Simulation of in situ uraninite leaching; Part 1: A partial equilibrium model of the NH[sub 4]HCO[sub 3]-(NH[sub 4])[sub 2]CO[sub 3]H[sub 2]O[sub 2] leaching system

Journal Article · Fri Apr 01 00:00:00 EST 1994 · Metallurgical Transactions, B (Process Metallurgy); (United States)

OSTI ID:7040858

Liddell, K C ^[1]; Bautista, R G ^[2]

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1. Washington State Univ., Pullman, WA (United States). Dept. of Chemical Engineering
2. Univ. of Nevada, Reno, NV (United States). Dept. of Chemical and Metallurgical Engineering

In situ leaching of uraninite is relevant to both uranium production processes and environmental remediation. In situ leaching of uraninite and calcite by H[sub 2]O[sub 2]-NH[sub 4]HCO[sub 3]-(NH[sub 4])[sub 2]CO[sub 3] solutions has been simulated using a partial equilibrium model which incorporates a one-parameter mixing cell model of solution flow. Rate laws for UO[sub 2] dissolution and for CaCO[sub 3] dissolution/precipitation were taken from the literature, as were equilibrium constants for solution phase reactions. Parameters of the model include the UO[sub 2] and CaCO[sub 3] ore grades, the concentrations of the H[sub 2]O[sub 2], NH[sub 4]HCO[sub 3], and (NH[sub 4])[sub 2]CO[sub 3] components, porosity, exit solution flow rate, ore and mineral densities, and mineral rate constants and surface areas. Mineral conversions, component and species concentrations, and porosity are among the time-dependent quantities calculated using the model. For the conditions simulated, calcite dissolved somewhat faster than uraninite. The results emphasize the importance of the coupling between the mineral reactions and solution flow. Changes in the concentrations of the CO[sup 2[minus]][sub 3] and HCO[sup [minus]][sub 3] species are particularly complicated and not predictable from the calcite kinetics alone or from a purely equilibrium model; although the simulations did not reveal any conditions under which the solution would become saturated with CaCO[sub 3], the pH continued to change throughout the calcite dissolution and is buffered only after calcite has been consumed.

• OSTI ID: 7040858
• Journal Information: Metallurgical Transactions, B (Process Metallurgy); (United States), Vol. 25:2; ISSN 0360-2141
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
54 ENVIRONMENTAL SCIENCES
AMMONIUM CARBONATES
SOLVENT PROPERTIES
HYDROGEN PEROXIDE
URANINITES
IN-SITU PROCESSING
LEACHING
MATHEMATICAL MODELS
REMEDIAL ACTION
AMMONIUM COMPOUNDS
CARBON COMPOUNDS
CARBONATES
DISSOLUTION
HYDROGEN COMPOUNDS
MATERIALS
MINERALS
OXIDE MINERALS
OXYGEN COMPOUNDS
PEROXIDES
PROCESSING
RADIOACTIVE MATERIALS
RADIOACTIVE MINERALS
SEPARATION PROCESSES
URANIUM MINERALS
050100* - Nuclear Fuels- Reserves
Exploration
& Mining
054000 - Nuclear Fuels- Health & Safety
540250 - Environment
Terrestrial- Site Resource & Use Studies- (1990-)