Radon and Its Effect on the Radiation Situation in the Chernobyl NPP Sarcophagus

Abstract

During studies performed in 2010–2014, in the under-reactor rooms and deaerator stack of the sarcophagus at the Chernoby NPP, the average volume activity of radon was ~100 Bq/m³ and the average coefficient of equilibrium of radon and its daughter products was ~0.7. The maximum volume activity of radon reached 666 Bq/m³. The daughter products complicate radiation monitoring of the aerosol situation. In the inspected rooms of the under-reactor space and deaerator stack, the radiation exposure of workers due to inhalation of radon, thoron, and their daughter products can exceed 10% of the maximum admissible effective dose. It was determined that the carrier aerosols of the daughter products are submicron aerosols with active median aerodynamic diameter ~0.1 μm. The arch erected above the sarcophagus at the end of 2016 can degrade the radon radiation situation because of reduction of the natural ventilation.