G. Matsumoto

The vaporization and thermochemical stability of lithium aluminates

Abstract The vaporization and thermal stability of various lithium aluminates were investigated by high temperature mass spectrometry. The decomposition reactions of them were determined as follows: Li5AlO4(c, 1 = 2.22 Li(g) + 0.02 LiO(g) + 0.88 Li2O(g) + 0.56 O2 + γ-LiAlO2(c), LiAlO2(c, 1) = 0.78 Li(g) + 0.008 LiO(g) + 0.008 Li2O(g) + 0.19 O2 + 0.2 LiAl5O2(c), LiAl5O8(c) = 0.998 Li(g) + 0.002 LiO(g) + 0.250 O2 + 2.500 Al2O3(c). The enthalpy of the reaction for Li5AlO4 was 1413 ± 40 kJ mol , and those for LiAlO2 and LiAl5O4 were 399 ± 12 and 531 ± 50 kJ mol , respectively. The heats of formation of these lithium aluminates are in agreement with those of previous work.

Neutron radiography of thick hydrogenous materials with use of an imaging plate neutron detector

Abstract The value of the neutron mass attenuation coefficient of hydrogen being very high, it is extremely difficult to image normal size, living animals with neutron radiography. However, the authors suggest the possibility of applying neutron radiography for biomedical specimens. The organs in the breast, bones and cartilages in the extremities, and the tail of mice and rats were clearly imaged by neutron radiography with Gd foils as neutron converters and X-ray films. However, no contours of the organs in the mouse abdomen were visible with neutron radiography with an exposure time of 200 s. By adding Gd or Li compounds as neutron converters to imaging X-ray plates, imaging plates have been developed for neutron detectors. A trial using these imaging plates for neutron radiography of water-filled containers and the abdomen of mice was completed. The roundness of a 100 ml-beaker was imaged with a neutron exposure of 180 s. Obscure contours of the liver and kidneys of the mouse were imaged with a neutron exposure of 100 s.

Mass spectrometric studies of lithium-containing oxides at high temperature

Abstract The sublimation and vaporization of various lithium containing oxides have been studied by high temperature mass spectrometry. The installed Knudsen cell apparatus gave some useful information about the vapor species, appearance potentials, partial pressures and heats of reactions involved. The investigated oxides are Li 2 O, Li 2 O-Al 2 O 3 , Li 2 O-MoO 2 and Li 2 O-SiO 2 systems. This paper mainly presents the most recent data for the Li 2 O-SiO 2 system. A relationship for the decomposition reaction of ortho -Li 4 SiO 4 was deduced. The heat of the reaction was determined by the third law method. The activity of the Li 2 O component in the double oxides was estimated from the partial pressures of the vapor species. γ-LiAlO 2 and meta-Li 2 SiO 3 showed fairly low activities in comparison with Li 2 O oxide. The activity coefficients decreased with the Li 2 O mole fraction in the lithium compounds. The heats of formation and atomization of LiO and Li 2 O gaseous species were determined.

Magnetic properties of uranium mononitride with fission fragment damage

Abstract Magnetic disorder in neutron-irradiated (fission fragment damage) uranium mononitride (UN) has been investigated by magnetic susceptibility measurements. The Neel point (TN ) shifted to lower temperatures with increasing fission dose and attained the lowest value at a dose of around 1018 f/cm3. After further irradiations, however, it recovered to the non-irradiated value. The shift of TN was in accordance with the change of the concentration of fission-induced vacancies. Other magnetic parameters showed a similar trend. These fission-fragment damage results are discussed in terms of the electronic state of 5 f electrons.

The vaporization and thermal stability of lithium molybdates

Abstract Two lithium molybdates, δ-Li4MoO5 and Li2MoO4, were evaporated and measured by high temperature mass spectometry. Various lithium and molybdenum oxide ions were observed, and their partial pressures were obtained. From the thermochemical calculation of evaporation, the heats of formation of the molybdates were obtained for the following reactions, Li 2 O(c) + 1 2 MoO 3 (c) = 1 2 δ-Li 4 Mo0 5 (c), ΔH r.298 o = − 120.4 kj.mol −1 , and Li 2 O(c) + MoO 3 (c) = Li 2 MoO 4 (c), ΔH r.298 o = − 154.7 kj.mol −1 . Thermochemically, Li 2 MoO 4 is less stable than δ-Li 4 MoO 5 .

