The measurements of the (p, n) cross sections for the nuclei of atomic number 22 to 30 by means of the activation method were summarized. The analysis of the experimental results was made for some typical examples on the basis of the statistical model of nuclear reaction, and the validity of this simple model was discussed.

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Since the importance function has the clear meaning in the reactor theory, the importance equation should also have a certain physical meaning. In the present paper the importance equation and its boundary condition in the diffusion approximation are examined, and it is shown that the equation and the boundary condition are based on the same physical approximation as the original reactor equation, to which the importance equation is adjoint.

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Characteristics of the U-Scope in general and some special characteristics of the first trial set of U-Scope No.1 of the Atomic Fuel Corp. are discussed and compared with the prototype constructed in the Univ. of Tokyo. Many improvements in electioiic circuits and mechanical constructions raised to some extent the possibility of finding out very weak radioactive sources in fields. With the prototype of U-Scope special patterns, the Simple and Compound patterns by isolated point sources of radioactive substances, are almost perfectly solved in the previous papers, -Journal of Applied Physics, Japan 27, No. 7 (1958); Proceedings of the II Geneve Conference on the Peaceful Use of Atomic Energy, 3 (1958)-with many illustrations and there a response function η (cf. II. 2. a (1)) performed an excellent role in the explanation of the constitution of these patterns. However, Diffused and Background Patterns by outcrops of granitic rocks, slates and so on, and those by scattered sources, for example, debris of stone fragments and gravel on the road, cannot be explained simply by the response function mentioned above.
To make it possible to solve these complicated problems the following three concepts are introduced:
(1) Substitution of equivalent radioactive surface charge on the outcrop for the actual source
(2) The integral response function Y=∫2α -2α η d ø
(3) The fundamental formulae for the calculation of responsibility of U-Scope for scattered sources of radioactivity.
This way of conducting the analysis is well supported by the outcome of discussions concerning the experiments carried out at Tokai, the Lake Biwa, and at the Bay of Kojima in March of 1959.

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Woosher type thermal cycling equipment are designed and constructed in June 1957. In Japan, however, it is difficult to make it to be as same as ANL Woosher type equipment due to poorer NaK technique. Therefore, evacuated silica capsules containing uranium specimens made by grooved mill rolling at 600° and 300°C, respectively, are used in this thermal cycling equipment. Cycling was performed between room temperature and 550°C up to 1, 000 cycles in maximum and the thermal cycling growth coefficients are measured at the three stages shown in Table 2 From this experiment, the uranium rod rolled at 300°C was always found to have higher thermal cycling growth coefficient than the rod made at 600°C irrespective of the holding time at room and elevated temperature. The effects of rolling temperature of uranium rods on the thermal cycling growth coefficient are also described. The specimens after 1, 000 cycles are metallographically examined and sub-grains having crystal orientation of 2 or 3 degrees different from each other are observed. This experiment is one of the surveying test to find the best fuel element for JRR-3 reactor in which natural uranium is to be used as fissile material.

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The behavior of recoil bromine atoms arising from the n, γ reaction on bromate samples in various physical states was studied. The samples irradiated with neutrons were bromate crystals, aqueous bromate solutions and anion exchange resins loaded with bromate ions.
A large fraction of radioactive bromine atoms appeared in such a chemical form as bromide which may be separable from bromate by ion exchange or solvent extraction, whereas the remaining active atoms were found in bromate form.
The degree of retention of active atoms as bromate was dependent strongly upon the physical state of the irradiated sample, decreasing in the following order; solid, solution, resin. The retention values in the solid, solution and resin samples were, respectively, about 20, 5 and 1%.
Clean-cut separation of bromate and active bromine in the irradiated resin samples was performed by successive treatment of the resin samples with 0.5M KNO₃ and then 2M KNO₃. The elution with 2M KNO₃ brought about an effluent containing active bromine atoms with an enrichment factor of, for instance, several hundred. It is worth mentioning that some fraction of active bromine was retained in the resin phase even after the elution with KNO₃ was completed.
Brief discussion was made regarding the mechanism of the retention of active atoms in solid, solution and resin phases.

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[in Japanese]

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