assessment of the sites was performed in two stages. The first stage involved the assessment of the probability of fulfilling the exclusion criteria (total 26), while the second stage involved the mutual comparison of the sites in terms of the defined key criteria (total of 13, divided into 38 indicators). The second stage involved the determination of weightings for the various criteria and indicators via the application of the SAATY method for the expert comparison of the significance of criteria. This method distinguished between relatively strongly weighted and less weighted criteria. The sites were graded with respect to the value estimation of the criteria; moreover, the grading of the sites considered various types of data.</p><p>A total of eight calculations were performed for five scenarios using various procedures for the estimation of the weightings and for data normalisation purposes. The first assessment stage indicated that all the sites fulfilled the DGR site assessment methodology requirements. The second stage, which comprised the assessment of the comparison of the site calculations (assessment grades) for each of the sites, was based on the levels of significance of the indicators and criteria and the resulting representative values for each site. The results of the subsequent comparison calculations indicated that the same four sites always occupied the first four positions with only minor variations in the order. The differences in the gradings of the four most suitable sites and the four relatively less suitable five sites ranged between 11% and 17.8% (between the fourth and fifth sites), which convincingly differentiated between the two groups of sites. One site was always in last position according to the calculations. In compliance with the assessment results, the four  sites were subsequently recommended to the Government of the Czech Republic for further follow-up research and analysis. Those sites that were not recommended for the next stage of research will continue to be considered as reserve (i.e. backup) sites.</p>


1989 ◽  
Vol 176 ◽  
Author(s):  
R. Khaleel ◽  
T. Legore

ABSTRACTScaling considerations relevant to porous media flow are reviewed. An analysis approach is presented for determining the sizing requirements of a large-scale, hydrology physical model. The physical model will be used to validate performance assessment codes that evaluate the long-term behavior of the repository isolation system. Numerical simulation results for sizing requirements are presented for a porous medium model in which the media properties are spatially uncorrelated.


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