Study of the Leaching Behaviour of Sintered UO2 in Groundwater Using Nuclear Microprobe Techniques

1994 ◽  
Vol 353 ◽  
Author(s):  
Patrick Trocellier ◽  
Jean Paul Gallien ◽  
Christelle Cachoir ◽  
Pierre Toulhoat
Keyword(s):  
Redox Potential ◽  
Partial Pressure ◽  
Nuclear Microprobe ◽  
Controlled Conditions ◽  
Reducing Conditions ◽  
Synthetic Groundwater ◽  
Leaching Behaviour ◽  
Solubility Control

AbstractThe leaching behaviour of sintered UO2 pellets has been studied in synthetic groundwater at 96 °C under strictly controlled conditions (CO2 partial pressure, O2 partial pressure, pH and redox potential). Results obtained in oxidizing conditions (O2 content varying from 5 to 25 ppm) show a strong initial uranium release in solution during the first five days and a solubility control essentially driven by the growth of U(VI) species such as oxides, hydrates and carbonates. Results obtained in reducing conditions (use of a mineralogical buffer of Ni(0)/Ni(ll) with E0 = -0.257 Volts) show a very weak uranium release in solution close to 10-11 mole/l and a solubility control essentially driven by the formation of U(IV) compounds such as coffinite or uraninite.

scholarly journals Arsenic Release from Contaminated Soil of Bangladesh in Natural Field Conditions

2009 ◽  
Vol 1 (2) ◽  
pp. 258-269 ◽  
Author(s):  
M. S. Azam ◽  
M. Shafiquzzaman ◽  
Iori Mishima ◽  
Jun Nakajima
Keyword(s):  
Redox Potential ◽  
Field Conditions ◽  
Iron Release ◽  
Natural Field ◽  
Primary Mechanism ◽  
Reducing Conditions ◽  
Groundwater Arsenic ◽  
Synthetic Groundwater ◽  
Calcium And Magnesium ◽  
The Difference

Leaching experiment was conducted to understand the mechanism of arsenic release from soil in the natural field conditions. Two types of column were run, one with de-ionized water (DW) and another with synthetic Bangladesh groundwater (GW) as influent which simulated rainfall and groundwater conditions, respectively. As the primary mechanism for the arsenic release from soil it was identified that the redox potential (Eh) was major importance. In highly reducing conditions both arsenic and iron release was high. Released mass of arsenic was higher in DW column than GW column. The difference was caused by the presence of calcium and magnesium ion in the synthetic groundwater. Comparing to the acid-alkali sequential extraction it was found that calcium and magnesium prohibited the release of arsenic bound with iron. The effect of calcium and magnesium was clarified in the batch experiment performed in the study.Keyword: Paddy field; Groundwater; Arsenic; Redox potential; pH. © 2009 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. DOI: 10.3329/jsr.v1i2.1708

Comparison of the Dissolution Behaviour of Various UO2Samples in Saline Solution at 100°C Under Reducing Conditions

1993 ◽  
Vol 333 ◽  
Author(s):  
S. Stroes-Gascoyne ◽  
J.C. Tait ◽  
R.J. Porth ◽  
J.L. McConnell ◽  
A.M. Duclos
Keyword(s):  
Saline Solution ◽  
Radiation Characteristic ◽  
Combined Effects ◽  
Used Nuclear Fuel ◽  
Reducing Conditions ◽  
Dissolution Behaviour ◽  
Gamma Radiolysis ◽  
Leaching Experiments ◽  
Leaching Behaviour ◽  
High Burnup

ABSTRACTThe separate effects of alpha- and gamma-radiolysis on UO2dissolution can be studied with unirradiated UO2, whereas studies vith used nuclear fuel necessarily always include both alpha- and gamma-radiolysis effects. This paper attempts to separate these effects by comparing the leaching behaviour in saline solution of a number of UO2samples (each vith a particular radiation characteristic or chemical property inherent to used fuel) vith the leaching behaviour of used fuel. Data from leaching experiments vith lov- and high-burnup CANDU (CANada Deuterium Uranium) fuels are also compared. The results indicate that the presence of an alpha field at 100°C under reducing conditions does not increase UO2dissolution but suggest that the combined effects of the beta and gamma fields in used CANDU fuel may enhance UO2dissolution.

