Calculation approach to building DCGLs of waste treatment facilility for Kori unit 1 decommissioning and comparative analysis of the results

•For the decommissioning of Kori-1, waste treatment facility were considered to derive the residual building DCGLs.•A methodology for calculating DCGLs using RESRAD-BUILD code was developed.•DCGLs for waste treatment facility and most likely rooms were derived and compared with those in other cases. The Derived Concentration Guideline Levels (DCGLs) of remaining buildings in decommissioning site realistically need to be considered because all nuclear power plants in Korea are operated with the adjacent plant in multi-unit site. In addition, a few buildings are expected to be utilized for the decommissioning such as waste treatment facility to reduce the final disposal volume of radioactive waste. Therefore, DCGLs of buildings postulated for the decommissioning of Kori site have been assessed by using RESRAD-BUILD code. As a result, DCGLs were derived, reflecting the site reuse criteria and input prameters based on site conditions and assumptions, and compared and analyzed how they differ from DCGLs of other nuclear plants depending on radionuclides. The occupancy and renovation scenarios were applied and more than half of the target radionuclides were conservatilvely evaluated in the occupancy scenarion, while some were evaluated in the renovation scenario. The approach and methodology presented in this paper, which can be considered at the level of the transition phase, can be utilized for deriving results that reflect reality at the time of license termination.