The non-equilibrium electrical conductivity and the relaxation of electron density in seeded plasma for MHD power generators were studied experimentally. The experiments were performed with use made of potassium seeded argon plasma (A+0.14%K) at 1, 800°∼2, 000°K, flowing in a rectangular duct at constant velocity (about 240m/sec) under atmospheric pressure. The dependence of the electrical conductivity on the electric current density was found to agree well with theoretical prediction based on the two-temperature model, if a value of 40 was chosen for the collision loss parameter. The effect of the radiative energy loss of potassium atoms was not significant in the present experiments. Furthermore, it was found that the relaxation of the electron density can be well expressed by the recombination coefficient for the electronic three-body recombination processes, and that the relaxation time is about 4×10^-4sec for the present experimental conditions.

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An anti-Compton γ-ray spectrometer has been developed, which possesses a number of characteristics particularly adapted to direct measurement of low-level complex mixtures of radionuclides in marine environmental samples.
The detector assembly consists of a 42.7cm³ coaxial Ge(Li) detector and a well-type 6" diam. ×4" NaI(Tl) detector for the anticoincidence shield. The sample to be measured is placed on the Ge(Li) detector inside the well of the NaI(Tl) crystal.
Suppression of the Compton background is particularly marked at the Compton edge when the assembly is operated in anticoincidence mode. The anticoincidence shield reduces the ¹³⁷Cs Compton edge by a factor of 6.6 to provide a peak-to-Compton edge ratio of 210:1 without reducing the full-energy peak efficiency by more than 2%. Similarly, for the 1, 332.5keV ⁶⁰Co γ-rays the Compton edge is reduced by a factor of 7 to give a peak-to-Compton ratio of 85:1, though in this case the peak efficiency is reduced by a factor of 1.8 due to the cascade decay.
This spectrometer has permitted the detection of a few pCi of fallout nuclides such as ¹³⁷Cs and ⁹⁵Zr, contained in 30g environmenal wet samples counted at inervals of 1, 000min.

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Pulsed neutron experiments in beryllium have been analyzed by the method of inelastic scattering expansion. Considering the full range of energy, the present method is applied to the calculation of the time dependent spectra within a system as well as at its surface. For obtaining the decay curve of the neutron counting rate, the neutrons are classified according to the number of specified inelastic scatterings that scatter the neutrons over the Bragg cutoff energy. The pseudo mode is, as a principal result, shown to correspond to an eigen solution of the thermal bounded equation. The buckling dependence of the eigenvalue and the eigen spectrum of the thermal bounded equation are studied, and useful approximate expressions are derived. The calculated results are compared with the experiments by Fullwood et al. and other authors.

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Several kinds of coated fuel particles, with their coating either intact or artificially cracked, were heated out-of-pile in such manner as to create a sharp temperature gradient across the particles (60°∼120°C per particle), at temperatures from 1, 500° to 1, 950°C. The purpose was to obtain information on the displacement of the kernel material relative to the coating. To examine this amoeba effect, the particles were observed, after heating, by both ceramography and X-ray radiography. The results revealed that:
(1) In the case of UO₂ kernel with artificially impaired coating, their kernels were found to move more readily toward the crack, regardless of the temperature gradient, as compared with UC₂.
(2) The amoeba effect is observed even in out-of-pile heating on intact coated particles with UO₂ kernel which moves down the temperature gradient. This UO₂ movement was given a new explanation based on the evaporation and subsequent condensation of the UO₂ within the particle, when the coating is intact.
(3) In case of UC₂ kernel, which moves up the temperature gradient, the sealing-in of the kernel by the intact coatings appears to assume a controlling factor, and the occurrence of evaporation is negligible.

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The peroxides of polymethylhydrogensiloxane, cellulose and a mixture of both were determined by ferrous ion method. The relation between the decomposition of the peroxide and the degree of grafting by standing at an elevated temperature after irradiation was examined.
The G-value for the peroxide formation of polymethylhydrogensiloxane was found to be 8.7, and the activation energy for the peroxide decomposition was determined from calculation to be 43kcal/mol. The ratio of G-values of silicone between those terminated by methoxy radical and by methyl radical is estimated to be about 2/1. It would thus appear certain that the rate of peroxidation is affected by the end group. The peroxidation is not a chain reaction at room temperature, and the peroxide is produced by the recombination of the peroxy radical. At least two types of peroxide are produced by irradiation in air, and one is decomposed at 80°C but the other is relatively stable.
On the other hand, the G-value for the peroxide formation of cellulose is equal to 5.6.
The tendency seen for the decrease of the peroxide corresponds to that of increasing degree of grafting, and it may be concluded that only 1/10 of the peroxides formed in the cellulose∼silicone system results in grafting, since it has been calculated that the G-value for the grafting through the peroxide is about 1.0.

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A method of calculation is proposed for finding the exact total flow rate of the entering stream fed to the separator in a step cascade in steady state and without losses. The method can be applied without approximation even to step cascades constituted of separators with large values of separation factor. A method of approximation is also presented for application to the case of infinitesimal separator. The reflux in each step can be chosen such that the total flow rate of the entering stream fed to the separator in the step cascade is minimized.
The effect on the total flow rate of the entering stream in the step cascade brought by such factors as the mole fraction of production, the number of steps, and the separation factor are revealed from the results of calculation using these methods. The optimization of the stripping section is found to be important for the design of plants producing low-enriched uranium required for nuclear power generation.

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This paper deals with experimental studies of performance characteristics of both constant-area (34×7×295mm) and diverging-area (23×7 to 43×7×295mm) MHD power generators with liquid mercury as working fluid, with particular reference to the pressure drop created in the inlet and outlet ducts as well as inside the generator channel, and comparisons are made with various theoretical results. Discussions are presented on the following aspects. In respect of the constant-area channel, pressure drop in laminar and turbulent flow inside the channel, transition Reynolds number for given Hartmann number, pressure drop in the inlet duct and eddy current created near the end of electrode, output electrical power. For diverging channel, applied magnetic field intensity required for zero pressure drop inside the channel, pressure distribution inside the channel, output electrical power in the case of zero pressure drop. The experimental conditions were as follows: Re<10⁵ and Ha<60.

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