Development and Characteristics of a New Porous Glass Crystalline Matrix (Gubka) for Stabilizing Radioactive and Hazardous Solutions

Abstract

This paper describes the results of a joint research program of Russian institutes at St. Petersburg, Krasnoyarsk and Zheleznogorsk and the Idaho National Engineering and Environmental Laboratory to develop a new material for stabilizing radioactive solutions and other uses, such as high-temperature catalysis. An open-cell glass crystalline porous material, Gubka, or “sponge” in Russian, having an open-cell porosity of up to 90 %, was produced from hollow glass crystalline microspheres (cenospheres) formed in fly ash from coal combustion. The cenospheres were separated into fractions based on grain size, density, magnetic properties, and whether or not they were perforated. Selected fractions were molded and agglomerated by sintering with or without a binder at high temperatures. Depending on the cenosphere fractions selected, sintering conditions and additional treatments, Gubka was formed with an open-cell porosity ranging from 40-90 %. The porous material has a bulk density of 0.3-0.6 g/cm3, and two types of porous openings: 0.1-30 micrometer flow-through pores in the cenosphere walls and 20-100 micrometer interglobular pores between the cenospheres. Examples of Gubka application described in this paper include stabilization of different surrogate radioactive waste solutions containing 0.0001 to 0.7 M nitric/hydrochloric acid and 0 to 1.2 M sodium nitrate. Waste solid loadings of 46-55 wt.% nitrate salts, or 26-37 wt.% oxides after calcination, were achieved in those tests.

An Inorganic Microsphere Composite for the Selective Removal of137Cesium from Acidic Nuclear Waste Solutions. 1: Equilibrium Capacity and Kinetic Properties of the Sorbent

“…[15] The material is an open-cell glass crystalline porous material, shown in Fig. 1, that is produced from hollow glass crystalline microspheres (cenospheres) formed as small mineral slag particles in fly ash from coal combustion.…”

Polyfunctional microspherical materials for long-term disposal of liquid radioactive wastes

“…The porous matrices were successfully tested at radiochemical plants in Russia and United States in different variants of the immobilization of liquid radioactive wastes, including the solidification with fixation of radionuclides in a free volume of the matrix with the aim of transporting to sites of storage or further repro- cessing [25,26]. It was demonstrated that the saturation of the porous matrices after calcination is as high as 45 wt % with respect to nitrates and 33 wt % with respect to oxides.…”

Immobilization of Cesium and Strontium Radionuclides in Framework Aluminosilicates with the Use of Porous Glass-Ceramic Matrices Based on Coal Fly Ash Cenospheres

“…Porous matrices were saturated to 55 wt % with nitrate salts, and calcinated products were saturated to 33 wt % with oxides [24][25][26]. These experiments showed that porous matrices based on coal fly ash cenospheres can be used for intermediate storage of solidified radioactive wastes and transportation to sites of reprocessing or long-term storage.…”