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[en] Hexagonal NaY_1-xYb_xF₄:Ln³⁺ (x=0.05-1.00, Ln³⁺=Er³⁺ or Tm³⁺) have been prepared through hydrothermal synthesis. Powder X-ray diffraction (XRD) patterns have been presented to characterize the synthesized samples. The concentration of doped rare earth and pumping power on the upconversion emissions have been extensively investigated under 980 nm excitation. NaY_1-xYb_xF₄:Er³⁺ emit green (²H_11/2, ⁴S_3/2→⁴I_15/2), red (⁴F_9/2→⁴I_15/2), weak violet (²H_9/2→⁴I_15/2) and weak UV (⁴G_11/2→⁴I_15/2) upconversion emission. NaY_1-xYb_xF₄:Tm³⁺ exhibit intense blue (¹G₄→³H₆, ¹D₂→³F₄), weak red (¹G₄→³F₄) and UV (¹D₂→³H₆) upconversion emission. A two-photon process account for the green and red emission of an Er³⁺ ion with the energy transfer from Yb³⁺ ion. One blue emission (¹G₄→³H₆) of Tm³⁺ results from a three-photon excitation, and the other (¹D₂→³F₄) from a four-photon process. The measured data about emission intensity suggest that hexagonal NaYF₄:Yb³⁺/Er³⁺ is a more efficient upconverting phosphor than cubic one. Comparison of the measured properties in our work with values from the reported literature suggests that hydrothermally synthesized NaYF₄:Yb³⁺/Er³⁺ (or Tm³⁺) samples emit more pure green or blue emission than solid-state synthesized samples with certain concentration of doping rare earth ions

[en] Highlights: • The presence of oxygen inhibited Cr(VI) removal efficiency with nZVI by near 3 times. • Cr(VI) removal with nZVI was related to adsorption, reduction, co-precipitation, and adsorption reactions. • Molecular oxygen activation competed donor electrons from Fe"0 core and surface bound Fe(II) of nZVI. • Thicker Cr(III)/Fe(III)/Cr(VI) oxyhydroxides shell of nZVI leaded to the electron transfer inhibition. - Abstract: In this study, we demonstrate that the presence of oxygen molecule can inhibit Cr(VI) removal with core–shell Fe@Fe_2O_3 nanowires at neutral pH of 6.1. 100% of Cr(VI) removal was achieved by the Fe@Fe_2O_3 nanowires within 60 min in the anoxic condition, in contrast, only 81.2% of Cr(VI) was sequestrated in the oxic condition. Removal kinetics analysis indicated that the presence of oxygen could inhibit the Cr(VI) removal efficiency by near 3 times. XRD, SEM, and XPS analysis revealed that either the anoxic or oxic Cr(VI) removal was involved with adsorption, reduction, co-precipitation, and re-adsorption processes. More Cr(VI) was bound in a reduced state of Cr(III) in the anoxic process, while a thicker Cr(III)/Fe(III)/Cr(VI) oxyhydroxides shell, leading to inhibiting the electron transfer, was found under the oxic process. The negative impact of oxygen molecule was attributed to the oxygen molecular activation which competed with Cr(VI) adsorbed for the consumption of donor electrons from Fe"0 core and ferrous ions bound on the iron oxides surface under the oxic condition. This study sheds light on the understanding of the fate and transport of Cr(VI) in oxic and anoxic environment, as well provides helpful guide for optimizing Cr(VI) removal conditions in real applications

[en] There is no specific definition for very low level waste up to now, but it has special characteristics-huge amount and little radioactive waste containing. Different countries have different methods for treating, disposal and management for this kind of waste. This paper puts emphasis on the French practice. The Practice, which has been taken in France, will benefit our country on this subject. (authors)

[en] An operational event of HBRSEP complicated reactor trip and loss of reactor coolant pump seal cooling due to fire by cable fault is described and analyzed. The process and the error of operator are introduced. The direct and root causes are analyzed and summarized from equipment, management and personnel training, etc. Specific suggestions for the operation and management of nuclear power plants in China are put forward. (author)

