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Byungkuk Lee,Seungchul Yang,Dongyong Kwak,Hyunkwang Jo,Youngwoo Lee,Youngmoon Bae,Jayhyung Lee Korean Nuclear Society 2023 Nuclear Engineering and Technology Vol.55 No.6
The existing wet reconversion processes for the recovery of scraps generated in manufacturing of nuclear fuel are complex and require several unit operation steps. In this study, it is attempted to simplify the recovery process of high-quality fuel-grade UO<sub>2</sub> powder. A novel wet reconversion process for uranyl nitrate hexahydrate solution is suggested by using a newly developed pulsed fluidized bed reactor, and the resultant chemical characteristics are evaluated for the intermediate ammonium uranate hydrate product and subsequently converted UO<sub>2</sub> powder, as well as the compliance with nuclear fuel specifications and advantages over existing wet processes. The UO<sub>2</sub> powder obtained by the suggested process improved fuel pellet properties compared to those derived from the existing wet conversion processes. Powder performance tests revealed that the produced UO<sub>2</sub> powder satisfies all specifications required for fuel pellets, including the sintered density, increase in re-sintered density, and grain size. Therefore, the processes described herein can aid realizing a simplified manufacturing process for nuclear-grade UO<sub>2</sub> powders that can be used for nuclear power generation.
Hwang, Junghwan,Park, Minjeong,Jang, Sukhun,Choi, Hyunkwang,Jang, Jintak,Yoo, Youngjo,Jo, Hyungho,Jeon, Minhyon American Scientific Publishers 2017 Journal of Nanoscience and Nanotechnology Vol.17 No.5
<P>Recently, both heat dissipation and the electromagnetic wave generated from the devices have emerged as critical issues as semiconductor devices are getting miniaturized and integrated densely. Thermal and electrical conductive adhesives using graphene-Cu particle composite materials were fabricated. Graphene oxide (GO) was synthesized by using improved Hummer's method and it was reduced by hydrazine. The surfaces of Cu particles were functionalized by 2,2'-Bithiophene to form the self-assembled monolayers (SAMs). The SAMs not only provide a convenient means for preparing covalent bond with functional groups of reduced-GO (rGO), but also it can prevent oxidation. The experimental results were analyzed by using Raman Spectroscopy, Fourier Transform Infrared Spectroscopy, Digital-multimeter, C-Therm TCi Thermal conductivity Analyzer, X-ray Photoelectron Spectroscopy. Our experimental results demonstrate that the functionalized Cu (F-Cu) attached with rGO composites could be a possible substitute for commercialized fillers at present (e.g., Ag-coated copper fillers) because our new F-Cu+rGO composite filler in conducting adhesives is cheaper and lighter than those of Ag-coated Cu fillers.</P>