Correction of scattering neutron effects on neutron CT

Abstract Correction of the scattering neutron effects in neutron computed tomography (CT) has been carried out. By subtracting the component of scattering neutrons in CT projection data, only the corrected direct transmitting component through objects is treated. By using the correction of the scattering component on neutron CT, the relatively low contrast on them by neutron electronic imaging method (TV) has been improved. Quantitative analyses with neutron CT have shown a better linear relationship between the neutron macroscopic cross sections and the CT outputs of metal objects.

Fast neutron radiography tests at the YAYOI-reactor, university of Tokyo

Fast neutron radiography (FNR) has been jointly studied by the members of neutron radiography laboratories in Japan by using the CR-39 nuclear track detector at the fast neutron source reactor “YAYOI” of the University of Tokyo. Three beam holes installed at the reactor are utilized, whose collimator ratios, LD, are up to 135, and the fast neutron fluxes are more than 106 ncm−2 s−1. Some well-defined FNR images of various types of objects are obtained with a fast neutron fluence of about 1010 n/cm2. Small holes of 0.5 mm in diameter and 10 mm in depth in an acrylic plate are well imaged through 60 mm thickness of iron plate. Hydrocarbon specimens placed behind thick iron plates (30 mm) are clearly imaged. For the ASTM image quality indicators (IQIs for thermal neutron radiography), very thin A1 spacers with 0.05 mm thickness in the SI indicator have been discernible. The scattering component of fast neutrons from object materials does not seriously degrade the resolution of the FNR image.

Track-Etch Neutron Radiography with a New Boron Carbide Converter

A track-etch method of neutron radiography using a new /sup 10/B/sub 4/C converter was studied. Various characteristics of the track-etch films were measured and compared with a conventional emulsion method. The etch pit production rates, resolution powers, and graininess relating to the etching conditions were precisely investigated. Various fine radiographs were obtained, including simulated fast breeder reactor fuel and irradiated fuel pins. The resolution power and the image quality of the track-etch radiography were comparable to those using a combination of gadolinium foil and fine grain films with shorter exposure times.

Physical and mechanical properties of fission-damaged UN

Abstract The electrical resistivity, the lattice parameter and the Knoop hardness of rod and powder UN were examined for their dependence on fission dose and thermal recovery was measured. The increase of these properties showed a saturation within the dose range between 10 23 and 10 24 f/m 3 , followed by a decrease with further fission dose. The lattice parameter took a negative elongation over 10 24 f/m 3 , whereas the resistivity still had a residual increase by 20% of the maximum change. Negative elongation of lattice parameter was considered as the effect of the accumulation of the vacancy type defects. Recovery steps for the fission-induced maximum resistivity increase were observed at 135, 280, 525 and 700°C, with the activation energies of 0.2, 0.3, 0.9 and 2.1 eV, respectively. The recovery of the lattice parameter, however, showed five steps and that of the Knoop hardness only three steps. This difference was discussed.

Neutron radiography experiments at JRR-4. I

Experiments have been performed at JRR-4 (Japan Research Reactor) to investigate the capability of neutron radiographic techniques in applying to the nondestructive inspection of UO2-PuO2 mixed-oxide fuels. The object of the inspection was to detect “Pu particles” in the mixed-oxide fuels. In place of the actual fuel, two stages of TiO2-EU2O3 mixed-oxide fuel dummy samples (the 1st stage for preliminary experiments and the 2nd stage for simulating the ATR fuel) were fabricated and radiographed with the direct exposure method using a Gd converter screen and high resolution films. Neutron radiographs of the 1st stage dummy samples showed the excellent capability of the detection technique. Those of the 2nd stage dummy samples, however, revealed the detection limit of the technique, which showed that the present technique had not enough capability to satisfy the requirements in the inspection and that improvements of the detection technique especially on the contrast should be accomplished.