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Title: Measurements of the effective diffusion coefficient of dissolved oxygen and oxidation rate of pyrite by dissolved oxygen in compacted sodium bentonite

Abstract

The redox condition of the near field is expected to affect the performance of engineered barrier systems. In particular, the oxygen initially existing in the pore spaces of compacted bentonites strongly affects the redox condition of the near field. To assess the influence of the oxygen, research was done to assess its transport parameters in the compacted bentonite and consumption process. To understand the diffusion of dissolved oxygen (DO) in compacted bentonite and to predict the effect of the DO, the measurements of the effective diffusion coefficient of DO in compacted sodium bentonite were made by electro-chemistry. As a result, the following relationship between the dry density of compacted sodium bentonite and the effective diffusion coefficient of DO in compacted sodium bentonite was derived: D{sub e} = 3.0 {+-} 0.5 {times} 10{sup {minus}9} exp({minus}3.7 {+-} 0.2 {times} 10{sup -3}p), where D{sub e} is the effective diffusion coefficient (m{sup 2}s{sup -1}) of DO in compacted sodium bentonite and p is the dry density (kg m{sup -3})of compacted sodium bentonite. The oxygen concentration in the bentonite is expected to be controlled by the oxidation of pyrite as an impurity in the bentonite. To investigate this idea, the rates of pyrite oxidation bymore » DO in compacted sodium bentonite were estimated from the experimental data in pyrite-bentonite systems using the obtained effective diffusion coefficient of DO. The results show that the average of the rate constants of pyrite oxidation by DO in compacted sodium bentonite was 1.16 {+-} 0.35 {times} 10{sup {minus}8}m s{sup {minus}1}, whereas the rate constant in a carbonate-buffered solution (pH = 9.24) was 1.46 {+-} 0.09 {times}10{sup {minus}9}m s{sup {minus}1}.« less

Authors:
; ;
Publication Date:
Research Org.:
Japan Nuclear Cycle Development Inst., Tokai, Ibaraki (JP)
OSTI Identifier:
20030427
Resource Type:
Journal Article
Journal Name:
Nuclear Technology
Additional Journal Information:
Journal Volume: 130; Journal Issue: 2; Other Information: PBD: May 2000; Journal ID: ISSN 0029-5450
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; 12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; RADIOACTIVE WASTE DISPOSAL; HIGH-LEVEL RADIOACTIVE WASTES; CONTAINMENT SYSTEMS; RADIOACTIVE WASTE FACILITIES; BENTONITE; GROUND WATER; DISSOLVED GASES; OXYGEN; OXIDATION; PYRITE

Citation Formats

Manaka, Mitsuo, Kawasaki, Manabu, and Honda, Akira. Measurements of the effective diffusion coefficient of dissolved oxygen and oxidation rate of pyrite by dissolved oxygen in compacted sodium bentonite. United States: N. p., 2000. Web.
Manaka, Mitsuo, Kawasaki, Manabu, & Honda, Akira. Measurements of the effective diffusion coefficient of dissolved oxygen and oxidation rate of pyrite by dissolved oxygen in compacted sodium bentonite. United States.
Manaka, Mitsuo, Kawasaki, Manabu, and Honda, Akira. Mon . "Measurements of the effective diffusion coefficient of dissolved oxygen and oxidation rate of pyrite by dissolved oxygen in compacted sodium bentonite". United States.
@article{osti_20030427,
title = {Measurements of the effective diffusion coefficient of dissolved oxygen and oxidation rate of pyrite by dissolved oxygen in compacted sodium bentonite},
author = {Manaka, Mitsuo and Kawasaki, Manabu and Honda, Akira},
abstractNote = {The redox condition of the near field is expected to affect the performance of engineered barrier systems. In particular, the oxygen initially existing in the pore spaces of compacted bentonites strongly affects the redox condition of the near field. To assess the influence of the oxygen, research was done to assess its transport parameters in the compacted bentonite and consumption process. To understand the diffusion of dissolved oxygen (DO) in compacted bentonite and to predict the effect of the DO, the measurements of the effective diffusion coefficient of DO in compacted sodium bentonite were made by electro-chemistry. As a result, the following relationship between the dry density of compacted sodium bentonite and the effective diffusion coefficient of DO in compacted sodium bentonite was derived: D{sub e} = 3.0 {+-} 0.5 {times} 10{sup {minus}9} exp({minus}3.7 {+-} 0.2 {times} 10{sup -3}p), where D{sub e} is the effective diffusion coefficient (m{sup 2}s{sup -1}) of DO in compacted sodium bentonite and p is the dry density (kg m{sup -3})of compacted sodium bentonite. The oxygen concentration in the bentonite is expected to be controlled by the oxidation of pyrite as an impurity in the bentonite. To investigate this idea, the rates of pyrite oxidation by DO in compacted sodium bentonite were estimated from the experimental data in pyrite-bentonite systems using the obtained effective diffusion coefficient of DO. The results show that the average of the rate constants of pyrite oxidation by DO in compacted sodium bentonite was 1.16 {+-} 0.35 {times} 10{sup {minus}8}m s{sup {minus}1}, whereas the rate constant in a carbonate-buffered solution (pH = 9.24) was 1.46 {+-} 0.09 {times}10{sup {minus}9}m s{sup {minus}1}.},
doi = {},
journal = {Nuclear Technology},
issn = {0029-5450},
number = 2,
volume = 130,
place = {United States},
year = {2000},
month = {5}
}