Impact of Temperature Increase On Nuclide Transport in Crystalline Rock On The Near Field Scale

2004 ◽  
pp. 413-418
Author(s):  
Hua Cheng ◽  
Vladimir Cvetkovic
Keyword(s):  
Temperature Increase ◽  
Near Field ◽  
Crystalline Rock ◽  
Field Scale ◽  
Nuclide Transport

Some Important Mechanisms and Processes in the Near Field of the Swedish Repository for Spent Nuclear Fuel

1992 ◽  
Vol 294 ◽  
Author(s):  
Ivars Neretnieks
Keyword(s):  
Molecular Diffusion ◽  
Spent Nuclear Fuel ◽  
Dominant Role ◽  
Near Field ◽  
Water Flow Rate ◽  
Crystalline Rock ◽  
Diffusive Transport ◽  
Actual Design ◽  
Natural Analogues ◽  
And Performance

ABSTRACTIn repositories for nuclear waste there are many processes that will be instrumental in damaging the canisters and releasing the nuclides. Based on experiences from studies of the performance of repositories and of an actual design, the major mechanisms influencing the integrity and performance of a repository are described and discussed. The paper addresses only conditions in crystalline rock repositories. The low water flow rate in fractures and channels plays a dominant role in limiting the interaction between water and waste. Molecular diffusion in the backfill and rock matrix, as well as in the mobile water, is an important transport process, but actually limits the exchange rate because diffusive transport is slow. Solubility limits of both waste matrix and of individual nuclides are also important. Complicating processes include alpha-radiolysis, which may change the water chemistry in the near-field. The sizes and locations of water flowpaths and damages in the canisters considerably influence the release rates. Uncertainties in data are large. Nevertheless the system is very robust in the sense that practically no reasonably conceivable assumptions or data will lead to large nuclide releases. Several natural analogues have been found to exhibit similarities with a waste repository and help to validate concepts and to increase our confidence that all major issues have been considered.

scholarly journals Field-scale water transport in unsaturated crystalline rock

1997 ◽  
Vol 33 (4) ◽  
pp. 589-598 ◽  
Author(s):  
T. Gimmi ◽  
M. Schneebeli ◽  
H. Flühler ◽  
H. Wydler ◽  
T. Baer
Keyword(s):  
Water Transport ◽  
Crystalline Rock ◽  
Field Scale

scholarly journals Multiphase Carbon-14 Transport in a Near-Field-Scale Unsaturated Column of Natural Sediments

2004 ◽  
Author(s):  
D. T. Fox ◽  
Mitchell A. Plummer ◽  
Larry C. Hull ◽  
D. Craig Cooper
Keyword(s):  
Near Field ◽  
Field Scale ◽  
Carbon 14

Determination of Near Field Excavation Disturbance in Crystalline Rock

1985 ◽  
Vol 50 ◽  
Author(s):  
Robert Koopmans ◽  
Robin W. Hughes
Keyword(s):  
Data Acquisition ◽  
Near Field ◽  
Crystalline Rock ◽  
Rock Discontinuities ◽  
Similar Concept

A procedure has been established to assess the effectiveness of various excavation techniques using a computerized borehole dilatometer system developed by the authors[l]. This system, which incorporates data acquisition and computer capabilities, allows data to be collected and analyzed quickly in the field. The zone of disturbance is determined by conducting borehole tests at relatively close intervals and profiling the results with depth from the excavation wall. A similar concept of using deformation moduli measurements from plate bearing tests to detect changes in bedrock conditions is discussed by Koopmans[2]. In general, lower moduli are obtained in disturbed zones which have become stress relieved due to rock relaxation and/or the presence of rock discontinuities while higher values are obtained in relatively undisturbed zones which have not become stress relieved due to an absence of rock relaxation and/or rock discontinuities.

