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The understanding of the R7T7 glass blocks long term behavior: chemical and transport coupling in fractured media; Comprehension de l'alteration a long terme des colis de verre R7T7: etude du couplage chimie transport dans un milieu fissure

Abstract

The long term behavior of nuclear waste glass blocks depends highly on chemical reactions which occur at the surface in contact with water. Studies carried out on inactive fractured glass blocks show that fracture networks play a significant part in reactive surface area. Nevertheless, the complexity of results interpretation, due to a weak knowledge of fracture networks and local lixiviation conditions, does not allow us to comprehend the physical and chemical mechanisms involved. Model cracks are a key step to study chemical and transport coupling in fractured media. Crack lixiviation in aggressive conditions (pH{>=}11) show that the crack's position (horizontal or vertical) determines the dominant transport mechanism (respectively diffusion or convection induced by gravity). This gravity driven flow seems to be negligible in lower pH conditions. The convective velocity is estimated by a 1D model of reactive transport. Two other parameters are studied: the influence of thermal gradient and the influence of interconnected cracks on alteration. A strong retroactive effect of convection, due to thermal gradient, on the alteration kinetic is observed inside the crack. These works lead to a complete alteration experiment of a 163 crack network subject to a thermal gradient. The use of the geochemical software, HYTEC,  More>>
Authors:
Publication Date:
Apr 15, 2008
Product Type:
Thesis/Dissertation
Report Number:
CEA-R-6208
Resource Relation:
Other Information: TH: These Ecole Doctorale 397: physique et chimie de materiaux. Specialite: Chimie; 149 refs
Subject:
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; BOROSILICATE GLASS; CHEMICAL REACTION KINETICS; COMPUTERIZED SIMULATION; CRACKS; FRACTURES; HIGH-LEVEL RADIOACTIVE WASTES; HYDROLYSIS; LEACHING; RESEARCH PROGRAMS; UNDERGROUND STORAGE; VITRIFICATION
OSTI ID:
21217234
Research Organizations:
Paris-6 Univ. Pierre et Marie Curie, 75 (France); CEA Marcoule, Dept. d'Etudes du Traitement et du Conditionnement des Dechets, Service d'Etude et Comportement des Materiaux de Conditionnement, 30 (France)
Country of Origin:
France
Language:
French
Other Identifying Numbers:
TRN: FR0902480086016
Availability:
Available from INIS in electronic form
Submitting Site:
FRN
Size:
216 pages
Announcement Date:
Oct 17, 2009

Citation Formats

Chomat, L. The understanding of the R7T7 glass blocks long term behavior: chemical and transport coupling in fractured media; Comprehension de l'alteration a long terme des colis de verre R7T7: etude du couplage chimie transport dans un milieu fissure. France: N. p., 2008. Web.
Chomat, L. The understanding of the R7T7 glass blocks long term behavior: chemical and transport coupling in fractured media; Comprehension de l'alteration a long terme des colis de verre R7T7: etude du couplage chimie transport dans un milieu fissure. France.
Chomat, L. 2008. "The understanding of the R7T7 glass blocks long term behavior: chemical and transport coupling in fractured media; Comprehension de l'alteration a long terme des colis de verre R7T7: etude du couplage chimie transport dans un milieu fissure." France.
@misc{etde_21217234,
title = {The understanding of the R7T7 glass blocks long term behavior: chemical and transport coupling in fractured media; Comprehension de l'alteration a long terme des colis de verre R7T7: etude du couplage chimie transport dans un milieu fissure}
author = {Chomat, L}
abstractNote = {The long term behavior of nuclear waste glass blocks depends highly on chemical reactions which occur at the surface in contact with water. Studies carried out on inactive fractured glass blocks show that fracture networks play a significant part in reactive surface area. Nevertheless, the complexity of results interpretation, due to a weak knowledge of fracture networks and local lixiviation conditions, does not allow us to comprehend the physical and chemical mechanisms involved. Model cracks are a key step to study chemical and transport coupling in fractured media. Crack lixiviation in aggressive conditions (pH{>=}11) show that the crack's position (horizontal or vertical) determines the dominant transport mechanism (respectively diffusion or convection induced by gravity). This gravity driven flow seems to be negligible in lower pH conditions. The convective velocity is estimated by a 1D model of reactive transport. Two other parameters are studied: the influence of thermal gradient and the influence of interconnected cracks on alteration. A strong retroactive effect of convection, due to thermal gradient, on the alteration kinetic is observed inside the crack. These works lead to a complete alteration experiment of a 163 crack network subject to a thermal gradient. The use of the geochemical software, HYTEC, within the framework of this study shows the potential of the software which is however limited by the kinetics law used. (author)}
place = {France}
year = {2008}
month = {Apr}
}