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Abstract: The uncertainty of the thermal expansion of simulated fuel was evaluated based on the Monte Carlo method. The uncertainties of the thermal expansion were divided into three components: initial sample length, system calibration factor, and an iterative measurement. For each component, a normal probability distribution function was assumed and the extended uncertainty was evaluated for various samples and batches. The results were compared with an international standard guide. Furthermore, the Shapiro–Wilk test was performed to establish a normality of the estimated sample means. [Copyright &y& Elsevier]

Abstract: Thermal expansions of simulated fuel (SS1) are measured by using a dilatometer (DIL402C) from room temperature to 1900K. The main procedure of an uncertainty evaluation was followed by the strategy of the UO2 fuel. There exist uncertainties in the measurement, which should be quantified based on statistics. Referring to the ISO (International Organization for Standardization) guide, the uncertainties of the thermal expansion are quantified in three parts—the initial length, the length variation, and the system calibration factor. Each part is divided into two types. The A type uncertainty is derived from the statistical iterative measurement of an uncertainty and the B type uncertainty comes from a non-statistical uncertainty including a calibration and test reports. For the uncertainty evaluation, the digital calipers had been calibrated by the KOLAS (Korea Laboratory Accreditation Scheme) to obtain not only the calibration values but also the type B uncertainty. The whole system, the dilatometer (DIL402C), is composed of many complex sub-systems and in fact it is difficult to consider all the uncertainties of sub-systems. Thus, a calibration of the system was performed with a standard material (Al2O3), which is provided by NETZSCH. From the above standard uncertainties, the combined standard uncertainties were calculated by using the law of a propagation of an uncertainty. Finally, the expanded uncertainty was calculated by using the effective degree of freedom and the t-distribution for a given confidence level. The uncertainty of the thermal expansion for a simulated fuel was also compared with those of UO2 fuel. [Copyright &y& Elsevier]

A thick deposit of yttria stabilized zirconia (YSZ) was fabricated by inductively coupled plasma spraying and its microstructure was investigated. During solidification the solute rejection occurred in the layers, but the interface condition of (dTq/dz)z=0>m(dC/dz)z=0 led to the formation columnar grains. In the middle part different to the other parts, large columnar grains, approximately 100 μm thick and 300 μm long, were developed through the layers with a strong adhesion. The heat of the droplets, the latent heat of the solidification, and a low thermal conductivity delay the heat transfer, and favor the growth of long columnar grains. The long columnar grain growth through the layers is supposed to be possible, when the previously solidified surface of the deposit acts as a seed. [Copyright &y& Elsevier]

Abstract: This work studied a process to recover uranium from contaminated (U,Gd)O2 scraps generated from nuclear fuel fabrication processes by using the dissolution of (U,Gd)O2 scraps in a carbonate with H2O2 and the precipitation of the dissolved uranium as UO4. The dissolution characteristics of uranium, Gd, and impurity metal oxides were tested, and the behaviors of UO4 precipitation and Gd solubility were evaluated with changes of the pH of the solution. A little Gd was entrained in the UO4 precipitate to contaminate the uranium precipitate. Below a pH of 3, the uranium dissolved in the form of uranyl peroxo-carbonato complex ions in the carbonate solution was precipitated as UO4 with a high precipitation yield, and the Gd had a very high solubility. Using these characteristics, the Gd-contaminated UO4 could be purified using dissolution in a 1-M HNO3 solution with heating and re-precipitation upon addition of H2O2 to the solution. Finally, an environmentally friendly and economical process to recover pure uranium from contaminated (U,Gd)O2 scraps was suggested. [Copyright &y& Elsevier]

Abstract: Hot corrosion studies were performed on superalloy specimens. The IN713LC superalloy were sprayed with an aluminized NiCrAlY-bond coat and then with an yttria–zirconia top coat. The bare superalloy reveals an obvious weight loss due to spalling of the scales by the rapid scale growth and thermal stress. The top coatings showed a much better hot corrosion resistance in the presence of LiCl–3 wt.% Li2O molten salt when compared with those of the bare superalloy and the aluminized bond coatings. These coatings have been found to be beneficial for increasing hot corrosion resistance of structural materials for lithium molten salts. [Copyright &y& Elsevier]

This work studied the dissolution of uranium dioxide and precipitation characteristics of uranyl ions in alkaline and acidic solutions depending on the presence of carbonate ions and H2O2 in the solutions at different pHs controlled by adding HNO3 or NaOH in the solution. The chemical structures of the precipitates generated in different conditions were evaluated and compared by using XRD, SEM, TG-DT, and IR analyses together. The sizes and forms of the precipitates in the solutions were evaluated, as well. The uranyl ions were precipitated in the various forms, depending on the solution pH and the presences of hydrogen peroxide and carbonate ions in the solution. In a 0.5 M Na2CO3 solution with H2O2, where the uranyl ions formed mixed uranyl peroxy-carbonato complexes, the uranyl ions were precipitated as a uranium peroxide of UO4(H20)4 at pH 3-4, and precipitated as a clarkeite of Na2U2Ox(OH)y(H2O)z above pH 13. In the same carbonate solution without H2O2, where the uranyl ions formed uranyl tris-carbonato complex, the uranyl ions were observed to be precipitated as a different form of clarkeite above pH 13. The precipitate of uranyl ions in a nitrate solution without carbonate ions and H2O2 at a high pH were studied together to compare the precipitate forms in the carbonate solutions.