• Journal of Radiation Protection and Research
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• 제41권4호
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• pp.350-353
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• 2016

Background: Various characteristics such as size distribution, chemical component and radio-activity have been analyzed for radioactive aerosols released from Fukushima Daiichi Nuclear Power Plant. Measured results for radioactive aerosols suggest that the potential transport medium for radioactive cesium was non-sea-salt sulfate. This result indicates that cesium isotopes would preferentially attach with sulfate compounds. In the present work the attachment behavior of fission products to aqueous solution aerosols of sodium salts has been studied using a generation system of solution aerosols and spontaneous fission source of $^{248}Cm$. Materials and Methods: Attachment ratios of fission products to the solution aerosols were compared among the aerosols generated by different solutions of sodium salt. Results and Discussion: A significant difference according as a solute of solution aerosols was found in the attachment behavior. Conclusion: The present results suggest the existence of chemical effects in the attachment behavior of fission products to solution aerosols.

• Nuclear Engineering and Technology
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• 제54권6호
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• pp.2077-2083
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• 2022

In the unlikely event of core disruptive accident in sodium cooled fast reactors, the reactor containment building would be bottled up with sodium and fission product aerosols. The behavior of these aerosols is crucial to estimate the in-containment source term as a part of nuclear reactor safety analysis. In this work, the evolution of sodium aerosol characteristics (mass concentration and size) is simulated using HAARM-S code. The code is based on the method of moments to solve the integro-differential equation. The code is updated to FORTRAN-77 and run in Microsoft FORTRAN PowerStation 4.0 (on Desktop). The sodium aerosol characteristics simulated by HAARM-S code are compared with the measured values at Aerosol Test Facility. The maximum deviation between measured and simulated mass concentrations is 30% at initial period (up to 60 min) and around 50% in the later period. In addition, the influence of humidity on aerosol size growth for two different aerosol mass concentrations is studied. The measured and simulated growth factors of aerosol size (ratio of saturated size to initial size) are found to be matched at reasonable extent. Since sodium is highly reactive with atmospheric constituents, the aerosol growth factor depends on the hygroscopic growth, chemical transformation and density variations besides coagulation. Further, there is a scope for the improvement of the code to estimate the aerosol dynamics in confined environment.

• Nuclear Engineering and Technology
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• 제56권1호
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• pp.132-140
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• 2024

In the event of a severe accident in Sodium Cooled Fast Reactors (SFR), the sodium combustion aerosols along with fission product aerosols would migrate to the environment through leak paths of the Reactor Containment Building (RCB) concrete wall under positive pressure. Understanding the characteristics of sodium aerosol transport through concrete leak paths is important as it governs the environmental source term. In this context, experiments are conducted to study the influence of various parameters like pressure, initial mass concentration, leak path diameter, humidity etc., on the transport and deposition of sodium aerosols in straight leak paths of concrete. The leak paths in concrete specimens are prepared by casting and the diameter of the leak path is measured using thermography technique. Aerosol transport experiments are conducted to measure the transported and plugged aerosol mass in the leak paths and corresponding plugging times. The values of differential pressure, aerosol concentration and relative humidity taken for the study are in the ranges 10-15 kPa, 0.65-3.04 g/m³ and 30-90% respectively. These observations are numerically simulated using 1-Dimensional transport equation. The simulated values are compared with the experimental results and reasonable agreement among them is observed. From the safety assessment view of reactor, the approach presented here is conservative as it is with straight leak paths.

• 한국안전학회지
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• 제11권2호
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• pp.79-88
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• 1996

A hypothetical accident in the containment vessel of liquid metal reactor could cause a pressure, temperature rise, and a strong aerosol release. The computer codes relating to the modelization of these accident make it necessary to use various input parameter, among which is the dynamic shape factor of aerosols produced. Combustion experiments of sodium spray fire carried out in a closed vessel, which was vertical cylinder made of 1.2m in diameter and 1.8m hight with a volume of 1.7$m^3$. The results of theoretical analysis presented here was compared to data obtained from experiments. The experimental results were summarized as follows. 1) The aerodynamic diameter and geometric diameter of aerosols are decreasing with increasing of injection pressure and injection temperature of sodium 2) The dynamic shape factor of aerosol is proportional to the aerodynamic diameter for a given particle. 3) The correspondence between the aerodynamic diameter and geometric diameter can be as $D_{ae}=0.70 D_{ge}$. 4) Peak pressure rose with increase in pressure and temperature of injection sodium, being more sensitive to the injection pressure than the injection temperature.

• Nuclear Engineering and Technology
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• 제53권12호
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• pp.3966-3978
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• 2021

ISFRA (Integrated SFR Analysis Program for PSA) computer program has been developed for simulating the response of the PGSFR pool design with metal fuel during a severe accident. This paper describes validation of the ISFRA aerosol model against the Aerosol Behavior Code Validation and Evaluation (ABCOVE) experiments undertaken in 1980s for radionuclide transport within a SFR containment. ABCOVE AB5, AB6, and AB7 tests are simulated using the ISFRA aerosol model and the results are compared against the measured data as well as with the simulation results of the MELCOR severe accident code. It is revealed that the ISFRA prediction of single-component aerosols inside a vessel (AB5) is in good agreement with the experimental data as well as with the results of the aerosol model in MELCOR. Moreover, the ISFRA aerosol model can predict the "washout" phenomenon due to the interaction between two aerosol species (AB6) and two-component aerosols without strong mutual interference (AB7). Based on the theory review of the aerosol correlation technique, it is concluded that the ISFRA aerosol model can provide fast, stable calculations with reasonable accuracy for most of the cases unless the aerosol size distribution is strongly deformed from log-normal distribution.

