O. S. Lagunenko, V. Ye. Khan, O. K. Kalynovskyi, V. O. Kashpur,
V. P. Kovalchuk, P. V. Sabenin, O. A. Svirid, A. V. Tkach, S. V. Yurchuk
Institute for Safety Problems of Nuclear Power Plants, NAS of Ukraine,
36a, Kirova st., Chornobyl, 07270, Ukraine
The results of monitoring of radioactive aerosols emissions from the Shelter object in 2018 are given. The maximum value of «unorganized» release rate was observed in November and was 4.6 kBq/(m2 ∙ day). The completion of construction and sealing of the enclosing contours of the New safe confinement (NSC) in 2018 completely limited the influence of meteorological environmental conditions: precipitation, temperature and wind on the Shelter object. As a result of changes in the temperature and humidity conditions inside the facility, water accumulations of radioactively contaminated water in rooms gradually dry up, air humidity decreases, which in turn helps to increase the secondary dust lift, including from the surfaces of fuel-containing masses. In 2018, the average daily density of radioactive particles precipitation on the light roofing totalled 2.2 kBq/(m2 ∙ day), which was higher than in the previous years. Increase in release of radioactive particles intensity on the Shelter object’s light roofing is provided by implementation of building and assembly works under the NSC Arch. The concentration of sum of long-lived beta-emitting aerosols-carriers (90Sr + 90Y and 137Cs) entering the atmosphere through the Bypass system was within the range of 0.1-2.6 Bq/m3. Besides, 137Cs share was 30%. The particles with 4.3-10 μm active median aerodynamic diameter acted as their carriers. Stable trend is observed in reducing the sum of long-lived beta-emitting aerosols in unorganized releases through «Bypass» system. Airflow movement within «Bypass» system has unstable character. In 2018, airflow direction inside the Shelter object was prevailing. The data on the contamination by radioactive aerosols of the atmosphere surface layer under the NSC Arch are represented.
Keywords: New safe confinement, Shelter object, aerosols, volume activity, activity median aerodynamic diameter.
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