Uranium Redox States in Borosilicate Compositions
- PDF / 324,655 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 97 Downloads / 146 Views
CC8.17.1
Uranium Redox States in Borosilicate Compositions A.S.Aloy, A.V. Trofimenko, O.A. Iskhakova, RPA « V.G. Khlopin Radium Institute» L.J. Jardine University of California, Lawrence Livermore National Laboratory, USA ABSTRACT The results of the studies of uranium valent states in the borosilicate glasses incorporating the components of uranium-containing sludge of Mining and Chemical Combine (MCC, Zheleznogorsks.) is presented in this work. The glasses were made under oxidative and reducing conditions. The optical spectrophotometry, nuclear gamma-resonance (NGR) and X-ray diffraction (XRD) showed that glasses produced under oxidative conditions are characterized by the presence of only U(6+), while U(4+) in the reducing conditions is present along with U(6+). The ratio U(6+)/ to U(4+) varies in depending on the synthesis conditions. The glass samples synthesized under oxidative conditions were researched at initial solid state. The others synthesized under reducing conditions was dissolved preliminary without distort of uranium valency. The effect of U(4+)/U(6+) ratio on the uranium leach rates from the glasses has been studied at 900С using MCC-1 test. INTRODUCTION It has been known [1-4] that uranium in aluminophosphate, aluminosilicate and borosilicate melts can be in three states, namely, (6+, 5+ and 4+). The ratio between different forms is depended on the redox conditions, melt composition and, to lesser degree, on temperature. In accordance with states, uranium at its low concentrations in the glasses (up to 1wt.% of oxide) can take part either as a glass network former in form of U(4+) or as the glass modifier in form of U(6+). The uranium structural position in a glass network effects on its mobility at leaching [58]. The uranium amounts in the separate probes of MCC sludge kept in the underground capacity reaches 77 g/l. It in terms of oxide is approximately 50 wt.%. So, uranium becomes the important glass macro component and thus its states and position in a glass network can influence on final product properties. The purpose of this paper was the study of the uranium states in the borosilicate glasses including the simulated uranium-containing sludge of MCC in depending of redox synthesis conditions and influence of uranium states on its leach rate. The uranium states in the glasses were determined using the optical spectrophotometry. The glass samples synthesized under oxidative conditions were researched at the initial solid state. The others synthesized under reducing conditions was dissolved preliminary without change of uranium valence.
CC8.17.2
THE SIMULATED COMPOSITIONS
SLUDGES
AND
SYNTHESIS
OF
BOROSILICATE
To obtain the simulated sludge, nitric acid solutions contained main cations presenting in the real sludge were reversed by alkaline precipitation with mixing at 95±50C. The sludges compositions in terms of oxide are shown in Table I. The simulated alkaline sludge was dried, calcined at 6000C till forming of oxides mixture. The oxidative synthesis was conducting in the air. The r
Data Loading...
