• Nuclear Engineering and Technology
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• v.52 no.6
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• pp.1297-1303
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• 2020

In this study, nuclear radiation shielding and rigidity parameters of Y (0.1-x)B0.6Bi1.8O3La2x glassy system were investigated in order to determine it's suitability for use as nuclear radiation shielding materials. Therefore, a group of bismuth borate glass samples with La₂O₃ additive were synthesized using the technique of melt quenching. According to the results, the increase of the La₂O₃ additive increases the density of the glass samples and the mass attenuation coefficient (μ_m) values, whereas the half-value layer (HVL) and mean free path (MFP) values decrease. The effective atomic number (Z_eff) is also enhanced with an increment of both mass removal cross section for neutron (Σ_R) and absorption neutron scattering cross section (σ_abs). In addition to the other parameters, rigidity parameter values were theoretically examined. The increase of La₂O₃ causes some other important magnitudes to increase. These are the average crosslink density, the number of bonds per unit volume, as well as the stretching force constant values of these glass samples. These results are in concordance with the increase of elastic moduli in terms of the Makishima-Mackenzie model. This model showed an increase in the rigidity of the glass samples as a function of La₂O₃.

• Nuclear Engineering and Technology
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• v.53 no.1
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• pp.216-233
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• 2021

In this work, Rhizophora spp. particleboard phantoms were made using SPI-based adhesives, modified with sodium hydroxide and itaconic acid polyamidoamine-epichlorohydrin (0, 5, 10, and 15 wt%). An X-ray computed tomography (CT) imaging system was used to ascertain the CT numbers and density distribution profiles of the particleboards. The SPI-based/NaOH/IA-PAE/Rhizophora spp. particleboard phantoms with 15 wt% IA-PAE addition level had the highest solid content, flexural strength, flexural modulus, and internal bonding strength of 36.06 ± 1.08%, 18.61 ± 0.38 Nmm^-2, 7605.76 ± 0.89 Nmm^-2, and 0.463 ± 0.053 Nmm^-2, respectively. The moisture content, mass density, water absorption, and dimensional stability were 6.93 ± 0.27%, 0.962 ± 0.037 gcm^-3, 22.36 ± 2.47%, and 10.90 ± 0.86%, respectively. The results revealed that the mass attenuation coefficients and effective atomic number values within the 16.59-25.26 keV photon energy region, were close to the calculated XCOM values in water, with a p-value of 0.077. Moreover, the CT images showed that the dissimilarities in the discrepancy of the profile density decreased as the IA-PAE concentrations increased. Therefore, these results support the appropriateness of the SPI-based/NaOH/IA-PAE/Rhizophora spp. particleboard with 15 wt% IA-PAE adhesive as a suitable tissue-equivalent phantom material for medical health applications.

• Journal of Radiation Industry
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• v.6 no.2
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• pp.189-197
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• 2012

This study was carried out to develop the improved useful mutants for yield or composition of stevia plants using the gamma ray or chemical mutagens treatments. The seeds of stevia 'Suwon No. 11' were irradiated up to 400 Gy of gamma ray. Chemical mutagens were treated on the seeds of the 'Suwon No. 11' using 0.07% colchicine, 10 mM sodium azide, or 10 mM NMU for various durations. The germination rate, and shoot and root growth of seedling were estimated at 30 days after gamma ray irradiation or chemical mutagen treatment, and the plant height, the number of branches, and leaf length and width were examined at 3 months after mutagenesis treatments. In the case of gamma ray treatments, the germination rate and early-stage growth were decreased as the increase of radiation dose, and the 50% lethal dose was found to be 200 Gy. the plant height was decreased as the increase of radiation dose, while the number of branches per plant and leaf length were increased. Leaf shape was modified to the relatively longer one compared to the control, which was identified more apparently at the treatments of higher than 150 Gy. In the treatment of chemical mutagens, the rate of germination and survival were decreased as the increase of incubation time. The 50% lethal dose for germination rate were identified as the conditions of the 15 hours incubation in 0.07% colchicine, the 4 hrs in 10 mM sodium azide, and the 2 hrs in 10 mM NMU, in the three chemical mutagens treatments. Chemical mutagens had no influence on shoot growth, while root growth was increased, especially as the incubation time was extended. The highest root growth occurred in the NMU treatment at 6 hrs incubation time. The plant height was decreased as the increase of incubation time in the chemical mutagens treatments. Among the chemical mutagens, NMU was the most effective to induce the mutants with long-shaped or the least lobed leaves.

