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Radiolytic Modelling: Application To Spent Fuel Dissolution Experiments

Published online by Cambridge University Press:  11 February 2011

Juan Merino ,
Esther Cera  and
Jordi Bruno
Juan Merino
Affiliation:
Enviros Spain, Pg. de Rubí, 29–31 08197 Valldoreix, Spain
Esther Cera
Affiliation:
Enviros Spain, Pg. de Rubí, 29–31 08197 Valldoreix, Spain
Jordi Bruno
Affiliation:
Enviros Spain, Pg. de Rubí, 29–31 08197 Valldoreix, Spain
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Abstract

In this work we describe our first efforts to simulate the chemical evolution of the spent fuel/water system in dissolution experiments using a radiolytic model. These experiments were carried out with spent fuel fragments in deionized water [1]. In order to build the radiolytic model, a set of reactions were selected, together with their kinetic constants, including the catalytic decomposition of H2O2 in the UO2 surface and a reaction mechanism for UO2 oxidation and dissolution. Averaged alpha and beta G-values were used, neglecting gamma radiation. Diffusion to the gas phase was treated thermodynamically assuming Henry's law. The computer code used in the simulations was CHEMSIMUL [9]. First attempts to simulate the experimental results were not successful and a sensitivity analysis was carried out. As a result of this, the kinetic constant of the reaction OH• + H2 → H• + H2O, the only reaction that consumes hydrogen in the system, was identified as a key parameter, together with the kinetic constants of the UO2 oxidation and dissolution reactions. Varying these parameters we were able to reproduce the experimental data. Although more simulations are needed, these results are encouraging because they give us more confidence in the use of radiolytic models as useful tools to predict the long-term alteration rate of the spent fuel under repository conditions, which is our ultimate goal.

Type
articles
Information
MRS Online Proceedings Library (OPL) , Volume 757: Symposium II – Scientific Basis for Nuclear Waste Management XXVI , 2002 , II9.10
Copyright
Copyright © Materials Research Society 2003

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References

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