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Journal Articles

Annealing effect of absorbing property for Cs and CsI in fullerene investigated by synchrotron X-ray photoelectron spectroscopy

Sekiguchi, Tetsuhiro; Yokoyama, Keiichi; Yaita, Tsuyoshi

e-Journal of Surface Science and Nanotechnology (Internet), 20(3), p.186 - 195, 2022/07

Cesium-135 having long life, 2.3 million y, that is contained in nuclear wastes may cause long-term pollution. Technology of isotopic separation of such long lived nuclide is indispensable not only for its volume reduction but also annihilation by nuclear transmutation. The recovery of atomic Cs from molecular CsI is mandatory. We have investigated fullerene C$$_{60}$$ as a potential absorber for Cs. Angle-resolved X-ray photoelectron spectroscopy, AR-XPS has been used to analyze the depth concentration distribution of Cs. Experiments were performed at soft X-ray beamline BL27A at KEK PF facility. We report on the annealing effect after deposition of Cs and the effect of heating substrate during deposition. For Cs/C$$_{60}$$ sample, the intensity ratio of Cs-3d/C-1s increased in double at the high temperature. This suggests that Cs atoms remain in the material at high temperatures. On the other hand, for CsI/C$$_{60}$$, the intensity ratio does not change much by elevating temperatures.

Journal Articles

Absorbent property of fullerene for cesium isotope separation investigated using X-ray photoelectron spectroscopy

Sekiguchi, Tetsuhiro; Yokoyama, Keiichi; Uozumi, Yuki*; Yano, Masahiro; Asaoka, Hidehito; Suzuki, Shinichi; Yaita, Tsuyoshi

Progress in Nuclear Science and Technology (Internet), 5, p.161 - 164, 2018/11

For nuclear transmutation of cesium-135 ($$^{135}$$Cs), which is long-lived fission product, we are developing selective absorbent which takes only Cs atom in, but does not CsI. In this study, absorbing property of Cs atom onto the surface of fullerene (C$$_{60}$$) film has been investigated using synchrotron-based angle-dependent X-ray photoelectron spectroscopy (XPS). The results were compared with those of CsI. It was found that Cs penetrates into C$$_{60}$$ deep bulk. In contrast, CsI deposits on shallow surface. Furthermore, XPS spectra were measured as a function of Ar$$^{+}$$-sputtering time in order to know Cs concentration profiles in deep region. Results showed that Cs penetrates into deep region of several hundreds ${AA}$.

Oral presentation

Depth concentration profile of cesium in fullerene absorbent studied by synchrotron X-ray photoelectron spectroscopy

Sekiguchi, Tetsuhiro; Yokoyama, Keiichi; Uozumi, Yuki*; Yano, Masahiro; Asaoka, Hidehito; Suzuki, Shinichi; Yaita, Tsuyoshi

no journal, , 

For nuclear transmutation of cesium-135 (Cs-135), which is long-lived fission product, we are developing selective absorbent which takes only Cs atom in, but does not CsI. In this study, absorbing property of Cs atom or CsI into fullerene (C$$_{60}$$) solid has been investigated using synchrotron-based angle-dependent X-ray photoelectron spectroscopy (ARXPS). It was found that Cs penetrates into C$$_{60}$$ deep bulk. In contrast, CsI does not diffuse into bulk, although CsI over-layer was formed on the shallow surface. Furthermore, XPS spectra were measured as a function of Ar$$^{+}$$-sputtering time in order to know Cs concentration profiles in further deep region. Results showed that Cs penetrates into deep region of several hundreds ${AA}$.

Oral presentation

Evaluation of C$$_{60}$$ fullerene absorbent for Cs-135 isotope separation, studied by photoelectron spectroscopy

Sekiguchi, Tetsuhiro; Yokoyama, Keiichi; Uozumi, Yuki*; Yano, Masahiro; Asaoka, Hidehito; Suzuki, Shinichi; Yaita, Tsuyoshi

no journal, , 

For nuclear transmutation of cesium-135 (Cs-135), which is long-lived fission product, we are developing selective absorbent which takes only Cs atom in, but does not CsI. In this study, absorbing property of Cs atom or CsI into fullerene (C$$_{60}$$) solid has been investigated using synchrotron-based angle-dependent X-ray photoelectron spectroscopy (ARXPS). It was found that Cs penetrates into C$$_{60}$$ deep bulk. In contrast, CsI does not diffuse into bulk, although CsI over-layer was formed on the shallow surface. Furthermore, XPS spectra were measured as a function of Ar$$^{+}$$-sputtering time in order to know Cs concentration profiles in further deep region. Results showed that Cs penetrates into deep region of several hundreds ${AA}$.

Oral presentation

Reduction and resource recycling of high-level radioactive wastes through nuclear transmutation, 4-6; Neutron capture cross-section measurements of long-lived fission product nuclide Cs-135

Nakamura, Shoji; Kimura, Atsushi; Hales, B. P.; Iwamoto, Osamu; Shibahara, Yuji*; Uehara, Akihiro*; Fujii, Toshiyuki*

no journal, , 

Under the ImPACT project, the neutron capture cross-section measurements of Cs-135 among the long-lived fission products have been performed at J-PARC and Kyoto University. In this presentation, the measurements of energy-dependent neutron capture cross-section for Cs-135 will be reported, and the neutron irradiations of Cs-135 at the KUR will be also presented.

Oral presentation

Development of theoretical scaling factor method for $$^{135}$$Cs caused by the Fukushima Daiichi NPP accident

Terashima, Kenichi; Sakamoto, Masahiro; Matsumura, Taichi; Okumura, Keisuke; Fujita, Manabu*

no journal, , 

no abstracts in English

Oral presentation

Study of adsorption and diffusion of cesium atoms in C$$_{60}$$ solid by depth analysis with photo-electron spectroscopy

Sekiguchi, Tetsuhiro; Yokoyama, Keiichi; Yano, Masahiro; Asaoka, Hidehito; Suzuki, Shinichi*; Yaita, Tsuyoshi

no journal, , 

In the recovery process for the laser isotope separation of cesium Cs-135, we need occlusion material that takes the photo-generated atomic Cs selectively, but does not take CsI molecules. In the present study, fullerene C$$_{60} $$ was selected as an occlusion material. Concentration depth distribution of Cs in the solid was evaluated using X-ray photo-electron spectroscopy (XPS). The dependence of the X-ray excitation energy for Cs$$^{-}$$ or CsI$$^{-}$$ dosed C$$_{60}$$ samples were measured. Difference in excitation energy dependence were observed between Cs and CsI. In Cs, the results were explained by the distribution that penetrated deeply into the solid. On the other hand, it was concluded that CsI did not penetrate into the solid.

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