Surface related laser induced white emission of Cr:YAG ceramic

In this work we report the white light emission in transparent Cr:YAG ceramic pellet upon irradiation with focused beam of CW infrared laser diode. It was found that this phenomenon is specifically related to interaction of laser beam with a surface of the pellet. The white light was emitted outside an irradiated spot at the surface of the pellet and did not penetrate inside the pellet. Moreover, the red emission related to two-photon absorption along the laser beam penetrating the Cr3+:YAG pellet was observed. Interaction of the laser beam with the surface of the pellet leads to an efficient white light emission from an outer side of the pellet. The resulting white light emission did not entry back the pellet. Multiphoton ionization leading to intervalence charge transfer followed by light emission was proposed as the mechanism of experimentally observed white light emission.

Microstructure of Aged 238Pu-doped La-monazite Ceramic and Peculiarities of its X-ray Emission Spectra

New data on microstructure of 16 years old (La, Pu)PO4 monazite ceramics doped with 8.1 wt% of 238Pu are presented. It is shown that the sample consists from at least two phases differing in La/Pu ratio and small precipitates of Pu-phosphate. Possible mechanisms of the compositional heterogeneity are discussed. Formation of Pu-containing rhabdophane after sample storage in air is observed. This phenomenon together with gradual mechanical destruction of the ceramic pellet formation of submicron particles will likely increase rate of radionuclides loss from the monazite-based waste form. X-ray emission lines produced by recoil uranium ions from Pu decay are analysed. It is suggested that careful examination of their relative intensities may provide important information about behaviour of "hot" recoils in nuclear waste forms.

Heterojunction Properties of p-CuO/n-CdS Diode

In this paper, p-CuO/n-CdS heterojunction was prepared by thermal evaporating CdS thin films on CuO 1 mm thick ceramic pellet substrate. The electrical properties of p-CuO/n-CdS heterojunction were investigated by forward current–voltage–temperature (I–V–T) characteristics in the temperature range of 100-300 K. The junction barrier height, ideality factor, and the series resistance values of the diode evaluated by using thermionic emission (TE) theory and Cheung’s method are 0.566 eV, 5.535 and 618.24 Ω at 300 K, respectively. The junction barrier height, ideality factor and series resistance were found to be strong temperature dependence. In part of C-V measurements at room temperature, the obtained built-in potential value being 0.538 V is well consistent with the junction barrier height value evaluated from I-V measurements

Preparation of Porous Zirconia-Yttria Ceramics by Thermal Removal of Potassium Iodide

Zirconia-8 mol% yttria porous solid electrolytes were obtained by mixing with different amounts (0 to 5 wt.%) of KI prior to sintering. Potassium iodide acts as sacrificial pore former, being removed from the ceramic pellet upon sintering at 1400 °C/2 h. The alkali halide content was evaluated by X-ray fluorescence analysis, the density of the pellets by the Archimedes method, and the pore content by observation in scanning probe (SPM) and scanning electron (SEM) microscopes of polished and etched surfaces. The oxide ion resistivity was determined by impedance spectroscopy analysis in the 5 Hz-13 MHz frequency range from 300 to 500 °C. Porous specimens with high skeletal density were obtained. The higher is the alkali halide content, the higher is the pore volume and the total electrical resistivity. A correlation is found between the pore content, evaluated by SEM and SPM, and the electrical behavior analysis from the impedance plots of the porous specimens.

Multiphysics Model Development and the Core Analysis for In Situ Breeding and Burning Reactor

The in situ breeding and burning reactor (ISBBR), which makes use of the outstanding breeding capability of metallic pellet and the excellent irradiation-resistant performance of SiCf/SiC ceramic composites cladding, can approach the design purpose of ultralong cycle and ultrahigh burnup and maintain stable radial power distribution during the cycle life without refueling and shuffling. Since the characteristics of the fuel pellet and cladding are different from the traditional fuel rod of ceramic pellet and metallic cladding, the multiphysics behaviors in ISBBR are also quite different. A computer code, named TANG, to model the specific multiphysics behaviors in ISBBR has been developed. The primary calculation results provided by TANG demonstrate that ISBBR has an excellent comprehensive performance of GEN-IV and a great development potential.

Synthesis of Actinide-Doped Ceramics: from Laboratory Experiments to Industrial Scale Technology

ABSTRACTThe experience of the Laboratory of Applied Mineralogy and Radiogeochemistry of the V.G.Khlopin Radium Institute on synthesis of Pu-Am-doped ceramics is summarized. During the last 5 years, dozens of actinide doped polycrystalline samples and single crystals have been successfully synthesized such as zircon, hafnon, cubic zirconia, monazite, Ti-pyrochlore, perovskite and garnet. Actinide loading has been varied as follows:-239Pu - from 5–6 wt.% in zircon (polycrystalline and single crystals), hafnon, garnet and perovskite to 10 wt.% in Ti-pyrochlore and up to 37 wt.% in zirconia;- 238Pu - from 2.5 wt.% in zircon single crystals to 5 wt. % in polycrystalline zircon and 10 wt.% in monazite and cubic zirconia;- 243Am - 20–23 wt.% in cubic zirconia and monazite.The weight of each single ceramic pellet varied from 0.2 to 2.0 grams. Special furnaces developed in KRI for ceramic synthesis allowed obtaining up to 7 ceramic pellets simultaneously during the same experiment. The highest amounts of actinides used under glove-box conditions in the same experiment were: 1.5–2.0 g for 239Pu, 0.6 g for 238Pu and 0.3 g for 243Am. Most experiments on synthesis of ceramics and single crystals doped with 239Pu, 238Pu and 243Am carried out at the KRI did not lead to contamination of internal walls of glove boxes. No release of Pu-Am-aerosols was observed as a result of sintering or melting at 1300–1600°C. These results allowed us to conclude that at the present the KRI has developed the experimental basis for transferring laboratory innovations to the industry of actinide immobilization. It is important that adopting ceramic synthesis methods at industrial scale does not require development of new special equipment.