Experiments on reactor malfunction diagnosis were conducted with an out-of-pile water loop with effective use made of subassembly outlet thermocouples. On-line meas-urements were carried out on temperature fluctuation amplitude, as well as on the average temperature. Experimental results revealed that the temperature fluctuation amplitude depends on the difference between the temperatures at channel inlet and at the point of observation and that monitoring of the temperature fluctuations should serve well for detecting of flow reduction and/or local hot spot in the fuel assemblies. The tempera-ture fluctuation is also shown to serve effectively as indicator for measuring the transit time of fluid flow.
Preliminary estimations on the temperature fluctuation amplitude made for the LMFBR indicate that the fluctuation amplitude should serve amply for effectively detecting anomalies in the fast breeder fuel assembly.

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The deposition behavior of solid fission products has been studied. Experiments were made in an in-pile helium loop for gas flow with Reynolds number ranging from 1, 300 to 13, 000 at a gas temperature of about 500°C. The distributions of the fission products deposited along stainless steel tubes which had been exposed to the flow were obtained from γ-ray spectra measured with a Ge(Li) detector.
The nuclides of the deposited fission products can be classified into three groups according to the distribution patterns : (a) ⁹⁵Zr-Nb, ⁹⁷Zr, ⁹⁹Mo, ¹⁰³Ru, ¹³²Te, (b) ⁹¹Sr, ¹⁴⁰Ba-La, ¹⁴¹Ce and (c) ¹³¹I and ¹³³I Cesium-137 shows features of both groups (b) and (c).
The deposition coefficients were obtained for the nuclides of group (a), which gave exponentially decreasing distributions. The effect of the flow rate (Reynolds number) on the deposition coefficients is discussed. For a stream with Reynolds number below 13, 000, the deposition rate of metallic fission products is largely determined by the mass transfer in the boundary layer of the stream rather than by the adsorption on the surface.

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Thorium dioxide, previously freed of uranium and protactinium contamination by means of ion-exchange, was irradiated for 70.5 and 140 hr respectively in the core and graphite thermal column positions of the KUR (Kyoto University Reactor). After being cooled for more than 11/2yr, the ²³³U produced was chemically purified by ion exchange, and the resulting ²²³U specimens were electro-deposited on a stainless steel plate for submission to a-spectrometric measurement with a silicon surface barrier detector. From the α-spectra thus obtained, the ²³²U to ²³³U atomic ratios of the specimens were evalu-ated and compared with the calculated values. This revealed that the rate of formation of ²³²U depended largely on the 232Th(n, 2n)231Th reaction by fast neutrons, and conse-quently, on the neutron energy distribution prevailing at the position of irradiation. The purest ²³³U sample obtained from the thorium target, irradiated with pure thermal neu-trons in the graphite thermal column, yielded a ²³²U to ²³³U atomic ratio of 3.02×10^-9, which corresponded to 6.62 × 10^-6 in α-activity ratio.

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Thin-layer chromatography was applied to radiochemical purity determination of sulfites (³⁵SO^2-₃) and iodides (¹³¹I^-), in which the samples were chromatographed on silica gel sheet with acetone-water mixture as solvent. Prior to actual application, certain compounds of S and I contained as impurities in the ³⁵SO^2-₃ and ¹³¹I^- were chromatograph-ically separated. The R_f values were determined as function of the concentration of the acetone solvent and of the concentration of the species in the sample solutions.
Acetone was found to be a very effective solvent, only requiring the ratio of mixture with water to be changed to yield the R_f value of any compound, thus permitting the selection of a wide variety of solvent composition according to the combination of compounds to be developed. The solvent composition also influenced the developing time, which furnished another criterion in selecting the solvent composition. The R_f value was also greatly affected by the concentration of the species to be developed. Species that readily oxidized during chromatography-such as SO^2-₃-tended to yield erroneous results.
The thin-layer chromatographic technique studied in this work should be successfully applicable to the mutual separation of I^-, I0^-₃ and I2, and SO^2-₃ and SO^2-₄; it can be con-sidered a very promising alternative to paper-chromatography or electrophoresis, as standard method for the identification and purity inspection of radioactive products.

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Uranium contamination in the coating layers of coated fuel particles will adversely affect the operation of high-temperature gas cooled reactors. It is thus of great impor-tance to reduce such contamination introduced in the course of manufacture of the particles, and to this end the need is felt for the establishment of an effective method of determining such contamination. In an attempt to answer this need, a comparative experimental study was undertaken on the alternative techniques of (a) isotope dilution mass spectrometry, (b) fluorometry, (c) α-counting and (d) mica foil method. The fission recoil range in the high density pyrolytic carbon, necessary for the determination by the mica foil method, was estimated experimentally. From the results, it is concluded that α-counting and mica foil methods should mutually complement the shortcomings pos-sessed by each method in determining the contamination of coated fuel particles by kernel material.

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