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Gurvan Rousseau, Massoud Fattahi, Bernd Grambow, F. Boucher, G. Ouvrard

Coprecipitation of thorium and lanthanum with UO_2+x(s) as host phase

Keywords: Coprecipitation, UO2, Radionuclides, Solubility

Coprecipitation may be a significant process in controlling radionuclide release during spent fuel dissolution/reprecipitation in a breached geological disposal site by water. The objective of this work was to study the coprecipitation of thorium and lanthanum with UO_2+x(s) as host phase under reducing conditions (pure N₂ and E_h=−300 mV/SHE) as a function of pH and [Th]/[U+Th] or [La]/[U+La] initial concentration ratios. At pH values between 3 to 9, the final concentrations of dissolved Th and La were found to be considerably lower than expected if pure phases, Th(OH)₄(s) and La(OH)₃(s) would have been formed. Coprecipitation phenomena and formation of solid solutions Th_yU_1-yO_2+x′(s) and (U,La)O_2+x′(s) are suggested to be responsible for the lower solubility.

Radiochimica Acta, Oldenbourg Wissenschaftsverlag

Print ISSN: 0033-8230
Volume: 94, 09/2006
Pages: 517 - 522

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