Using the single-level and the Adler-Adler multi-level resonance formulas for ²³⁵U, whose parameters were derived by fitting to common experimental data, group constants were obtained for the energy region from 59.8 to 0.215eV, having the same group structure as the 70 group JAERI-FAST set.
It was found that use of the multi-level formula is preferable to the single-level alternative, the former being able to reproduce the experimental data more accurately than the latter. The resulting difference in the values of the group constants amounted to about 40% for some groups.
The group constants of ²³³U, determined by means of multi-level formula are also presented for the energy region from 36.0 to 0.215eV.

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The electrolytic separation factor between hydrogen and deuterium was examined using mercury or else platinum cathode immersed in 1F NH₄Cl in 10v/0D₂O water containing cobalt sulfide powder in suspension. Several other kinds of powdered materials in suspension were also studied. In the case of mercury pool electrode, the materials added in suspension were effective in enhancing the hydrogen/deuterium separation factor, but powder suspension was ineffective on platinum plate electrode. The powdered material added in suspension served as catalyst on the hydrogen evolution reaction at the mercury cathode. The influence of the applied potential on the separation factor was studied over the temperature range of 15°∼80°C. The results provided an indication of the rate-determining steps governing the electrolytic hydrogen evolution.
The experimental values obtained for the separation factor and activation energy gave an insight into the mechanism of the rate-determining step of the hydrogen evolution at the working electrode.

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Making use of the wavelength dependency of the critical angle for the total reflection of neutrons, the possibility of determining the energy spectrum of cold neutrons by means of a liquid mirror is examined. A carbon tetrachloride mirror, combined with a pair of fine slits, are used for the measurement of the angular distribution of the reflection intensity of beryllium filtered neutrons. For determining the correction required to account for non-reflected neutrons detected by the counter, the direct beam component is measured by disturbing the liquid mirror surface with small ripples generated by an ultrasonic vibrator submerged in the liquid, and the value obtained with this clouded mirror is subtracted from that determined with the clear undisturbed liquid mirror. The experimental results qualitatively show good agreement with those obtained with a helical-slot neutron velocity selector, and further reveal even better resolution than possible with the latter method, in the cold neutron energy region.

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In the nuclear reactor core, particularly in that of the Liquid Metal Cooled Fast Breeder Reactor, it is required that local incidents be detected in their earliest possible phases. For this purpose, it is important to design an efficient in-core monitoring system. Systems that are too complicated, however, are liable to cause unwarranted diminution of plant availability. In this paper are considered two problems, that represent different approaches to this thesis: one to find a means of selecting the optimum locations for the detectors, and the other to find the same for optimizing the sampling rates of the signals from a large number of in-core local detectors. These two approaches are studied as "decision under uncertainty" problems, using the minimax principle of the two-person zero-sum game theory, the idea being to minimize loss in the worst event. This involves an exhaustive search procedure in the former approach, and a linear programming technique in the latter. It is found that the methods used in this study are effective for designing an efficient in-core monitoring system, and that advantages worthy of note can be expected for them in practical applications, this despite the fact that the values of the parameters used in the numerical examples may not necessarily be reprsentative of actual conditions.

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The frequency functions of photon particle intensity were experimentally determined for bremsstrahlung produced by a 4 MeV electron linac during a pulse width of 1.6μsec. The measurements were carried out with a plastic scintillator and electronic integrator method, making it possible to separate multiple photons that are detected during a single linac pulse. The measured distributions were compared with the Poisson distribution with the same mean value, using the chi-square test.
This method can be extended to the photon energy spectrum determination.

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Several forms of cation exchange resins with different crosslinkages have been subjected to ⁶⁰Co γ-radiation, in wet or dry state and the effects of such variables as adsorbed ionic species, crosslinkage of the resin, and the water content in the resin on radiation damage to organic resin have been examined in their relation to γ-radiation dose. The result showed that radiation caused marked changes in the chemical and physical properties of the resin, and phenomena such as de-crosslinking, loss of strong-acid capacity, formation of a functional group composed of a weak-acid exchange group were observed. The degree of such degradation phenomena was not affected by adsorbed ions when their valency states were kept unchanged during irradiation, but when the adsorbed ions were reduced during exposure, the extent of degradation was found inhibited to a significant extent. It may be concluded from the results that the decomposition of the cation exchange resin is mainly initiated by reaction with the resin produced by radiation-formed reducing species, i. e., H atoms. A mechanism of resin degradation is also proposed.

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A correlation function for reactor noise is determined through a conditional polarity-correlation technique in which the polarity of neutron-counting fluctuations is analyzed with the start condition that the counting rate reaches a preset level. This technique, evidently, is an example of flash-start technique, developed for the purpose of improving the efficacy of reactor noise analysis. In the present case, the conditional polarity-correlation function is described mathematically assuming that the counting fluctuations of the detector conform with a Gaussian distribution. The expression thus derived reveals that this function is approximately proportional to a cross-correlation function and is a differential type of polarity-correlation function.
In order to examine the validity of the obtained expression, an experiment was performed in a graphite-moderated reactor at slightly subcritical state to measure the conditional polarity-correlation function. A novel contrivance was adopted in the experiment to eliminate the dead-time effect created during the busy time of the multi-channel time analyzer. The dependence on the preset level-i. e. flash-start condition-exhibited by the conditional polarity-correlation function showed good agreement with that expected from the mathematical expression. The prompt mode neutron decay constants were determined from the experimental data within statistical error of 3∼4%.

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