한빛원전 폐수지 제염공정 개발연구

Abstract

When reactor coolant leaks occur due to cracks of a steam generator’s tube, radioactivematerials contained in the primary cooling water in nuclear power plant are forced out towardthe secondary systems. At this time the secondary water purification resin in the ion exchangeresin tower of the steam generator blowdown system is contaminated by the radioactivity ofthe leaked radioactive materials, so we pack this in special containers and store temporarilybecause we could not dispose it by ourselves. If steam generator tube leakage occurs, it producescontaminated spent resins annually about 5,000~7,000 liters. This may increase the amount ofnuclear waste productions, a disposal working cost and a unit price of generating electricity inthe plant. For this reasons, it is required to develop a decontamination process technique forreducing the radioactive level of these resins enough to handle by the self-disposal method. In thisresearch, First, Investigated the structure and properties of the ion exchange resin used in a steamgenerator blowdown system. Second, Checked for a occurrence status of contaminated spent resinand a disposal technology. Third, identified the chemical characteristics of the waste radionuclidesof the spent resin, and examined ionic bonding and separation mechanism of radioactive nuclearspecies and a spent resin. Finally, we carried out the decontamination experiment using chemicals,ultrasound, microbubbles, supercritical carbon dioxide to process these spent resin. In the caseof the spent resin decontamination method using chemicals, the higher the concentration of thedrug decontamination efficiency was higher. In the ultrasound method, foreign matter of thespent resin was removed and was found that the level of radioactivity is below of the MDA. In themicrobubbles method, we found that the concentration of the radioactivity decreased after theexperiment, so it can be used to the decontamination process of the spent resin. In supercriticalcarbon dioxide method, we found that it also had a high decontamination efficiency. Accordingto the results of these experiments, almost all decontamination method had a high efficiency, butconsidering the amounts of the secondary waste productions and work environment of the nuclearpower plant, we judged the ultrasound and supercritical carbon dioxide method are suitable forapplication to the plant and we established the plant applicable decontamination process systemon the basis of these two methods.