• 한국안전학회지
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• 제13권3호
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• pp.32-44
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• 1998

Analysis on the study for the sodium fire mitigation was carried out using the CONTAIN-LMR code. Sodium loop building was partitioned into the many cells, in which the safety venting systems were installed for the purpose of improving the sodium fire safety and minimizing its effect on the sodium loop building. The effects of sodium fire on sodium loop building partitioned into the many cells and not partitioned were investigated. The peak pressure and temperature of each cell accompanied by sodium fire in sodium loop building partitioned were lower than those of sodium loop building not partitioned. In the case of partitioning sodium loop building, the pressures, temperatures and aerosols into cells were transferred through propagation path of CONTAIN-LMR sodium fire model simulated by this study, and the effect of sodium spray fire on sodium loop building was mitigated by partitioning building. In addition, the excessive rise of pressure into cells was prevented by installing the over-pressure exhaust valve and under-pressure exhaust valve on the flow path between cells.

• 대한기계학회논문집B
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• 제27권12호
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• pp.1734-1743
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• 2003

Aerosol generator using an electrically heated tube furnace is a stable apparatus to supply nanometer sized aerosols by using the evaporation and condensation processes. Using this method, we can generate highly concentrated polydisperse aerosols with relatively narrow size distribution. In this work, characteristics of particle size distribution, generated from a tube furnace, were experimentally investigated. We evaluated effects of several operation parameters on particle generation: temperature in the tube furnace, air flow rates through the tube, size of boat containing solid sodium chloride(NaCl). As the temperature increased, the geometric mean diameter increased and the total number concentration also increased. Dilution with air affected the size distribution of the particles due to coagulation. A smaller sized boat, which has small surface area to contact with air, brings smaller particles of narrow size distribution in comparison of that of a larger boat. Finally, we changed the electrical mobility diameter of aggregate sodium chloride particles by varying relative humidity of dilution air, and obtained non-aggregate sodium chloride particles, which are easy to generate exact monodisperse particles.

• Nuclear Engineering and Technology
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• 제50권6호
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• pp.849-853
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• 2018

Mechanistic calculations for wet scrubbing of aerosol/vapor from gas bubble rising in liquid pool are essential to safety of sodium-cooled fast reactor. Hence, scrubbing of volatile fission product from mixed gas bubble rising in sodium pool is presented in this study. To understand this phenomenon, a theoretical model has been setup based on classical theories of aerosol/vapor removal from bubble rising through liquid pools. The model simulates pool scrubbing of sodium iodide aerosol and cesium vapor from a rising mixed gas bubble containing xenon as the inert species. The scrubbing of aerosol and vapor are modeled based on deposition mechanisms and Fick's law of diffusion, respectively. Studies were performed to determine the effect of various key parameters on wet scrubbing. It is observed that for higher vapor diffusion coefficient in gas bubble, the scrubbing efficiency is higher. For aerosols, the cut-off size above which the scrubbing efficiency becomes significant was also determined. The study evaluates the retention capability of liquid sodium used in sodium-cooled fast reactor for its safe operation.

• 한국대기환경학회지
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• 제19권1호
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• pp.67-76
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• 2003

Recently consideration of health and interest on bio aerosols have been growing steadily. In this study, inertial impactor, which can be used to collect airborne particles and bio aerosols, was newly devised for real-time observation on the particles collected on impaction plate. and named Visual Impactor. Flow field and particle trajectory in the space between nozzle and impaction plate was analyzed numerically, and the collection effciencies were calculated. Calibration and performance evaluation of the Visual Impactor was conducted with polydisperse aerosols generated from 0.1％ sodium chloride solution. Cut-off diameter from numerical simulation was in good agreement with that from experimental results. Because of particle bounce and particle deposition on nozzle tip due to short jet-to-plate distance, the collection efficiencies from numerical and experimental analyses were different slightly. Visual Impactor was used to collect airborne particles, and the features of collected particles could be seen in real-time. Airborne particles in different weather conditions (fine, cloudy, and rainy) were sampled and compared one another The features of collected airborne particles were dependent strongly upon relative humidity. In addition, with hours elapsing, shapes and colors of collected particles were changed by evaporation and surface tension, etc.

• Journal of Korean Society for Atmospheric Environment
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• 제24권E1호
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• pp.24-31
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• 2008

In this study, a new PM (particulate matter) sampler was developed and fabricated to collect fine particles in the atmosphere, and laboratory and field tests were carried out to evaluate the performance of the sampler. The PM sampler, which was based on impingers, employed an aerosol condensation system as a PM magnifier to improve its collection efficiencies. Sodium chloride, ammonium sulfate and ammonium nitrate aerosols were used as test particles, because these components are rich in ambient aerosols. As a result, it was found that the collection efficiency of the novel PM sampler was very high. Thus, it is believed that the PM sampler is an effective device for sampling fine particles. In addition, it was demonstrated that this work could contribute to the collection or removal of fine particles and be applied to the semicontinuous sampling of ambient aerosols for chemical composition analysis.