Activity Median Aerodynamic Diameter Research Articles

Development of a method of evaluating PuO2 particle diameters using an alpha-particle imaging detector.

It is very important to evaluate the diameters (activity median aerodynamic diameter) of plutonium dioxide (PuO2) particles for internal exposure dose evaluation. In this study, a method of evaluating PuO2 particle diameters using an alpha-particle imaging detector was developed. PuO2 particles with different diameters were modeled by Monte Carlo simulation, and the change in the shape of the energy spectrum for each particle diameter was evaluated. Two different patterns were modeled, namely, the case of 239PuO2 and the case of PuO2 (including isotopic composition of Pu). Multiple regression analysis was performed to determine the PuO2 particle diameter from the obtained parameters. The simulated diameters and the diameters obtained with the regression model were in good agreement. The advantage of using the alpha-particle imaging detector is to measure the alpha energy spectrum for individual particle, and this allows accurate measurement of particle diameter distribution.

Estimation of the activity median aerodynamic diameter of plutonium particles using image analysis

ABSTRACT The aerodynamic radioactive median diameter (AMAD) and the absorption type are necessary information for internal exposure assessment. In 2017, at a plutonium-handling facility in the Oarai site of the Japan Atomic Energy Agency, an accidental contamination occurred, and five workers were contaminated with radioactive materials, including plutonium. In this study, some smear papers and a dust sampling filter were measured with the imaging plate, and some particles were observed with an electron microscope. The minimum AMADs for the two absorption types of plutonium were estimated for the conservative dose assessment. Two AMADs were calculated for Type M as plutonium nitrate and Type S as plutonium dioxide. Excluding the extremely large particle found in a smear sample, the AMAD estimation results showed that the minimum AMADs of plutonium nitrate from smear papers were 4.3–11.3 μm, while those of plutonium dioxide were 5.6–14.4 μm. Moreover, the minimum AMAD of plutonium nitrate from a dust sampling filter was 3.0 μm, while that of plutonium dioxide was 3.9 μm.

Reconstructed lung doses for the million person study cohort of 26,650 Tennessee Eastman corporation workers employed between 1942 and 1947

Tennessee Eastman Corporation workers were exposed to uranium dust resulting in high-linear energy transfer (LET) irradiation to lung tissue. In this work, radiation lung doses were reconstructed for 26 650 men and women working at the plant between 1942 and 1947. Site air monitoring data of uranium concentrations and payroll records were used to determine the daily inhaled activities and annualized lung doses. Variations in the activity median aerodynamic diameter of the uranium dust, the solubility of particulate matter in the lungs and the sex-specific breathing rate were investigated as part of a sensitivity analysis. Male and female mean lung doses of 18.9 and 32.7 mGy, respectively, from high-LET alpha irradiation, and there was general agreement with evaluations from previously published epidemiological studies. Annual lung dose estimates and sensitivity analysis for the 26 650 workers in the TEC cohort have been archived on the United States Department of Energy Comprehensive Epidemiologic Data Resource.

Biokinetics and Internal Dosimetry of Tritiated Steel Particles.

Decommissioning fission and fusion facilities can result in the production of airborne particles containing tritium that could inadvertently be inhaled by workers directly involved in the operations, and potentially others, resulting in internal exposures to tritium. Of particular interest in this context, given the potentially large masses of material involved, is tritiated steel. The International Commission on Radiological Protection (ICRP) has recommended committed effective dose coefficients for inhalation of some tritiated materials, but not specifically for tritiated steel. The lack of a dose coefficient for tritiated steel is a concern given the potential importance of the material. To address this knowledge gap, a “dissolution” study, in vivo biokinetic study in a rodent model (1 MBq intratracheal instillation, 3-month follow-up) and associated state-of-the-art modelling were undertaken to derive dose coefficients for model tritiated steel particles. A committed effective dose coefficient for the inhalation of 3.3 × 10−12 Sv Bq−1 was evaluated for the particles, reflecting an activity median aerodynamic diameter (AMAD) of 13.3 µm, with the value for a reference AMAD for workers (5 µm) of 5.6 × 10−12 Sv Bq−1 that may be applied to occupational inhalation exposure to tritiated steel particles.

