• Polymer(Korea)
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• v.38 no.1
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• pp.69-73
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• 2014

In this study, polysaccharide-poly(vinyl alcohol) (PVA) hydrogels were prepared by using ${\gamma}$-ray and evaluated for potential application as an anti-inflammation patch. Ulmus davidiana var. japonica (UD), one of polysaccharides has been particularly used as an oriental remedy for the treatment of inflammation and ulcers. PVA as a biocompatible polymer and glycerin as a moisturizer were blended with the UD, and its hydrogels were prepared by radiation crosslinking. Characterizations for UD hydrogels were performed by using cytotoxicity assay, antioxidant activity test, and physicochemical test such as gel fraction ratio, and swelling behavior. The results showed that these UD hydrogels had excellent physical properties, anti-inflammation activity, and non-cytotoxicity on the cells. Therefore, these polysaccharide based-UD hydrogels can be effectively used as an inflammation patch.

• Nuclear Engineering and Technology
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• v.49 no.5
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• pp.1044-1062
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• 2017

The construction project of the Kijang research reactor (KJRR), which is the second research reactor in Korea, has been launched. The KJRR was designed to use, for the first time, U-Mo fuel. Plate-type U-7 wt.% Mo/Al-5 wt.% Si, referred to as U-7Mo/Ale5Si, dispersion fuel with a uranium loading of $8.0gU/cm^3$, was selected to achieve higher fuel efficiency and performance than are possible when using $U_3Si_2/Al$ dispersion fuel. To qualify the U-Mo fuel in terms of plate geometry, the first miniplates [HANARO Miniplate (HAMP-1)], containing U-7Mo/Al-5Si dispersion fuel ($8gU/cm^3$), were fabricated at the Korea Atomic Energy Research Institute and recently irradiated at HANARO. The PIE (Post-irradiation Examination) results of the HAMP-1 irradiation test were analyzed in depth in order to verify the safe in-pile performance of the U-7Mo/Al-5Si dispersion fuel under the KJRR irradiation conditions. Nondestructive analyses included visual inspection, gamma spectrometric mapping, and two-dimensional measurements of the plate thickness and oxide thickness. Destructive PIE work was also carried out, focusing on characterization of the microstructural behavior using optical microscopy and scanning electron microscopy. Electron probe microanalysis was also used to measure the elemental concentrations in the interaction layer formed between the U-Mo kernels and the matrix. A blistering threshold test and a bending test were performed on the irradiated HAMP-1 miniplates that were saved from the destructive tests. Swelling evaluation of the U-Mo fuel was also conducted using two methods: plate thickness measurement and meat thickness measurement.

• Korean Journal of Health Education and Promotion
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• v.4 no.2
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• pp.46-70
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• 1987

