Innovation in radioactive wastewater-stream management: Part one

摘要

Treatment of radioactive wastewater streams is receiving considerable attention in most countries that have nuclear reactors. The first Egyptian research reactor ETRR-1 has been operating for 40 years, resulting in accumulation of large quantities of wastewater collected in special drainage tanks called SDTs. Previous attempts were aimed at the volumetric reduction of streams present in SDTs, by reverse osmosis systems, which previously succeeded in reducing the water volume present in SDTs from 450 m~3 to 50 m~3 (during the period 1998-2000). The main drawbacks of the RO system are the additional amount of secondary wastes (turbidity and emulsion filters media replacement, and the excessive amounts of chemicals for the membrane cleaning, flushing and storing), and a limited contaminant release in the SDTs area, resulting in the decommissioning of the RO system. Meanwhile, the SDTs waste contents recently reached 500 m~3. Recently, the invention of a system for volume reduction of the wastewater streams present in SDTs has been achieved. This system substantially utilises the air conditioning and ventilation techniques in water transfer from the wastewater to air. This process is promoted by a mutual heating and humidification of a compressed dry air introduced through SDTs. From the probable release of radioactive nuclides point of view, the analysis of the evapouration of waste streams present in SDTs has indicated that the proposed optimal evaporating temperature is around 75℃. The design curve of the daily volumetric reduction of the wastewater streams vs. the necessary volumetric airflow rates at different operating temperatures has been achieved. Recently, an experimental facility is being constructed to obtain the optimal operating parameters of the system, regarding the probable emissions of the radioactive nuclides within the permissible release limits.