Experimental Study of Colloid Filtration by Compacted Bentonite

1996 ◽  
Vol 465 ◽  
Author(s):  
Susumu Kurosawa ◽  
Mikazu Yui ◽  
Hideki Yoshikawa
Keyword(s):  
Colloidal Particles ◽  
Sea Water ◽  
Silica Sand ◽  
Radionuclide Transport ◽  
Colloidal Transport ◽  
Saline Groundwater ◽  
Compacted Bentonite ◽  
Repulsion Potential ◽  
Colloid Filtration ◽  
High Level

ABSTRACTIn this study, the transport behavior of colloids through compacted bentonite and sand-bentonite mixtures was investigated. Colloidal gold was used to simulate mobile colloids because it was well characterized and its dispersivity was controlled. The bentonite used was a sodium bentonite. The sand-bentonite mixtures were prepared by mixing up to 50wt.% silica sand with the bentonite. The bentonite and the sand-bentonite mixtures were compacted to dry densities of 1000 and 1800 kg/m3 and then saturated with distilled water. The sand-bentonite mixture was also saturated with synthetic sea-water. Column experiments were performed to investigate colloidal transport. Further, colloidal particles stabilities in high ionic strength water such as bentonite porewater or saline groundwater were interpreted based on the repulsion potential from the double layer force and the attraction potential from the van der Waals force.The results indicated that the colloidal particles were effectively filtered by both the compacted bentonite and the sand-bentonite mixtures. This study indicated that the effect of colloids on radionuclide transport in compacted bentonite is negligible for the safety assessment of high level radioactive waste (HLW) disposal.

Diffusion of Uranium in Compacted Bentonite in the Presence of Carbon Steel

1993 ◽  
Vol 333 ◽  
Author(s):  
K. Idemitsu ◽  
H. Furuya ◽  
Y. Tachi ◽  
Y. Inagaki
Keyword(s):  
Carbon Steel ◽  
Pore Water ◽  
Silica Sand ◽  
High Level Waste ◽  
Dry Density ◽  
Compacted Bentonite ◽  
Reducing Conditions ◽  
Order Of Magnitude ◽  
The Difference ◽  
High Level

ABSTRACTIn a high-level waste repository, a carbon steel overpack will be corroded by consuming oxygen trapped in the repository after closure. This will create a reducing environment in the vicinity of repository. Reducing conditions are expected to retard the migration of redox-sensitive radionuclides such as uranium.The apparent diffusivities of uranium were measured in compacted bentonite (Kunigel VI®, Japan) in contact with carbon steel under reducing conditions or without carbon steel under oxidizing conditions for comparison. The apparent diffusivities of uranium were 3.5 × 10-14 to 1.1 × 10-13 m2/s under reducing conditions and 9.0 × 10-13 to 1.4 × 10-12 m2/s under oxidizing conditions. There was no significant effect of dry density (1.6 to 1.8 g/cm3) and silica sand (0 or 40%) on the apparent diffusivities.Since the bentonite pore water would be buffered at a pH between 8 and 9, uranium in the bentonite pore water would probably exist as a neutral hydroxide complex under reducing conditions and as an anioníc carbonate or hydroxide complex under oxidizing conditions. The anion exclusion theory cannot explain the difference of diffusivities between the two conditions. The uranium concentrations in bentonite under oxidizing conditions were one order of magnitude higher than those under the reducing conditions. The uranium concentration in the bentonite pore water under the reducing condition is estimated to be two orders of magnitude lower than that under the oxidizing conditions under the assumption of diffusion in porous media.

Measurement of Soil Suction and Soil-Water Characteristics of Bentonite-Sand Mixtures

2010 ◽  
Author(s):  
Pan Hu ◽  
Qing Yang ◽  
Maotian Luan
Keyword(s):  
Soil Water ◽  
Vapor Phase ◽  
Unsaturated Soils ◽  
Characteristic Curve ◽  
Phase Method ◽  
Soil Suction ◽  
Compacted Bentonite ◽  
Water Characteristics ◽  
Wide Range ◽  
High Level

The soil-water characteristic curve (SWCC) is a widely used experimental means for assessing fundamental properties of unsaturated soils for a wide range of soil suction values. The study of SWCC is helpful because some properties of unsaturated soils can be predicted from it. Nowadays, much attention has been paid to the behaviours of highly compacted bentonite-sand mixtures used in engineering barriers for high level radioactive nuclear waste disposal. It is very important to study the various performances of bentonite-sand mixtures in order to insure the safety of high-level radioactive waste (HLW) repository. After an introduction to vapor phase method and osmotic technique, a laboratory study has been carried out on compacted bentonite-sand mixtures. The SWCC of bentonite-sand mixtures has been obtained and analyzed. The results show that the vapor phase method and osmotic technique is suitable to the unsaturated soils with high and low suction.

