scholarly journals Coupled Processes Modeling in Rock Salt and Crushed Salt Including Halite Solubility Constraints: Application to Disposal of Heat-Generating Nuclear Waste

2018 ◽  
Vol 124 (1) ◽  
pp. 159-182 ◽  
Author(s):  
Laura Blanco-Martín ◽  
Jonny Rutqvist ◽  
Alfredo Battistelli ◽  
Jens T. Birkholzer
Keyword(s):  
Nuclear Waste ◽  
Rock Salt ◽  
Coupled Processes

THM analysIs of natural and engineered barriers for large excavations in deep nuclear waste repository

2021 ◽  
Author(s):  
Matias Alonso ◽  
Jean Vaunat ◽  
Minh-Ngoc Vu ◽  
Antonio Gens
Keyword(s):  
Nuclear Waste ◽  
Host Rock ◽  
Thermal Load ◽  
Water Pressure ◽  
Large Diameter ◽  
Coupled Processes ◽  
Nuclear Waste Repository ◽  
Damaged Zone ◽  
Waste Repository ◽  
The Impact

<p>Argillaceous rocks have great potential as possible geological host medium to store radioactive waste.  Andra is leading the design of a deep geological nuclear waste repository to be located in the Callovo-Oxfordian formation. In the framework of this project, excavations of large diameter galleries are contemplated to access and to store intermediate-level long-lived nuclear waste at repository main level. The closure of the repository will be realized by building sealing structures of expansive material.</p><p>The response of such structures is affected by several thermo-hydro-mechanical coupled processes taking place in the near and far field of the argillaceous formations. They include the formation of an excavation induced damaged zone around the galleries, the impact of the thermal load on host rock pressures and deformations, the long-term interaction with support concrete structural elements and the hydration and swelling of sealing materials. As a result, the study of their performance requires to perform simulation works of increasing complexity in terms of coupling equations, problem geometry and material behaviour. As well, challenging computational aspects, as the ones related to fractures creation and propagation, have to be considered for a representative analysis of the problem.</p><p>This work presents advanced large scale THM numerical models to provide keys about the response of the host rock around large diameter galleries during excavation and further thermal load as well as to analyse the performance of large diameter sealing structures. Particular features of the models include on one hand advanced constitutive laws to capture the development of the fractured zone around excavations, the behaviour of host rock/gallery support interfaces and the multi-scale response of bentonitic backfill. On the other hand, simulations consider geometries including constructive details of interest at decimetre scale within large discretization domain covering the whole formation stratigraphic column.</p><p>These challenging simulations provided qualitative and quantitative results on key aspects for natural and engineered barrier integrity, like extension of the damaged zone, impact of the thermal load and water pressure variations in the surrounding geological layers, duration of natural hydration phase, swelling pressure development and seals global stability.</p>

scholarly journals Reservoir Response to Heat Generating Nuclear Waste Disposal in Bedded Salt

2020 ◽  
Author(s):  
Richard Jayne ◽  
Kristopher Kuhlman
Keyword(s):  
United States ◽  
Nuclear Waste ◽  
The United States ◽  
Department Of Energy ◽  
Coupled Processes ◽  
Rock Properties ◽  
Complex Nature ◽  
Self Healing ◽  
Glass Waste ◽  
Nuclear Waste Storage

<p> <span>The disposal of heat generating nuclear waste is increasingly becoming a concern for several countries worldwide. This issue is of particular concern for the United States because of the 364,000 m</span><sup><span>3</span></sup><span> of heat-generating nuclear waste currently in temporary storage. Numerous concepts for the disposal of heat generating nuclear waste have been investigated internationally, such as, mined repositories in crystalline, argillite, and salt formations, and deep borehole disposal. Currently, salt formations are being investigated as candidate disposal host rocks for heat-generating nuclear waste in the United States, Germany, the Netherlands, and the United Kingdom. Salt formations may be an ideal host media due to salt’s extremely low permeability, high thermal conductivity, and self-healing capability. Salt lacks circulating groundwater, but it is not dry. Brine availability in salt has multiple implications for the safety and design of a nuclear waste storage facility. Brine transport is a potential off-site radionuclide transport vector, brine leads to corrosion of metallic and glass waste forms and waste packages, chloride in brine can reduce criticality concerns, and accumulated brine can provide back-pressure that resists long-term creep closure of porosity associated with mining the repository. In order to improve understanding of brine migration in heated salt, borehole heater experiments are being conducted at the Waste Isolation Pilot Plant (WIPP) in Carlsbad, New Mexico. The salt heater test collaboration aims to collect data to gain a better understanding of brine availability, transport, and thermal evolution of salt in response to heating up to 140 °C. Due to the complex nature and coupled processes that take place within bedded salt, this study will utilize 1D, 2D, and 3D numerical simulations of the salt heater test to deconvolve the parametric controls on brine availability and migration. The purpose of this study is two-fold, in addition to understanding the hydrogeology of salt formations, we utilize two different subsurface flow codes in a code comparison study, TOUGH and PFLOTRAN. Preliminary results from this study illustrate the importance of understanding the host rock properties and the initial/boundary conditions of the salt and multiphase fluid flow near the excavation site.</span></p><p> </p><p><em>Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.</em></p>

scholarly journals Towards best possible safety – current regulatory research for the German site selection process for high-level radioactive waste disposal

