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RISS 인기검색어
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Woo-Yong Kim,Sang June Park,Sungjun Kim,Suil Bang,Moonoh Kim 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.2
Glass fiber (GF) insulation is a non-combustible material, light, easy to transport/store, and has excellent thermal insulation performance, so it has been widely used in the piping of nuclear power plants. However, if the GF insulation is exposed to a high-temperature environment for a long period of time, there is a possibility that it may be crushed even with a small impact due to deterioration phenomenon and take the form of small particles. In fact, GF dust was generated in some of the insulation waste generated during the maintenance process. In the previous study, the disposal safety assessment of GF waste was performed under the abnormal condition of the disposal facility to calculate the radiation exposure dose of the public residing/ residents nearby facilities, and then the disposal safety of GF waste was verified by confirming that the exposure dose was less than the limit. However, the revised guidelines for safety assessment require the addition of exposure dose assessment of workers. Therefore, in this study, accident scenarios at disposal facilities were derived and the exposure dose to the workers during the accident was evaluated. The evaluation was carried out in the following order: (1) selection of accident scenario, (2) calculation of exposure dose, (3) comparison of evaluation results with dose limits, and confirmation of satisfaction. The representative accident scenarios with the highest risk among the facility accident were selected as; (a) the fire in the treatment facility, (b) the fire in the storage facility, and (c) fire after a collision of transport vehicles. The internal and external exposure doses of the worker by radioactive plume were calculated at 10m away from the accident point. In evaluation, the dose conversion factors ICRP-72 and FGR12 were used. As a result of the calculation, the exposure dose to workers was derived as about 0.08 mSv, 0.20 mSv, and 0.10 mSv, due to fire accidents (vehicle collision, storage facilities, treatment facilities). These were 0.2%, 0.4%, and 0.2% of the limit, and the radiation risk to workers was evaluated to be very low. The results of this study will be used as basic data to prove the safety of the disposal of GF waste. The sensitivity analysis will be performed by changing the radiation source and emission rate in the future.
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Adsorption Effect of Silicon Sorption Artifacts by Using an Ultra-Precision Balance in Vacuum
Sungjun Lee,Jin Wan Chung,Woo Gab Lee 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.I
We, the Korea Research Institute of Standards and Science (KRISS) mass laboratory, study the adsorption effect of the weight and the surface of silicon (Si) by using an ultra-precision mass comparator operated in vacuum and in air. Si sorption artifacts (SAs) are fabricated, and the dimension and roughness are measured. Preliminary experiments are carried out in vacuum and in air. We examine the adsorption mass measurement of 1-kg Si sphere (Si-S), SA cylinder (SA-C), and SA disks (SA-D).
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Analysis on Factors to Be Considered for the Safety Assessment of Colloids
Hyun Woo Song,Moonoh Kim,Sang June Park,Sungjun Kim,Jun-gi Yeom 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.1
Concerns with colloids, dispersed 1~1,000 nm particles, in the LILW repository are being raised due to their potential to enhance radionuclide release. Due to their large surface areas, radionuclides may sorb onto mobile colloids, and drift along with the colloidal transport, instead of being sorbed onto immobile surfaces. To prevent adverse implications on the safety of the repository, the colloidal impact must be evaluated. In this paper, colloid analysis done by SKB is studied, and factors to be considered for the safety assessment of colloids are analyzed. First, the colloid generation mechanism should be analyzed. In a cementitious repository, due to a highly alkaline environment, colloid formation from wastes may be promoted by the decomposition of organic materials, dissolution of inorganic materials, and corrosion of metals. Radiolysis is excluded when radionuclide inventory is moderate, as in the case of SKB. Second, colloid stability should be evaluated to determine whether colloids remain in dispersion. Stable colloids acquire electric charges, allowing particles to continuously repel one another to prevent coagulation. Thus, stability depends on the pH and ionic condition of the surroundings, and colloid composition. For instance, under a highly alkaline cementitious environment, colloids tend to be negatively charged, repelling each other, but Ca2+ ion from cement, acting as a coagulant, makes colloid unstable, promoting sedimentation. As in the case of SKB, the colloidal impact is assumed negligible in the silo, BMA, and BTF due to their extensive cement contents, but for BLA, with relatively less cement source, the colloidal impact is a potential concern. Third, colloid mobility should be assessed to appraise radionuclide release via colloid transport. The mobility depends on the density and size of colloids, and flow velocity to commence motion. As a part of the assessment, the filtration effect should also be included, which depends on pore size and structure. As in the case of SKB, due to static hydraulic conditions and engineering barriers, acting as efficient filters, colloidal transport is expected to be unlikely. In the domestic underground repository, the highly alkaline environment would lead to colloid formation, but due to high Ca2+ concentration and low flow velocity, colloids would achieve low stability and mobility, thus colloidal impact would be a minor concern. In the future, with further detailed analysis of each factor, waste composition, and disposal condition, reliable data for safety evaluation could be generated to be used as fundamental data for planning waste acceptance criteria.