The Coarse Particle Influence on the Strength of Wax Deposition

2020 ◽  
Author(s):  
Xun Zhang ◽  
Qiyu Huang ◽  
Yu Zhang ◽  
Yaping Li ◽  
Xin Liu
Keyword(s):  
Yield Stress ◽  
Colloidal Particles ◽  
Critical Mass ◽  
Solid Particles ◽  
Coarse Particle ◽  
Silica Sand ◽  
Coarse Particles ◽  
Wax Deposition ◽  
Wax Deposits ◽  
The Impact

Abstract Wax deposition has always been an essential issue for flow assurance, especially in subsea pipelines. The coarse particles, which are usually measured in millimeters, will be carried out by oil flow during the deep-water oil fields production. However, due to insufficient understanding of the structure of wax deposits and the complexity of sandy crude oil deposition, the interaction between coarse particles and wax deposits in the pipeline have rarely been investigated. In this paper, the effect of coarse particles on the yield stress of wax deposits has been studied. The sample was mixed at reversible structure temperature so that the impact of shear history could be eliminated, and the rapid particle settlement at high temperature could be avoided. Experimental results have found that there is a critical fraction in coarse particle influences, below which a small number of coarse particles added will lead to a slight increase in bulk yield stress. On the contrary, a dramatic decrease in yield stress when exceeding the critical mass fraction and increasingly marked enhancement of yield stress as the fraction increases. This phenomenon has been explicated microscopically by the structural interaction between coarse particles and wax deposits. The interlock between wax crystals is the major contribution of the structure as the less particle fraction contains. Even though the silica sand is a typical non-colloidal particle, the asphaltene and resin could be absorbed on the surface of particles and forming a cluster of colloidal particles. As the fraction of particles slightly increased, the slip between colloidal particles and wax crystal interlock accelerates structural failure. Nevertheless, more particles involved the overall yield stress may depend on the friction and the adhesive force between solid particles. The subtle changes induced by coarse particles would have a harder deposit, which can hinder pig passing and affect pipeline pigging operations.

Some Aspects on the Use of Iron Canisters for HLW

1985 ◽  
Vol 50 ◽  
Author(s):  
Ivars Neretnieks
Keyword(s):  
Bentonite Clay ◽  
Potential Effect ◽  
Hydrogen Gas ◽  
Lithostatic Pressure ◽  
Equilibrium Pressure ◽  
Capillary Suction ◽  
Compacted Bentonite ◽  
High Level Nuclear Waste ◽  
High Level ◽  
Rock Overburden

AbstractIron canisters for high level nuclear waste embedded in compacted bentonite in deep geologic repositories will corrode forming hydrogen gas. The equilibrium pressure (when corrosion would stop) has been estimated to be between 500 and 1000 atm. under repository conditions. As this is much higher than the lithostatic pressure (weight of rock overburden) the gas must be allowed to escape before it disrupts the repository. Escape by diffusion alone is not sufficient but recent experiments have demonstrated that the larger pores in the bentonite are blown free of water and let the gas escape before excessive pressures build up.The potential effect of a capillary breaking layer (CBL) has been explored. A fine layer nearest the canister (e.q. quartz sand) would have much lower capillary suction pressures than the bentonite clay and would keep the water out as long as there is sufficient overpressure. As long as the CBL is void of liquid water no radionuclides can escape, even if the canister is penetrated.

scholarly journals Problems of water supply of the population and application of the method of electrolysis-structural activation for partial solution

2018 ◽  
Vol 193 ◽  
pp. 02019
Author(s):  
Ludmila Prikhodko ◽  
Galina Bryukhanova ◽  
Ekaterina Beljakova
Keyword(s):  
Water Supply ◽  
Reverse Osmosis ◽  
Arid Regions ◽  
Sea Water ◽  
Partial Solution ◽  
Global Scale ◽  
Membrane Technology ◽  
Saline Groundwater ◽  
Desalinated Water

We analyzed the problems of water supply for the population of global scale and regional importance. A method for the electrolysis-structural activation of water oriented on the use of initial fresh rainwater or desalinated membrane technology of sea water in a mix with biologically purified household sewage waters. This method can be used on sea vessels, in arid regions of the planet, and in areas with saline groundwater. Activation of water is achieved by mixing biologically purified wastewater obtained by technology that ensures the quality of purified water at the level of requirements for release in a fishery pond and desalinated water (rainwater) or obtained by reverse osmosis in a ratio of their volumes not more than 10:1

scholarly journals Sorption-Capacity Limited Retardation of Radionuclides Transport in Water-Saturated Packing Materials

