The dry distillation method was studied for rapid separation of ^99mTc from neutron irradiated MoO₃.
Upon heating, ^99mTc produced in MoO₃ crystal by the ⁹⁸Mo(n, γ)⁹⁹Mo ^β-→^99mTc process was found to be released by diffusion.
From observations made of the deposition temperature, it was concluded that ^99mTc was present in the form of ^99mTc(IV) in the MoO₃ crystal lattice and that it was released in the form of ^99mTcO₂, which, in air, further oxidized to ^99mTc₂O₇.
The release of ^99mTc from neutron irradiated MoO₃ powder was studied in the temperature range of 480°∼700°C, and its behavior was found to be in good agreement with the bulk diffusion mechanism based on Fick's law. The diffusion coefficient varied with temperature in compliance with Arrhenius'relation, except in the region of temperatures above 700°C.
The separation of ^99mTc from MoO₃ was performed with a yield higher than 80% upon heating for 30min at 800°C in air. The decontamination factor for ₉₉Mo was consistently found higher than 10⁵.

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A study was made on the preparation of ³⁵S-labeled sulfite by the pyrolyzation of labeled Cu(II) sulfate.
Factors such as the amount of carrier sulfate and the NaOH concentration of the absorbing solutions, which were thought to affect the yield and radiochemical purity of the final products, were examined together with the chemical stability of the sodium sulfite (³⁵S) thus obtained in aqueous solutions.
The method has proved to be useful for practical preparation of ³⁵S-labeled sulfite. With Cu(II) sulfate carrier ranging 20∼176mg, more than 80% of ³⁵S can be recovered as sulfite.
Carrier-free sulfite (³⁵S) can also be obtained by merely replacing the Cu(II) sulfate carrier with Cu(II) chloride and carrier-free H₂³⁵SO₄.

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The propagation of a thermal neutron beam into a water assembly containing various concentrations of Cd has been studied by solving the diffusion equation in the multigroup formalism. The Nelkin model has been used for the scattering kernel. It is observed that for very high Cd concentrations the experimentalist measures a pseudomode which dominates at small distances from the source. This pseudomode decays very slowly to reach the asymptotic distribution at very large distances from the thermal neutron source and at such large distances the neutron density would become so small that it would be difficult to detect these neutrons.

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The magnetic susceptibility of solid solutions of U(C, N) (up to 50mol/0 UN) and U(C, O) (up to 25mol/0 UO) was studied in the temperature range of 77°∼300°K. These solid solutions all exhibit paramagnetism. With U(C, N), the susceptibility rises with increasing content. With U(C, O), the susceptibility scarcely changes up to approximately 5mol/0 UO, beyond which point it increases with oxygen content. The temperature dependence of the susceptibility, though very weak, increases with oxygen content. The density of state curve is considered on the assumption that the variation of susceptibility with composition is due to Pauli paramagnetism, and the magnetic behavior of U(C, N) and U(C, O) is explained by considering the shift of the Fermi level with progressive substitution of carbon by nitrogen or oxygen.

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A phonon-type expansion of the differential scattering cross section of slow neutrons is carried out in an entirely general way. The formula thus obtained can be applied to arbitrary target systems, in particular, to non-Gaussian systems such as anharmonic crystals and molecules with an arbitrary structure. A well-defined quasiclassical approximation is presented along the line of reasoning of our previous paper. When the present formalism is applied to a system of molecules, it results in an expansion in terms of the quanta of the rotational motion of the molecule. The effectiveness of our new formula is demonstrated in numerical calculations for HCl gas.

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The chemical shifts of the photon magnetic resonance of p-toluenesulfonic acid in aqueous solution were measured as a function of acid concentration. The acid dissociation constant for p-toluenesulfonic acid calculated from the chemical shifts is 3.4. These results show that the p-toluenesulfonic acid is a strong acid.

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A method of calculating the neutron flux in a heterogeneous system, utilizing a combination of two different energy meshes-coarse and fine-is presented. The method has been programmed into a computer code EXRE-2. This method is particularly suitable for computations of fast reactor spectra that carry both broad and fine undulations.
Pointwise cross section curves are prepared by superposition of the Breit-Wigner single level formura. In the energy region where the resonance is not resolved, a random sampling procedure is used for the derivation of resonance parameters.
Group averaged resonance capture and fission cross sections and the temperature dependence of these quantities are computed for a typical fast reactor. An examination is made of the applicability of the conventional narrow resonance (NR) approximation applied over a rather wide energy group, and the heterogeneity effect on the resonance cross sections, near the sodium resonance at 2.85keV.
The error due to the NR approximation was found fairly large in the case of the heterogeneous model, but negligible in the homogeneous. The heterogeneity effect was also negligible except for the Doppler cross sections in the immediate neighborhood of 2.85keV.

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The energy and directional distributions of the photon flux in air lm above mono-energetic semi-infinite isotropic volume sources were calculated with Monte Carlo technique for 5 different γ-ray energies from 0.35 to 2.65 MeV. The energy and directional distributions of the flux from U, Th and K were obtained with use made of the results of the mono-energetic calculations. The results agreed well with previously measured data on an actual natural radiation field.

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