Leaching Behaviour of Metals from a Sphalerite Concentrate in Sulfuric Acid-Oxygen System

2011 ◽  
Vol 201-203 ◽  
pp. 1725-1731
Author(s):  
Cun Xiong Li ◽  
Chang Wei ◽  
Hong Sheng Xu ◽  
Ji Qiang Liao ◽  
Zhi Gan Deng ◽  
...  
Keyword(s):  
Experimental Data ◽  
Particle Size ◽  
Sulfuric Acid ◽  
Partial Pressure ◽  
Elemental Sulphur ◽  
Partial Pressure Of Oxygen ◽  
Mineralogical Analysis ◽  
Oxygen System ◽  
Copper Indium ◽  
Leaching Behaviour

Leaching behaviors of zinc, copper, indium and iron from a sphalerite concentrate in sulfuric acid-oxygen system has been investigated in the present paper. Various parameters were studied including particle size, concentration of sulfuric acid, partial pressure of oxygen, leaching temperature, and leaching time. The experimental data indicated that under the typical plant conditions employed up to 99% zinc , 85% copper and 90% indium extraction were achieved. The mineralogical analysis of the residue showed that the main minerals are elemental sulphur, unreacted pyrite and quartz, the amount of sulphide sulphur oxidized to sulfur during leaching is 81%. This process provides an effective way for the extraction of zinc, copper and indium from sphalerite concentrate.

Dissolution Behavior of Waste Glass Under Reducing Condition

1993 ◽  
Vol 333 ◽  
Author(s):  
Tsuyoshi Imakita ◽  
Kaoru Sasakawa ◽  
Fumio Matsuda ◽  
Ryutaro Wada
Keyword(s):  
Carbon Steel ◽  
Corrosion Rate ◽  
Redox Potential ◽  
Corrosion Test ◽  
Waste Glass ◽  
Dissolution Behavior ◽  
Leaching Behavior ◽  
Reducing Conditions ◽  
Reducing Condition

ABSTRACTA corrosion test of a model waste glass was carried out with and without carbon steel, and the leaching behavior of the glass was studied under reducing condition in a glove box purged with N2. The redox potential and pH were monitored, and the concentration of Fe, Na, Si, and Mo in the leachates were measured to understand the leaching behavior of the glass. The redox potential of the leachates obtained in the corrosion test coexisting with carbon steel under reducing conditions showed initially that it was based on an Fe0/Fe2+ redox potential, and gradually it increased to that based on Fe2+/Fe3+ one. The corrosion rate of the glass under oxidizing conditions was ten times greater than that obtained with carbon steel, and that under reducing condition with carbon steel was negligible small.

scholarly journals INFLUENCE OF DRAINAGE REGIME ON THE CHEMISTRY AND MORPHOLOGY OF SOME MANITOBA SOILS: SANDY CHERNOZEMIC AND GLEYSOLIC SOILS OF THE LOWER ASSINIBOINE DELTA

1984 ◽  
Vol 64 (4) ◽  
pp. 587-604 ◽  
Author(s):  
W. MICHALYNA ◽  
R. H. RUST
Keyword(s):  
Redox Potential ◽  
Soil Temperature ◽  
Early Summer ◽  
Near Surface ◽  
Groundwater Levels ◽  
Reducing Conditions ◽  
Exchangeable Ca ◽  
Morphological Criteria ◽  
Water Tables

A number of imperfectly and poorly drained sandy soils from the Almasippi Association of the Lower Assiniboine Delta in Manitoba, traditionally classified as Gleyed Chernozems and Gleysols, were characterized by morhological descriptions, chemical and physical analyses. Soil temperature, groundwater levels, and redox potential of both soil and water were determined at selected sites for various periods to a maximum of 2 years. The upper 30 cm of the soils, traditionally considered as Gleysols, had undergone strong reducing conditions (100 to −200 mV) for at least 2 mo in the spring and early summer; these areas were covered with hydrophytic vegetation and remained saturated at or near surface to July. The subsoil below 45 cm remained in an oxidized state throughout the year. Exchangeable Ca/Mg ratio was near unity in the Gleysols and substantially greater in the Gleyed subgroups. Oxalate to dithionite-extractable iron ratios were greater than 0.45 in the lower part and below the solum of Gleysolic and Gleyed soils. In soils classified as Gleyed subgroups, water tables were below 1.3 m throughout the season and soil profiles were in an oxidized condition. Classification of these soils according to the present Canadian and U.S. system would require a change in concept and approach from the traditional view of Gleysolic soils in Canada. Key words: Redox potential, chemical criteria, morphological criteria, water table, soil temperature

