Radiological assessment of the decontaminated and decommissioned Korea Research Reactor-1 building

The radiation dose of the Korea Research Reactor-1 (KRR-1), which had been decontaminated and decommissioned following shut down in 1995, was evaluated to assess the possibility of reusing the building as a memorial hall. The KRR-1 holds symbolic significance as the first reactor in Korean nuclear history and is designated as a registered cultural property of Korea. Exposure scenarios for visitors and the building manager were evaluated to examine the radiological safety of the building. Radioactive contamination inside the KRR-1 building was measured using gamma survey meter, surface alpha and beta contamination monitor, low level gas proportional counter, and semiconductor detector. The exposure dose rate for real radioactivity measurement was calculated using the RESRAD-BUILD code and uncertainty analysis was performed. The radionuclides of 60Co, 137Cs, and 152Eu were in the ranges of 0.09-0.011, 0.005-0.041, and 0.013-0.097 Bq/g, respectively, on the surface of the reactor building. The external dose rate in the reactor building in the first year of the measurement ranged from 1.05 × 10−7 to 3.76 × 10−6 mSv/h. The maximum exposure doses on the building manager and visitors in the first year were 1.82 × 10−4 and 1.07 × 10−6 mSv/y, respectively, satisfying the dose limit for unrestricted release of the building. Thus, the radiological safety of the KRR-1 building was confirmed.