Transport and Storage Properties of CST Slurries for the Savannah River Site

Abstract

Pumping tests have shown that a 24 wt % slurry of CST in water can be transported at fluid velocities of 4.3 ftls (45 gpm in a 2-in. pipe) with no visible settling of the CST particles, while a 5 wt 1% slurry will stay suspended at a velocity of 3.8 Ms. The CST was easily mobilized after purposely plugging sections of pipe. The CST particles were rapidly broken up by a centrifugal pump into very small particles (<150 Km, with the majority being <1 .um). A progressing cavity (Moyno) pump caused less damage to the CST particles.Slurries of CST in water showed low abrasivity to 304L stainless steel and moderate abrasivity to A106 mild steel. A slurry of CST in median supemate (2.9 MNaOH plus other salts) showed low abrasivity to A106 steel, so the higher abrasivity result for CST in water was probably caused by oxidative corrosion. Sludge simukmt slurries showed low abrasivity, but mixtures of sludge and zeolite showed moderate abrasively.Storage of cesiurn-loaded CST in supemate simukmts has shown possible leaching of the cesium from the CST into median and high-concentration (13.5 illNaOH) supemate sirnulants at 80°C. There was no measurable leaching after 105 days in any of the simukmts at 25 'C, or in lowconcentration simulant (0.01 MNaOEl) at 80"C.Mixtures of CST in SRS sludge simulants have shown minimal tendency to cause caking or hard layers. Supernate sinmkmts that cover the range of solutions in the SRS high-level waste storage tanks have shown minimal effect on the particle size of the CST sorbent.

Literature Reviews to Support Ion Exchange Technology Selection for Modular Salt Processing

“…Other studies indicated only minor decreases (1-2%) in cesium loading resulting from 55 ºC exposure for 14 days (Wilmarth, 2000b). Initial studies conducted at 80 ºC indicated that these conditions lead to as much as a 72% decrease in cesium capacity (Taylor, 1999b). Storage in waste simulant for 6 months at 80 ºC lead to a 15% decrease in cesium capacity (after correction for aluminosilicate mass) in other studies.…”

“…Irreversible cesium desorption from IE-911 has also been observed after media exposure to temperatures as low as 50 ºC for 60 days and 55 ºC for 14 days in waste simulant (Taylor, 1999b;Su, 2001). Other studies indicated only minor decreases (1-2%) in cesium loading resulting from 55 ºC exposure for 14 days (Wilmarth, 2000b).…”

“…Mixing and distribution of IE-911 in sludge solids appears to alleviate these issues. IE-911/sludge mixtures show minimal tendencies to cake or form hard layers (Taylor, 1999b).…”