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Kinetic and thermodynamic studies of uranium minerals. Assessment of the long-term evolution of spent nuclear fuel

Abstract

We have studied the dissolution behavior of uraninite, becquerelite, schoepite and uranophane. The information obtained under a variety of experimental conditions has been combined with extensive solid phase characterizations, performed in both leached and unleached samples. The overall objective is to construct a thermodynamic and kinetic model for the long-term oxidation alteration of UO{sub 2}(s), as an analogy of the spent nuclear fuel matrix. We have determined the solubility product for becquerelite (logK{sub s0} 32.7{+-}1.3) and uranophane (logK{sub s0} = 7.8{+-}0.8). In some experiments, the reaction progress has shown initial dissolution of uranophane followed by precipitation of a secondary solid phase, characterized as soddyite. The solubility production for this phase has been determined (logK{sub s0} = 3.0{+-}2.9). We have studied the kinetics of dissolution of uraninite, uranophane and schoepite under oxidizing conditions in synthetic granitic groundwater. BET measurements have been performed for uraninite and uranophane. For schoepite, the measurement has not been performed due to lack of sufficient amount of sample. The normalized rates of dissolution of uraninite and uranophane have been calculated referred to the uranium release, as 1.97x10{sup -8} moles h{sup -1} m{sup -2} and 4.0x 10{sup -9} moles h{sup -1} m{sup -2}, respectively. For schoepite, the dissolution  More>>
Authors:
Casas, I; Bruno, J; Cera, E; [1]  Finch, R J; Ewing, R C [2] 
  1. MBT Tecnologia Ambiental, Cerdanyola (Spain)
  2. Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM (United States)
Publication Date:
Oct 01, 1994
Product Type:
Technical Report
Report Number:
SKB-TR-94-16
Reference Number:
SCA: 052002; 360104; PA: AIX-26:042120; EDB-95:068931; ERA-20:015039; NTS-95:021997; SN: 95001382331
Resource Relation:
Other Information: PBD: Oct 1994
Subject:
05 NUCLEAR FUELS; 36 MATERIALS SCIENCE; BECQUERELITE; DISSOLUTION; SCHOEPITE; URANINITES; URANOPHANE; GROUND WATER; OXIDATION; RADIOACTIVE WASTE DISPOSAL; REACTION KINETICS; SOLUBILITY; THERMODYNAMICS; UNDERGROUND DISPOSAL; URANIUM OXIDES
OSTI ID:
38841
Research Organizations:
Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden)
Country of Origin:
Sweden
Language:
English
Other Identifying Numbers:
Journal ID: ISSN 0284-3757; Other: ON: DE95627051; TRN: SE9500048042120
Availability:
INIS; OSTI as DE95627051
Submitting Site:
SWDN
Size:
80 p.
Announcement Date:
May 15, 1995

Citation Formats

Casas, I, Bruno, J, Cera, E, Finch, R J, and Ewing, R C. Kinetic and thermodynamic studies of uranium minerals. Assessment of the long-term evolution of spent nuclear fuel. Sweden: N. p., 1994. Web.
Casas, I, Bruno, J, Cera, E, Finch, R J, & Ewing, R C. Kinetic and thermodynamic studies of uranium minerals. Assessment of the long-term evolution of spent nuclear fuel. Sweden.
Casas, I, Bruno, J, Cera, E, Finch, R J, and Ewing, R C. 1994. "Kinetic and thermodynamic studies of uranium minerals. Assessment of the long-term evolution of spent nuclear fuel." Sweden.
@misc{etde_38841,
title = {Kinetic and thermodynamic studies of uranium minerals. Assessment of the long-term evolution of spent nuclear fuel}
author = {Casas, I, Bruno, J, Cera, E, Finch, R J, and Ewing, R C}
abstractNote = {We have studied the dissolution behavior of uraninite, becquerelite, schoepite and uranophane. The information obtained under a variety of experimental conditions has been combined with extensive solid phase characterizations, performed in both leached and unleached samples. The overall objective is to construct a thermodynamic and kinetic model for the long-term oxidation alteration of UO{sub 2}(s), as an analogy of the spent nuclear fuel matrix. We have determined the solubility product for becquerelite (logK{sub s0} 32.7{+-}1.3) and uranophane (logK{sub s0} = 7.8{+-}0.8). In some experiments, the reaction progress has shown initial dissolution of uranophane followed by precipitation of a secondary solid phase, characterized as soddyite. The solubility production for this phase has been determined (logK{sub s0} = 3.0{+-}2.9). We have studied the kinetics of dissolution of uraninite, uranophane and schoepite under oxidizing conditions in synthetic granitic groundwater. BET measurements have been performed for uraninite and uranophane. For schoepite, the measurement has not been performed due to lack of sufficient amount of sample. The normalized rates of dissolution of uraninite and uranophane have been calculated referred to the uranium release, as 1.97x10{sup -8} moles h{sup -1} m{sup -2} and 4.0x 10{sup -9} moles h{sup -1} m{sup -2}, respectively. For schoepite, the dissolution process has shown two different rates, with a relatively fast initial dissolution rate of 1.97x10{sup -8} moles h{sup -1} followed, after approximately 1000 hours, by a slower one of 1.4x10{sup -9} moles h{sup -1}. No formation of secondary phases has been observed in those experiments, although final uranium concentrations have in all cases exceeded the solubility of uranophane, the thermodynamically more stable phase under the experimental conditions. 24 refs, 45 figs.}
place = {Sweden}
year = {1994}
month = {Oct}
}