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Journal of Radioanalytical and Nuclear Chemistry
Authors: T. Maruyama, D. Kaji, T. Kaneko, S. Goto, K. Tsukada, H. Haba, M. Asai, S. Ichikawa, Y. Nagame, and H. Kudo

Abstract  

Rapid chemical separation of berkelium is essential in order to measure the unknown isotope 252Bk. An anion exchange system of mineral acid and methanol was examined. An elution curve of Bk was obtained using 250Bk produced by the 248Cm+18O system and the 251Bk activity could be measured in the preliminary experiments. The whole chemical separation was completed within 30 minutes.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: A. Toyoshima, K. Tsukada, H. Haba, M. Asai, S. Goto, K. Akiyama, I. Nishinaka, S. Ichikawa, Y. Nagame, and A. Shinohara

Abstract  

The anion exchange behavior of 255No produced by the 248Cm(12C,5n) reaction has been investigated in 11.5M HCl, 4M HCl and 8M HNO3 to deduce the behavior of 'primordial 257No' produced via 248Cm(18O,5n)261Rf 257No before anion exchange separation in the 261Rf experiment. It was found that 255No is mostly eluted from the anion exchange column with these solutions. The contribution of 'primordial 257No' to the -decay events of 261Rf in the 261Rf experiment was evaluated based on the present results.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: S. Goto, D. Kaji, I. Nishinaka, Y. Nagame, S. Ichikawa, K. Tsukada, M. Asai, H. Haba, S. Mitsuoka, K. Nishio, M. Sakama, Y. Zhao, K. Sueki, K. Tanikawa, K. Takamiya, H. Kudo, and H. Nakahara

Abstract  

To study the correlation between fragment mass distributions and shell structures of fission fragments, fragment mass and energy distributions in proton-induced fission of 232Th and uranium isotopes, 233,235,238U, were precisely measured using a double-TOF method. It was found that the lighter side of the heavier wing of asymmetric mass distributions shifts to larger fragment mass number corresponding to the N/Z value of the fissioning nucleus. The results are explained qualitatively by the change of the most probable mass number of fission fragments of Z = 50 proton-shell.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: Y. Nagame, I. Nishinaka, Y. Zhao, K. Tsukada, S. Ichikawa, Z. Qin, H. Ikezoe, Y. Oura, K. Sueki, H. Nakahara, M. Tanikawa, T. Ohtsuki, S. Goto, H. Kudo, Y. Hamajima, K. Takamiya, K. Nakanishi, and H. Baba

Abstract  

The correlation among the fission threshold energy, the scission configuration and the mass yield distribution has been studied in proton-induced fission of light actinides. It was found that there exist at least two fission paths from the threshold region to the scission. The elongated scission configuration is related with the fission process that goes over a higher threshold energy and results in a symmetric mass division mode, while the compact scission configuration with the process that experiences a lower threshold and ends up with an asymmetric mass division mode.

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