During the period from May, 1986 to November, 1987 the aerosol samples were collected around the Chernobyl nuclear power plant to define radioactive aerosol particle sizes by filter pack technique. The parameters of lognormal distribution (activity median aerodynamic diameter, AMAD, and geometric standard deviation) were defined for various radionuclides in aerosol form. The submicron aerosol particle were only shown to be produced by the damaged block-4 during the initial period after the accident. AMAD was increased up to 4–6 μm at the following stages when the secondary updraft of aerosol particles from contaminated surfaces became the dominant source of radioactive aerosols.

The results of five-year studies in Shelter subreactor rooms are summarized. At height elevations from 0 to 12 m, the mean volume activity (VA) of 212Pb-bearing aerosols is about 10 Bq m−3. The main source of 220Rn and of its daughter 212Pb is 232Th contained in the building structures. The maximal 212Pb VA is observed in the warm period of a year, and the minimal VA, in the cold period. In ventilation releases through the Bypass system, VA of 212Pb is 4–5 times lower than in subreactor room. The activity median aerodynamic diameter (AMAD) of 212Pb-bearing aerosols in most cases was within the range 0.06–0.4 µm. During works in subreactor space, the irradiation via 212Pb inhalation can amount to 3–5% of the annual effective dose limit (20 mSv) adopted in Ukraine.

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.

The results of the physicochemical studies of radioactive aerosols inside and outside the Shelter construction at the Arch construction stage of the Chernobyl Nuclear Power Plant (ChNPP) in 2000–2015 were presented. The dominant isotopes were shown to be cesium, strontium, americium, plutonium, and uranium. They are carried by disperse particles of 2–7 μm. In subreactor rooms, in particular, 012/7, the composition of aerosols is affected by the erosion of the fuel-containing mass formed in 1986. Submicron cesium carrier aerosols appear as a result of evaporation and condensation during fires and welding works. Radiocesium is a well-soluble component of aerosols, while plutonium isotopes are not readily soluble components. In several rooms, the contents of radon, thoron, and their daughter products exceeded the permissible values. In April–June 2011, the intake of radionuclides from the accident at the Japanese Fukushima-1 NPP, which had AMAD of ~0.5 μm, was detected and tracked using Petryanov multilayer filters. The productivity of filtration units under the dusty conditions in the exclusion zone of ChNPP and in fogs and haze was investigated. Hydrophilic prefilters with 7–10 μm fibers were recommended.

Data on the radionuclide composition, volume activity, and dispersity of aerosols taken in 2010–2014 using Petryanov’s filters in rooms 012/7, 012/15, and 210/7 of the Shelter object, into which the lava-like fuel-containing materials (LFCMs) flew after the accident, are presented. In room 012/7, the volume activities of aerosols carrying the Chernobyl accident products are higher by an order of magnitude than those in rooms 012/15 and 210/7. In all the rooms, the carriers of the radioactive products of the accident are, as a rule, aerosols with the activity median aerodynamic diameter larger than 1 µm. This value suggests the dispersion origin of the aerosols. In room 012/7, the aerosols are larger than in the other two rooms. The identity of the radionuclide composition of aerosols and LFCMs in room 012/7 shows that aerosols arise from the degradation of the lava. Considerable difference in the radionuclide compositions of aerosols and LFCMs in rooms 012/15 and 210/7 shows that the lava degradation in these rooms is less intense and that the aerosol generation from the lava surface does not influence the radionuclide composition of aerosols.

Results of the statistical analysis of dynamics of parameters of a radioactive aerosol in ventilating Bypass system during 2003 - 2012 have been presented. For volume concentration of aerosol carriers of activity 137Cs, 241Am and sums of -emitting nuclide the distinct exponential global trends were established. Quantitative esti-mates of seasonal trend component of characteristics of radioactive aerosol in the "Bypass" were received.

Using the data from the Chernobyl meteorological station for 2000–2010 and the wavelet analysis, the seasonal variations are analyzed of the average daily wind speed, wind gusts, wind speed variability, and instability coefficient (the ratio of the maximum wind speed to the average wind speed for each measurement). It is revealed that all parameters have pronounced seasonal variations, and the positions of seasonal maximum and minimum values of all variables under study are shifted relative to each other. The mean values of the shift between the seasonal variations of maximum and the average wind speed amount to 60–70 days, and those of the shift between the average speed and the instability coefficient, to about 145 days. The mentioned peculiarities of the display of seasonal variations are explained by atmospheric turbulent conditions. Proposed is a model that interprets the variability of the parameters under consideration as the statistics of separate eddies in the atmosphere.

Presented are the results of observations of the impact of fog and haze on the operation of filtering units for the sampling of radioactive aerosols in the process of monitoring radiation conditions in the Chernobyl exclusion zone. It is revealed that the performance of installations decreases in the case of the formation of fog and mist (as a rule, at the relative air humidity of more than 90%). This is associated with the settling of finest water droplets on the fibers and with the clogging of the filter. As the fog disappears, the droplets evaporate from the filtering fibers and the performance of the unit increases. In the case of fog and haze at night in November 2012, the performance of AURA-02.11 installation decreased almost by three times as compared with the initial one. To reduce the negative impact of fog and haze on the operation of units, it is reasonable to use the filters made of hydrophobic fibers.

