Analysis of the Long-Term Yearly Average Volumetric Activity of Radionuclides and the Yearly Absorbed Dose in the Surfac
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ANALYSIS OF THE LONG-TERM YEARLY AVERAGE VOLUMETRIC ACTIVITY OF RADIONUCLIDES AND THE YEARLY ABSORBED DOSE IN THE SURFACE AIR WITH CONTINUOUS RADIOACTIVE EMISSIONS (FOR LENINGRAD NPP-2) T. V. Perevolotskaya and A. N. Perevolotskii
UDC 614.876,551.521,574.46
The purpose of the present work is to analyze the long-term yearly average volumetric activity in the surface air and the yearly absorbed dose of β- and γ-radiation in the spread zone of continuous emissions from NPP. The particulars of the spreading of the emission radionuclides and the associated yearly absorbed radiation dose are determined. It is shown that the atmospheric volumetric activity of radionuclides due to continuous emissions is 105 times lower than the NRB-99/2009 standards and the yearly absorbed dose is 1000 times lower than the level of the natural radiation background.
The activity of the yearly emissions from NPP with VVER can reach 1014 Bq /1 GW of power-generating unit capacity. Radioactive inert gases, which scarcely settle onto the ground surface, make the main contribution in the total activity, but their β- and γ-radiation in the continuous emission zone is a factor impacting biological objects [1–3]. Thus, the purpose of the present investigation is to analyze the distribution of the long-term average нearly volume activity in the surface air and the expected yearly absorbed dose of β- and γ-radiation in the spread zone of the continuous emissions from NPP. Materials and procedure. A Gaussian model was used to predict the volume activity of radionuclides in the continuous emission in the surface air [4, 5]. The activity of the yearly emission of radionuclides and the aerological characteristics of the territory – the most likely category of atmospheric stability and the weighted-mean wind speed – were taken in accordance with the data in [6]. The calculations were performed for radionuclides which were distinguished by physicochemical properties: 3Н, 85Kr, 133Xe, 131I, and 137Cs. The relatively close activity of the indicated and other radionuclides makes it possible to estimate their long-term yearly average activity in the yearly emissions [3, 6]. So, the yearly emission of 88Kr and 135 Xe will be compared with the emission of 3H. The emissions of 14С, 83mKr, 87Kr, 131mXe, and 138Xe are close in terms of activity to 85Kr. The radioactive isotopes of iodine have close activity in the yearly emissions, correspondingly the long-term yearly average volumetric activity of 132–135I in the studied territory is comparable with 131I. The distribution of 51Cr, 54Mn, 60 Co, 89Sr, 90Sr, and 134Cs emitted as part of aerosols can be evaluated in terms of the activity of 137Cs. The yearly absorbed dose of β- and γ-radiation was calculated on the basis of the long-term average yearly volumetric activity of radionuclides in the surface air. The radiation geometry was taken to be a semi-infinite space with uniformly distributed volumetric activity of the radionuclides in the continuous emissions in the surface air. The calculation of the absorbed
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