A study on the optimization through the evaluation of radiation exposure by scenarios during steam generator dismantling

Steam generator (SG) replacements in South Korea began with the Kori No. 1 unit in 1998 due to performance degradation. Currently, 20 steam generators have been replaced in total. While additional decommissioning of dozens of steam generator will be required soon due to life-expiration of several nuclear power plants, there has been no actual dismantling performance of steam generators yet, and the replaced decommissioned steam generators are currently stored in intermediate storage facilities. To minimize waste volume and facilitate site reuse, it's necessary to proactively dismantle steam generators. These components are less radioactively contaminated and easier to dismantle compared to primary equipment like reactors. Additionally, securing related dismantling technology is essential for managing future replacements or equipment that has been stored. Establishing a process scenario about where and how the steam generator will be safely dismantled is important. It is necessary to analyze the advantages and disadvantages of each scenario to study the timing, location, and method of dismantling, and to develop an optimal process scenario through analysis of worker radiation exposure and dismantling costs. For this purpose, simulations were conducted on the radiation dose to workers according to the timing and method of dismantling, using 3D dismantling simulation software developed by Cyclife Digital Solutions, a subsidiary of French EDF, and the results were reviewed by mathematically modeling and analyzing the radiation doses exposed to workers over the years using an exponential decay model.