The survey with questionnaire were conducted to grasp the actual condition of four cautious drugs-antibiotics, sedative hypnctics, mincr tranquilizer, analeptics-self -medication behavior through drugstore use and to analyze the primary factors connected with it. The following six objectives were established. 1) To catch the reason why the man who medicate himself buy four cautious drugs at a drugstore, and to know the choice motive of each drug purchased. 2) To grasp the distribution of four cautious drug taken by the man who medicate himself and to analyse the reason of taking the drug. 3) To find out whether the buyer has taken the same drug past and to know the duration and the frequency. 4) To grasp the degree of recognition about four cautious drugs and the attitude toward continuous taking them. 5) To analyze the degree of recognition about the influence on human body and the attitude of medication behavior. 6) To know "the experience of side-effects" and to grasp the kind of the side-effects. The data were collected from 15 drugstores with 677 respondents in seoul from August 17 to september 21, 1987. The following results were obtained. 1) The reasons for drugstore use were first, "for easy access and convenience" (53.7%) second, "for the slightness of illness" (19.9%) third "for the cheap price" (13.2%). According to that result, the factor of "the easy access of drugstore" was most influential. In case of the poor, the factor "for the cheap price "was revealed second (37.3%). And "for the slightness of illness" was second reason in the medically insured (22. 9%), "for the cheap price" was second reason in the others (29%). 2) The kind of drugs purchased were antibiotics (62.8%), analeptics(17.2%), minor tranquilizer(13.3%) and sedative hypnotics (6.7%) on the whole. In teenagers, besides antibiotics the percentage of taking analepits came second (42.4%) and it was revealed that the percentage of sedative hypnotics, minor tranquilizer increase with age. But in proportion to the increase of age, the taking of analeptis decreased. 3) The choice motives of each drug purchased were all different. In case of antibiotics "recommendation of pharmacist" was 39.6%, sedative hypnotics "recommendation of pharmacist" and "my own judgement", 28.9%, respectively, minor tranquilizer "my own judgement", 35.2%. and in case of analeptics "my oun judgement" was most common with 53.5%. 4) The reasons for taking drugs were as follows. antibiotics was taken for the inflammation mitigation of a wound and a swelling (38.5%), sedative hypnotics for the removal of insomnia (97.5%), minor tranquilizer because of restlessness and qloominess(39.3%), and analeptics for the shortening of sleeping hours (35.1%). 5) Those experienced in taking four cautious drugs were 78.2% on the average. It was revealed that antibiotics use duration was "from one week to one month" (38.9%), the frequency was "rarely" (62.1%), sedative hypnotics and minor tranquilizer; "More than three years", (35.7%, 30.4%), respectively, "Somtimes", (43.8%, 35%), respectively. analeptics ; "from one year to three years", (27.6%), "Sometimes", (42.7%). 6) In regard to the source of information in taking drugs, 35.3 percent of male were relied on "recommendation of pharmacist", 32.6 percent of female "my own judgement", There was a difference between below the middle school graduates and over the high school graduates Thease were relied on "recommendation of pharmacist" first, those "my own judgement" first. And "my own judgement" was the first source of specialist(40%), labours(41.4%), salesman(43.5%), and jobless men(36.8%), "recommendation of ralatives on friends" was the first source of students (30.4%), "recommendation of pharmacist" was the first soure of teachers, administrative office workers (39%) and housewives (40.7%). 7) The degree of recognition about four cautious drugs was as follows. "know a little" was (43.0%), "don't know" (30.2%), "know" (26.8%), respectively. In regard to the attitude toward continuous taking them, it was revealed that "I will take it according to circumstamces" was first (56.2%), " I will not take it as possible" was first(56.2%), "I dont know well" (12.9%), "I will take it continuously" (8.3%). 8) About the influence on human body, "if proper, it is effect" was common attitude toward antibiotics (43.6%), "Probably bad influence on the health" was first toward the other drugs (46.2%), In terms of the degree of observance to taking-time and dose of drugs, "suitably" was first (37.3%), "relatively correctly" second (27%), "correctly" (17%). 9) The percentage of four cautious drugs side-effects was 27.5 on the average. The kind of side-effects were eruption and urticaria (28.5%), heart acceleration and so forth. (25.4%), headache and Giddiness, dyspepsia (23%), respectively.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.4 no.2
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• pp.117-131
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• 2006

A coupled T-H-M(Thermo-Hydro-Mechanical) analysis was carried out for KENTEX (KAERI Engineering-scale T-H-M Experiment for Engineered Barrier System), which is a facility for validating the coupled T-H-M behavior in the engineered barrier system of the Korean reference HLW(high-level waste) disposal system. The changes of temperature, water saturation, and stress were estimated based on the coupled T-H-M analysis, and the influence of the types of mechanical constitutive material laws was investigated by using elastic model, poroelastic model, and poroelastic-plastic model. The analysis was done using ABAQUS, which is a commercial finite element code for general purposes. From the analysis, it was observed that the temperature in the bentonite increased sharply for a couple of days after heating the heater and then slowly increased to a constant value. The temperatures at all locations were nearly at a steady state after about 37.5 days. In the steady state, the temperature was maintained at $90^{\circ}C$ at the interface between the heater and the bentonite and at about $70^{\circ}C$ at the interface between the bentonite and the confining cylinder. The variation of the water saturation with time in bentonite was almost same independent of the material laws used in the coupled T-H-M processes. By comparing the saturation change of T-H-M and that of H-M(Hydro-Mechanical) processes using elastic and poroelastic material mod31 respectively, it was found that the degree of saturation near the heater from T-H-M calculation was higher than that from the coupled H-M calculation mainly because of the thermal flux, which seemed to speed up the saturation. The stresses in three cases with different material laws were increased with time. By comparing the stress change in H-M calculation using poroelasetic and poroelasetic-plastic model, it was possible to conclude that the influence of saturation on the stress change is higher than the influence of temperature. It is, therefore, recommended to use a material law, which can model the elastic-plastic behavior of buffer, since the coupled T-H-M processes in buffer is affected by the variation of void ratio, thermal expansion, as well as swelling pressure.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.5
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• pp.587-609
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• 2019