• Journal of the Korean Society of Food Science and Nutrition
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• v.32 no.5
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• pp.673-678
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• 2003

Changran Jeotgal (aged and seasoned intestine of Alaska pollack) was prepared as the same method as commercial one and irradiated at 0, 2.5, 5.0 and 10 k㏉ by gamma ray for industrial application. Changran Jeotgal using 10 k㏉-irradiated red pepper powder was also prepared to compare with control (0 k㏉). Commercial red pepper powder was already contaminated at 3.8$\times$10$^{6}$ CFU/$m\ell$ level by total plate count and 10k㏉ of irradiation reduced the number about 4 log cycles. Gamma irradiated Changran Jeotgal at 2.5,5.0, and 10k㏉ showed 3 6, and 7 log cycles of reduction compared to the non-irradiated control in the total plate count after 12 weeks of storage at 1$0^{\circ}C$. Using irradiated (10k㏉) red pepper powder reduced the microbial contamination significantly by 2 log cycles compared to the control. Sensory evaluation showed that the sample irradiated at 2.5 k㏉ was the most acceptable, followed by the sample using irradiated red pepper powder and non-irradiated control. Thus, 2.5 k㏉ of irradiation of Changran Jeotgal was effective to improve safety during distribution and storage without change of sensory quality. Furthermore, using the irradiated red pepper powder is also recommended for safety enhancement of the products.

• Journal of Science Education
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• v.39 no.1
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• pp.15-27
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• 2015

This study investigated whether there was a difference of the change in perspective of the nature of science depending on subjects of the history of science, after designing for two kinds of topics of role play programs based on the history of science to be transformed into a modern perspective. Before the history of science-role plays, the degree of the modern perspective was statistically no difference between group I(the atomic model transition-role play) and group II(the Mendeleev's periodic table-role play). However after treatment of the history of science-role plays for the each group, the degree of group I was higher than the degree of group II in the modern perspective. The results of this study indicate that the degree of changes into modern perspective of the nature of science by performing a history of science-role play may be depend on the subject of the history of science combined with the role play, and suggest the possibility that may be more effective to change the nature of science into the modern perspective, in case of performing of role play based on the history of science that includes the scientific knowledge established by a number of scientists with time series.

• Korean Journal of Food Science and Technology
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• v.33 no.3
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• pp.338-344
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• 2001

The effect of gamma-irradiation on the microbiological and general qualities of Kanjang (fermented soy sauce, Korean type) and Shoyu (fermented soy sauce, Japanese type) was studied. Samples were prepared, irradiated at 5, 10 and 20 kGy, and then stored at $25^{\circ}C$ for 18 weeks. The results showed that the Bacillus spp. was inactivated by 3 log cycles with the irradiation dose of 10 kGy and the number of Bacillus cells that survived from 10 to 20 kGy of gamma irradiation was decreased gradually during storage. Yeasts and Lactobacillus were nearly eliminated at 5 to 10 kGy of irradiation. The $D_{10}$ values of Bacillus, yeast and Lactobacillus in Shoyu were 2.67 kGy, 0.81 kGy and 1.30 kGy, in Kanjang were 2.75 kGy, 0.99 kGy and 1.47 kGy, respectively. The general quality of gamma irradiated Shoyu and Kanjang, such as total nitrogen, amino nitrogen, protease activity and pH were more stable than that of control during storage periods. Decolorization was observed just after irradiation, but the color was recovered during storage. The sensory evaluations showed that irradiated samples were more acceptable. Therefore, it was considered that gamma irradiation was effective for maintaining better quality of Shoyu and Kanjang during storage.

• Journal of Radiation Protection and Research
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• v.33 no.2
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• pp.67-76
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• 2008