1984 ◽  
Vol 44 ◽  
Author(s):  
C. Pescatore ◽  
T. Sullivan
Keyword(s):  
Sorption Capacity ◽  
Retardation Factor ◽  
High Level Waste ◽  
Radionuclide Transport ◽  
Breakthrough Time ◽  
Packing Materials ◽  
Sorption Data ◽  
Waste Package ◽  
High Level ◽  
Water Saturated

AbstractRadionuclides breakthrough times as calculated through constant retardation factors obtained in dilute solutions are non-conservative. The constant retardation approach regards the solid as having infinite sorption capacity throughout the solid. However, as the solid becomes locally saturated, such as in the proximity of the waste form-packing materials interface, it will exhibit no retardation properties, and transport will take place as if the radionuclides were locally non-reactive. The magnitude of the effect of finite sorption capacity of the packing materials on radionuclide transport is discussed with reference to high-level waste package performance. An example based on literature sorption data indicates that the breakthrough time may be overpredicted by orders of magnitude using a constant retardation factor as compared to using the entire sorption isotherm to obtain a concentrationdependent retardation factor.

scholarly journals The adaptations of Lasaea rubra (Montagu), a small intertidal lamellibranch

1957 ◽  
Vol 36 (2) ◽  
pp. 383-405 ◽  
Author(s):  
J. E. Morton ◽  
A. D. Boney ◽  
E. D. S. Corner
Keyword(s):  
Sea Water ◽  
Low Level ◽  
High Level ◽  
Considerable Range

A study has been made of the ecology of the small intertidal lamellibranch Lasaea rubra at various tidal levels at Plymouth and Wembury. In addition, experiments have been carried out to investigate physiological and behavioural differences arising from varying amounts of submersion at different tidal levels, and the following findings have been made.During the first hour after their submersion by sea water, L. rubra from high up the shore filter at a rate approximately twice that of animals which live lower down. After 2 h, however, both sets of animals filter at the same rate.High-level animals respond significantly faster to wetting by splash and can tolerate a considerable range of salinity. They also respire at a rate approximately twice that of low-level animals. Respiration, however, is not detectable when the animal is not immersed in sea water.

scholarly journals The origin of brackish and saline groundwater in the coastal area of the Netherlands

2003 ◽  
Vol 82 (2) ◽  
pp. 133-147 ◽  
Author(s):  
V.E.A. Post ◽  
H. Van der Plicht ◽  
H.A.J. Meijer
Keyword(s):  
The Netherlands ◽  
Critical Review ◽  
Coastal Area ◽  
Sea Water ◽  
Early Pleistocene ◽  
Low Permeability ◽  
Salinity Distribution ◽  
Saline Groundwater ◽  
Carbon 14 ◽  
Saline Waters

AbstractAn explanation is presented for the origin of brackish to saline groundwater in the coastal area of the Netherlands based on geological, chemical (chlorinity), isotopic and geophysical data. A critical review of all possible salinization mechanisms shows that the origin of the brackish water is related to former transgressions. Both the vertical salinity distribution and the carbon-14 activity of the groundwater indicate that connate sea water from the Pliocene to Early Pleistocene is not the source of the brackish to saline waters in the overlying Pleistocene fluvial aquifers. Instead, it derives from Holocene transgressions. The salinization mechanism is discussed in relation to the paleogeographical development during the Holocene and the occurrence of low-permeability strata. Finally, freshening of the aquifers following retreat of the sea is briefly considered.

What really happens to the “vanishing overpack”?

2012 ◽  
Vol 1475 ◽  
Author(s):  
I. G. McKinley ◽  
F. B. Neall ◽  
E. M. Scourse ◽  
H. Kawamura
Keyword(s):  
Radionuclide Transport ◽  
Spent Fuel ◽  
Geological Disposal ◽  
Failure Times ◽  
Bentonite Buffer ◽  
Physical Barriers ◽  
Safety Assessments ◽  
High Level ◽  
Radionuclide Release

ABSTRACTConcepts for the disposal of high-level radioactive waste (HLW) and spent fuel (SF) in several countries include a massive steel overpack within a bentonite buffer. In past conservative safety assessments to demonstrate feasibility of geological disposal, overpacks are assumed to provide complete containment for a given lifetime, after which all fail simultaneously. After failure, they are ignored as physical barriers to radionuclide transport. In order to compare different repository designs for specific sites, however, a more realistic treatment of overpack failure and its subsequent behaviour is needed. In addition to arguing for much longer lifetimes before mechanical failure and a distribution of overpack failure times, such assessment indicates that the presence of the failed overpack greatly constrains radionuclide release from the waste matrix and subsequent migration through the engineered barrier system. It also emphasises the key role of the bentonite buffer and the need to be able to assure its performance over relevant timescales.

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