In-situ analysis of chemical expansion and stability of SOFC cathodes

2014 ◽  
Vol 1655 ◽  
Author(s):  
Mirela Dragan ◽  
Scott Misture
Keyword(s):  
High Temperature ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Lattice Parameter ◽  
Low Oxygen ◽  
X Ray Diffraction ◽  
Chemical Expansion ◽  
X Ray ◽  
Reducing Conditions ◽  
The Stability

ABSTRACTIn this work high-temperature X-ray diffraction has been used to investigate thermal and chemical expansion as well as overall phase stability for various cathode materials: Ba0.5Sr0.5Co0.8Fe0.2O3 (BSCF), La0.3Sr0.7CoO3 (LSC37), La0.6Sr0.4CoO3 (LSC64) and La0.6Sr0.4Fe0.8Co0.2O3 (LSCF), as a function of temperature in reducing conditions. When perovskites materials are under a low oxygen partial-pressure condition, the lattice parameter and overall dimension increase. Their chemical expansion has comparable values. From the viewpoint of the stability of these phases, the high-temperature X-ray diffraction results indicate no phase decomposition can be one of the reasons for material failure at the current experimental oxygen partial pressure. LSF is most stable, while LSC and LSCF form oxygen vacancy-ordered phases and then decompose when heated to 1000°C under atmospheres with pO2 as low as 10-5 atm.

Redox state affects methane flux in a northern boreal flark fen

2020 ◽  
Author(s):  
Markku Koskinen ◽  
Hanna Finné ◽  
Tarmo Virtanen ◽  
Annalea Lohila ◽  
Raija Laiho ◽  
...  
Keyword(s):  
Redox Potential ◽  
Methane Flux ◽  
Initial Step ◽  
Continuous Variable ◽  
Electron Acceptors ◽  
Soil Redox Potential ◽  
Soil Redox ◽  
Reducing Conditions ◽  
Production And Consumption ◽  
Flux Measurements

<p>Long-term continuous measurement of reduction-oxidation (redox) potential is an emerging tool for analysing ecosystem status. Redox processes are intrinsically linked to methane (CH<sub>4</sub>) production and consumption in soils. Under highly reducing conditions, acetate and carbon dioxide (CO<sub>2</sub>) are reduced into CH<sub>4</sub>, while at less reducing conditions, CH<sub>4</sub> is readily oxidised into CO<sub>2</sub>. These oxidation processes do not necessarily require oxygen; other electron acceptors such as nitrate (NO<sub>3</sub><sup>-</sup>) and iron can also be used by microbes. The prevalence of different electron acceptors and donors is reflected in the redox potential of the soil solution which can be measured. Thus measurements of soil redox potential could in principle be used for predicting CH<sub>4</sub> flux.</p><p>We measured soil redox potential at 4 depths between 5 and 40 cm continuously over one growing season on nine measurement plots on three different microsites (flark, lawn and string), in a north boreal flark fen, while concurrently measuring CO<sub>2</sub> and CH<sub>4</sub> flux of the same plots using the manual chamber method. Flux measurements were conducted five to seven times per week from late June to late September, 2019. Along with the redox potential, water table level (WTL), air and soil temperature (Tair, Tsoil) and several vegetation characteristics were also measured.</p><p>Tsoil was found to be the major control of the momentary CH<sub>4</sub> flux, but after standardizing the flux to 10 C using the Lloyd-Taylor equation, including the soil redox potential was found to significantly (p < 0.001) improve the prediction of the flux over a model incorporating only WTL and momentary Tsoil.</p><p>This is an initial step towards inclusion of redox potential as a continuous variable describing the processes active in the soil into CH<sub>4</sub> production/consumption models.</p>

Sign in / Sign up

Export Citation Format

Share Document