Radiological safety during sodium diuranate dissolution process: A radiological data study

The article presents an overview of the occupational radiation protection aspects of experimental sodium diuranate transferring and handling processes required for refining utilization. The health physics aspects and associated monitoring programs necessary to adequately measure and control radiological exposures to workers during the process is described here. A particle size distribution study was also carried out and estimated the activity median aerodynamic diameter (AMAD) for the process. The AMAD varied from 4.6 to 7.7 μm and geometric standard deviation ranged from 1.9 to 2.8. Obtained data serve the purpose of comparison for formulating a detailed radiological safety protocol during regular operation.

Cosmogenic 7Be: Particle size distribution and chemical composition of 7Be-carrying aerosols in the atmosphere in Japan

The particle size distributions of airborne aerosols with 7Be were measured using cascade impactors at Dazaifu, a city in western Japan, in 2018 to observe their seasonal variation. Beryllium-7 was found to be adsorbed to aerosols with a particle size of less than 2.1 μm; in general, particles sized 0.43–0.65 μm had the highest 7Be activity concentrations. The activity median aerodynamic diameter (AMAD) of 7Be fluctuated less over the year within the range of 0.40–0.52 μm, which is the size range of particles that can reach human alveoli, and had an annual mean of 0.43 ± 0.034 μm. The activity concentrations of 7Be were significantly lower in summer, which affected 7Be activity concentration for each particle size fraction. The particle size distribution of 7Be-carrying aerosols was also affected by that of the aerosol particles in the atmosphere. Finally, findings suggest that 7Be was mainly adsorbed to sulfate aerosols (particularly ammonium sulfate aerosols).

Plutonium dioxide particle imaging using a high-resolution alpha imager for radiation protection

The internal exposure of workers who inhale plutonium dioxide particles in nuclear facilities is a crucial matter for human protection from radiation. To determine the activity median aerodynamic diameter values at the working sites of nuclear facilities in real time, we developed a high-resolution alpha imager using a ZnS(Ag) scintillator sheet, an optical microscope, and an electron-multiplying charge-coupled device camera. Then, we designed and applied a setup to measure a plutonium dioxide particle and identify the locations of the individual alpha particles in real time. Employing a Gaussian fitting, we evaluated the average spatial resolution of the multiple alpha particles was evaluated to be 16.2 ± 2.2 μmFWHM with a zoom range of 5 ×. Also, the spatial resolution for the plutonium dioxide particle was 302.7 ± 4.6 µmFWHM due to the distance between the plutonium dioxide particle and the ZnS(Ag) scintillator. The influence of beta particles was negligible, and alpha particles were discernible in the alpha–beta particle contamination. The equivalent volume diameter of the plutonium dioxide particle was calculated from the measured count rate. These results indicate that the developed alpha imager is effective in the plutonium dioxide particle measurements at the working sites of nuclear facilities for internal exposure dose evaluation.

Estimation of Inhaled Effective Doses of Uranium and Thorium for Workers in Bayan Obo Ore and the Surrounding Public, Inner Mongolia, China.

Uranium and thorium are two common natural radioactive elements with high concentrations in Earth’s crust. The main aim of this study is to estimate the inhaled effective dose of uranium and thorium caused by a typical radioactive rare earth ore to the occupational population and the surrounding public. The particulate matter (PM) concentrations in the atmosphere of four typical workplaces and one surrounding living area were obtained by a high-flow sampling equipment with a natural cellulose filter membrane. The critical parameter for the inhaled effective dose estimation—the activity median aerodynamic diameter (AMAD)—was determined. The AMAD values of uranium and thorium in the atmosphere PM were 3.36 and 3.64 μm, respectively. The estimated median effective dose caused by inhalation thorium among the occupational population ranged from 15.3 to 269.0 μSv/a, and the corresponding value for the surrounding public was 2.3 μSv/a. All values for the effective dose caused by the inhalation of uranium were in the nSv magnitude.

Dosimetry of inhaled 219Rn progeny.

