Leaching of Radioactive Waste Surrogates from a Glassy Matrix and Migration of the Leaching Products in Gneisses

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Changes in the glassy matrix containing high-level waste surrogates after 24-h heating in an autoclave at 300°С with steam at 66% relative humidity were studied. Experiments were performed with an Na–Al–P glass sample containing Cs, Sr, Ce, Nd, and U. The effect of crystallization on the leaching of the elements from the glassy matrix and the form in which the waste surrogates are released into water were determined. The transport of the leaching products in a gneiss sample taken from the core of a borehole of the Yeniseiskii site of the Nizhnekansky massif was studied. REE and U occur in the solution after leaching mainly in the colloidal form. Colloidal particles of elements exhibit high mobility in migration in the rock.