Experimental studies on isotope separation of natural Ar have been carried out using a 1.0m long hot wire diffusion column made of glass. The effect on the separation performance of the column brought by the presence of spacers for centering the hot wire was studied by changing the number of spacers.
The separation factors obtained experimentally in the column without spacer were markedly low compared with the theoretical values calculated on the basis of the LennardJones potential model. With spacers present, the separation factor was found to increase with the number of spacers until a maximum was reached at 7 spacers, beyond which number the separation factor tended to decrease again.
Moreover, from experiments carried out with spacers arranged for eccentric placement of the hot wire in column, it was revealed that improvements in separation performance could be expected mainly from better centering of the hot wire, and that disturbance of the gas flow by the spacers should not significantly affect separation.

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The steam volume fraction of a two phase mixture was measured in the low quality and low mass velocity region, as the fluid flowed upward under atmospheric pressure in 4-rod and 7-rod bundle geometries of triangular lattice (9.5mm O.D. and 1m long, 1.37 and 1.79p/d ratio).
The experiments were performed with use made of a capacitance-type void meter described in previous papers, and by supplying various heat inputs into each rod heater.
The results indicate that:
(1) In the bubble flow region, a significant peaking in void fraction was observed in the transition to slug flow in all the experimental runs. This is probably related to the effects of turbulent interchonge and diversion cross-flow between adiacent subchannels, under conditions of two phase flow.
(2) In the slug flow and annular flow regions with large disturbance waves, 4-rod bundle data were 5% lower than those in circular tube and concentric annulus, and 7-rod bundle data 10% lower. These results can be explained by Griffith's⁽³⁾ correlation with bubble rising velocity, in which channel geometries are considered. Taking account of channel geometry, the authors' correlation proposed in the previous paper is also valid in predicting the void fraction in rod bundle geometries.

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The decontaminability and the optimum conditions were studied on the flocculation of rodioactive contaminoted sea water containing radioisotopes of F.P. components. Flocculation is one of the best methods of treating high salt content liquid waste.
The results obtained showed that ¹³⁷Cs and ¹⁰⁶Ru were removed to the extent of 99% with 500ppm of copper ferrocyanide (Cu₂[Fe(CN)₆])floc at pH5-6, whie ¹⁴⁴Ce, ¹⁴⁷Pm and ⁹⁵Zr-⁹⁵Nb Were also removed by 99% With 500ppm of calcium phosphate (Ca₃(PO₄)₂) floc at pH 10-11, and ⁹⁰Sr-⁹⁰Y could be removed to an extent of over 90% with 2, 000ppm of Ca₃(PO₄)₂ accompanied with 500ppm of Sr(NO₃)₂ at pH 10-11.
Addition of a high polymer coagulant, poly acryl amide, did not enhance at all the decontaminability of the flocculation. It may possibly be effective in the treatment of flocculation sludge to support the growth of sedimentation floc.

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The present status of progress in methods of assessment of the Pu lung burden is reviewed, and is given a disscussion on the difficulties encountered in the assessment e.g. those which are inherent to high-sensitivity counting of low energy X-rays, those due to the differences in the isotopic composition of various Pu isotopes and Am which are encountered in the calibration of the detection efficiency for low energy X-rays.

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