During prostate cancer treatment with 223Ra. 219Rn (actinon) occurs and may be exhaled by the patient. Nurses and other hospital employees may inhale this radionuclide and its decay products. The alpha-emitting decay products of actinon deposited within a body will irradiate tissues and organs. Therefore. it is necessary to evaluate organ doses of actinon progeny. The purpose of this study is to set up a dosimetric method to assess dose coefficients for actinon progeny. The effective dose coefficients were calculated separately for three modes. The unattached mode which concerned the activity median thermodynamic diameter (AMTD) of 1 nm. and the nucleation and accumulation modes which are represented by activity median aerodynamic diameters (AMAD) of 60 and 500 nm respectively. The recent biokinetic models of actinon progeny developed in the Occupational Intakes of Radionuclides (OIR) publications series of the International Commission of Radiological Protection (ICRP) were implemented on BIOKMOD (Biokinetic Modeling) to calculate the number of nuclear transformations per activity intake of actinon progeny. The organ equivalent and effective dose coefficients were determined using the dosimetric approach of the ICRP. The inhalation dose coefficients of actinon progeny are dominated by the contribution of lung dose. The calculated dose coefficients of 211Pb and 211Bi are 5.78 × 10−8 and 4.84 × 10−9 Sv.Bq−1 for unattached particles (AMTD = 1 nm). and 1.4 × 10−8 and 3.55 × 10−9 Sv.Bq−1 for attached particles (AMAD = 60 nm). and 7.37 × 10−9 and 1.91 × 10−9 Sv.Bq−1 for attached particles (AMAD = 500 nm). These values are much closer to those of the recently published ICRP 137.

Fuel particles in consequences of the accident at the ChNPP

As a result of the nuclear explosion at the fourth block of the Chornobyl NPP (ChNPP), the radioactive cloud containing an aerodispersed system with aerosols formed at the explosion appeared in air above the ChNPP territory. The accident occurred at the end of the reactor company before the assumed reloading of the active zone. Thus, the cloud composition included the products of fission and activation of uranium that were accumulated in the reactor fuel during the company. On that night, the east wind carried the radioactive cloud to the west, by leaving the aerosol fallouts on Earth’s surface as a radioactive trace. The results of the own studies (1986–1990) of aerosol fallouts on the west trace formed at once after the explosion at the ChNPP are presented. On this basis, the characteristics [physico-chemical forms, radionuclidic composition, activity median aerodynamic diameters (AMADs), etc.] of the aerodispersed system created at once after the explosion of the active zone of the reactor are reconstructed. In the frame of the respiratory model given in ICRP Publication 66, the contributions caused by the inhalation of fuel particles (microscopic particles which are fragments of exploded fuel elements and have conserved mainly their radionuclidic characteristics) to the doses of irradiation of parts of respiratory organs and gastrointestinal tract (GIT) are evaluated. It is shown that the cause for a mass cough in the summers of 1986 and 1987 on territories underwent the action of emergency fallouts was the inhalation of radionuclides of ruthenium in the form of RuO4 that was formed in “hot” particles contacting with air and then evaporated from them. The “hot” particles are compact inclusions formed by fission products. They consist mainly of atoms close to noble metals (molybdenum, ruthenium, rhodium, etc.) formed during a regular operating period in fuel tablets and released from the latter at the explosion of the active zone. The reasons for the disagreement between the clinic consequences and the ascribed values of the dose for the sufferers who were present in premises of the NPP at the emergency time and then died from acute radiation sickness in three-four weeks after the accident are explained.

Radioactive Aerosols within Conditions of the New Safe Confinement in 2017–2020

The results of monitored behavior of radioactive aerosols within the conditions of the New Safe Confinement (NSC) in 2017–2020 are presented. Maximum “unorganized” flux of beta-emitting products of the Chornobyl accident from the Shelter object through the process openings and leakages of light roofing in the NSC basic volume observed in 2017 made 7.9 kBq/(m2 ∙day). Mean annual density of radionuclide deposition onto the light roofing during four years has been changing within the range of 1.7–2.2 kBq/(m2 ∙day). Over these years, mean annual volumetric activity of sum of long-lived beta-emitting nuclides coming in the “Bypass” system dropped from 0.84 to 0.17 Bq/m3 . Their carriers were aerosol particles with activity median aerodynamic diameter, mainly, from 4.3 to 10 μm. The data are given on radioactive contamination of near-surface air layer in the NSC basic volume.

Uranium Aerosol Activity Size Distributions at a Nuclear Fuel Fabrication Plant.

