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Study of SIMFUEL corrosion under hyper-alkaline conditions in the presence of silicate and calcium

  • Alexandra Espriu-Gascon (a1), David W. Shoesmith (a2), Javier Giménez (a1), Ignasi Casas (a1) and Joan de Pablo (a1) (a3)...

Abstract

Cement has been considered as a possible material present in the Deep Geological Disposal (DGD) [1] . In order to determine the effect of cementitious waters on the oxidation of the surface of Spent Fuel (SF), a series of electrochemical experiments were performed, to study the influence of two main components of cementitious water: calcium and silicate.

Test solutions with Na2SiO3 and/or CaCl2 were prepared at pH 12 and NaCl 0.1 mol·dm-3 as ionic medium. A 3 at.% doped SIMFUEL was used to perform cyclic voltammetric (CV), potentiostatic and corrosion potential (ECORR) experiments. After potentiostatic and ECORR experiments, the SIMFUEL surface was analyzed using X-Ray Photoelecton Spectroscopy (XPS).

The results showed that the presence of silicate decreased the SIMFUEL oxidation between -100 mV and 300 mV. When Ca2+ was added, the whole oxidation process was shifted to higher potentials which indicated a protective effect of the combination of Ca2+ and SiO32- . The XPS results obtained after potentiostatic experiments at 200 mV showed that the presence of silicate partially suppressed the oxidation of SIMFUEL, as indicated by the contribution of both U(IV) and U(V) XPS to the U 4f7/2 band (∼ 38%). After the addition of calcium, the predominant uranium oxidized state contribution on the surface was U(V) (40%). After the ECORR experiments, the ECORR values were similar either with or without silicate in solution (-80 mV and -70 mV respectively). The resulting surface also exhibited a similar composition. When calcium was added to the electrolyte, the ECORR value was suppressed to -105 mV, and XPS showed that the surface was less oxidized than with the other two electrolytes.

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Keywords

Study of SIMFUEL corrosion under hyper-alkaline conditions in the presence of silicate and calcium

  • Alexandra Espriu-Gascon (a1), David W. Shoesmith (a2), Javier Giménez (a1), Ignasi Casas (a1) and Joan de Pablo (a1) (a3)...

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