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Oral presentation

Radiochemical analysis of rubble collected from reactor buildings at Fukushima Daiichi Nuclear Power Station

Aono, Ryuji; Sato, Yoshiyuki; Konda, Miki; Tanaka, Kiwamu; Ueno, Takashi; Ishimori, Kenichiro; Kameo, Yutaka

no journal, , 

A large amount of contaminated rubble was generated by the accident at the Fukushima Daiichi Nuclear Power Station (F1NPS). For safe decommissioning of F1NPS, it is important to evaluate the composition and concentration of radionuclides in the rubble. To characterize the rubble collected at F1NPS, radiochemical analysis was conducted. From the rubble collected from reactor buildings, $$^3$$H, $$^{14}$$C, $$^{60}$$Co, $$^{63}$$Ni, $$^{79}$$Se, $$^{90}$$Sr, $$^{99}$$Tc, $$^{129}$$I, $$^{137}$$Cs, $$^{154}$$Eu, $$^{238, 239+240}$$Pu, $$^{241}$$Am and $$^{244}$$Cm were detected. The radioactivity concentrations of $$^{60}$$Co, $$^{90}$$Sr and $$^{238}$$Pu are correlated that of $$^{137}$$Cs. The radioactive ratio of $$^{60}$$Co/$$^{137}$$Cs, $$^{90}$$Sr/$$^{137}$$Cs and $$^{238}$$Pu/$$^{137}$$Cs were similar between the rubble collected from 1st floor and 5th floor of unit 1 reactor building. This result implied that regardless of sampling location in reactor building, the radioactive ratios of $$^{60}$$Co/$$^{137}$$Cs, $$^{90}$$Sr/$$^{137}$$Cs and $$^{238}$$Pu/$$^{137}$$Cs were consistent.

Oral presentation

Basic study on radiolysis of potassium nickel ferrocyanide

Arai, Yoichi; Watanabe, So; Takahatake, Yoko; Nakamura, Masahiro; Nomura, Kazunori; Nakajima, Yasuo

no journal, , 

Potassium nickel ferrocyanide (KNiFC) is one of the most effective adsorbents for decontamination of $$^{137}$$Cs in the radioactive waste solutions. Although the ferrocyanides are known to be chemically stable, HCN and H$$_{2}$$ gases are suspected to be generated by radiolysis. Generations of those gases should be suppressed or controlled in order to prevent hazards. In this study, $$gamma$$ ray irradiation experiment on KNiFC absorbing Cs was carried out to evaluate stability of used ferrocyanides. $$gamma$$ ray irradiation was performed using $$^{60}$$Co source, and the integrated dose was 0.13-6.0 MGy. After the irradiation, concentrations of H$$_{2}$$ gas, of CN$$^{-}$$ and of Cs were analyzed. G-value of H$$_{2}$$ calculated from the concentration of H$$_{2}$$ gas showed that generation of H$$_{2}$$ gas prompted by adding KNiFC into water. And the Cs charge in the compound did not influenced on the G-value. Therefore, concentration of H$$_{2}$$ gas in the tank for the used KNiFC has to be attenuated by ventilation. Although analyses on CN$$^{-}$$ and Cs revealed that KNiFC is stable up to 3 MGy irradiation, small amounts of them were observed in the liquid phase after 6 MGy irradiation.

Oral presentation

Characterization of carbonate slurry waste from multi-radionuclide removal system in Fukushima Daiichi Nuclear Power Station

Hinai, Hiroshi; Shibata, Atsuhiro; Nomura, Kazunori

no journal, , 

Multi-Radionuclide Removal System (MRRS) has been operating to decontaminate the contaminated water in Fukushima Daiichi Nuclear Power Station. Although this system removes most of the radioactive materials, significant amount of secondary radioactive wastes (slurry, spent adsorbent) were generated subsequently to the treatment. In particularly, because of the high radioactivity and the abundance of generation amount, the carbonate slurry waste is required to characterize preferentially. It is necessary to various properties investigation for selecting suitable treatment and disposal methods. Therefore, the carbonate slurry samples taken from the MRRS were transferred from Fukushima Daiichi Nuclear Power Station to the Chemical Processing Facility (CPF) in Nuclear Fuel Cycle Engineering Laboratories of Japan Atomic Energy Agency (JAEA), and was analyzed for radioactivity, amount of element composition and particle size distribution. The radioactive analysis showed that the main nuclides of carbonate slurry were Sr-90/Y-90. In addition, small amount of alpha-ray emitting nuclides was determined. As the result of elemental analysis, it is estimated that most of slurry are composed by CaCO$$_{3}$$ and Mg(OH)$$_{2}$$. The median particle diameter of carbonate slurry samples was found to be several micrometre.

Oral presentation

Development of determination methods for $$beta$$ ray emitting nuclides at CPF

Motoyama, Risa; Hinai, Hiroshi; Ichige, Yoshiaki; Shibata, Atsuhiro; Nomura, Kazunori

no journal, , 

Various properties of radioactive wastes generated at the Fukushima Daiichi Nuclear Power Station have been analyzed at Chemical Processing Facility (CPF) in Japan Atomic Energy Agency (JAEA) to contribute to their future treatment and disposal studies. The radioactive concentration of $$beta$$ ray emitting nuclides is one of the essential information as well as those of $$alpha$$ ray and $$gamma$$ ray emitting nuclides. It needs to develop separation and purification methods for each $$beta$$-emitter from unfamiliar mediums to the nuclear fuel cycle field. Due to the restrictions of the facility, these methods should avoid using halogen reagents. The steady analysis procedures of H-3, Sr-90 and I-129 have been already developed and in practice. Among them, the analysis method of I-129 will be presented and the determination method for Se-79 will be reported as issue currently under consideration.

Oral presentation

Development of novel analytical methods for measurement of radioactive elements

Do, V. K.; Yamamoto, Masahiko; Taguchi, Shigeo; Kuno, Takehiko; Miura, Katsue; Iwasaki, Maho; Sato, Soichi

no journal, , 

Technical support for environmental restoration of Fukushima and decommissioning of Fukushima Daiichi Nuclear Power Station (1F) are the most important mission of Japan Atomic Energy Agency (JAEA). In this presentation, we outline Okuma Analysis and Research Center and our mission on technical development for analyzing rubble and wastes from the decommissioning of 1F. Novel analytical methods are being developed at the center for determining difficult-to-measure nuclides. In addition, some analytical techniques based on liquid electrode plasma optical emission spectrometry, a novel optically spectroscopic method, for measuring elemental composition of highly active liquid wastes is reported.

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