The dynamic behavior of a 1, 000 MWth sodium-cooled oxide-fuel fast breeder reactor was analyzed. To determine the stability of fast reactors, a new analytical model was introduced. The transfer function of EBR-I Mark IV calculated therewith agreed closely with experimental data, and the stability study on the model case was carried out with this model. The present analysis was extended to cover such accidents as reactivity insertion, coolant flow coast down and loss of coolant flow, which are commonly considered in fast reactor safety analysis, and further, the influence of changes in reactivity coefficients upon the consequences of such accidents was also surveyed.
The results indicated no appearance of instability in large fast reactors under credible conditions, and that fuel center melting should occur prior to sodium boiling in the case of a reactivity insertion accident, when the Doppler coefficient should have great influence, in contrast to the sodium coefficient, whose effect should be small. It was also ascertained that there should be no fear of coolant flow coast down from pumping power failure if the scram system operates normally, and that in the event of channel blockage sodium should begin to boil within a few seconds at about two thirds of core height. Compared to the case of reactivity insertion, the effects of the individual coefficients were found to act in the inverse direction in these latter cases.

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An in-pile calorimeter of twin-rod conduction type has been developed for measuring simultaneously neutron-induced and γ-induced energies.
Calorimetric measurements with the apparatus were carried out in the horizontal experimental hole of JRR-1 (water boiler reactor) at a position 41.5cm from the core edge. The thermal neutron flux was 4.55×10¹¹ n/cm²•sec at 40kW reactor power. The rates of γ-induced and neutron-induced energies per unit mass of polyethylene were 2.72(mW/g) and 1.04 (mW/g) respectively. These measured data were reasonably consistent with the values obtained with adiabatic calorimeter.

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A washing method using potassium dichromate as oxidizing reagent was applied to remove fission products and their complexing agents from kerosene degraded with nitric acid.
The fission products and their complexing agents were both effectively removed from the degraded kerosene, their removal percentage increasing with rising concentration of sulfuric acid and potassium dichromate. The removal percentage of fission products also increased slightly with shaking time of the mixture of degraded kerosene and acidic potassium dichromate solution. Change in volume ratio (O/A) however hardly affected the removal percentage.
Lowering of the absorption bands due to carboxylic acids, nitrate esters and nitro compounds were observed in the infrared spectra of the degraded kerosene treated with acidic solution of potassium dichromate.
Infrared analysis of TBP/kerosene treated with acidic potassium dichromate solution showed that no chemical degradation of the solvent had occurred to any extent.

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A study was conducted on the preparation of a high specific activity ¹²⁸I utilizing hot atom effects.
Crystalline iodine pentoxide, ammonium iodate and iodic acid were irradiated in the pneumatic tube and the rotary rack of a TRIGA-II reactor. Variation of the ¹²⁸I retention with duration of irradiation and with neutron beam intensity was determined. The retention of 128I in the iodate fractions was found to increase during the first 30 min, after which it stabilized. Ammonium iodate showed the lowest values for ¹²⁸I retention. The retention generally increased with neutron beam intensity.
The specific activity of ¹²⁸I was determined from the amount of iodine simultaneously produced by the decomposition of the samples by radiation. The radiation decomposition increased linearly with irradiation time. Ammonium iodate was found to have decomposed much more than iodine pentoxide and iodic acid.
The enrichment factors of ¹²⁸I were calculated on the basis of the results obtained from these experiments. Ammonium iodate showed the highest enrichment factor. Consequently, a high specific activity ¹²⁸I was prepared by irradiating 500 mg of ammonium iodate for 30 min in pneumatic tube. The resulting enrichment factor of 128I was 1.3×10⁴. Active impurities in the product were found to be less than 1 ppm.

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An analytical procedure for the frontal process has been developed for the case in which (1) the mobile fluid phase proceeds stepwise from one contacting unit to the next, (2) isotopic exchange equilibrium is attained between the mobile and stationary phases in all the units, and (3) chemical refluxing occurs always at the frontal edge of the region containing the fluid phase.
Equations were derived for the isotopic abundance ratio of a chemical substance at any refluxing unit and for the early part of a breakthrough curve. It was possible to obtain an approximate estimate for the separation factor and for the number of contacting units when a breakthrough curve was drawn from experiment. Finally, a comparison of the frontal process with the reverse frontal process was made with some numerical examples.

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A method has been developed for the preparation of US² using UCl⁴, as a first step in the preparation of uranium monosulfide. The reaction of UCl⁴, Al and H²S has been proved to be quite practical. It was confirmed by chemical analysis and X-ray diffraction analysis that almost pure US² was obtained at temperatures above 400°C, and the conversion efficiency of uranium reached almost 100%.

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