The FEBEX Project. General Overview

1997 ◽  
Vol 506 ◽  
Author(s):  
F. Huertas ◽  
J.L. Santiago
Keyword(s):  
Large Scale ◽  
Numerical Models ◽  
Near Field ◽  
Thermal Response ◽  
Crystalline Rock ◽  
Full Scale ◽  
Deep Geological Disposal ◽  
Heating Test ◽  
Large Scale Tests ◽  
Term Performance

ABSTRACTUnderstanding the near-field evolution of a deep geological disposal system for HLW is crucial for assessing its long term performance and, therefore, safety. For that reason ENRESA devised the FEBEX Project, a Full Scale Engineered Barriers Experiment in crystalline rock. The project consists of a full-scale “in-situ” heating test, a large-scale laboratory mock-up and supporting materials tests, and modelling.Even though the object of the project is to contribute to the search for methods of behaviour and of safety analyses for a repository, other subinvestigations have been/are being included. The stated objectives are to demonstrate the procedures of constructing an engineered barrier system (EBS), especially the fabrication, handling, and installation of bentonite blocks (buffer) at an almost industrial scale, to improve and validate the numerical models for thermo-hydro-mechanical behaviour, and to investigate the geochemical processes that are produced in the buffer including canister corrosion, as well as the generation and transport of gas. Since early 1997, with the commencement of the heating phase, both large-scale tests have been fully operative. At this point it can be said that the demonstration objective of constructing the EBS has been successfully achieved. The measured thermal response of the buffer follows the pattern predicted in the preliminary modelling. The saturation rate of the buffer and associated mechanical processes are being continuously monitored.

Bacterial Transport in Fractured Rock – A Field-Scale Tracer Test at the Chalk River Nuclear Laboratories

1988 ◽  
Vol 20 (11-12) ◽  
pp. 81-87 ◽  
Author(s):  
D. R. Champ ◽  
J. Schroeter
Keyword(s):  
Water Movement ◽  
Fractured Rock ◽  
Tracer Tests ◽  
Crystalline Rock ◽  
Tracer Test ◽  
Breakthrough Curves ◽  
Water Recovery ◽  
Field Scale ◽  
Particulate Contaminants ◽  
Conservative Tracers

The potential for transport of bacteria by groundwater in fractured crystalline rock was assessed in a series of field-scale tracer tests. The breakthrough curves for injected Escherichla coll and “non-reactive” particle tracers were compared with those for conservative inorganic and radioactive tracers. Rapid transport, relative to the conservative tracers, of both bacteria and non-reactive particles was observed. The first appearance of both was with, or slightly before, the conservative tracers for water movement. Removal of the bacteria and particles by filtration processes occurred and was quantified through the calculation of filter factors. The filtration process in this fracture system is similar to that found in a gravel aquifer. From the results we can conclude that particulate contaminants can be very rapidly transported in fracture systems and that continuing sources of contamination could lead to relatively high local concentrations of particulate contaminants compared with the average at any given distance from the source. It was also concluded that the use of traditional conservative tracers, for water movement, to assess the potential for movement of particulate contaminants could lead to significant underestimates of exposure to particulate contaminants due to consumption of water from water recovery wells located in fractured media.

Nuclear Waste Repositories in Crystalline Rock- an Overview of Flow and Nuclide Transport Mechanisms

1994 ◽  
Vol 353 ◽  
Author(s):  
Ivars Neretnieks
Keyword(s):  
Nuclear Waste ◽  
Field Experiments ◽  
Fracture Network ◽  
Crystalline Rock ◽  
Transport Mechanisms ◽  
The Matrix ◽  
Nuclide Transport ◽  
Waste Repositories ◽  
And Diffusion ◽  
Diffusion Properties

AbstractNuclides eventually escaping from nuclear waste repositories in crystalline rock will move with the seeping water in the fracture network. Most important nuclides interact physically or chemically with the rock and are expected to be considerably retarded allowing them to decay to insignificant concentrations. Velocity variations may allow some portions of the nuclides to move faster. Matrix diffusion and sorption on the surfaces of the rock are by far the most powerful retardation mechanisms and depend, in addition to the sorption and diffusion properties, directly on the magnitude of the “flow wetted surface”which is the contact surface between the mobile water carrying the nuclides and the fracture surfaces over which the nuclides diffuse into the matrix.A number of field experiments have been performed over the last 15 years to help validate the concepts and models and to obtain data. A number of such experiments are described and discussed in relation to the above issues.

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