scholarly journals Radionuclide migration through fractured rock: Effects of multiple fractures and two-member decay chains

1985 ◽  
Author(s):  
J. Ahn ◽  
P.L. Chambre ◽  
T.H. Pigford
Keyword(s):  
Fractured Rock ◽  
Radionuclide Migration ◽  
Multiple Fractures

Effect of colloids on radionuclide migration for performance assessment of HLW disposal in Japan

2001 ◽  
Vol 73 (12) ◽  
pp. 2027-2037 ◽  
Author(s):  
S. Kurosawa ◽  
S. Ueta
Keyword(s):  
Performance Assessment ◽  
Metal Ion ◽  
Fractured Rock ◽  
Experimental Studies ◽  
Radionuclide Migration ◽  
Metal Ion Hydrolysis ◽  
Engineered Barrier ◽  
Bentonite Colloid ◽  
Major Factors ◽  
High Level

Colloidal effect is one of the major factors to enhance the migration of radionuclides in groundwater. The experimental and theoretical studies of colloid mobility and colloid-facilitated radionuclide transport for the performance assessment of high-level radioactive waste (HLW) geological disposal is presented in this paper. The major aims of the study are (1) to study the filtration effect on colloids by the engineered barrier system, (2) to study bentonite colloid generation by erosion of the engineered barrier system, and (3) to calculate radionuclide migration with groundwater colloids through fractured rock systems. Alternative coagulants based on prehydrolyzed forms of aluminium or iron can be more effective than the traditional materials in many cases, but their mode of action is not completely understood, especially with regard to the role of charge neutralization and hydroxide precipitation. Basic principles of colloid stability and metal ion hydrolysis are briefly reviewed, and the action of hydrolyzing metal coagulants is then discussed, with some examples from recent experimental studies. Although it is possible to interpret results reasonably well in terms of established ideas, there are still some uncertainties that need to be resolved

Modeling of Radionuclide Migration Through Fractured Rock in a HLW Repository With Multiple Canisters

2008 ◽  
Vol 1107 ◽  
Author(s):  
Doo-Hyun Lim ◽  
Masahiro Uchida ◽  
Koichiro Hatanaka ◽  
Atsushi Sawada
Keyword(s):  
Numerical Model ◽  
Host Rock ◽  
Fractured Rock ◽  
Current Model ◽  
Design Parameters ◽  
Radionuclide Migration ◽  
Waste Package ◽  
Tunnel Diameter ◽  
Water Saturated ◽  
Hlw Repository

AbstractAn integrated numerical model for groundwater flow and radionuclide migration analyses in a water-saturated HLW repository with a multiple-canister configuration is developed by incorporating the heterogeneity of fractured host rock based on the previous multiple-canister model (MCFT2D [1, 2]). The current model incorporates i) heterogeneity of the fractured host rock represented stochastically by discrete fractures, ii) disposal-pit vertical emplacement concept, iii) representation of the waste package consisting of a waste canister and a bentonite-filled buffer, and iv) a user-determined repository configuration of multiple canisters using the repository parameters such as disposal tunnel spacing, waste package pitch, tunnel diameter, the number of tunnels in a repository, and the number of canisters in a tunnel. The current model can facilitate investigations into the effects of heterogeneous fractured host rock on water flow and nuclide migration for the different configurations of multiple canisters, as well as optimization of the repository design parameters in terms of release of nuclides from the repository.

Geological control of fracture permeability in the Carnmenellis granite, Cornwall: implications for radionuclide migration

1985 ◽  
Vol 49 (351) ◽  
pp. 233-244 ◽  
Author(s):  
M. J. Heath
Keyword(s):  
Fractured Rock ◽  
Radioactive Tracer ◽  
Horizontal Stress ◽  
Fracture Permeability ◽  
Radionuclide Migration ◽  
Flow Paths ◽  
Geological Features ◽  
Characteristic Features ◽  
Maximum Horizontal Stress ◽  
Geological Control

