Kweon Ho Kang

Erratum to: Effect of burn-up on the radioactivation behavior of cladding hull materials studied using the ORIGEN-S code

The effect of fuel burn-up on the radioactivation behavior of cladding hull materials was investigated using the ORIGEN-S code for various materials of Zircaloy-4, Zirlo, HANA-4, and HANA-6 and for various fuel burn-ups of 30, 45, 60, and 75 GWD/MTU. The Zircaloy-4 material is the only one that does not contain Nb as an alloy constituent, and it was revealed that 125Sb, 125mTe, and 55Fe are the major sources of radioactivity. On the other hand, 93mNb was identified as the most radioactive nuclide for the other materials although minor radioactive nuclides varied owing to their different initial constituents. The radioactivity of 94Nb was of particular focus owing to its acceptance limit against a Korean intermediate-/low-level waste repository. The radioactivation calculation results revealed that only Zircaloy-4 is acceptable for the Korean repository, while the other materials required at least 4,900 of Nb decontamination factor owing to the high radioactivity of 94Nb regardless of the fuel burn-up. A discussion was also made on the feasibility of Zr recovery methods (chlorination and electrorefining) for selective recovery of Zr so that it can be disposed of in the Korean repository.

Thermal expansion of simulated spent PWR fuel and simulated DUPIC fuel

Thermal expansions of simulated spent PWR fuel and simulated DUPIC fuel were studied using a dilatometer in the temperature range from 298 to 1900 K. The densities of simulated spent PWR fuel and simulated DUPIC fuel used in the measurement were 10.28 g⋅cm−3 (95.4% of TD) and 10.26 g⋅cm−3 (95.1% of TD), respectively. The linear thermal expansions of the simulated fuels are higher than that of UO2, and the difference between these fuels and UO2 increases progressively with temperature. However, the difference between simulated spent PWR fuel and simulated DUPIC fuel is extremely small, less than the experimental error. For the temperature range from 298 to 1900 K, simulated spent PWR fuel and simulated DUPIC fuel have the same average linear thermal expansion coefficient of 1.39×10−5K−1. As the temperature increases to 1900 K, the relative densities of simulated spent PWR fuel and simulated DUPIC fuel decrease to 93.8% of initial densities at 298 K.

Oxidation behavior of U3Si (3.9 wt% Si) in air at 250–400°C

Abstract The oxidation of U 3 Si was studied using a thermogravimetric analyzer and an XRD in the temperature range from 250 to 400°C in air. From XRD studies it was found that U 3 Si converted to UO 2 , U 2 O 5 and Si after 200 h at temperatures up to 275°C and it converted to UO 2 , U 3 O 7 , SiO and SiO 2 after 200 h at the temperature of 300°C. U 3 O 5 began to be formed at the temperature of 325°C. The linear reaction rate was observed at lower temperatures up to 275°C in the experimental range of reaction time. For higher temperatures, however, the reaction rate was nearly linear at initial stage of reaction and more sharply increased after a certain time due to cracking, breaking and pulverizing in the specimen. The reaction was controlled by diffusion rather than chemical reaction kinetics. The averaged rate assuming a linear rate equation could be expressed with activation energies that were 122.29 kJ/mol and 69.65 kJ/mol the temperature ranges of 250≤ T (°C) ≤ 300 and 300 ≤ T (°C) ≤ 400 respectively.

Quaternary Pt2Ru1Fe1M1/C (M=Ni, Mo, or W) catalysts for methanol electro-oxidation reaction

Quaternary Pt2Ru1Fe1Ni1/C (M=Ni, Mo, or W) catalysts were investigated for the methanol electro-oxidation reaction (MOR). Electrocatalytic activities of the quaternary catalysts for CO electro-oxidation were studied via CO stripping experiments, and the Pt2Ru1Fe1Ni1/C and Pt2Ru1Fe1W1/C catalysts exhibited lowered on-set potential compared to that of a commercial PtRu/C catalyst. MOR activities of the quaternary catalysts were determined by linear sweep voltammetry (LSV) experiments, and the Pt2Ru1Fe1Ni1/C catalyst outperformed the commercial PtRu/C catalyst by 170 and 150% for the mass and specific activities, respectively. X-ray photoelectron spectroscopy (XPS) was employed to analyze surface oxidation states of constituent atoms, and it was identified that the structure of the synthesized catalysts are close to a nano-composite of Pt and constituent metal hydroxides and oxides. In addition, the XPS results suggested that the bi-functional mechanism accounts for the improved performance of the Pt2Ru1Fe1Ni1/C and Pt2Ru1 Fe1W1/C catalysts.

The Thermal Conductivity of Simulated DUPIC Fuel

The thermal diffusivity and the thermal expansion of simulated DUPIC fuel were measured using a laser flash apparatus in the temperature range from room temperature to 1473 K and dilatometer in the temperature range from room temperature to 1900 K, respectively. The relative density of simulated DUPIC fuel is lower than that of UO2 fuel. At a low temperature to 600 K, the difference of the relative densities is small and increases as temperature increases. As temperature increases to 1900 K, the relative density of the simulated DUPIC fuel decreases to 93.764 % of the initial density at 298 K. The thermal conductivity of simulated DUPIC fuel is lower than that of UO2 fuel. The difference of thermal conductivity between simulated DUPIC fuel and UO2 fuel is large at room temperature, and it decreases as the temperature increases. The thermal conductivity of simulated DUPIC fuel decreases from 5.77 W/m.K (78.12 % that of UO2) at 373 K to 2.35 W/nr K (87.79 % that of UO2) at 1473 K.

Oxidation behavior of U–10 wt% Mo alloy in air at 473–773 K

Abstract The oxidation behavior of U–10 wt% Mo alloy was studied using an XRD and a thermogravimetric analyzer in the temperature range from 473 to 773 K in air. It was found from the XRD study that U–10 wt% Mo alloy was completely converted to U 3 O 8 at temperatures above 673 K. The oxidation rate of U–10 wt% Mo was lower than that of uranium. The activation energy for oxidation of U–10 wt% Mo was determined to be 66.64 kJ/mol in the temperature range of 473–773 K and it was higher than that of uranium.

Oxidation behavior of U-10 at% Zr alloy in air at 300–500 ‡c

AbstractThe oxidation behavior of U-10 at% Zr alloy was studied using an X-Ray Diffractometer (XRD) and a thermogravimetric analyzer in the temperature range from 300 to 500 ‡C in air. From XRD, Infrared Spectroscopy (IR) and chemical analysis studies it was found that U-Zr alloy after complete oxidation was converted to U3O8 and ZrO2 broken into several pieces of thin plates and some blocks. From the slope value (l/n=0.562-0.872) of the log-log plots of the weight gain against time, the oxidation kinetics was analyzed by a paralinear equation. The activation energy of 20 % conversion of U-Zr alloy to U3O8 and ZrO2 was 57.02 kJ/mol and the oxidation rate per unit time and area was obtained to be :1

A Development of Air Controlled Oxidizer for Treatment of Depleted Uranium Chip Waste

dw/dt = 1.41 \times 10^6 e\left( {\frac{{ - 57.02kJ/mol}}{{RT}}} \right)mg/min - cm^2 ,