Uranouranic oxides prepared from various uranium compounds by various methods were physically and chemically examined.
It is concluded that uranouranic oxide obtained from UPO is the most reactive, and that the difference of these reactivity does not depend upon impurities, but essentially upon some physical properties, such as the specific surface area and the crystal structure.
Present paper concerns with the comparative study of the mechanism on the thermal decomposition of UNH, ADU and UPO by a semiautomatic recording thermal balance, a X-ray diffractometer and its high temperature apparatus. The results are as follows;
(1) On the way of thermal decomposition of UNH, uranic oxide is formed in the temperature range of 320° to 570°C, and its compound may be of monoclinic.
(2) On the thermal decomposition fo ADU, uranic oxide is formed in the range of 340° to 550°C, and its product may be of a new crystal system.
(3) On the thermal decomposition of UPO, amorphous UO₃ is formed in the range of 320° to 500°C.
(4) The uranouranic oxides are always orthorhombic crystals.

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In the calculation of the nuclear properties of a cubic reactor, rectangular parallelepiped core with multi-reflector, IBM-650 machine is generally unsuitable for difference equations by few group diffusion theory. However, if a determinant method is used, the critical equations of the cubic reactor derived from three group diffusion theory can be numerically calculated by IBM-650.
Assuming separability of neutron flux into three components which are functions of x, y and z respectively, three determinants, |X|, |Y| and |Z|, are derived from boundary conditions for neutron flux and current. Therefore the critical conditions are |X|=0, |Y|=O and |Z|=O, where these three determinants are function of three eigenvalues; μx, μz, and μy.
This paper presents the content of the nuclear code for the aforecited theme by IBM-650, CUBE, which contains calculations of determinants and these elements, and procedure for simultaneous convergence of three determinant to zero.
Since the convergency is very rapid, CUBE is useful for parameter survey of the nuclear properties of the cubic reactor, though there are some restrictive conditions for nuclear constant and size of reactor to be calculated.

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A sample of primary cooling water taken from the stainless steel loop facility of JRR-1 on May 9, 1959, had gamma activities of about 10^-4μc/ml.
The gamma spectrum of the sample showed peaks at 0.32, 0.51, 0.83, 1.1 and 1.3 MeV. The separation of radionuclides was done as follows: The sample solution was dried, dissolved with 11.4N hydrochloric acid, and transferred to a Dowex 1 (H type) anion exchange resin column bed (∅ 1cm, h 10cm, 100200 mesh). The nuclides absorbed on the column were successively eluted with acid solutions of decreasing acidities (11.4, 6.0 and 3.0N hydrochroric acid) to separate fractions of nickel, manganese, cobalt and iron.
The gamma activties of the frations were measured with a 256 channel pulse hight analyzer. The nuclides were identified by their gamma energie, chemical properties and half-lives, which are given in Table l as well as the probable ways of formation.

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Data on the preparation of the uranium monocarbide are reported. In order to obtain the uranium monocarbide in high purity, the uranium powder produced by the formation at 250°C and the following decomposition of uranium hydride at 450°C was supplied to the reaction with propane. Effects of the initial pressure of propane and the reaction temperature upon the reaction rate and the yield of the uranium monocarbide produced were studied by measuring the electrical resistance of a tangsten filament in the Pirani gauge and the increase of the gas pressure. The uranium monocarbide produced in a favorable condition had the crystal structure of NaCl type, having the lattice parameter of 4.949 Å, and contained 4.74% carbon. The optimum condition for the synthesis of uranium monocarbide from powdered uranium and propane was as follows; the reaction temperature was about 700°C, and the initial pressure of propane was about five times as much as the required stoichiometrically. Under such a condition, the reaction was nearly completed within 10 to 20 minutes.

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Selectivity coefficients, K¹⁵₁₄ (N), between ¹⁵NH⁺₄ and ¹⁴NH⁺₄ on sulfonated polystyrene divinylbenzene copolymers of various crosslinking, were determined in ethanol-H₂O mixtures containing 0.1M NH₄Cl.
The obtained values for K¹⁵₁₄ (N) lie between 0.999 and 1.006. It seems that the maximum value for K¹⁵₁₄ (N) value locates at about 2030 vol. % ethanol mixture.
There is an appreciable increase in the K¹⁵₁₄ (N) value with increasing crosslinking of the cation exchagers.
The experimental data are discussed from a thermodynamic point of view.

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This paper is a review on reactor physics experiments using subcritical systems. Experimental facilities and techniques are described, and the correlations of theory and experiments are discussed. Some of the interesting pulsed neutron experiments utilizing subcritical systems are also discussed.

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In Part I descriptions are given of the site of the reactor from the viewpoint of seismology and subsoil condition as well as of the basic idea of aseismic design with proposed specification based on the foregoing idea.
In drawing up the seismic specification, as this reactor is the first large scale reactor in Japan, the safety of the reactor itself and the protection of residents near the reactor from damage during an earthquake were made the primary requisites. From this viewpoint, the seismic coefficient exceeding 0.2 stipulated in the Japanese Building Code was adopted; particularly with regard to the main part of the reactor, the horizontal seismic coefficient was required to be 3 times the standard value and the vertical seismic coefficient one half of the horizontal coefficient. Also, lest relative displacements between each part of the reactor during earthquakes should hinder the operation, the whole building and structures were made rigid, i.e., the graphite core structure was supported by a steel cylinder and the pressure vessel, steam raising units and gas ducts were firmly fixed to the biological shield concrete. The actual design drawn up by the G. E. C. based upon this aseismic specifications will be described in Part II.

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We have derived from the Boltzmann equation a new integral equation governing the slowing down of neutrons in a lump, assuming a spatially uniform neutron flux inside it. In the first approximation we have solved the equation using the asymptotic energy dependence of the neutron flux and proposed a new resonance integral formula. In the limit of both the narrow resonance and the wide resonance, the fo mula tends to be equal to that derived in the conventional narrow and wide resonance approximations. In the second approximation we calculated effects of the deviation of the Placzek function from its asymptotic form by a method similar to that used by Weinberg and Wigner for homogeneous systems. We have shown that the resonance integral of the usual narrow and wide resonance approximations become equal for a certain value of T_n/T, irrespective of the resonance width. Some numerical results are given.

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