[en] Aiming at selective adsorption and separation of Y(Ⅲ) from the Y(Ⅲ)-Sr(Ⅱ) group in acid solution, a silica-based TODGA impregnated adsorbent [(TODGAþ1-dodecanol)/SiO₂-P-F600] has been prepared. Batch adsorption experiments were conducted under the effect of contact time, acid concentration, solution temperature, and adsorption capacity etc. Chromatography recovery of more than 90% Y(Ⅲ) was successfully achieved under elution with 0.01 M DTPA solution in nitric acid adsorption system, and 0.1 M HCl solution in hydrochloride adsorption system, respectively

[en] By solving the optical Bloch equations with the rate-equation approximation, we calculate the time dependence of the magnetic sublevel populations of Doppler-broadened atoms. With an increase of the left-circularly polarized pump intensity, the population fraction of a certain sublevel of the excited state almost reaches 0.3, resulting in anisotropy in the excited state, which is important to the optical filter based on circular birefringence and dichroism. Furthermore, numerical results show that the real saturation pump intensity for the moving atoms is much larger than that for the resting atoms.

[en] The paper suggests to establish the national information database of radiation sources in China, based on the analysis of the present situation and problems in radiation sources and application of nuclear technology in China. The paper also discusses the contents and information that the information database should include. (authors)

[en] LiNi_0_._8Co_0_._1_5Al_0_._0_5O_2 (NCA) microspheres covered by a nanoscale Li_2TiO_3-based shell were synthesized by a facile strategy based on a solvothermal pre-coating treatment combined with a post-sintering lithiation process. The morphology, structure and composition of the Li_2TiO_3-coated NCA samples were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning scanning electron microscope (SEM) with an energy-dispersive X-ray spectroscope (EDS), and transmission electron microscopy (TEM). Owing to the complete, uniform and nanoscale Li_2TiO_3 coating shell, the resultant surface-modified NCA microspheres used as Li-ion battery cathode materials manifest remarkably enhanced cycling performances, attaining 94% and 84% capacity retention after 200 and 400 cycles at 0.5 C, respectively, which is much better than the pristine NCA counterpart (60% retention, 200 cycles). More impressively, the surface-modified NCA also shows an intriguing storage stability. After being stored at 30 °C for 50 days, the coated NCA-based cells are subjected to be cycled both at room and elevated temperatures, in which the aged cells can still remain 84% capacity retention after 200 cycles at 25 °C and 77% capacity retention after 200 cycles at 55 °C, respectively. All these results demonstrate that the Li_2TiO_3-coated LiNi_0_._8Co_0_._1_5Al_0_._0_5O_2 microsphere is a promising cathode material for Li-ion batteries with long lifespan. - Graphical abstract: Nanoscale Li_2TiO_3-based shell encapsulated LiNi_0_._8Co_0_._1_5Al_0_._0_5O_2 (NCA) microspheres are fabricated through a solvothermal pre-coating treatment combined with post-lithiation process. The surface-coated NCA as cathode materials shows a remarkably enhanced cycling performance and storage stability for long lifespan Li-ion batteries. - Highlights: • Li_2TiO_3 is used as coating materials for layer structured LiNi_0_._8Co_0_._1_5Al_0_._0_5O_2 cathode. • Solvothermal coating strategy is employed to strengthen surface coating. • Coating layer improves the velocity of Li"+ migration on electrode surface. • Erosion from the HF and CO_2 on electrode is greatly suppressed.

[en] Safety assessment principles, assessment points and review practice of fuel fabrication facility for PWR are introduced. Safety assessment principles include basic principles, engineering principles and management principles. Assessment points include: UF_6 leakage, nuclear criticality, fire and explosion. Any accident happened mentioned above will lead to radioactive material release in different levels or make emission damage. As for Yi Bin fuel fabrication plant (YFP), it should be included in main assessment that aerosol concentration in some UO_2 powder process posts are higher than the design value except above mentioned assessment points because there are some shortcomings in ventilation system. (authors)