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Modelling of the spent fuel dissolution rate evolution for repository conditions. Matrix Alteration Model results and sensitivity analysis

Published online by Cambridge University Press:  21 March 2011

J. Quiñones ,
E. Iglesias ,
A. Martínez-Esparza ,
J. Merino ,
E. Cera ,
J. Bruno ,
J. de Pablo ,
I. Casas ,
J. Giménez  and
F. Clarens
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J. Quiñones
Affiliation:
Ciemat. Avda. Complutense22, 28040-Madrid., SPAIN
E. Iglesias
Affiliation:
Ciemat. Avda. Complutense22, 28040-Madrid., SPAIN
A. Martínez-Esparza
Affiliation:
ENRESA, C/ Emilio Vargas 7, 28043-Madrid., SPAIN
J. Merino
Affiliation:
ENVIROS, Passeig de Rubi, 29-31, 08197 Valldoreix, Barcelona. SPAIN
E. Cera
Affiliation:
ENVIROS, Passeig de Rubi, 29-31, 08197 Valldoreix, Barcelona. SPAIN
J. Bruno
Affiliation:
ENVIROS, Passeig de Rubi, 29-31, 08197 Valldoreix, Barcelona. SPAIN
J. de Pablo
Affiliation:
Dept. of Chemical Engineering. ETSEIB-UPC, Diagonal 647 H-4, 08028 Barcelona., SPAIN
I. Casas
Affiliation:
Dept. of Chemical Engineering. ETSEIB-UPC, Diagonal 647 H-4, 08028 Barcelona., SPAIN
J. Giménez
Affiliation:
Dept. of Chemical Engineering. ETSEIB-UPC, Diagonal 647 H-4, 08028 Barcelona., SPAIN
F. Clarens
Affiliation:
Dept. of Chemical Engineering. ETSEIB-UPC, Diagonal 647 H-4, 08028 Barcelona., SPAIN
M. Rovira
Affiliation:
Dept. of Chemical Engineering. ETSEIB-UPC, Diagonal 647 H-4, 08028 Barcelona., SPAIN
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Abstract

This paper focuses on how to extrapolate current knowledge of spent fuel matrix alteration processes from laboratory to repository conditions, i.e., the influence of changes in both the environmental conditions and the range of time scale considered. Therefore, a spent fuel matrix alteration model allowing the alteration rate evolution to be predicted as a function of both the host rock considered and evaluation time scale of interest is described.

At present, the model assumes that alteration of the spent fuel will start when the groundwater reaches the solid surface and that only the radiolytic species of the groundwater (oxidants generated by α-radiation of spent fuel) will produce the surface oxidation process and subsequent matrix dissolution; O2, H2O2 and OH· are the species that react with UO2(s) for oxidation of the pellet surface. The dissolution process of the surface sites that are oxidized is modelled in two steps: first, a surface co-ordination of the oxidized layer with aqueous ligands and, second, detachment (dissolution) of the product species. Taking this mechanism into account, the model gives the evolution of the spent fuel matrix alteration rate over periods as long as 1,000,000 years.

In this work the matrix alteration rate results obtained for two repository environments, granitic and argillaceous, will be presented. Furthermore, a sensitivity analysis study has been performed on the influence of the following variables: type of spent fuel considered, α-dose rate evolution, α-range in groundwater, carbonate and iron concentration in groundwater, H2 partial pressure, container time failure and specific surface area of the pellet.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 932: Symposium – Scientific Basis for Nuclear Waste Management XXIX , 2006 , 78.1
Copyright
Copyright © Materials Research Society 2006

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References

REFERENCES

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