Sheltering management to protect the population: A case study of radiological impact assessment under a postulated accident condition in Indonesia's first NPP site

Indonesia is committed to achieving net zero greenhouse gas emissions by 2060. To meet this objective, a diversified energy strategy is needed, which includes the deployment of nuclear power plants in addition to other renewable energy sources. It is planned that the first NPP in Indonesia will be introduced in 2032 or no later than 2034, with a target of approximately 31 GWe by 2060. To meet this demand, various reactor types will be considered based on geographical and demographic conditions, including Small Modular Reactors (SMRs). One potential site, Pantai Gosong in West Kalimantan, is currently under evaluation. An important aspect of site evaluation is the radiological safety assessment for accident conditions. The assessment includes the air concentration and ground deposition of several isotopes, individual effective doses, and early countermeasures. Site-specific meteorological data, were taken from the relevant national agencies. This study focuses on assessing radiation doses and formulating early countermeasure strategies, specifically for shelter management, in response to a hypothetical accident involving an SMR at the site, based on two potential release scenarios. Simulations were conducted using PC-Cosyma code. The sheltering pattern generated by the PC Cosyma is displayed using GIS and combined with settlement area, existing buildings suifigura for shelter, and the road network. Simulation results show that the calculated individual effective doses to the public remain well below reference levels. Nevertheless, a cautious approach to early countermeasures must be applied by implementing sheltering within a specific radius. This strategy aims to reduce the risk of radiation exposure while also preparing for potential subsequent actions, such as evacuation or the distribution of stable iodine (KI) tablets, if necessary. Proposed special protection zones within a 2 km radius can be established for immediate response measures. The existing public facilities are adequate to shelter the population within a 2 km radius. However, the presence of arterial roads within this area poses a potential risk of radiation exposure. Thus, alternative routes outside the 2 km radius should be suggested to enable effective traffic management in the event of an emergency.