2020 ◽  
Vol 54 ◽  
pp. 157-163
Author(s):  
Axel Liebscher ◽  
Christoph Borkel ◽  
Michael Jendras ◽  
Ute Maurer-Rurack ◽  
Carsten Rücker
Keyword(s):  
Radioactive Waste ◽  
Nuclear Waste ◽  
Waste Disposal ◽  
Rock Salt ◽  
Site Selection ◽  
State Of The Art ◽  
Selection Process ◽  
Fault Zones ◽  
Radioactive Waste Disposal ◽  
Methodological Approaches

Abstract. The Federal Office for the Safety of Nuclear Waste Management (BASE – Bundesamt für die Sicherheit der nuklearen Entsorgung) is the German federal regulatory authority for radioactive waste disposal. It supervises the German site selection process and is responsible for the accompanying public participation. Task related research is an integral part of BASE's activities. The projects MessEr and übErStand compiled the state-of-the-art science and technology regarding surface based exploration methods suitable for addressing the criteria and requirements specified in the German Site Selection Act. The results support BASE to review and define the surface-based exploration programs to be executed by the national implementer BGE (Bundesgesellschaft für Endlagerung mbH). To support BASE in reviewing the application of the exclusion criteria “active fault zones” according to the Site Selection Act, the project KaStör reviewed the current knowledge on active faults and fault zones in Germany and recommends methodological approaches to date and identify the activity of faulting. For the time being, the Site Selection Act defines 100 ∘C as a draft limit on the temperature at the outer surface of a repository container for all host rocks. The project Grenztemperatur studied the temperature dependency of the different thermal-hydraulic-mechanical-chemical/biological (THMC/B) processes according to available features-events-processes (FEP) catalogues for rock salt, clay stone, and crystalline rock and describes ways to defining host rock specific maximum temperatures based on specific disposal and safety concepts. Safety oriented weighting of different criteria and comparison of different potential regions and sites are key challenges during the siting process. The project MABeSt studied and reviewed methodological approaches to this weighting and comparison problem with special emphasis on multi criteria analysis (MCA) and multi criteria decision analysis (MCDA). A key requirement for safe geological disposal of nuclear waste is barrier integrity. The project PeTroS performed the first triaxial flow-through experiments on natural rock salt samples at disposal relevant p−T conditions and studied potential percolation mechanisms of fluids within rock salt. The data substantiate that the minimum stress criterion and/or the dilatancy criterion are the prime “percolation thresholds” in rock salt. The research results support BASE in fulfilling its tasks as national regulator according to state-of-the-art science and technology and are also relevant to other stakeholders of the siting process.

Corrosion of Carbon-Steel Containers for Heat-Generating Nuclear Waste in Brine Environments Relevant for A Rock-Salt Repository

1991 ◽  
Vol 257 ◽  
Author(s):  
E. Smailos ◽  
W. Schwarzkopf ◽  
B. Kienzler ◽  
R. KÖster
Keyword(s):  
Carbon Steel ◽  
Corrosion Rate ◽  
Nuclear Waste ◽  
Rock Salt ◽  
Corrosion Behaviour ◽  
Carbon Steels ◽  
General Corrosion ◽  
Fine Grained ◽  
Corrosion Studies ◽  
Salt Brine

ABSTRACTIn previous corrosion studies, carbon steels, especially the fine-grained steel TStE355, were identified as promising materials for heat-generating nuclear waste containers acting as a barrier in a rock-salt repository. In the present study detailed investigations have been performed on fine-grained steel to determine the influence of important parameters on its corrosion behaviour in disposal-relevant salt brines. These parameters are: brine composition (Mg Cl2-rich and NaCI-rich brines), temperature (90°C, 170°C), and salt impurities, such as H2S concentrations of 25 mg/I-200 mg/I salt brine.Under the conditions of the tests used here, carbon steel was subjected to general corrosion. Pitting and crevice corrosion or stress-corrosion cracking were not observed. The increase in temperature from 90°C to 170°C strongly enhanced the corrosion rate of the steel. In the MgCl2-rich brines, considerably higher rates (37-70 μm/a at 90°C, 200-300 °m/a at 170°C) were observed than in the NaCI-rich brine (5 μm/a at 90°C, 46 μm/a at 170°C). H2S concentrations in the MgCl2-rich Qbrine of up to 200 mg/l did not influence significantly the corrosion rate of the steel. The corrosion rates determined imply corrosion allowances that are technically acceptable for thick-walled containers. In view of these results, fine-grained steel continues to be considered as a promising material for long-lived HLW containers.

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