• Applied Chemistry for Engineering
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• v.16 no.3
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• pp.354-360
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• 2005

Polyvinyl alcohol (PVA) hydrogels were prepared by the irradiation and heating. Irradiation and heating processes were carried out to improve the heat resistance of PVA hydrogels at high temperature. The physical properties such as gel content, degree of swelling and gel strength for the synthesized hydrogels were examined. The structure variations were investigated using the following techniques: differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Gel content and gel strength of the hydrogels were higher when the two steps of irradiation followed by heat treatment were used rather than only with the irradiation. The hydrogels prepared by the irradiation and the two steps had good heat resistance at high temperature.

• Korean Journal of Food Science and Technology
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• v.38 no.3
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• pp.378-384
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• 2006

Intrinsic viscosity of starch irradiated with Co-60 (0.25-9.1 kGy) significantly decreased, and swelling power and solubility measured at $80^{\circ}C$ linearly increased with increasing irradiated dose. Radiation treatment up to 1 kGy increased amylose content of starch. Water-binding capacity increased rapidly up to 3 kGy. Peak viscosity of irradiated starches by Rapid visco Analyser and Visco/amylo/Graph indicated that the decrease in peak viscosity was dose-dependent. Gamma irradiation showed no effect on endothermic temperatures of irradiated starches, but decreased endothermic enthalpy with increasing dose level. Viscosity of starch autoclaved at $120^{\circ}C$ and air-dried significantly decreased with increasing irradiation dose. Resistant starch content slightly decreased upon irradiation.

• Nuclear Engineering and Technology
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• v.54 no.6
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• pp.2094-2106
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• 2022

The solid-state core of a heat pipe cooled reactor operates at high temperatures over 1000 K with thermal and irradiation-induced expansion during burnup. The expansion changes the gap thickness between the solid components and the material properties, and may even cause the gap closure, which then significantly influences the thermal and mechanical characteristics of the reactor core. This study developed an irradiation behavior model for HPRTRAN, a heat pipe reactor system analysis code, to introduce the irradiation effects such as swelling and creep. The megawatt heat pipe reactor MegaPower was chosen as an application case. The coupled irradiation-thermal-mechanical model was developed to simulate the irradiation effects on the heat transfer and stresses of the whole reactor core. The results show that the irradiation deformation effect is significant, with the irradiation-induced strains up to 2.82% for fuel and 0.30% for monolith at the end of the reactor lifetime. The peak temperatures during the lifetime are 1027:3 K for the fuel and 956:2 K for monolith. The gap closure enhances the heat transfer but caused high stresses exceeding the yield strength in the monolith.

• Advances in materials Research
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• v.3 no.4
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• pp.183-197
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• 2014

Copolymers of gelatin and poly (vinyl alcohol), (PVA) grafted by acrylic acid (AAc) with excellent water absorption and retention abilities under neutral conditions were successfully synthesized using $^{60}Co$ gamma radiations in presence of ammonium persulphate (APS), as water soluble initiator and sodium bicarbonate ($NaHCO_3$) as foaming agent. The optimum synthesis conditions pertaining to maximum swelling percentage were evaluated as a function of gelatin/PVA ratio, amount of water, concentration of APS, $NaHCO_3$, monomer concentration and total irradiation dose. Maximum percent swelling (1694.59%) of the copolymer, gelatin-co-PVA, was obtained at optimum $[APS]=2.92{\times}10^{-1}mol/L$, $[NaHCO_3]=7.94{\times}10^{-2}mol/L$ and 1.5 mL of water at total dose of 31.104 kGy while in case of grafted copolymer, (gelatin-co-PVA)-g-poly(AAc), maximum percent swelling (560.86%) was obtained using $8.014{\times}10^{-1}mol/L$ of AAc in 9 mL water with 31.104 kGy preirradiation dose. The pristine and grafted copolymers were characterized by Fourier Transform Infrared Spectroscopy (FTIR), Scanning electron Microscopy (SEM), Thermal gravimetric analysis (TGA) and X-Ray Diffraction (XRD) methods. The copolymers loaded with an antiseptic, Povidone, were used as wound dressing materials for wounded gastrocnemius muscle of mice and the results exhibit that (gelatin-co-PVA)-g-poly (AAc) copolymer is a potent wound dressing material as compared to the copolymer.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.17 no.1
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• pp.7-20
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• 1987

The author studied the acute reaction of cobalt-60 irradiation to buccal mucosa in rats and difference of the effects of single versus fractionated exposure. 195 Sprague Dowley strain rats, weighing about 120gm, were used in this experiment. 3 rats served as controls and the remaining 192 rats were divided into six groups of 32 rats each. Experimental group Ⅰ, Ⅱ, Ⅲ were received a single dose of 15Gy, 16.5Gy, 18Gy and group Ⅳ, Ⅴ, Ⅵ were received two equal sized fractionated dose of 9Gy, 9.75Gy, 10.5Gy at 4 hour intervals, respectively. The experimental groups were irradiated with cobalt-60 teletherapy unit, Picker model 4M 60 (Field size, 12x5 cm, SSD, 50㎝, Dose rate, 222cGy/min, Depth, 1㎝). The animals were sacrificed at 1, 2, 3, 6, 12 hours, 1, 3, 7 days after irradiation and the changes of the irradiated buccal mucosa were observed by electron and light microscopy. The results were as follows: 1. A single exposure was more damaging than fractionated exposure, and as the radiation dose increased, the changes of cell organelles became faster, but the healing of radiation-induced damage in fractionated exposure was faster than in single exposure. 2. The radiation-induced changes of the basal cells were the most prominent in 18Gy-single exposure group, and the least in 18Gy-fractionated exposure group. 3. Electron-microscopically, there appeared nuclear changes, swelling of mitochondria and rough endoplasmic reticulum, decrease of free ribosome, presence of vesicles, widening of intercellular space, and loss of basal lamina. The early remarkable changes were partly loss of nuclear membrane and swelling of mitochondria. 4. Light-microscopically, derangement and pyknosis of basal cells, hydropic changes of spinous cells, enlargement of granular cells, indistinctness of basement membrane, and proliferation of epithelium were observed.

