Ceramics-Silikáty 46, (3) 86 - 96 (2002)

The study is concerned with the corrosion of ultrapotash uranium glasses from the Rejštejn - Klášterský Mlýn locality in Šumava Mountains, Czech Republic. The glass samples were taken from the dump of a former glassworks. They stemmed from the year 1925 ± 5 years (the dating was done historically). The section also comprises soil, coal slag and alluvial sediments from the Otava river. Planar beta activity was measured in the section: the lowest one of 0.34 kBq/m² in soil and the highest of 3.25 kBq/m² in the horizon of the U-glasses. Four types of U-glasses were distinguished: yellow, green alabaster, green and green-blue. They contain 0.088 to 0.33 wt.% U and 8 to 14 wt.% K. The pH (aqueous extract) varies from 5.11 in coal slag to 7.70 in the glass layers. The total content of U in the ˂ 2 mm grain size fraction in the section was in the range from 4.8 ppm in the alluvial deposit up to 56.5 ppm in the glass layer. The content of U leachable by 1M CH₃COONa ranges from 7 ppb in soil to 65 ppb in the glass horizon. Uranium migrates into the alluvium in the underlying bed of the dump (content of up to 58.9 ppb of leachable U). Under the given conditions in alluvium one can suppose the immobilisation of U, whereas As and Pb are transported further. The green alabaster U-glass at the surface and along cracks has become corroded to a depth of 10 to 400 mm. Contraction fissures in the corroded layer are coated with precipitated calcite. The corrosion involves leaching of alkalies (up to 14 wt.% of glass) from the glass, redistribution of uranium and sorption of lead on the surface. IR spectroscopy prove the hydration of the glass, which is the result of K⁺ ↔ H₃O⁺ exchange.