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Proposal on the Cellulose Degradation Model for the Domestic 1st Phase Underground Repository
Hyun Woo Song,Moonoh Kim,Sang June Park,Sungjun Kim,Jun-gi Yeom 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.1
With the recent concern regarding cellulose enhancing radionuclide mobility upon its degradation to ISA, disposal of cellulosic wastes is being held off until the disposal safety is vindicated. Thus, a rational assessment should be conducted, applying an appropriate cellulose degradation model considering the disposal environment and cellulose degradation mechanisms. In this paper cellulose degradation mechanisms and the disposal environment are studied to propose the best-suitable cellulose degradation model for the domestic 1st phase repository. For the cellulose to readily degrade, the pH should be greater than 12.5. As in the case of SKB, 1BLA is excluded from the safety assessment because the pH of 1BLA remains below 12.5. Furthermore, despite cellulose degradation occurring, it does not always produce ISA. At low Ca2+ concentration, the ISA yield rate is around 25%, but at high Ca2+ concentration, the ISA yield rate increases up to 90%. Thus, for the cellulose to be a major concern, both pH and Ca2+ concentration conditions must be satisfied. To satisfy both conditions, the cement hydration must be in 2nd phase, when the porewater pH remains around 12.5 and a significant amount of Ca2+ ion is leaching out from the cement. However, according to the safety evaluation and domestic research, 2nd phase of cement hydration for silo concrete would achieve a pH of around 12.4, dissatisfying cellulose degradation condition like in 1BLA. Thus, cellulose degradation would be unlikely to occur in the domestic 1st phase repository. To derive waste acceptance criteria, a quantitative evaluation should be conducted, conservatively assuming cellulose is degraded. To conduct a safety evaluation, an appropriate degradation model should be applied to determine the degradation rate of cellulose. According to overseas research, despite the mid-chain scission being yet to be seen in the experiments, the degradation model considering mid-chain scission is applied, resulting in an almost 100% degradation rate. The model is selected because the repositories are backfilled with cement, achieving a pH greater than 13, so extensive degradation is reasonably conservative. However, under the domestic disposal condition, where cellulose degradation is unlikely to occur, applying such model would be excessively conservative. Thus, the peeling and stopping model derived by Van Loon and Haas, which suggests 10~25% degradation rate, is reasonably conservative. Based on this model, cellulose would not be a major concern in the domestic 1st phase repository. In the future, this study could be used as fundamental data for planning waste acceptance criteria.
