The Impact of Full-System Decontamination of Kori Unit 1 on the Radioactive Waste Classification of Steam Generator Tubes

Abstract

Kori Unit 1, which was permanently shut down on 18 June 2017, is planned to undergo full-system decontamination prior to major decommissioning activities. One of the advantages of performing FSD is the downgrading of the classification level of radioactive waste. From this perspective, the impact on the steam generator (SG) tubes, which account for a considerable portion of the total surface area during FSD operation, was examined. Initially, the CRUDTRAN code was used to predict the radioactivity inventory of the Kori Unit 1 SG tubes, which turned out to be approximately 21% more conservative than the measured value. To estimate the radioactivity in the tubes after FSD, decontamination factor values from overseas cases in the SG tubes section were selected and applied. Then, the regulations for radioactive waste in Korea were reviewed, and the specific activity was calculated by predicting the mass of the SG tubes. As a conclusion, it was confirmed that the SG tubes will be classified as low-level radioactive waste, whether FSD is performed or not. Furthermore, it was observed that even if a high efficiency of FSD is achieved, if stored, it would take more than 50 years for clearance.