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JAEA Reports

Data of radon measurement in underground facilities of Mizunami Underground Research Laboratory

Aoki, Katsunori; Yamanaka, Hiroki*; Watanabe, Kazuhiko*; Sugihara, Kozo

JAEA-Data/Code 2020-018, 45 Pages, 2021/02


Mizunami Underground Research Laboratory (MIU) Project is pursued by Japan Atomic Energy Agency (JAEA) in the crystalline host rock (granite) as a part of geoscientific study of JAEA, and underground facilities of MIU are constructed down to 500m blow the ground surface. As small amount of Uranium is normally contained in granite, high concentration of radon is sometimes detected in the air of the underground facilities constructed in granitic rocks depending on their ventilation conditions. Radon concentrations in underground facilities of MIU have been measured according to the excavation progress of underground facilities or the change of ventilation system. It is recognized that the data obtained by the actual measurement of radon concentration in such underground facilities are rare and valuable. This repot summarizes the measured data from fiscal 2010 to fiscal 2020, together with the information of ventilation conditions and air temperature which affect radon concentrations in underground facilities. The variation of the equilibrium factors of radon is also examined with the actually measured data. As a result, it has been found that radon concentration in the drift is high in summer and low in winter according to the natural ventilation caused by the seasonal temperature difference between in and out of the underground facilities. Furthermore, the temporary increase in the equilibrium factor of radon in the drift at the start of ventilation is supposed to be due to the aerosol increase by the ventilation flow, such as the dust blown up.

Journal Articles

Reaction rate analyses of accelerator-driven system experiments with 100 MeV protons at Kyoto University Critical Assembly

Pyeon, C. H.*; Vu, T. M.*; Yamanaka, Masao*; Sugawara, Takanori; Iwamoto, Hiroki; Nishihara, Kenji; Kim, S. H.*; Takahashi, Yoshiyuki*; Nakajima, Ken*; Tsujimoto, Kazufumi

Journal of Nuclear Science and Technology, 55(2), p.190 - 198, 2018/02

 Times Cited Count:14 Percentile:85.81(Nuclear Science & Technology)

At the Kyoto University Critical Assembly, a series of reaction rate experiments is conducted on the accelerator-driven system (ADS) with spallation neutrons generated by the combined use of 100 MeV protons and a lead and bismuth target in the subcritical state. The reaction rates are measured by the foil activation method to obtain neutron spectrum information on ADS. Numerical calculations are performed with MCNP6.1 and JENDL/HE-2007 for high-energy protons and spallation process, JENDL-4.0 for transport and JENDL/D-99 for reaction rates. The reaction rates depend on subcriticality is revealed by the accuracy of the C/E (calculation/experiment) values. Nonetheless, the accuracy of the reaction rates at high-energy thresholds remains an important issue in the fixed-source calculations.

Journal Articles

Controlling the dissociative ionization of ethanol with 800 and 400 nm two-color femtosecond laser pulses

Yazawa, Hiroki*; Shioyama, Tadamasa*; Suda, Yoshitaka*; Yamanaka, Mio*; Kannari, Fumihiko*; Itakura, Ryuji; Yamanouchi, Kaoru*

Journal of Chemical Physics, 127(12), p.124312_1 - 124312_5, 2007/09

 Times Cited Count:10 Percentile:34.69(Chemistry, Physical)

Ethanol molecules were irradiated with a pair of temporally overlapping ultrashort intense laser pulses (10$$^{13}$$-10$$^{14}$$ W/cm$$^{2}$$ with different colors of 400 and 800 nm, and the dissociative ionization processes have been investigated. The yield ratio of the C-O bond breaking with respect to the C-C bond breaking was varied in the range of 0.17-0.53 sensitively depending on the delay time between the two laser pulses, and the absolute value of the yield of the C-O bond breaking was found to be increased largely when the Fourier-transform limited 800 nm laser pulse overlaps the stretched 400 nm laser pulse, demonstrating an advantage of the two-color intense laser fields in controlling chemical bond breaking processes.

Oral presentation

Innovative study on negative crystal formed in oxide

Serizawa, Hiroyuki; Haga, Yoshinori; Machida, Masahiko; Nakamura, Hiroki; Yamanaka, Shinsuke*; Oishi, Yuji*

no journal, , 

Because the shape of a negative crystal is closely related to the morphology of the crystal structure, its formation and growth mechanism is an important subject in the physical sciences. In addition, negative crystals formed in a large single-crystal mass have attracted interest as expensive jewellery because of their mysterious appearance and rarity. However, it is difficult to arbitrarily control the shapes of these polyhedral cavities embedded in a solid medium. Here, we report a discovery on the negative crystal growth process. We found that precipitated helium forms a negative crystal in UO$$_{2}$$; the shape changes dramatically with the conditions of helium precipitation. This article discusses the shape transformation mechanism. Our investigation implies that the shapes of negative crystals can be arbitrarily controlled by controlling the precipitation conditions.

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