Inhalation of uranium aerosols is a concern in nuclear fuel fabrication. Determination of committed effective doses and lung equivalent doses following inhalation intake requires knowledge about aerosol characteristics; e.g., the activity median aerodynamic diameter (AMAD). Cascade impactor sampling of uranium aerosols in the breathing zone of nuclear operators was carried out at a nuclear fuel fabrication plant producing uranium dioxide via ammonium uranyl carbonate. Complementary static sampling was carried out at key process steps. Uranium on impaction substrates was measured using gross alpha counting and alpha spectrometry. Activity size distributions were evaluated for both unimodal and bimodal distributions. When a unimodal distribution was assumed, the average AMAD in the operator breathing zone at the workshops was 12.9–19.3 μm, which is larger than found in previous studies. Certain sampling occasions showed variable isotope ratios (234U/238U) at different impactor stages, indicating more than one population of particles; i.e., a multimodal activity size distribution. When a bimodal distribution (coarse and fine fraction) was assumed, 75–88% of the activity was associated with an AMAD of 15.2–18.9 μm (coarse fraction). Quantification of the AMAD of the fine fraction was associated with large uncertainties. Values of 1.7–7.1 μm were obtained. Static sampling at key process steps in the workshops showed AMADs of 4.9–17.2 μm, generally lower than obtained by breathing zone sampling, when a unimodal distribution was assumed. When a bimodal distribution was assumed, a smaller fraction of the activity was associated with the coarse fraction compared to breathing zone sampling. This might be due to impactor positioning during sampling and sedimentation of large particles. The average committed effective dose coefficient for breathing zone sampling and a bimodal distribution was 1.6–2.6 μSv Bq−1 for 234U when Type M/S absorption parameters were assumed (5.0 μSv Bq−1 for an AMAD of 5 μm). The corresponding lung equivalent dose coefficient was 3.6–10.7 μSv Bq−1 (29.9 μSv Bq−1 for an AMAD of 5 μm). The predicted urinary excretion level 100 d after inhalation intake was found to be 13-34% of that corresponding to an AMAD of 5 μm. Uranium aerosols generated at a nuclear fuel fabrication plant using ammonium uranyl carbonate route of conversion were associated with larger AMADs compared to previous work, especially when sampling of aerosols was carried out in the operator breathing zone. A bimodal activity size distribution can be used in calculations of committed effective doses and lung equivalent doses, but parameters associated with the fine fraction must be interpreted with care due to large uncertainties.

Atmospheric residence times and excess of unsupported 210Po in aerosol samples from the Kuwait bay-northern gulf

The concentration of cosmogenic radionuclide 7Be and the naturally occurring radionuclide 222Rn and its progenies 210Pb, 210Po, and 214Pb were measured in the ground surface air in the urban area of the northern Arabian Gulf close to Kuwait Bay. A high-volume air sampler connected with a five-stage cascade impactor was used to collect approximately 1800 cubic meter weekly for a period of one year. The concentrations of 210Pb and 210Po varied from 0.35 to 1.65 mBq m−3 and from 0.23 to 3.2 mBq m−3, respectively; the 210Po/210Pb activity ratio was close to one. The average concentration of 7Be was 6.24 mBq m−3, ranging from 3 to 10 mBq m−3. The temporal variations of 210Pb, 210Po and 7Be showed maximum concentrations of 210Po and 7Be in occurred summer months. The observed excess of 210Po concentrations can be attributed to the local and long-range transport of suspended dust with 210Pb and 210Po in radioactive equilibrium state, oil industry emissions, local resuspended dust and the sea-salt-aerosols from the Arabian Gulf. The range of the residence time estimation using the 222Rn/210Pb and 214Pb/210Pb activity ratio methods ranged from three to five days. Moreover, the estimated residence time by the application of 7Be from the activity median aerodynamic diameter method was 4.2 days. The method of using the 210Po/210Pb activity ratio was invalid because of the excess 210Po sources of anthropogenic origin. Therefore, extensive accurate diurnal measurements of 214Pb and 222Rn can be applied in hot arid regions for better aerosols residence time estimation.

Deposition of Aerosolized Lucinactant in Nonhuman Primates.