Short-and long-term stabilities of bentonite, favored material as buffer in geological repositories for high-level waste were reviewed in this paper in addition to alternative design concepts of buffer to mitigate the thermal load from decay heat of SF (Spent Fuel) and further increase the disposal efficiency. It is generally reported that the irreversible changes in structure, hydraulic behavior, and swelling capacity are produced due to temperature increase and vapor flow between $150{\sim}250^{\circ}C$. Provided that the maximum temperature of bentonite is less than $150^{\circ}C$, however, the effects of temperature on the material, structural, and mineralogical stability seems to be minor. The maximum temperature in disposal system will constrain and determine the amount of waste to be disposed per unit area and be regarded as an important design parameter influencing the availability of disposal site. Thus, it is necessary to identify the effects of high temperature on the performance of buffer and allow for the thermal constraint greater than $100^{\circ}C$. In addition, the development of high-performance EBS (Engineered Barrier System) such as composite bentonite buffer mixed with graphite or silica and multi-layered buffer (i.e., highly thermal-conductive layer or insulating layer) should be taken into account to enhance the disposal efficiency in parallel with the development of multilayer repository. This will contribute to increase of reliability and securing the acceptance of the people with regard to a high-level waste disposal.

• Tunnel and Underground Space
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• v.31 no.4
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• pp.289-308
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• 2021

This study conducts coupled thermo-hydro-mechanical numerical modeling to investigate the maximum temperature and conditions for securing mechanical stability of the high-level radioactive waste repository when temperature criteria of bentonite buffer are 100℃ and 125℃, respectively. In case of temperature criterion of buffer as 100℃, the maximum temperatures at the interface between canister and buffer are calculated to be 99.4℃ and 99.8℃, respectively for a case with disposal tunnel spacing of 40 m and deposition hole spacing of 5.5 m and for the other case with disposal tunnel spacing of 30 m and deposition hole spacing of 6.5 m. In case of temperature criterion of buffer as 125℃, spacings of disposal tunnel and deposition hole could be decreased to 30 m and 4.5 m, respectively, which reduces the disposal area up to 55% compared to the disposal area of KRS⁺. According to analysis of mechanical stability for various disposal spacings, RMR of rock mass for KRS⁺ should be larger than 72.4 which belongs to good rock in RMR classification to prevent failure of rock mass. As disposal spacing is decreased, required RMR of rock mass is increased. In order to prevent failure of rock mass for a case with disposal tunnel spacing of 30 m and deposition hole spacing of 4.5 m, RMR larger than 87.3 is needed. However, mechanical stability of the repository is secured for all cases with RMR over 75 considering the enhancement of rock strength due to confining stress induced by swelling of the bentonite buffer and backfill.

• Tunnel and Underground Space
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• v.32 no.1
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• pp.30-58
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• 2022

The deep geological repository for high-level radioactive waste disposal is a multi barrier system comprised of engineered barriers and a natural barrier. The long-term integrity of the deep geological repository is affected by the coupled interactions between the individual barrier components. Erosion and piping phenomena in the compacted bentonite buffer due to buffer-rock interactions results in the removal of bentonite particles via groundwater flow and can negatively impact the integrity and performance of the buffer. Rapid groundwater inflow at the early stages of disposal can lead to piping in the bentonite buffer due to the buildup of pore water pressure. The physiochemical processes between the bentonite buffer and groundwater lead to bentonite swelling and gelation, resulting in bentonite erosion from the buffer surface. Hence, the evaluation of erosion and piping occurrence and its effects on the integrity of the bentonite buffer is crucial in determining the long-term integrity of the deep geological repository. Previous studies on bentonite erosion and piping failed to consider the complex coupled thermo-hydro-mechanical-chemical behavior of bentonite-groundwater interactions and lacked a comprehensive model that can consider the complex phenomena observed from the experimental tests. In this technical note, previous studies on the mechanisms, lab-scale experiments and numerical modeling of bentonite buffer erosion and piping are introduced, and the future expected challenges in the investigation of bentonite buffer erosion and piping are summarized.