• Korean Journal of Food Science and Technology
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• v.32 no.2
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• pp.396-401
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• 2000

The effect of gamma-irradiation on quality changes of Samjang, Korean traditional seasoned soy paste, was studied. Samjang was prepared, irradiated at 0, 2.5, 5, 10 kGy, and then stored at $25^{\circ}C$ and $37^{\circ}C$, respectively. Non-irradiated control, sample 2%- ethanol added and sample heated at $80^{\circ}C$ for 30 min were prepared with the same conditions to be compared. The results showed that yeasts were completely eliminated by gamma-irradiation with dose at 2.5 kGy or more, and total bacteria decreased by 5 log cycles with doses at 10 kGy, showing a significant decrease during storage. The gamma irradiation treatment showed repressive effect on the swelling by gas production and browning formation of Samjang during storage. Also, the indicators of enzyme activity, such as amino nitrogen, protease activity and pH change in the gamma irradiation treatment were more stable than control. The sensory evaluations showed that irradiated samples were more acceptable. Therefore, it was considered that gamma irradiation was effective for processing Samjang and for maintaining better quality during subsequent storage.

• Nuclear Engineering and Technology
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• v.45 no.7
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• pp.847-858
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• 2013

Since 2001, a series of five irradiation test campaigns for atomized U-Mo dispersion fuel rods, KOMO-1, -2, -3, -4, and -5, has been conducted at HANARO (Korea) in order to develop high performance low enriched uranium dispersion fuel for research reactors. The KOMO irradiation tests provided valuable information on the irradiation behavior of U-Mo fuel that results from the distinct fuel design and irradiation conditions of the rod fuel for HANARO. Full size U-Mo dispersion fuel rods of 4-5 $g-U/cm^3$ were irradiated at a maximum linear power of approximately 105 kW/m up to 85% of the initial U-235 depletion burnup without breakaway swelling or fuel cladding failure. Electron probe microanalyses of the irradiated samples showed localized distribution of the silicon that was added in the matrix during fuel fabrication and confirmed its beneficial effect on interaction layer growth during irradiation. The modifications of U-Mo fuel particles by the addition of a ternary alloying element (Ti or Zr), additional protective coatings (silicide or nitride), and the use of larger fuel particles resulted in significantly reduced interaction layers between fuel particles and Al.

• Polymer(Korea)
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• v.29 no.1
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• pp.91-95
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• 2005

The PVA hydrogels were prepared by the chemical and irradiation method to improve the heat resistance of these hydrogels at the high temperature. The physical properties such as the gel content, the degree of swelling and the gel strength for the synthesized hydrogels were examined. Gel content increased as the chemical reaction time and the irradiation dose increased, and gel content of the hydrogels were higher when the two-steps of chemical and irradiation method were used rather than only the chemical method. Gel strength increased as the chemical reaction time increased, and as the irradiation dose decreased. The hydrogels prepared by the chemical reaction for 5 hours and the two-steps had the heat resistance at the high temperature.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.11
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• pp.281-285
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• 1996

Pulsatile swelling behaviors and their application to drug delivery system were studied by using interpenetrating polymer networks(IPN) hydrogels constructed with poly(vinyl alcohol) and poly(acrylic acid). The PVA/PAAc IPNs hydrogels were symthesized by UV irradiation tallowed by repetitive freezing and thawing method. These hydrogels showed pH and temperature sensitive swelling behaviors. From the release experiment, the release amount of model drug incorporated into these hydrogels showed pulsatile patterns. Permeability coefficients obtained by various solutes differed in response to changes of permeation conditions.

• Korean Journal of Food Science and Technology
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• v.36 no.4
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• pp.547-552
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• 2004

Attempt was made to establish identification methods for irradiated starch. Commercial starches (corn starch/CS, sweet potato starch/SS, and potato starch/PS) were irradiated at 0-6.0 kGy and used to measure viscosity with Brookfield DV-III programmable rheometer. Starch suspensions were prepared at 8.0 (7.2%, d.b.), 8.5 (7.3%, d.b.), and 9.0% (7.3%, d.b.) for CS, SS, and PS, respectively at 100 rpm in spindle speed. Results showed viscosities of samples significantly decreased (p<0.05) as irradiation dose increased, with $R^2$ 0.9754, 0.9618, and 0.9888 for CS, SS, and PS, respectively. Irradiation dose at 1.5 kGy induced decrease in viscosity as compared to non-irradiated control by 34, 57, and 51% in CS, SS, and PS, respectively, suggesting viscometry could lie applied to identify irradiated starches. Solubility and alkali number of irradiated starches significantly increased with irradiation doses, while swelling power decreased (p<0.05). Results suggested solubility, alkali number, and swelling power for irradiated starches complement identification results of viscometry.