A new method for decontamination of radioactive waste using low-pressure arc discharge

In this paper, the decontamination features of the low-pressure arc-discharge method for radioactive waste generated in the operation and maintenance of nuclear power plants were examined. The low-pressure arc-discharge method was applied to type 304 stainless-steel, type 316L stainless-steel, alloy 600 and carbon-steel covered with radioactive corrosion products. Approximately, 80% of the radioactivity build up on stainless-steels could be removed by the low-pressure arc discharge.     

In situ observation of the change in domain structure due to phase transformation in a perovskite La2MnGaO6

The microstructure of a perovskite, La₂MnGaO₆, was studied by Transmission Electron Microscopy (TEM). An idiomorphic grain exhibited a domain structure at ambient temperature, and each domain possessed a common b-axis and axial relation, [1 0 0]//[0 0 1]. When the grain was heated by a convergent electron beam, the domains vanished after the orthorhombic to rhombohedral phase transformation taking place at 423 K. The domains reappeared when cooled, although domain boundaries moved and the domains rotated by 90° with respect to the b-axis.     

Phase Behavior of Rare Earth Manganites

Among complex oxides containing rare earth and manganese BaLn2Mn2O7(Ln=rare earth) with the layered perovskite type and Ln2(Mn,M)O7 with pyrochlore-related structure were studied since these compounds show many kinds of phases and unique phase transitions. In BaLn2Mn2O7 there appear many phases, depending on the synthetic conditions for each rare earth. The tetragonal phase of so-called Ruddlesden-Popper type is the fundamental structure and many kinds of deformed modification of this structure are obtained. For BaEuzMn207 at least five phases have been identified from the re-sults of X-ray diffraction analysis with the space group P42/mnm, Fmmm, Immm and A2/m in addition to the fundamental tetragonal 14/mmm phase. In the pyrochlore-related type compounds, LnzMn2-xMxO7(M=Ta,Nb,W etc),there also appear several phases with different crystal structures. With regard to every rare earth, Ln2MnTaO7 phase is stable only for excess Ta and can be obtained under high oxygen partial pressure process. This group has trigonal structure with zirkelite type (P3121 space group). On the other hand Ln2Mn2/3Nb4/307 phase has monoclinic (C2/c space group)and zireonolite type structure. All of these structural models have the fundamental structure based on HTB (hexagonal tungsten bronze) layers formed by the arrangement of oxygen octahedra.     

Role of ferrite and austenite phases on the deformation behavior and mechanical properties in heterogeneous nanostructured duplex stainless steel aged at different temperatures

Journal of Materials Science - The effects of aging on the mechanical properties of a heavily cold-rolled ferrite–austenite duplex stainless steel were systematically investigated. The...     

Antioxidant effects of d-tocopherols at different concentrations in oils during microwave heating

The effects of d-tocopherols at different concentrations (50 to 1000 ppm) on the oxidative stability of ethyl linoleate and tocopherol-stripped oils were investigated under microwave heating conditions. Purified substrate oils were prepared by aluminum oxide column chromatography. After the addition of tocopherols (α-, β-, γ- or δ-) to the oils, peroxide, carbonyl andp-anisidine values were measured in the samples after heating in a microwave oven. Further, the residual amount of tocopherol homologues in the oils after heating was determined by high-performance liquid chromatography for evaluation of their effects at different concentrations on oxidative deterioration. Microwave heating resulted in some acceleration in the oxidation of the purified substrate oils. Optimum concentrations of tocopherols required to increase oxidative stability were 100 ppm for α-, 150–200 ppm for β- or γ- and 500 ppm for δ-tocopherol, respectively. The antioxidant effect of tocopherols decreased in the order α>β ≒ γ>δ at each level, in all substrates. Therefore, α-tocopherol was consumed first, followed by β- or γ-tocopherol, and δ-tocopherol was consumed more slowly. The tocopherols had no further significant antioxidant activity (P>0.05) at concentrations higher than 500 ppm.     

Radiation-induced copolymerization of maleimides and acenaphthylene in the solid state

The γ-ray-induced polymerizations in the binary systems of maleimide-acenaphthylene and N-methylmaleimide-acenaphthylene have been studied. The phase diagrams of the two systems show that an eutectic was formed in each system. It has been proven by the solvent extraction and the turbidimetric titration of obtained polymer that copolymer was formed in the eutectic of each system together with homopolymers. The fraction of total homopolymers in the maleimide-acenaphthylene system was nearly the smallest in the monomer mixture of the eutectic composition. The composition of the copolymer, which was isolated by the extractions, was almost independent of the monomer composition. In order to elucidate these results, it was postulated that the copolymerization occurred at grain boundaries between the two components in the eutectic.     

Synthesis of solid superacid of silica treated with sulfuryl chloride

A solid superacid catalyst was synthesized from silica gel, which was obtained from the decomposition of Si(OC₂H₅)₄ with HNO₃ solution, by exposing to SO₂Cl₂ followed by calcination in air at 673 K. The catalytic activity for ethanol decomposition was higher than that of SiO₂-Al₂O₃.     

Anomalous Sign Change in Hall Coefficient of κ-(BEDT-TTF)2Cu[N(CN)2]Br Under Pressure

We studied the normal state properties of an organic superconductor, κ- (BEDT-TTF)₂Cu[N(CN)₂]Br, through the measurement of the Hall effect as functions of temperature and pressure. At low pressure, the Hall coefficient shows the peak structure. From the coincidence of the temperature and its pressure evolution with those of anomalies observed in other physical properties, the peak temperature is considered to be T*. At high pressure, we observed the drastic decrease and sign change of the Hall coefficient. From the incompatibility with the behavior of a similar compound, κ- (BEDT-TTF)₂Cu(NCS)₂, we concluded that this behavior originate from the singularity of the Fermi surface of this salt.     

EPR Study of the Electronic States of β’-(BEDT-TTF)(TCNQ)

β’-(BEDT-TTF)(TCNQ) is a compound of BEDT-TTF (=ET) and TCNQ molecules aligned orthogonally with each other, forming two-dimensional sheets and one-dimensional columns of 1/4-filled π band, respectively. It is known that the metal-insulator transition occurs at 330 K at ambient pressure. We have measured the electronic spin susceptibility by means of the EPR-NMR method at 50 MHz, and the angular dependence of g-factor and line width of EPR both at Q (34 GHz) and W (94 GHz) band. We successfully confirmed that the antiferromagnetic transition occurs in ET sheets and TCNQ columns, independently.