The results of a determination of the concentration and dispersity of radioactive aerosols in the local zone of the Cover in spring 2011 are presented. Aside from aerosols – products of the accident at the Chernobyl NPP in 1986, technogenic 131,132I, 132Te, and 134,136Cs contained in the emissions from the damaged units of the Fukushima-1 NPP and spreading in the Northern Hemisphere were found. It was determined that technogenic 131I and 134Cs and naturally occurring 7Be and 210Pb were present on the carriers of similar activity median aerodynamic diameter <1 μm. It is shown that the content of radioactive aerosols – products of the accident at the Fukushima-1 NPP did not exceed the admissible concentration of radionuclides in air for the population and did not make a substantial additional contribution to the dose load to workers at the site of the Cover.

A meteorological situation is under consideration during a dust storm observed on September 5–7, 1992 over the Ukraine and Belarus territory contaminated by radionuclide products after the Chernobyl accident. The highest average wind speed in Chernobyl and Pripyat was 10–12 m/s, wind gusts reached 20 m/s. It was found that the radioactive aerosol concentration in the zone of alienation of the Chernobyl NPP increased by one or two orders of magnitude. The transfer of radioactive dust particles to the Vilnius outskirts is recorded.

Three-hour and daily mean measurements of the module of an average speed and wind gusts were analyzed over 2001–2006 in the Chernobyl NPP region using wavelet analysis and the method of the Herst normalized range. Diurnal and seasonal fluctuations are revealed, the periodicity of 8, 16, and 60 days is not well-pronounced. The derived Herst high-value coefficients (∼0.7–0.8) against the background of well-pronounced seasonal and other fluctuations of an average wind speed are indicative of the fact that its temporal variability is far from being random. The analysis is performed to predict the concentration of radioactive aerosols released from the Ukrytie object (the damaged unit 4 of the ChNPP), whose changes correlate with the wind speed.

In 2003–2007, the content of 212Pb (220Rn daughter product) inside the Shelter was, as a rule, in the range 0.5–5 Bq m−3. No seasonal and time dynamics of the 212Pb concentration and no relationship with the technical activity were revealed. At simultaneous sampling of aerosols, the volume activities of 212Pb in the bypass were higher by 1–2 orders of magnitude than in the surrounding medium (local zone). Hence, the sources of 220Rn emanation, in particular, 232U are inside the Shelter. Among 220 samples taken in the bypass, 94% had the activity median aerodynamic diameter of aerosol particles bearing 222Rn and 220Rn daughter products in the range from 0.05 to 0.4 μm. For the Shelter staff members, 222Rn and 220Rn daughter products, and also submicron size of their carriers are negative factors which were not taken into account previously when determining ionizing irradiation doses. The additional inhalation doses can reach tens of percents of the permissible annual dose.

Carbon foam based on carbonized polyamide fibres with palladium was modified. The carbon foam modified with palladium can adsorb hydrogen and methane under pressure and desorb then on heating. The possibility of using palladium-modified fibres as a solid support for reversible storage of hydrogen and methane was demonstrated.

The results of measurements of the volume activity and dispersity of aerosol carriers of β-emitting radionuclides during the acute phase of the accident and 20 years later are presented. It is determined that in August–October 1986, when samples were taken 10–50 m from the surface of the destroyed reactor, the concentration was about 1 kBq/m3, which is 100–1000 times higher than the value recorded in July–August of the same year from an aircraft flying at altitudes 200–1000 m. Thus, already in mid-summer 1986, because of the decrease in temperature, the aerosol emissions did not reach the survey altitude of the aircraft. Therefore, the sampling performed from the aircraft did not permit a quantitative assessment of the emissions of radioactive materials during this period of time. In 2003–2005, the total β activity was 10–100 times less than in fall 1986, because of the radioactive decay of 95Zr, 95Nb, 103,106Ru, 134Cs, 141,144Ce, and other radionuclides. Since the 137Cs concentration decreased negligibly, it seems that the roof constructed in 1986 above the Shelter was of little use.

Results of measurements of radionuclide and disperse compositions of aerosols in ventilation system "Bypass" of the object "Shelter" of the Chernobyl NPP are presented. The Bypass is used for releasing contaminated air from the destroyed reactor of Block-IV to the atmosphere. In aerosols, the experimentally found ratio of 137Cs concentration to the sum of beta-emitting radionuclides more than 1.5 times exceeds the calculated ratio for nuclear fuel (in December, 2003). Using the data of meteorological station "Chornobyl", which situated 15 km SE from the Chernobyl NPP, we found that the wind with mean velocity of 4-5 m/sec or more and gusts of 10-11 m/sec led to increasing the aerosol concentration in the Bypass by more than power of magnitude. With the help of filter pack technique sizes of aerosol particles--the carriers of Chernobyl's radioactivity--were measured. It was found that the range of activity median aerodynamical diameter (AMAD) is 2-5 microns.

Radionuclide composition in particles of the smoke plume from the forest fire in the 30-km zone around the Chernobyl NPP was studied. The activity ratios of the radioactive isotopes of cesium, cerium, and plutonium in the forest combustible materials and in the aerosols yielded by the fire showed that these aerosols are enriched in radioactive cesium occurring predominantly on submicron particles transported to long distance. The fire area gets depleted in cesium radioisotopes and, to a lesser extent, in other radioactive products generated by the Chernobyl accident.

It is shown that high wind velocity outdoors results in a higher concentration of radioactive aerosols in the ventillation exhaust from the sarcophagus. Aerosol samples from manholes in the roof of the sarcophagus have been collected, for the first time ever, in January–December 2002 on trilayer filter packets. The 137Cs concentration in outgoing flows is 0.7–2.3 Bq/m3. The activity median aerodynamic diameter of the aerosol carrier particles is 0.7–1.8 μm. At the same time, the 137Cs concentration in the atomspheric layer at the ground dear the sarcophagus was 1000 times lower and the carrier-particle sizes 2–4 times larger.