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Attachment Behavior of Fission Products to Solution Aerosol
Takamiya, Koichi,Tanaka, Toru,Nitta, Shinnosuke,Itosu, Satoshi,Sekimoto, Shun,Oki, Yuichi,Ohtsuki, Tsutomu The Korean Association for Radiation Protection 2016 방사선방어학회지 Vol.41 No.4
Background: Various characteristics such as size distribution, chemical component and radio-activity have been analyzed for radioactive aerosols released from Fukushima Daiichi Nuclear Power Plant. Measured results for radioactive aerosols suggest that the potential transport medium for radioactive cesium was non-sea-salt sulfate. This result indicates that cesium isotopes would preferentially attach with sulfate compounds. In the present work the attachment behavior of fission products to aqueous solution aerosols of sodium salts has been studied using a generation system of solution aerosols and spontaneous fission source of $^{248}Cm$. Materials and Methods: Attachment ratios of fission products to the solution aerosols were compared among the aerosols generated by different solutions of sodium salt. Results and Discussion: A significant difference according as a solute of solution aerosols was found in the attachment behavior. Conclusion: The present results suggest the existence of chemical effects in the attachment behavior of fission products to solution aerosols.
Oki, Yuichi,Tanaka, Toru,Takamiya, Koichi,Osada, Naoyuki,Nitta, Shinnosuke,Ishi, Yoshihiro,Uesugi, Tomonori,Kuriyama, Yasutoshi,Sakamoto, Masaaki,Ohtsuki, Tsutomu The Korean Association for Radiation Protection 2016 방사선방어학회지 Vol.41 No.3
Background: Very fine radiation-induced aerosol particles are produced in intense radiation fields, such as high-intensity accelerator rooms and containment vessels such as those in the Fukushima Daiichi nuclear power plant (FDNPP). Size measurement of the aerosol particles is very important for understanding the behavior of radioactive aerosols released in the FDNPP accident and radiation safety in high-energy accelerators. Materials and Methods: A combined technique using wire screens and imaging plates was developed for size measurement of fine radioactive aerosol particles smaller than 100 nm in diameter. This technique was applied to the radiation field of a proton accelerator room, in which radioactive atoms produced in air during machine operation are incorporated into radiation-induced aerosol particles. The size of $^{11}C$-bearing aerosol particles was analyzed using the wire screen technique in distinction from other positron emitters in combination with a radioactive decay analysis. Results and Discussion: The size distribution for $^{11}C$-bearing aerosol particles was found to be ca. $70{\mu}m$ in geometric mean diameter. The size was similar to that for $^7Be$-bearing particles obtained by a Ge detector measurement, and was slightly larger than the number-based size distribution measured with a scanning mobility particle sizer. Conclusion: The particle size measuring method using wire screens and imaging plates was successfully applied to the fine aerosol particles produced in an intense radiation field of a proton accelerator. This technique is applicable to size measurement of radioactive aerosol particles produced in the intense radiation fields of radiation facilities.
Origin of Spherule Samples Recovered from Antarctic Ice Sheet-Terrestrial or Extraterrestrial?
Sekimoto, Shun,Kobayashi, Takayuki,Takamiya, Koichi,Ebihara, Mitsuru,Shibata, Seiichi Korean Nuclear Society 2016 Nuclear Engineering and Technology Vol.48 No.2
Thirty-eight spherules from the Antarctic ice sheet were analyzed using neutron activation analysis under two different conditions to investigate their origin. In almost all of these spherules, the contents of iron, cobalt, and manganese were determined to be 31% to 88%, 17 mg/kg to 810 mg/kg, and 0.017% to 7%, respectively. A detectable iridium content of 0.84 mg/kg was found in only one spherule, which was judged to be extraterrestrial in origin. A comparison of elemental compositions of the Antarctic spherules analyzed in this study with those of deep-sea sediment spherules and those of terrestrial materials revealed that most of the Antarctic spherules except for the sample in which iridium was detected could not be identified as extraterrestrial in origin.
Characteristics of Radiation-Resistant Real-Time Neutron Monitor for Accelerator-Based BNCT
Nakamura, Takemi,Sakasai, Kaoru,Nakashima, Hiroshi,Takamiya, Koichi,Kumada, Hiroaki The Korean Association for Radiation Protection 2016 방사선방어학회지 Vol.41 No.2
Background: For an accelerator-based BNCT, we have fabricated a new detector consisting of quartz optical fibers that have excellent radiation-resistant characteristics. Materials and Methods: The developed detectors were irradiated at Kyoto University Research Reactor. Results and Discussion: The experimental results showed that the new detector had good output linearity for the neutron intensity, and the response of the new detector did not decrease during the irradiation. Conclusion: The new detector consisting of quartz optical fibers can be applied to measurement of neutron field of an accelerator-based BNCT.