Radiological shielding performance for offsite emergency center near research reactor

• Shielding performance of an offsite emergency center under beyond design basis accident conditions. • HotSpot and PHITS simulations show effective attenuation of sky-shine, ground-shine, and roof deposition. • The emergency center meets national dose limits for short-term nuclear emergency response. Gerrit Agustinus Siwabessy Multi-Purpose Reactor (RSG-GAS) is Indonesia’s largest research reactor. This research reactor needs radiation risk mitigation in a densely populated area. This study examines the radiation shielding effectiveness of Building No. 93 as an offsite emergency center during a Beyond Design-Basis Accident (BDBA). An Anticipated Transient Without Scram (ATWS) scenario with five fuel element meltdowns was simulated using HotSpot, a Gaussian plume-based atmospheric dispersion software, and dose attenuation was performed using Monte Carlo. The result shows that the dual-layered concrete wall can reduce the incoming total dose rate to 0.558 mSv/hour, allowing safe occupancy for 3.74 days before reaching Indonesia’s emergency dose limit of 50 mSv for workers and the public. This study confirms that Building No. 93 meets regulatory standards and is suitable as an offsite emergency center for emergency operators during severe nuclear incidents. This study established a framework for future emergency evaluation and management strategy.