Background: Lucinactant for inhalation is an investigational noninvasive, aerosolized surfactant replacement therapy for treatment of preterm neonates with respiratory distress syndrome. Lucinactant for inhalation consists of lyophilized lucinactant and the Aerosurf® Delivery System (ADS). The objective of this study was to characterize the total and regional pulmonary deposition of lucinactant delivered by the ADS in nonhuman primates (NHPs).Methods: Lucinactant was radiolabeled by the addition of technetium-99m (99mTc)-sulfur colloid. The radiolabeled aerosol was characterized and validated using a Mercer cascade impactor. An in vivo deposition study was performed in three cynomolgus macaques. Radiolabeled lucinactant was aerosolized using the ADS and delivered via nasal cannula under 5 cm H2O nasal continuous positive airway pressure (nCPAP) for 5–9 minutes. A two-dimensional planar image was acquired immediately after aerosol administration, followed by a three-dimensional single-photon emission computed tomography (SPECT) image and a second planar image. The images were analyzed to determine the pulmonary (lungs) and extrapulmonary (nose + mouth, trachea, stomach) distribution. The SPECT data were used to determine regional deposition.Results: The radiolabed lucinactant aerosol had a mass median aerodynamic diameter = 2.91 μm, geometric standard deviation (GSD) = 1.81, and an activity median aerodynamic diameter = 2.92 μm, GSD = 2.06. Aerosolized lucinactant was observed to deposit in the lungs (11.4%), nose + mouth (79.9%), trachea (7.3%), and stomach (1.4%). Analysis of the SPECT image demonstrated that the regional deposition within the lung was generally homogeneous. Aerosolized lucinactant was deposited in both the central (52.8% ± 1.2%) and peripheral (47.2% ± 1.2%) regions of the lungs.Conclusion: Aerosolized lucinactant, delivered using the ADS via constant flow nCPAP, is deposited in all regions of the lungs demonstrating that surfactant can be aerosolized and delivered noninvasively to NHPs.

Activity size distribution of radioactive nuclide 7Be at different locations and under different meteorological conditions

The activity size distributions of the natural radionuclide tracer 7Be in different size fractions (<0.4 μm, 0.4–0.7 μm, 0.7–1.1 μm, 1.1–2.1 μm, 2.1–3.1 μm, 3.1–4.2 μm, 4.2–5.8 μm, 5.8–9.0 μm > 9.0 μm) were determined at four different site places in Northern Italy during the four seasons of the year 2011. One cascade impactor operated at the LASA-station considered the reference station and the other used for simultaneous measurements at the three other sites. Three sets of independent samples were collected during every season of the year 2011. The initial activity distribution inverted into smooth size distribution. The model parameters successfully defined to obtain the best fit-curve and two or three modes were resolved, with the predominant fit at the accumulation range. The lowest Activity Median Aerodynamic Diameter (AMAD) values were observed during summer. The AMAD values were anticorrelated with 7Be activities, while they were correlated with Relative Humidity. Similar AMAD values in suburban and urban regions were observed during all periods of the year. AMAD values of 7Be aerosol particles in areas with poor air quality were greater than those at the less polluted environments far from anthropogenic activities regions. This indicates that 7Be AMAD values could be used as an index of air quality conditions in areas like the Po Valley.

The Influence of Aerosol Density and Shape Factor on the Assessment of Internal Exposure to 239Pu.

Internal exposure due to inhalation of aerosols depends on the ratio of aerodynamic shape factor (χ) to aerosol mass density (ρ). Inhaled aerosol parameters may differ from the default ρ and χ values provided by the International Commission on Radiological Protection, which are adopted for the assessment of internal exposures. This paper focuses on the influences of χ/ρ on the assessment of internal exposure to Pu for reference workers. Regional deposition fractions are found to decrease with increasing χ/ρ, and larger decreases are observed with smaller activity median aerodynamic diameter aerosols, while the slow clearance fractions (fs) in the tracheobronchial region are more sensitive for larger activity median aerodynamic diameter aerosols. Results from biokinetics calculations reveal that both the time-dependent content (excretion) and cumulative activities are determined mainly for particles initially deposited in the alveolar-interstitial region, while fs affects the local cumulative activities in the tracheobronchial region. χ/ρ is proven to have different influences for aerosols with different activity median aerodynamic diameters. The default χ/ρ values can be used when activity median aerodynamic diameters are greater than 1 μm, while one should pay attention to the value of χ/ρ when activity median aerodynamic diameters are less than 1 μm, where significant influence may be anticipated.

212Pb-Bearing Aerosols in Subreactor Rooms of the Chernobyl NPP Shelter

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.

