Author: M. KolarPublisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
Review of methods used to model gas generation and gas migration from an underground waste repository
Author: M. KolarA Mathematical Model for Gas Migration In Natural and Engineered Barriers for Radioactive Waste Disposal
Author: Elias Ernest DagherPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
This work provides a comprehensive assessment into the processes governing two-phase flow in a swelling geomaterial under critical gas pressures whereby the material strength of the soil may be exceeded and for which dilation and dilation-controlled gas flow is expected to occur. The author first provides background on the importance of understanding such processes in the safe geological disposal of radioactive waste. This is followed by a review of experimental studies to describe mechanisms of gas migration processes through natural (host rock formations) and engineered barrier materials, and an evaluation of existing studies that have attempted to numerically model multi-phase flow in expansive soils. Finally, the author provides a literary synthesis of the hydraulic and mechanical behaviour of bentonite clays observed in laboratory experiments under saturated and unsaturated conditions. The novel contribution of this work is then presented through a series of articles. The author first develops a fully-coupled hydro-mechanical (HM) mathematical model for advective-diffusive visco-capillary controlled two-phase flow through a geomaterial and applies it to simulate a 1-dimensional (1D) flow problem using the Finite Element Method (FEM) commercial code COMSOL Multiphysics®. The model results are compared to experimental data and although several key-features of the experimental results were realized, additional flow mechanisms would be necessary to achieve complete gas breakthrough of the sample. In the second article, a verification study is performed, whereby analytical solutions for a 1D steady-state and 1D transient gas flow problem under constant volume boundary conditions were derived. Successful verification of the numerical model was completed by comparing the pore-gas pressure evolution and stress evolution to that of the results of the analytical solution, which showed near-perfect agreement. Building upon the authors original mathematical model, an investigation of enhanced processes and characteristics which may be contributing to dilation-controlled gas flow were conducted. These processes included the introduction of material heterogeneity, consideration of the Klinkenberg "slip flow" effect, and the presence of a swelling strain, and were applied to simulate the same 1D flow problem. The results showed significant improvement over the previous work, including observing complete breakthrough and matching experimental stress evolution. However, the results showed a high degree of gas saturation within the sample and a plug outflow behavior, which were not characteristic of dilation-controlled gas flow. To further improve the mathematical model, the author conducted a detailed investigation of the highly coupled relationship between mechanical deformation and flow. This included assessing the effect of plasticity, damage, and non-localization to dilation-controlled gas flow, while incorporating the knowledge gained from previous studies. These advanced mathematical models were applied to numerically simulate 1D flow and a 3D spherical flow under constant boundary conditions. Some results demonstrated very good agreement with experimental data and provide further understanding of the processes involved. The collection of this research provides much needed insight into the possible mechanisms controlling two-phase flow and the capability of continuum models to do so. The intent of this research is to expand the literature further and provide a few steps closer in the development of a robust numerical model that can be used to support long-term safety assessments for radioactive waste disposal, by correctly capturing major features of two-phase flow.
Energy Research Abstracts
Author: Annual Report
Author: OECD Nuclear Energy AgencyPublisher:
ISBN:
Category : Nuclear energy
Languages : en
Pages : 294
Book Description
Numerical Modeling of Gas Migration at a Proposed Repository for Low and Intermediate Level Nuclear Wastes at Oberbauenstock, Switzerland
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 30
Book Description
Hydrologic impacts of corrosive gas release from a hypothetical L/ILW nuclear waste repository at Oberbauenstock are explored by means of numerical simulation. A schematic two dimensional vertical section through the mountain is modeled with the simulator TOUGH, which describes two-phase flow of water and gas in porous and fractured media. Two reference cases are considered which represent the formations as a porous and as a fractured-porous (dual permeability) medium, respectively. Both cases predict similar and rather modest pressure increases, from ambient 10 bars to near 25 bars at the repository level. These results are to be considered preliminary because important parameters affecting two-phase flow, such as relative permeabilities of a fractured medium, are not well known at present. 24 refs., 15 figs., 5 tabs.
Selected Water Resources Abstracts
Author: Nuclear Science Abstracts
Author: ERDA Energy Research Abstracts
Author: Numerical Analysis of Gas Flow Within a Municipal Solid Waste Landfill
Author: Natalya Viktorovna UsovaPublisher: LAP Lambert Academic Publishing
ISBN: 9783659513466
Category :
Languages : en
Pages : 140
Book Description
Numerical analysis and modelling of gas flow within MSW landfill has the potential to significantly enhance the efficiency of design and performance of operation for landfill gas extraction and utilization projects. Available models implement a simple theoretical basis and treat the landfilled waste fill purely as a porous medium with the conservation of mass inherently assumed and the ongoing gas generation thus ignored. The research described in this work was intended to evaluate the error introduced into estimates of the intrinsic permeability of waste from landfill gas pumping tests if the ongoing gas generation within the landfilled MSW is ignored when the pumping tests are evaluated to yield estimates of the permeability. Two different approaches were used to simulate gas flow in the unsaturated waste fill: GeoStudio2007 software suite and a 1-D FD solution. This work demonstrated that the gas generation term should not be ignored when the gas flow is evaluated for MSW. Thus, the correction charts is developed as a first step toward a reliable method that would enable such widely used software to be used with a correction factor to enable improved simulations of gas flow.
ERDA Energy Research Abstracts
Author: United States. Energy Research and Development AdministrationPublisher:
ISBN:
Category : Medicine
Languages : en
Pages : 818
Book Description