Nuclear Analysis最新文献

In this research work, the monodisperse CeO₂ microspheres were prepared by using the sol-gel processes via a single emulsion. The needle-tube capillary microfluidic device was integrated to generate water-in-oil (W/O) single emulsion droplets with a Ce-based sol as the inner phase. By polymerizing acrylamide monomers inside of the sol, the Ce-based precursor formed the spherical structure during the healing process. The size of the droplets was investigated by studying the effect of the viscosity, interfacial energy, and flow rate of both phases. The CeO₂ ceramic microspheres were fabricated following drying and sintering processes. Comprehensive characterizations of the sol-gel process and as-synthesized ceramic microspheres have been conducted. This paper describes detailed information about the sol-gel process and single emulsion to generate the ceramic microspheres.

Fe13.5Cr4.7Al alloy was irradiated in-situ with 400 keV Fe⁺ in TEM at RT and 748 K. The evolution of dislocation loops under the influence of temperatures, irradiation dose, dislocation lines and precipitates were characterized in detail. The loop rafting was found at RT irradiation for the first time and the growth direction of the rafted loops was along g = 110 direction. However, this phenomenon was not observed at 748 K and only the dislocation complex was appeared. The formation conditions of loop rafting were low temperature and a certain value of irradiation dose. The average size and number density of dislocation loops as a function of irradiation dose in the regions with dislocation lines, precipitates and no dislocation lines/precipitates were constructed and analyzed comparatively. At the same irradiation dose, sample irradiated at higher temperature has larger average loop size and lower loop number density. There was a complex interaction between dislocation line-loop at 748 K, but few interactions were observed at RT. At any irradiation dose, the loop number density in the region with dislocation lines was smaller than that in the region without dislocation lines, but the average loop size was slightly opposite. Moreover, the higher the irradiation temperature, the more obvious the effects of precipitates and dislocation lines on loop evolution were. Our current results provide a fundamental insight into how the dislocations, precipitates and dose affect loop evolution and characteristics in FeCrAl alloy at elevated temperatures.

Anthropogenic radionuclides of plutonium and ¹³⁷Cs in the environment were usually applied for tracing the environmental impact of nuclear activities as well as establishing the chronology of recent lake sediment. In this study, the vertical distribution and spatial differentiation of plutonium and ¹³⁷Cs in lake sediments of China were systematically contrastive analyzed to elucidate the regional influence by the local fallout from Chinese nuclear tests. The results demonstrated that the inventory of ¹³⁷Cs and ^239,240Pu, and their isotopic composition in lake sediments in northwestern China were obviously different from other regions, indicating that a portion of radionuclides in lakes in northwest China were originated from the Chinese Lop Nor Nuclear Test site (CNTs), and radionuclides in lakes of other regions may be completely originated from global fallout. Usually, the anthropogenic radionuclides recorded in lake sediments showed a single peak corresponding to the maximum deposition of 1964. However, two or three accumulation peaks of radionuclides were also observed in a few lakes. For the application of radionuclides on the dating of recent sediment, the accumulative peak of ^239,240Pu and ¹³⁷Cs signed to the period of 1963–1964 is the only practicable time marker for lake sediments in other regions of China. Isotopic information, such as ²⁴⁰Pu/²³⁹Pu ratio and ^239,240Pu/¹³⁷Cs activity ratio, may be useful for accurate sediment chronology, as well as used as a fingerprint to identify the source of the associated radioactive substance in the environment.