The studies of the isotope separation using ion exchange chromatography or electromigration have been done by many researchers, but the continuous operation of these separation processes has still some difficulties to be solved.
A new type of apparatus was devised on the basis of simultaneous use of ion exchange and electromigration for a continuous isotope enrichment.
To examine the efficiency of this apparatus, the experiments of lithium isotope separation were carried out. At the stationary state of continuous operation, the separation factors of Li₂CO₃ system and LiOH system were found to be 1.0069 and 1.0049 respectively.
Apart from the advantage of continuous operation, these values are larger than that of 1.001 obtained with Diaion SK#1-LiCl system, 1.002 with Dowex 50X-8-LiCl system and 1.0038 obtained by the electromigration in LiNO₃ aqueous solution, while smaller than 1.008 obtained by the electromigration in ion exchange membrane.

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The studies on corrosion of impermeable graphite by molten bismuth and molten bismuth-lead alloy were made under several conditions. The graphite samples, which were isothermally immersed in molten bismuth or bismuth-lead alloy at 450°, 550° or 700°C for 210 hr, were observed changes in neither weighing test nor microscopic test.
If the thermal cycle of heating (550°C)-cooling (solidification) was added to the bismuth in which the graphite samples were dipped, the cracks were induced in the samples. It was found by the microscopic method and the autoradiography that the result abovementioned was caused by the volume expansion of bismuth. When the bismuth filled in pin-holes of graphite solidified, the bismuth expand and spread the pin-holes. These pin-holes were connected each other and grew into cracks.

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Smear survey is carried out in order to measure the amount of loose contamination on the surface. The value measured by the smear method depends on the nature of surface material, contaminants, or smear pressure, therefore, it is desirable to make clear the relations between them for radiation protection. In this work the smear survey was performed in various experimental conditions stated above, and the results obtained were compared with those of field tests.
The non-permeable surface materials such as vinyl sheet were contaminated with various radioisotopes and were smeared. These experiments show that 5080% of loose contamination and about 50% of total contamination were detected in the model experimental conditions. On the other hand, the same experiments were also carried out using permeable materials. In this case, 5080% of loose contamination and 250% of total contamination were detected. From these results, it is possible to estimate the amount of surface contamination, by assuming that 10% and 50% of the amount of total contamination are transfered to the smear disk for permeable and non-permeable surface materials with contaminants, respectively.

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The purpose of this trial calculation is to get an instantaneous and direct control mechanism for the reactor neutron reactivity.
When a neutron is incident on a slab of fine grained ferromagnetic material, the angular distribution of the scattering intensity depends on the angle between the magnetization vector and the incident direction of neutron.
The expression for the difference in the forward scattering intensity is given, when the saturation magnetization vector is varied from parallel to perpendicular to the slab axis.

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An approximate calculation method in γ ray transmission problems is shown for multiple layers.
In this method, the differential energy flux of incident γ rays is expressed by a vector, and the shielding property of each slab is represented by a matrix. The matrix is constructed by a relatively simple procedure, using the data of penetration in infinite media calculated by the moments method and the data of the effect of finite slabs calculated by the Monte Carlo method. The compound shielding property of multiple layers is also represented by the matrix which is obtained by the multiplication of the matrix corresponding to the each slab. The differential energy flux of transmitted γ ray is given by multiplying the incident vector by the matrix.
The results of the method are compared with those of the Monte Carlo calculation for Pb-H₂O and H₂O-Pb stratified slabs, and also with those of experiments for Pb, Fe and Al stratified slabs. The comparison shows that this method is useful for all combinations of materials for high incident energy, and when low energy γ rays enter the heavy layer followed by a light or heavy layer.

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