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Park, SungJun,Park, Hye Hun,Ko, Young-Seon,Lee, Su Jin,Le, The Son,Woo, Kyoungja,Ko, GwangPyo Elsevier 2017 Science of the Total Environment Vol.609 No.-
<P><B>Abstract</B></P> <P>Silver nanoparticles (AgNPs) have long been considered a powerful disinfectant for controlling pathogenic microorganisms. However, AgNPs might have adverse effects on both human health and our ecosystems due to their potential cytotoxicity and the difficulty in recovering them after their release into the environment. In this study, we characterized the antimicrobial efficacy caused by a novel micrometer-sized magnetic hybrid colloid (MHC) containing 7, 15, or 30nm sized monodispersed AgNPs (AgNP-MHCs), which can be re-collected from the environment using simple procedures, such as a magnet or centrifugation. We evaluated the antibacterial capabilities of AgNP-MHCs against target bacteria (<I>Legionella pneumophila, Bacillus subtilis</I>, <I>Escherichia coli</I>, and <I>Clostridium perfringens</I>) and compared them with the inactivation efficacy of AgNPs ~30nm in diameter (nAg30s). Among the different AgNP-MHCs composites evaluated, Ag30-MHCs had the greatest antibacterial effect. After 1h of exposure, more than a 4-log<SUB>10</SUB> reduction of <I>L. pneumophila</I> and 6-log<SUB>10</SUB> reduction of <I>B. subtilis</I> was achieved by 4.6×10<SUP>9</SUP> particles/mL of Ag30-MHCs and Ag30-MHC-Ls. In addition, Ag30-MHC-Ls maintained their strong antibacterial capabilities under anaerobic conditions. Our results indicate that AgNP-MHCs can be considered excellent tools for controlling waterborne bacterial pathogens, with a minimal risk of release into the environment.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The use of AgNPs for controlling pathogens is hindered by several major obstacles. </LI> <LI> AgNP-MHCs can prevent the aggregation of AgNPs and be re-collected easily after use. </LI> <LI> AgNP-MHCs showed great antibacterial capabilities in various environmental conditions. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Hong, Sungjun,Chung, Yanghon,Woo, Chungwon Elsevier 2015 ENERGY Vol.79 No.-
<P><B>Abstract</B></P> <P>South Korea, as the 9th largest energy consuming in 2013 and the 7th largest greenhouse gas emitting country in 2011, established ‘Low Carbon Green Growth’ as the national vision in 2008, and is announcing various active energy policies that are set to gain the attention of the world. In this paper, we estimated the decrease of photovoltaic power generation cost in Korea based on the learning curve theory. Photovoltaic energy is one of the leading renewable energy sources, and countries all over the world are currently expanding R&D, demonstration and deployment of photovoltaic technology. In order to estimate the learning rate of photovoltaic energy in Korea, both conventional 1FLC (one-factor learning curve), which considers only the cumulative power generation, and 2FLC, which also considers R&D investment were applied. The 1FLC analysis showed that the cost of power generation decreased by 3.1% as the cumulative power generation doubled. The 2FCL analysis presented that the cost decreases by 2.33% every time the cumulative photovoltaic power generation is doubled and by 5.13% every time R&D investment is doubled. Moreover, the effect of R&D investment on photovoltaic technology took after around 3 years, and the depreciation rate of R&D investment was around 20%.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We analyze the learning effects of photovoltaic energy technology in Korea. </LI> <LI> In order to calculate the learning rate, we use 1FLC (one-factor learning curve) and 2FLC methods, respectively. </LI> <LI> 1FLC method considers only the cumulative power generation. </LI> <LI> 2FLC method considers both cumulative power generation and knowledge stock. </LI> <LI> We analyze a variety of scenarios by time lag and depreciation rate of R&D investment. </LI> </UL> </P>
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Antiviral Properties of Silver Nanoparticles on a Magnetic Hybrid Colloid
Park, SungJun,Park, Hye Hun,Kim, Sung Yeon,Kim, Su Jung,Woo, Kyoungja,Ko, GwangPyo American Society for Microbiology 2014 Applied and environmental microbiology Vol.80 No.8
<P>Silver nanoparticles (AgNPs) are considered to be a potentially useful tool for controlling various pathogens. However, there are concerns about the release of AgNPs into environmental media, as they may generate adverse human health and ecological effects. In this study, we developed and evaluated a novel micrometer-sized magnetic hybrid colloid (MHC) decorated with variously sized AgNPs (AgNP-MHCs). After being applied for disinfection, these particles can be easily recovered from environmental media using their magnetic properties and remain effective for inactivating viral pathogens. We evaluated the efficacy of AgNP-MHCs for inactivating bacteriophage ϕX174, murine norovirus (MNV), and adenovirus serotype 2 (AdV2). These target viruses were exposed to AgNP-MHCs for 1, 3, and 6 h at 25°C and then analyzed by plaque assay and real-time TaqMan PCR. The AgNP-MHCs were exposed to a wide range of pH levels and to tap and surface water to assess their antiviral effects under different environmental conditions. Among the three types of AgNP-MHCs tested, Ag30-MHCs displayed the highest efficacy for inactivating the viruses. The ϕX174 and MNV were reduced by more than 2 log<SUB>10</SUB> after exposure to 4.6 × 10<SUP>9</SUP> Ag30-MHCs/ml for 1 h. These results indicated that the AgNP-MHCs could be used to inactivate viral pathogens with minimum chance of potential release into environment.</P>
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