AbstractMulti-packer hydraulic tests and radioactive tracer experiments carried out in boreholes in the Carnmenellis granite have shown that the flow of water through the rock is largely confined to narrow zones separated by zones of very low permeability. Correlation of the hydraulic data with geological data from oriented cores has shown that most of the flow is associated with discrete geological features, including pegmatitic and other veins, and elvan (quartz-feldspar porphyry) dykes, characteristic features of the granite of the area. Joints have also been found to conduct water, particularly in the upper 250 m of the granite. The permeability of the granite has been found not to be simply a function of fracture frequency, long sections of highly fractured rock having no associated flow under test conditions. While flow paths have been found to become less frequent with depth, flow rates do not vary over the depths studied, the highest flow rate recorded at the site being associated with a vein at 637 m. Water-conducting fractures have been found to have certain preferred orientations which vary with depth. A set striking 155°C is particularly well developed in the upper 250 m of the granite. This orientation is significant in that it is parallel to the cross-courses in the nearby mineralized belt with which the younger (Tertiary) mineralization tends to be associated and from which thermal brines issue into several local mines. These fractures are also approximately parallel to the maximum horizontal stress which affects the granite and which appears to be responsible for the selective opening of joints of certain orientations.

The Modification and Application of the Geochemical Modelling Code CHEQMATE to Simulate Transport and Chemical Processes within Fractured Media

1993 ◽  
Vol 333 ◽  
Author(s):  
A. V. Chambers ◽  
A.C. Smith
Keyword(s):  
Fractured Rock ◽  
Chemical Processes ◽  
Fractured Media ◽  
Single Fracture ◽  
Radionuclide Transport ◽  
Continuum Approach ◽  
Multiple Fractures ◽  
Intermediate Level Radioactive Waste ◽  
The Uk ◽  
Fracture Distribution

ABSTRACTThe UK current plans for a repository for the disposal of intermediate-level radioactive waste involve the use of a cementitious backfill within the repository vaults. Radionuclide transport could be concentrated within cracks that may form in the cement, or in fractures within the rock surrounding the repository. A version of CHEQMATE (CHemical EQuilibrium with Migration And Transport Equations) that includes a representation of transport through fractured media has been developed. This paper describes modifications of the code, to allow simulation of transport through either a single fracture, or, by adopting a continuum approach to represent fracture distribution, through multiple fractures. Successful verification of the modified program against analytical solutions for transport through fractured rock and cracked cementitious media is presented. An application of the modified program to study the evolution of the aqueous chemistry within a repository vault containing a single fracture through the cementitious backfill is also discussed.

The EL Berrocal Project: Geological Characterisation and Radionuclide Migration Studies in a Fractured Granitic Environment

1994 ◽  
Vol 353 ◽  
Author(s):  
W. M. Miller ◽  
L. Pérez Villar ◽  
P. Gómez ◽  
M. Ivanovich ◽  
B. de la Cruz ◽  
...  
Keyword(s):  
Quartz Vein ◽  
Fractured Rock ◽  
Calcium Sulphate ◽  
Uranium Mine ◽  
Radionuclide Migration ◽  
Central Spain ◽  
Sulphide Minerals ◽  
Mineral Growth ◽  
Geological Repository ◽  
And Migration

AbstractEl Berrocal is an abandoned uranium mine in a mineralised quartz vein hosted by a Hercynian granite in central Spain. This mine is the focus of an international project to characterise and model natural elemental migration in a fractured-rock environment as an aid to understanding and predicting processes that may occur in a geological repository for radioactive wastes.Uranium in the mineralised quartz vein has been shown to have originated from the orthomagmatic uraninite in the granite with the elemental removal and migration occurring predominately by hydrothermal fluids. Mobilisation of uranium from the mineralised quartz vein and from granite adjacent to hydraulically-active fractures away from the vein occurred over the geologically-recent past and in the present-day. The most recent mobilisation is evidenced by dissolution features seen in SEM photomicrographs; mineral growth and sorption signatures identified by enhanced uranium concentrations on the surfaces of preexisting minerals; and measured disequilibrium in the uranium series for whole rock close to fracture walls.Present-day groundwaters in the studied area are young meteoric waters. They are generally calcium-sulphate enriched, oxidising and mildly acidic near the surface, becoming more bicarbonate-rich with near neutral pH in the deeper zones, except around the mineralised vein where the waters are acid (pH around 3) due to oxidisation of the sulphide minerals. No deep, chemically-reducing groundwaters have yet been identified in the El Berrocal boreholes.

Sign in / Sign up

Export Citation Format

Share Document