A new phenomenological method is proposed for the calculation of double differential scattering cross sections in respect of thermal neutron scattering from simple monatomic liquid metals such as liquid sodium.
A general expression for the coherent part of the cross section has been obtained from a system of classical Vlasov equations for fully ionized ions and electrons interacting with each other through Coulomb or effective potentials. It is demonstrated that the fine structure seen in the reduced scattering law for liquid sodium measured by Randolph can be consistently explained by means of our method.
The quantum effects of electrons have been estimated by applying the Balescu equation to electrons, with the result that the effects are not as important as in solid metals.
Comparison of our ion-electron model with Nelkin-Ranganathan's neutral atom model reveals a marked improvement over the latter, due mainly to the explicit consideration of charges and of the presence of conduction electrons.
The gross structure of the reduced scattering law is largely determined by incoherent scattering. The incoherent part of the scattering law has been calculated in the present work by combining the effective width model and the harmonic lattice model.
The overall reduced scattering law is given by a combination of the coherent and incoherent parts. The calculated reduced scattering law for liquid sodium shows excellent qualitative and quantitative agreement with experimental values, except for energy transfers comparable to the energy of thermal motions of ions in liquid sodium.

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An experimental study on the friction and wear properties of ball bearings has been conducted in liquid sodium at 400°C. Out of a number of materials compatible with sodium, Stellite 6, Hastelloy C and austenitic stainless steel (AISI 316) were chosen. A medium size, single-row, deep groove, radial type ball bearing was selected for the form of test bearings. The following conclusions were obtained from this study:
(1) Of the three materials, the hardest material (Stellite 6) showed the highest resistance against wear, and the greatest recovery effect from friction.
(2) Liquid sodium appears to contribute little as lubricant, due to its low viscosity and extremely high chemical activity. No tendency toward self-welding was, however, observed at temperatures up to 400°C, despite the mean compression stress applied having been over three times the yield strength.
(3) The wear of ball bearings in liquid sodium is considered to be caused by local sliding friction. The wear rate is higher the softer the material in contact.

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Monochlorobenzene and its para- or meta-substituted derivatives were irradiated with γ-rays in methanol, ethanol and n-propanol containing nitrous oxide to elucidate the reactivities of these organic solutes toward solvated electrons, and also the effect of the substituent for the aromatic nucleus on the reactivities of these solutes. The value of G(N₂) is seen to decrease with increasing concentration of the organic solute. Relative rate constants of these organic solutes toward solvated electrons have been determined from the competition with nitrous oxide by observing the G(N₂) in there systems. Based on the results, the rate constants of the reactions of these derivatives of monochlorobenzene with solvated electrons relative to monochlorobenzene can be related to Hammett's σ function. The ρ value has been observed to be 3.3, 2.1 and 1.8 for methanol, ethanol and n-propanol respectively. The present data, together with that by Sherman(1) for 2-propanol, indicates that the ρ value is correlated linearly to the dielectric constant of the solvent. Some discussions are presented on the results thus obtained.

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A very local disturbance in a subassembly could propagate to gross failure over the core in large liquid metal cooled fast breeder reactor plants. The recent practice is to install a number of thermocouples in the outlet of each subassembly, but the protection thus provided is limited in extent. Probe type eddy current flowmeters are under development in many countries but the accuracy, simplicity and stability do not at present provide satisfaction.
A unique proposal of "sheathed-thermocouple-electrode flowmeter" is hereby presented. A pair of magnets and pole-pieces mounted inside a subassembly shell gives a transverse magnetic field in the outlet open channel. A pair of grounded type sheathed CA thermocouples is inserted into this field. The electromotive forces emerging from the four wires of the thermocouple pairs, by combination, should provied useful information on the outlet temperature, channel flow rate, sodium boiling, fission gas release resulting from pin failure, and cover gas entrainment. Essentially it requires no additional sacrifice on the part of reactor and fuelhandling designs compared with current outlet thermocouple installations. A preliminary feasibility study has been made of this new type of flowmeter, and ample proof has been obtained of its practicability.

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A theoretical study with use made of the collision probability method has been undertaken on the effect of photo-reactions brought upon the effective yield β of delayed neutrons in a pressure tube type heavy water reactor loaded with ²³⁵U. It is concluded that the shielding effect of the reactor structural materials for the hard γ-rays emitted from fission products reduces the contribution of the photo-neutrons to β from the currently used value of 1.00×10^-3 to 2.2×10^-4.

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An experimental study has been made on the oxidation of two thorium nitrides ThN and Th₃N₄, in oxygen under a pressure of 1/5 atm. The Th₃N₄ was prepared by reacting thorium hydride with N₂ gas, and the ThN by decomposing Th₃N₄ in vacuo. The thorium nitrides were idenfied by X-ray powder diffractometry. The values of N/Th ratio were determined by chemical analysis to be 0.90∼0.92 for ThN and 1.22 for Th₃N₄. Powder specimens of both thorium nitrides were isothermally oxidized in the temperature range of 340°∼480°C. The oxidation behavior of ThN powder was found to be independent of oxygen pressure (1/5∼1atm). The reaction kinetics of both thorium nitrides were found amenable to representation by linear plots for the most part of the reaction. The apparent activation energies were 18±3kcal/mole for ThN and 15±2kcal/mole for Th₃N₄. X-ray examination revealed the oxidation product of both nitrides to be solely ThO₂, and no other product was detected.

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