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Abstract  

Thermal neutron activation analysis of hafnium in zircaloy was investigated with a Van de Graaff accelerator. Thermal neutrons were obtained by moderating Be−D fast neutrons with paraffin blocks.179mHf isotope with a half-life of 18.6 s, produced by178Hf(n, γ)179mHf reaction, was utilized in the present analysis. This method made it possible to analyze hafnium rapidly and non-destructively by using scandium as an internal standard material. Several tens to hundreds of ppm of hafnium in zircaloy samples were determined within 2 minutes with a precision of about ±1%.

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Journal of Thermal Analysis and Calorimetry
Authors: K. Fujii, Y. Matsumoto, Y. Kaieda, D. Kobayashi, Y. Umebayashi, and S. Ishiguro

Abstract  

Cobalt(II) chloro complexation has been studied by titration calorimetry and spectrophotometry in solvent mixtures of N-methylformamide (NMF) and N,N-dimethylformamide (DMF). It revealed that a series of mononuclear CoClnn (2–n)+ (n=1–4) complexes are formed in the mixtures of NMF mole fraction x NMF=0.05 and 0.25, and the CoCl+, CoCl3 and CoCl4 2– complexes in the mixture of x NMF=0.5, and their formation constants, enthalpies and entropies were obtained. As compared with DMF, the complexation is markedly suppressed in the mixtures, as well as in NMF. The decreasing formation constant of CoCl+ with the NMF content is mainly ascribed to the decreasing formation entropy. DMF is aprotic and thus less-structured, whereas NMF is protic to form hydrogen- bonded clusters. In DMF-NMF mixtures, solvent clusters in neat NMF are ruptured to yield new clusters involving DMF, the structure of which depends on the solvent composition. The entropy of formation of CoCl+ will be discussed in relation to the liquid structure of DMF, NMF and their mixtures.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: W. Sato, H. Ueno, H. Watanabe, H. Ogawa, H. Miyoshi, N. Imai, A. Yoshimi, K. Yoneda, D. Kameda, Y. Kobayashi, and K. Asahi

Abstract  

A new 19F probe disintegrated from short-lived 19O has been developed for the first time for time-differential perturbed angular correlation method. The angular correlation coefficient for the relevant cascade has been experimentally estimated to be A22 = -0.17±0.01. As the first application of this technique to condensed matter physics, the probe was implanted in polycrystalline fullerene C60. We have observed two contrastive perturbations acting on the probe nuclei, which reflect electrostatic and dynamic interactions with the extranuclear field.

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