Comparison of radioactive aerosol size distributions (Activity, number, mass, and surface area)

Information regarding the number, mass, and specific surface area distributions of aerosols is extremely important for assessments of exposure to radiation due to the intake of radioactive aerosols by inhalation. In this study, these distributions were compared with the activity size distributions for radon decay products. The experiments were conducted in a radon chamber under controlled conditions for the aerosol concentrations and with size distributions in the range from 5 nm to 10 µm. The activity size distributions of the aerosols were measured by using a diffusion battery and two types of cascade impactors. The aerosol concentrations during the experiments were in the range from 2 × 103 to 2.5 × 105 cm–3. The measurements obtained with a diffusion battery demonstrated that at the low aerosol concentration, up to 80% of activity of the radon decay products was connected with aerosol particles with an activity median thermodynamic diameter (AMTD) ~1 nm (unattached fraction). After injecting the aerosols into the experimental chamber, the activity of the unattached fraction decreased to practically zero but we observed the presence of the activity of aerosols with AMTD values ~10–20 nm. After injecting the aerosols, the distribution of the aerosol specific surface area exhibited a bimodal distribution, where the median diameter in the accumulation mode was ~120 nm and the geometric standard deviation (GSD) was 1.3. The median diameter in the coarse mode changed with time due to the deposition of aerosols on the walls of the chamber, where it decreased from 5 µm (GSD = 1.6) at 15 min after injection to 2 µm (GSD = 2.5) at 120 min after injection. The distribution of the aerosol activity measured by the cascade impactor was virtually independent of the time from the moment when the aerosols were injected. The parameters used to assess the activity distribution comprised an activity median aerodynamic diameter (AMAD) ~500–650 nm and GSD = 1.5. Comparisons of the activity distributions with the distributions for the number, mass, and specific surface area showed that the closest correspondence was with the average distribution over the specific surface, whereas there were no exact correspondences with the other distributions.

Radiolabeling an Electronic Cigarette Aerosol Using Technetium Carbon Ultrafine Particles.

Electronic cigarettes (ECIGs) are widely used, but their health effects are not well known. ECIG exposure is difficult to quantify, and a direct measurement of deposition would be beneficial to in vivo and in vitro toxicity studies. The aim of this study was to demonstrate effective radiolabeling of an ECIG. A technetium-99m-labeled carbon ultrafine (TCU) aerosol was generated and introduced to a fourth-generation ECIG before nucleation and aerosol formation. The aerosolized e-liquid was a commercially available strawberry flavor containing 1.2% nicotine in a 55% propylene glycol and 45% vegetable glycerine base. An ECIG power setting of 100 W was selected. Mass and radioactivity were measured on each stage within a Sierra Cascade Impactor at 14 L/min to verify the labeling technique using the calculated aerodynamic diameters. A strong positive correlation (R2 > 0.95) between the percent activity and percent mass deposition on each stage provides a reliable validation of colocation. Unlabeled ECIG aerosol from the chosen e-liquid produced a mass median aerodynamic diameter (MMAD) of 0.85 μm. An ECIG labeled with TCU produced an aerosol with an activity median aerodynamic diameter of 0.84 μm and an MMAD of 0.84 μm. The relative mass versus radioactivity on each plate was highly correlated (average R2 = 0.973, p < 0.001). A TCU radiolabel was generated and shown to associate with the mass of an aerosol produced by a typical commercially available ECIG. Thus, the radioactivity of the deposited aerosol may be used to determine ECIG aerosol deposition for the future in vivo and in vitro dosimetry studies of the third- and fourth-generation ECIGs.

AEROSOL SIZE DISTRIBUTION IN URANIUM PROCESSING FACILITY FOR APPLICATION IN THE ASSESSMENT OF INTERNAL EXPOSURE.

In circumstances of inhalation exposure the radiotoxicity of radionuclide depends on the fractional deposition of inhaled activity, which is governed by the aerodynamic characteristics of the particles. Although International Commission on Radiological Protection (ICRP) provides default size distribution parameters for work place aerosols, inhaled aerosol characteristics may be different depending on the physical and chemical conditions of aerosol generation process. The present study is undertaken to determine the particle activity-size distribution during operation of various significant processes of uranium metal production facility of Bhabha Atomic Research Centre (BARC). Activity median aerodynamic diameter (AMAD) and its geometric standard deviation (GSD) were estimated for these process areas for uranium aerosol particles. The AMAD varied from 3.2 to 10.06 µm and GSD ranged from 1.5 to 3.0. Also, the obtained size distribution was tested by Pearson's chi-squared distribution test method to ascertain the assumption that the particle size distribution is best described by log-normal relationship.