Study on In-Drum Drying Technology of Waste Concentrates

Abstract

The aim was to achieve the radioactive waste minimization in nuclear power plants by the treatment technology that can decrease the volume of waste concentrates, and the technological process of in-drum drying and the in-drum drying prototype device have been developed based on the investigation and survey, bench tests, and pilot experiments. Performances of in-drum drying of simulated waste concentrates are studied by the prototype device, in which boron concentrations are around 44,000 ppm and 30,000 ppm. The performances evaporated velocity of moisture, humidity and character of drying product, volume reduction ratio, and efficiency of decontaminate. The control parameters are optimized, and the prototype device is improved. The device has been improved, which is constituted with storage tank that maintains temperature by hot water, pneumatic diaphragm pump that transmits concentration, metering tank that can control the concentration volume of adding, infrared heater that controls temperature by adjusting power, jet pump that produces negative pressure, and pipe bundle condenser that condensates steam. The results show that average evaporated velocity of moisture can be attained as 5.94 kg/h, humidity of drying product is under 1.6% that meets anticipated target, character of drying product is contented demand, and the volume reduction ratio is around 5.25; treatment simulated waste concentrates whose boron concentration is around 44,000 ppm at the condition of heat temperature of 170 °C, small negative pressure in drum, adding 170 L concentration at first time, and maintaining high liquid level. It can be seen that the simulated concentrates can be disposed by the in-drum drying prototype device, and the technological targets can be met. Furthermore, the achievements of this study have been appraised in leading domestic level by China National Nuclear Corporation.