The nuclear facilities at Korea Atomic Energy Research Institute (KAERI) have generated a variety of organic liquid radwaste and most of the organic liquid have low-level radioactivity or lower levels. At KAERI, the organic liquid rad-wastes have been stored at Radioactive Waste Treatment Facility (RWTF) temporarily due to the absence of the recognized treatment technique while inorganic liquid radwaste can be treated by evaporation, bituminization and solar evaporation process. Therefore, it should be treated by regulatory clearance to secure the storage safety.
The organic liquid radioactive waste such as spent oil, cutting oil, acetone, ethanol, etc. was generated from the nuclear facilities at KAERI. The total amount of the organic liquid radioactive waste was about 7,000 L from 2008 to 2018. Among the organic liquid radioactive wastes, spent oil is particularly significant. Above all, radionuclides and activity concentrations should be analyzed for the regulatory clearance, and the results must meet the standards of Nuclear Safety Act of Korea. To analyze radionuclides and activity concentrations of radwaste for regulatory clearance, representative samples of the organic liquid radwaste were collected by 50 ml beaker at a ratio of 1 L to 200 L. The radionuclides identification and radioactivity concentration of collected samples were analyzed by a High-Purity Germanium (HPGe) detector.
According to the Nuclear Safety Act of Korea, it is recommended that activity concentration for regulatory clearance should be less than 0.1 Bq/g for Co-60 and Cs-137. The analysis results show that radioactivity concentrations of the radwaste are satisfied to the regulatory clearance and mixed two radionuclides (Co-60 and Cs-137) values are less than 1. So, the results have indicated that the recommendations of the Nuclear Safety Act of Korea were met A scenario for the regulatory clearance was set up using the RESRAD Code, and parameters of this code were used for assessment. Maximum radioactivity concentration values were used for conservative assessments. The results of the assessment must meet the criteria set by the Nuclear Safety Act of Korea (individual dose < 10 μSv/year, collective dose < 1 man×Sv/year) to get the permission from regulatory body. The assessment results met these criteria. By use of these clearance procedures, disposal costs for radwaste will be greatly saved. Additionally management of radwaste will become more efficient in view of storage capacity.