Ion exchange has proven useful for decontamination of radioactive waste waters. Zeolites are now used for this task. Zeolites show several advantages over other ion exchange materials. Ion exchange rates and capacity of zeolites are high. Zeolites are also easily handled. However, optimum size of zeolites for ion exchange is approximately 10-50 mesh. The hot zeolite must be converted to a glass-like brick; 10-50 mesh zeolite does not melt evenly to form a suitable solidified mass. The hot zeolite must be ground to fine sizes. Prototype ultrasonic grinders have been developed. Most of the development work has been performed using coal. The principle of operation is to cause the coal particles to vibrate ultrasonically. Fatigue crack growth occurs along grain boundaries and discontinuities within several hundred cycles. Remarkably narrow particle size distributions have been observed with coals at modest power inputs. The current prototype configuration, a 4-in. resonant tube-auger, is capable of grinding water-slurried coal at a rate of about 130 kg/hr. A single sample of zeolite has also been ground, and comminuted product of 10-30 um has been observed. It is planned to examine the grinding variables that control zeolite comminution. The prototype grinders have variable gaps, and the gap size required to produce optimized ground zeolite will be determined as will the optimized grinding rate to produce properly comminuted zeolite. The latter data will be used to size a grinder to grind hot zeolite at a rate of not less than 20 kg/hr. Design work will be started on feed, collection, and operating controls for use in a hot cell. Remote-operating features will be used whenever possible. The new grinder will be designed so that all parts have no single dimension larger than 0.6 m.Anticipated Results/Potential Commercial Applications as described by the awardee:It is anticipated that a successful Phase I effort will lead to the development of a prototype grinder. The grinder will be capable of comminuting zeolites to 50-um size range during remote operation. The grinder will be capable of processing at least 20 kg/hr zeolites in water slurry. Successful Phase II effort will result in the enhanced ability of the nuclear industry to decontaminate reactors. Better control of radioactive wastes could lead to increased use of nuclear power. Commercial partners will be sought to further develop the Phase II prototype grinding system into a commercial system. The developed system will be supplied to the nuclear industry.
