Search

Respiratory masks are the primary and most effective means of protecting individuals from airborne hazards such as droplets and particulate matter during public engagements. However, conventional electrostatically charged melt-blown microfiber masks typically require thick and dense membranes to achieve high filtration efficiency, which in turn cause a significant pressure drop and reduce breathability. In this study, we have developed a multielectrospinning system to address this issue by manipulating the pore structure of nanofiber networks, including the use of uniaxially aligned nanofibers created via an electric-field-guided electrospinning apparatus. In contrast to the common randomly collected microfiber membranes, partially aligned dual-nanofiber membranes, which are fabricated via electrospinning of a random 150 nm nanofiber base layer and a uniaxially aligned 450 nm nanofiber spacer layer on a roll-to-roll collector, offer an efficient way to modulate nanofiber membrane pore structures. Notably, the dual-nanofiber configuration with submicron pore structure exhibits increased fiber density and decreased volume density, resulting in an enhanced filtration efficiency of over 97% and a 50% reduction in pressure drop. This leads to the highest quality factor of 0.0781. Moreover, the submicron pore structure within the nanofiber networks introduces an additional sieving filtration mechanism, ensuring superior filtration efficiency under highly humid conditions and even after washing with a 70% ethanol solution. The nanofiber mask provides a sustainable solution for safeguarding the human respiratory system, as it effectively filters and inactivates human coronaviruses while utilizing 130 times fewer polymeric materials than melt-blown filters. This reusability of our filters and their minimum usage of polymeric materials would significantly reduce plastic waste for a sustainable global society.

This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause.

The meteorological conditions of Korean nuclear power plant sites were analyzed by using the integral parameters developed by Allwine and Whiteman. The method of integral parameters was applied to 76 sites in Korea which are evenly distributed. The integral quantities of stagnation and recirculation were calculated at four nuclear power plant (NPP) sites and these values were analyzed with the distribution of the integral quantities estimated with the results of the 76 sites. The comparative study shows that the meteorological conditions of the four NPP sites in Korea are quite good from the meteorological aspects.

A model, called METRO-K, has been developed for a radiological dose assessment due to a radioactive contamination for the Korean urban environment. The model has been taking part in the Urban Remediation Working Group within the IAEA’s EMRAS project to provide an opportunity to compare the modeling approaches and the predictive results of models that describe the behavior of radionuclide in an urban environment. The modeling approaches of METRO-K and the predictive results that have been carried out as a part of the Working Group's activities are presented and discussed. Contribution of contaminated surfaces to absorbed dose rates revealed a distinct difference for the locations of a receptor.

In an accidental release of radioactive materials to the environment, the contaminative influence of animal products due to the inhalation of air and the ingestion of soil of cattle, both of which are considered as minor contaminative pathways in most radioecological models but may be important ones, was investigated with the improvement of the Korean radioecological model DYNACON. Although mathematical models for both contaminative pathways have been established for considering all animal products and incorporated into the model, investigation was limited to milk. As a result, it was found that both pathways are influential in the contamination of milk during the non-grazing period of dairy cows. Precipitation was an influential factor in milk contamination due to the ingestion of soil, especially for 137Cs. In the case of an accidental release during the grazing period of dairy cows, the contaminative influence due to the inhalation of air was negligible irrespective of the existence of precipitation during an accidental release.

A three-dimensional wind field and an atmospheric dispersion model have been developed for real-time accident generation of a wind field over the whole domain using several measured data. A Lagrangian particle model was used for the calculation of the concentration distribution of the radionuclides in the atmosphere. The field tracer experiment near the Younggwang nuclear power plant was carried out for the purpose of analyzing the site-specific environmental characteristics and validating the atmospheric dispersion model in May 1996. The calculated concentration the most important factors for calculating the concentration of the released particles in the dispersion model. Several numerical experiments using the measured wind data were performed to get more accurate concentration distributions compared with the results of the field tracer experiment of SF6. The developed numerical models are being used as a basic tool for emergency preparedness in Korea.

A methodology for determining optimal durations for the use of contaminated crops as fodder was designed based on cost-benefit analysis. Illustrative results of the application of this methodology to pigs are presented for the hypothetical deposition of radionuclides on August 15 when a number of crops are fully developed in Korean agricultural conditions. For investigating the appropriateness of the use of contaminated crops as fodder, the net benefit from this action was compared with the imposition of a ban on human consumption of contaminated crops without alternative use. The time-dependent radionuclide concentrations in crops and pork after the deposition event were predicted from a dynamic food-chain model DYNACON. The net benefit from the actions was quantitatively evaluated in terms of cost equivalent of the doses incurred or averted and the monetary costs needed to implement the action. The optimal duration for the use of contaminated crops as fodder depended on a number of factors such as radionuclide, variety of crops fed as fodder and duration of the action. Such action was more cost effective for 137Cs deposition than for 90Sr or 131I deposition. The use of contaminated crops as fodder can be an effective response to a public reluctance to consume contaminated crops.

A dynamic food chain model DYNACON was developed to simulate the radionuclide transfer on agricultural ecosystems. DYNACON estimates the radioactivity in each compartment of food chains for three radionuclides, nine plant species and five animal products as a function of the deposition date. A number of the parameter values used in this study are representative of Korean agricultural conditions. The model was expressed by coupled differential equations and the radioactivity in each compartment was solved as a function of time following an acute deposition. Although DYNACON is structurally based on existing models, it was designed in order to simulate more realistic radionuclide behavior in Korean agricultural conditions and to save computation time. It was found that the radioactivity in foodstuffs depends strongly on the date of deposition. A comparative study between DYNACON and an equilibrium model showed good agreement for depositions that occur during the growing season of plants. DYNACON is going to be implemented in a Korean real-time dose assessment system FADAS.

The gamma-ray exposure doses in decontamination operation after a nuclear accident were evaluated with a consideration of various geometrical conditions and specific gamma-ray energies. The calculation domain is organized with three residence types and each form is divided into two kinds of geometrical arrangements. The position-wise air KERMA values were calculated with an assumption of evenly distributed gamma-ray source based on Monte Carlo radiation transport analysis using the MCNP code. The radioactivity is initially set to be unity to be multiplied by the deposition value measured in the actual accident condition. The workforce data set depending on the target object was determined by modifying the Fukushima report. The external exposure doses for decontamination workers were derived from the calculated KERMA values and the workforce analysis. These results can be used to efficiently determine the workforce required by the characteristics of the area and the structure to be decontaminated within the dose limits.