Assessment of Public Dose due to Gaseous Radioactive Effluent in Decommissioning Nuclear Power Plant

Background: In order to gain approval of decommissioning of nuclear power plants (NPPs), the operator has to submit a final decommissioning plan (FDP) to the regulatory body. The safety assessment is an essential part to be described in the FDP. In safety assessment, dose of the general public near the plant site due to decommissioning activities should be evaluated and described. As gaseous radioactive effluents are expected to be released in the process of decommissioning, it is necessary to assess the public dose. In this study, we assessed the public dose due to gaseous radioactive effluents released in NPP decommissioning activities.Materials and Methods: The source term of gaseous radioactive effluent was set based on the decommissioning scenarios suggested in the NUREG-0130. The critical group assumed the maximum individual for adults on the exclusion area boundary. Public exposure pathway was set in accordance with the guideline 2.2 of the Korea Institute of Nuclear Safety (KINS). In addition, the public dose was assessed through the GASPAR computer code with the factors suggested by the KINS.Results and Discussion: In the decommissioning scenario, the source term for gaseous radioactive effluent was set by using the nuclide fraction according to the contamination type of structures, systems, components in the reference reactor. As a result of the public dose assessment,total annual public dose in the overall decommissioning scenario was 1.95×10<sup>–2</sup> μSv/yr. Segmentation on non-activated stainless steel task was the highest at 1.43×10<sup>–2</sup> μSv/yr. In the overall scenario, the nuclide with the highest contribution to the public dose was Co-60. As a result of the assessment, it was found that the public dose due to the gaseous radioactive effluent during the decommissioning of the NPP was insignificant compared to the legal dose limit.Conclusion: The results of this study can be used as a basis for radiological safety assessment and the management of radioactive effluents in the decommissioning of NPP.