The neutron thermalization and diffusion parameters in graphite were determined by pulsed technique for the neutron flux and the neutron density spectra, respectively. Measurements were performed on assemblies of geometrical bucklings between 2.26×10^-3/cm² and 15.58×10^-3/cm², in which, by suitable arrangement of the neutron source and detector, the higher modes of spatial harmonics were diminished.
The results indicated that it was necessary to wait 1.5∼2msec after the injection of 14 MeV neutrons, in order to let the neutron spectrum attain its asymptotic form, independent of assembly size. The thermalization and diffusion parameters for both neutron flux and neutron density spectra were in good agreement with theoretical values.

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The results of a series of experiments aimed at the realization of nonequilibrium ionization in generators using magnetically induced ionization are described. The experiments were performed with two Faraday-type MHD generators, using potassium-seeded argon plasma in the temperature range of 1, 600° to 2, 000°K at about 1 atm.
In the first experiment, the mechanical and the thermal performances of the generator channel and also its electrical characteristics were observed in quasi-equilibrium state, the results of which indicated satisfactory operation.
In the second experiment, the electrical characteristics of the generator with an improved configuration were measured. The experimental results were explained with use made of the four-terminal network theory which involves the nonequilibrium ionization and instability effects, and the experimental results agreed well with theory. Despite the small experimental scale, an increase in power output by magnetically induced ionization was successfully achieved with good reproducibility, when preionization was suitably applied.

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The Milne problem of neutron wave propagation in polycrystalline media is solved by using the half-range orthogonality for the complete set of eigenfunctions derived in a previous paper.
The emergent distribution at the free surface exhibits a singularity when the discrete space eigenvalue attains the continuums in the spectral plane. This resonance phenomenon is demonstrated by numerical calculations for beryllium and graphite. The deformation of the energy spectrum in the directions parallel and perpendicular to the free surface are also shown for various oscillation frequencies.

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A theoretical study is made on stochastic fluctuations in power reactors. The theory is demonstrated by treating a specific but widely existing example of liquid-cooled and -moderated reactor operated with either natural convection or forced circulation.
Attention is first directed to the thermodynamical analysis of the elementary transport processes of the energy released by fissions through the fuel and coolant. A set of equations for the lumped reactor system are derived for the state variables, i. e. coolant flow-rate, coolant temperature and fuel temperature.
In the present paper, a noise source bringing about fluctuations of the coolant flow-rate is assumed to be the most influential among all the noise sources. This idea is taken into the stochastic model by using the Langevin method.
As a result of the above treatment, a stochastic description is given for the transport processes of nuclear, thermal and hydraulic quantities by deriving the Markoffian master equation and subsequently the moment equations. The theory is examined by reference to the neutron noise spectrum for the two kinds of the coolant flow pattern. It is shown that the theory can describe quantitatively, at least in part, the actual observed noises, in particular the anomalous growth of neutron noise spectra at lower frequencies.

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The effect of the presence of a reentrant hole for extracting the neutron beam from within experimental systems of two different geometries is analyzed theoretically with use made of multi-group 2-dimensional discrete S_n method without resorting to bold assumptions for neutron transport nor drastic simplification of geometry. One of the two experimental systems is a rectangular light water prism 12cm high of 40×40cm² cross section, poisoned with Cd and/or In, and provided with a 1, 2 or 3cm diameter reentrant hole. The other system is a 1" thick natural uranium plate sandwiched between two layers of pure light water, each 4.6cm thick, which also is provided with a 1cm diameter reentrant hole.
The following is concluded by comparing the angular neutron flux with and without the reentrant holes. With the first experimental system, perturbations of the order 10∼25% is caused, which is particularly strong below about 0.3eV, except when the hole diameter is 1cm. The perturbation effect increases as the reentrant hole becomes larger in diameter and shallower in depth. In the case of the second experimental system, the effect results in about 2% increase of the neutron flux at the bottom of the reentrant hole when the bottom is located in the natural uranium plate. On the other hand, if the bottom is in the light water region, the neutron flux is reduced by about 2∼4% at the peak of the thermal neutron spectra.

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An amalgamation method is described for the determination of both hydroxide and non-hydroxide hydrogen in sodium. Using a mercury ejector pump and a Toepler pump, hydrogen (non-hydroxide hydrogen) liberated from sodium amalgam at 200°C under vacuum is collected and determined by gas chromatography. Then, the vessel containing the remaining sodium amalgam is filled with argon to a pressure of 600mmHg and heated at 400°C under argon stream. The hydrogen (hydroxide hydrogen) collected is in the gas phase of a cold trap maintained at liquid nitrogen temperature, which condenses the argon but not hydrogen. The hydrogen thus collected is determined by gas chromatography. The detection limits for non-hydroxide and hydroxide hydrogen possible with this proposed method are 0.05 and 0.1ppm in sodium, respectively.

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