As the first comprehensive attempt at a national implementation, this study aims at assessing the external costs of major electricity generation technologies in Korea, particularly an evaluation of the impacts on human health resulting from exposures to atmospheric radiological emissions from nuclear power plants, and a monetary quantification of their damages. The methodology used for the assessment of the externalities of the selected fuel cycles has been developed by the International Atomic Energy Agency (IAEA), namely the SimPacts Model Package. The model is internationally recognized as a tool which can be applied to a wide range of fuels, different technologies and locations, for an externalities study. In this study, the relevant emissions are quantified first and then their impacts on human health are evaluated and compared. The study focused on all the nuclear power plants for the last 6 years ($2001{\sim}2006$) in Korea. With respect to nuclear power, the impact analysis only focuses on a power generation, however the front- and back-end nuclear fuel cycles are not included, namely uranium mining, conversion, enrichment, reprocessing, conditioning, etc., because these facilities are not present in Korea. The analysis results show that nuclear power in general, generates low external costs. The highest damage costs from the nuclear power plants among the 4 sites in Korea were estimated to be 3.9 mills/MWh, which is about 1/20th of the result for a similar case study conducted in the U.K., implemented through the ExternE project. This difference is largely due to the number of radionuclides included in the study and the amount of released radioactive emissions based on up-to-date information in Korea. In this study, the sensitivities of the major factors for nuclear power plants were also calculated. The analysis indicates that there was around a ${\pm}3%$ damage costs variation to a ${\pm}15%$ change of the reference population density and a ${\pm}1%$ damage cost variation to a $1{\sim}30$ meters change of the effective release height, respectively. These sensitive calculations show that there is only a minor difference when the reference costs are compared.

• Korean Journal of Plant Resources
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• v.25 no.6
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• pp.731-738
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• 2012

Dandelion has been widely utilized for medicinal and edible purposes. This research was conducted to evaluate the effect of supplemental LED (light-emitting diode) light on germination, growth characteristics and anthocyanin content of dandelion (Taraxacum officinale) seedling using LED blue (460 nm), red (660 nm, R), blue + red (B:R=6:4) and fluorescent lamp light treatment. By LED illumination to T. officinale seed germination speed was delayed, and germination rate was the highest in the fluorescent light. The growth characteristics (plant height, number of leaves, root length and fresh weight) were greatly influenced by supplemental LED light compared with control treatment, and the growth promotion was the most effective in the red LED illumination. After 60 days of red and mixed LED light treatments, anthocyanin content of dandelion plants was significantly changed. The anthocyanin content was increased by 12~19 mg/100 g under the red LED and the mixed light conditions compared with the control and the blue LED. Results indicate that illumination with red and mix LEDs, compared with other light treatments, is beneficial for promotion of growth and anthocyanin content in dandelion.

• Journal of the Korean Society for Nondestructive Testing
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• v.15 no.4
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• pp.561-567
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• 1996

As nuclear industry in Korea is being expended, the number of user for radioisotope and radiation generators has being remarkably increased. As a result, radiation shielding problem for radiation safety has rasied as a question of great interest nowaday. In this report, gamma scanning test (GST), one of the nondestructive test methods of radiation shielding material was introduced and the review of the test method and its application were described. In addition for accurate evaluation of the test result, necessary basic equipments for the test and for improvement of the equipment were suggested. If the effective test method described above were widely and properly applied by GST related companies, the technology would be used effectively, as one of the safe nondestructive test for radiation shielding material in future.

• Composites Research
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• v.31 no.3
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• pp.83-87
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• 2018

An object in the Low Earth Orbit (LEO) is affected by many environmental conditions unlike earth's surface such as, Atomic oxygen (AO), Ultraviolet Radiation (UV), thermal cycling, High Vacuum and Micrometeoroids and Orbital Debris (MMOD) impacts. The effect of all these parameters have to be carefully considered when designing a space structure, as it could be very critical for a space mission. Polybenzimidazole (PBI) is a high performance thermoplastic polymer that could be a suitable material for space missions because of its excellent resistance to these environmental factors. A thin coating of PBI polymer on the carbon epoxy composite laminate (referred as CFRP) was found to improve the energy absorption capability of the laminate in event of a hypervelocity impact. However, the overall efficiency of the shield also depends on other factors like placement and orientation of the laminates, standoff distances and the number of shielding layers. This paper studies the effectiveness of using a PBI coating on the front bumper in a multi-shock shield design for enhanced hypervelocity impact resistance. A thin PBI coating of 43 micron was observed to improve the shielding efficiency of the CFRP laminate by 22.06% when exposed to LEO environment conditions in a simulation chamber. To study the effectiveness of PBI coating in a hypervelocity impact situation, experiments were conducted on the CFRP and the PBI coated CFRP laminates with projectile velocities between 2.2 to 3.2 km/s. It was observed that the mass loss of the CFRP laminates decreased 7% when coated by a thin layer of PBI. However, the study of mass loss and damage area on a witness plate showed CFRP case to have better shielding efficiency than PBI coated CFRP laminate case. Therefore, it is recommended that PBI coating on the front bumper is not so effective in improving the overall hypervelocity impact resistance of the space structure.