Experimental results are presented on the flow behavior, average void fraction and pressure drop in air-water two-phase flow mixture flowing upward through a C-shaped bend curved in vertical plane. The curved test section of transparent acrylic resin tubing was varied in four versions of (a) 90mm, (b) 132.5mm and (c) 180mm radii of curvature with 16 mm inside diameter tube, and (d) 135 radius with 24mm diameter tube. The combined action of gravity and centrifugal force acting on the two-phase flow is expressed in terms of a modified Froude number representing the balance of radial forces between those acting on the liquid and the gaseous phases of the flow passing through the reclined vertical U-bend. The average void fraction in the curved test section was determined, and empirically correlated to the pressure drop, by means of a series of nondimensional numbers.

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Time dependent neutron spectra from lithium assemblies were measured to assess the neutron cross sections of 7Li in ENDF/B-IV, which is important nuclide for the D-T fusion reactor blanket material. Pulsed neutrons produced by D-D or D-T reaction were used to measure leakage neutron spectra from cubical lithium assemblies as a function of time by the use of NE213 liquid scintillator. Calculations of time dependent neutron spectra were carried out by the Monte Carlo code SIMON, which was prepared for this study. The group constants used in these calculations were processed from ENDF/B-1V data. The calculated and the measured neutron spectra were compared for the following three; a stationary spectrum, spectra at each time interval and decay curves for specified energy groups. Discrepancies between the measured and the calculated neutron spectra were found in these comparisons. In order to assure the cause of these discrepancies, some calculations were carried out with recently measured cross sections of inelastic scattering which excite 0.478 and 4.63 MeV level of ⁷Li. It was concluded that some of the neutron cross section data of ⁷Li in ENDF/B-IV should be ameliorated.

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A method for improving the accuracy of finite element solutions to diffusion equations has been developed. The author previously suggested a method for improving the accuracy of finite element solutions to neutron diffusion equations, a kind of Helmholtz equations, within a short computing time. The method has been generalized so that it can be applied to problems described by the Laplace equation, too, such as temperature distributions and electric fields. In this generalized method, 3 'imaginary' nodal points are added at the midsides of each data-given triangular element and the element is subdivided into 4 triangular subelements of the same dimension to improve accuracy. Then, approximate expressions, which express solutions at the 'imaginary' nodal points using those at 'real' nodal points, are derived by Jacobi's iteration method. These approximate expressions are used to reduce the number of unknowns in the final linear equations. The computing time required for the method described here is much shorter than that required for the straight-forward method of increasing the number of elements 4 times under the same accuracy.

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The Hertzian indentation technique is used to study the cracking behavior and to measure the fracture surface energy of UO₂ and ThO₂ of high density containing simulated fission products (Nb, Zr). UO₂+ZrO₂ of 98% density showed permanent "plastic" deformation in addition to Hertzian cone crack formation thus making a quantitative analysis impossible. The Nb₂O₅ containing oxides, in particular ThO₂+Nb₂O₅, had a more suitable microstructure and showed less or no permanent deformation. The fracture surface energy of ThO₂+0.1 mol/o Nb₂O₅ was γ=(2.6±0.4)Jm^-2, and thus comparable to that of ThO₂ without additives, (2.5±0.3)Jm^-2, indicating that the effect of Nb impurities and of excess oxygen introduced together with the Nb⁺⁵ cancel each other.

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Irradiation experiments using ⁶⁰Co γ-rays were undertaken on CCl₃F to examine the radiation damage of fluorocarbon, used as solvent in the recovery of ⁸⁵Kr from the off-gas of fuel reprocessing plants operating on the solvent absorption. The conditions of irradiation were varied in the range of 2.3×10⁴1.1×10⁶ rad/h in terms of dose rate and -3016°C in temperature, to assemble information on the kinds of degradation products generated, the relationship between decomposition rate and absorbed dose, and the effects on the decomposition exerted by certain factors (dose rate, temperature, impurities, wall materials). The results obtained included the following findings : (1) The degradation products of CCl₃F comprised halogen ions and thirteen kinds of fluorocarbons. (2) The rate of decomposition of CCl₃F and the yield of the individual degradation products were roughly proportional to the absorbed dose ; the energy decomposition of CCl₃F at -30°C was 0.013 mol/o /Mrad (G=1.4) under a dose rate of 1.1×10⁶ rad/h. (3) The decomposition rate of CCl₃F was inhibited by increasing dose rate, and promoted by rising irradiation temperature. (4) The yields of halogen ions and C₂Cl₄F₂, and the decomposition rate of CCl₃F increased with the addition of air. (5) No appreciable influence on the decomposition of CCl₃F was observed to be exercised by the presence of such materials as stainless steel, Cu and Al.

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Extraction of lithium from sea water was investigated. It was found that a corrosion product of metallic aluminum immersed in sea water extracts lithium from it selectively. Effects of the temperature and the pH of sea water, and of the initial concentration of lithium in it were examined. On the basis of the analysis of the surface deposit on aluminum, which is a corrosion product of aluminum, the selectivity coefficients were calculated. For the extraction of lithium from natural sea water, the values ofK^Li_Na, K^Li_Mg, K^Li_Ca and K^Li_K were 9.9×10², 1.1×10, 4.5×10 and 4.4×10², respectively.

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Magnetic susceptibility of UCl₃ was measured from room temperature to 1.7 K. Below Neel temperature 22 K, susceptibility decreases down to 1.7 K, showing no long-range ordering. The data were analyzed by the model of one-dimensional magnetic chain of anisotropic exchange interaction with acceptable agreement.

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A helium jet system supplied with aerosols controlled in particle-size and particle-number density by an aerosol generator has been designed and constructed. The overall efficiency of transporting and collecting products formed in the 252Cf spontaneous fission and the α-particle induced 232Th fission was measured for several operating conditions of aerosol generator. The efficiency has almost attained to a value of 100% for fission products other than iodine and rare gases, and was always stable over for 2 weeks of running time and was reproducible over a period of about 6 months.

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