Gamma-ray production cross sections were measured for Al(n, xγ) and Cu(n, xγ) reactions at neutron energy of 5.3 MeV using the Dynamitron accelerator. A Ge (Li) detector was used for the γ-ray detection and data were obtained for emission angle of 55°. Absolute differential production cross sections of discrete γ-ray lines were presented with probable origins of the transitions. The measured γ-rays were 17 lines ranging of 7924, 811 keV for Al and 32 lines ranging of 6672, 330 keV for Cu. The experimental results were compared with previous measurements. The present results are relatively large for Al and agreement is fair for Cu.

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In this paper, by a two-dimensional analysis in the duct cross section perpendicular to the plasma flow, the authors investigate comparatively the current distribution, the electrical efficiency etc. in the diagonal type nonequilibrium plasma generator of the window frame construction and the one of the insulating sidewall. Their numerical computations are made for an example of the cesium-seeded helium in nonequilibrium ionization, where it is assumed that the ionization instability does not occur.
It is shown that the current in the generator duct of the diagonal conducting wall tends to flow uniformly in the cross section of the duct, and on the other hand, the cur-rent in the duct of the insulating sidewall does in its central part ; thus the performance characteristics of the former becomes better than those of the latter. This tendency increases with the load factor and wall temperature of the generator. Also the generator characteristics are improved with increasing the inclination factor, and the electrode volt-age drop decreases with the load factor.

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Transient sodium boiling experiments have been conducted in an electrically heated single-pin annular channel under loss-of-flow conditions. Each run was made by reducing or stopping the flow at constant heater power. Records were obtained of the changes of temperatures, flow rates, pressures and voids. The experimental results were compared with analytical calculations.
There was no strong effect of temperature ramp rate on the incipient-boiling (IB) wall superheat in the range of the present experimental conditions.
The pressure rise at the initial vaporization compared well with the vapor pressure corresponding to the IB wall superheat. The pressure pulse occurred at the vapor col- lapse correlated reasonably well with the collision velocity between the re-entrant liquid columns, but the measured value was less than the theoretical value predicted from the sodium hammer analysis.
The observed voiding pattern agreed fairly well with the calculation by the NAIS-P2 code (single-bubble slug expulsion model). The initial expulsion acceleration of liquid agreed well with the theoretical prediction from the one-dimensional liquid column ex- pulsion analysis. The thickness (0.05 and 0.29 mm) of the residual liquid film became thinner with higher IB wall superheat.

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The influence of inert gas on performance characteristics of liquid metal heat pipe was experimentally studied over a wide range of gas loading. In this experiment, potas-sium was used as a working fluid and argon was loaded in the heat pipe. The loading amount of argon ranged in initial pressure 10^-210²Torr at room temperature. As the results, the followings became evident.
During a start-up, an axial heat flux of the heat pipe is reduced from that correspond-ing to the sonic vapor flow by the presence of inert gas accumulating in the condenser section. In the region of high initial gas pressure, an over-all thermal conductance of the heat pipe can be described with the model due to "flat-front", but, with decreasing initial gas pressure, the over-all thermal conductance deviates from the theoretical values obtained from the flat-front model and approaches to that corresponding to the sonic vapor flow. Also, the over-all thermal conductance is influenced by the effect of the gravitational force on the wick pumping ability of the heat pipe and the decrease of the thermal conductance depends on the initial gas pressure.

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Space time synthesis and time synthesis codes were developed and applied to the space-dependent kinetics benchmark problem of a two-dimensional fast reactor model, and it was found both methods are accurate and economical for the fast reactor kinetics study. Comparison between the space time synthesis and the time synthesis was made. Also, in space time synthesis, the influence of the number of trial functions on the error and on the computing time and the effect of degeneration of expansion coefficients are investigated. The matrix factorization method is applied to the inversion of the matrix equation derived from the synthesis equation, and it is indicated that by the use of this scheme space-dependent kinetics problem of a fast reactor can be solved efficiently by space time synthesis.

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Commercial purity polycrystalline niobium was irradiated in the JMTR to neutron fluences of 3.5 x 10¹⁸ and 6.9 × 10¹⁸ n/cm² (E>1 MeV) and then deformed in tension at temperatures between 77 and 340°K in order to investigate the mechanical properties, particularly the temperature dependence of yield stress and the activation volume and activation energy for thermal activated motion of dislocations. From the force acting on radiation-produced defects, it was deduced that the radiation defects observed by trans-mission electron microscopy do not account for the thermal component of yield stress because of the extremely large defect sizes. In addition, a comparison was made between the athermal component of yield stress and the stress which was derived from the defect distribution as determined by transmission electron microscopy. The measured data amount to about 1.4 and 2 times larger than the calculated values. These discrepancies may be ascribed to the interaction between interstitial impurities and the radiation defects. In the room temperature deformation, dislocation channeling was observed in the specimens irradiated to 6.9 × 10¹⁸ n/cm² but not to 3.5 × 10¹⁸ n/cm².

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The precipitations of thorium and uranium(VI) sulfito complex ions with hexammine cobalt(X) chloride as the precipitant have been studied.
The orange-colored uranium(VI) precipitate obtained is [Co(NH₃)₆]₄[UO₂(SO₃)₃]₃22H₂O, which is in the form of square bipyramid, about 4 μm across in a cubic symmetry of the diamond type with a =10.40 Å It decomposes to an oxide mixture of Co₃0₄ and U₃O₈ above 850°C in the air through a sulfate mixture of CoSO₄ and UO₂SO₄.
Composition of the thorium precipitate varies with the precipitation conditions. Therefore, it is considered that the thorium precipitate contains thorium hydroxide and basic thorium sulfite.

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The determination procedure for extremely low-level radio-iodine (¹³¹I) in milk ( (23) × 10^-9 μCi/ml) which corresponds to 15 mrem/yr of exposure dose for thyroid of a critical person (i.e. a baby) were published recently by both United States Atomic Energy Com-mission and Battelle Pacific Northwest Laboratories. However, error of determination, lower limit of detection and time required for preconcentration and radiation counting were not shown. Therefore we examined these conditions for those two kinds of methods to know whether they are useful for practical performance or not.
(1) Recovery of iodine in milk was about 7075 % in both methods.
(2) Lower limit of detection of 131I in milk was 6.7 x 10^-11 μCi/ml with 30.4% of CV for counting. The determination conditions are : (1) sample volume 4l, (2) counting time 1, 000 min (16 2/3 hr), (3) iodine recovery 70 (4) efficiency of β-ray counting 30 %, background counting 0.8 cpm.
(3) In case of two-sample treatment in parallel, it took about 1.52 days for preconcentration procedure, and about 45 days for over-all determination.
(4) From the result mentioned above, it was clarified that extremely low-level radioiodine in milk which corresponds to 15 mrem/yr could be practically carried out by the both methods with experimental conditions mentioned in (2).

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