Estimating volume activity and absorbed dose rate due to gamma-emitting noble gas radionuclides released into the air during routine operation of the Belarus nuclear power plant

Authors present prognostic estimates of volume activity in surface air and absorbed dose rate of gamma-radiation emitted by noble gas radionuclides released during a routine operation of the Belarus NPP. Distribution of noble gas radionuclides in surface air was estimated with the Gaussian dispersion model. Average volume activity, absorbed dose rate and atmospheric dilution factor of a specific radionuclide in the plume of the released radionuclides were calculated for the following scenario: scheduled daily release and single emergency release. In the case of scheduled daily release and neutral atmospheric stability (D class) the highest volume activities of noble gas radionuclides are expected to be 800-2500 meters from the NPP. Volume activity of 1 3 3Xe will not exceed 2 Bq/m 3, 135Xe - 0.4 Bq/m 3, and for other radionuclides it will be less than 10 -2 Bq/m 3. In the case of that scenario insignificant increase in gamma-radiation absorbed dose rate is expected to be registered at a height of 1 m from the surface, it will be less than 4×10 -11 Gy/h at a distance of 300-800 m from the NPP. This value is 1000 times lower than the natural background radiation absorbed dose rate, that is 10×10 -8 Gy/h.