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Oto, Tsutomu; Asano, Norikazu; Kawamata, Takanori; Yanai, Tomohiro; Nishimura, Arashi; Araki, Daisuke; Otsuka, Kaoru; Takabe, Yugo; Otsuka, Noriaki; Kojima, Keidai; et al.
JAEA-Review 2020-018, 66 Pages, 2020/11
JAEA-Review-2020-018.pdf:8.87MB
A collapse event of the cooling tower of secondary cooling system in the JMTR (Japan Materials Testing Reactor) was caused by the strong wind of Typhoon No.15 on September 9, 2019. The cause of the collapse of the cooling tower was investigated and analyzed. As the result, it was identified that four causes occurred in combination. Thus, the soundness of the cooling tower of Utility Cooling Loop (UCL cooling tower), which is a wooden cooling tower installed at the same period as the cooling tower of secondary cooling system, was investigated. The items of soundness survey are to grasp the operation conditions of the UCL cooling tower, to confirm the degradation of structural materials, the inspection items and inspection status of the UCL cooling tower, and to investigate the past meteorological data. As the results of soundness survey of the UCL cooling tower, the improvement of inspection items of the UCL cooling tower was carried out and the replacement and repair of the structural materials of the UCL cooling tower were planned for safe maintenance and management of this facility. And the renewal plan of new cooling tower was created to replace the existing UCL cooling tower. This report is summarized the soundness survey of the UCL cooling tower.
Tachi, Yukio; Nakazawa, Toshiyuki*; Ochs, M.*; Yotsuji, Kenji; Suyama, Tadahiro; Seida, Yoshimi; Yamada, Norikazu*; Yui, Mikazu
Radiochimica Acta, 98(9-11), p.711 - 718, 2010/11
Times Cited Count：25 Percentile：84.21(Chemistry, Inorganic & Nuclear)Diffusion and sorption of radionuclides in compacted bentonite are the key processes in the safe geological disposal. The effects of carbonate and salinity on Np(V) diffusion and sorption in compacted montmorillonite were investigated by experimental and modeling approaches. Effective diffusion coefficients (
) and distribution coefficients (
) of Np in montmorillonite compacted to dry density of 800 kg/m
were measured under four conditions with different salinities (0.05/0.5 M NaCl) and carbonate concentrations (0/0.01 M NaHCO
). The for carbonate-free conditions decreased as salinity increased, and those for carbonate conditions showed the opposite dependency. The decreased by one order of magnitude under high carbonate condition. Diffusion and sorption behaviors were interpreted by coupling the thermodynamic aqueous speciation, the thermodynamic sorption model based on ion exchange and surface complexation, and the diffusion model based on electrical double layer theory in narrow pores. The mechanistic model could be useful in predicting the sorption and diffusion behavior of complex species in compacted systems.
Seida, Yoshimi; Terashima, Motoki; Tachi, Yukio; Iijima, Kazuki; Nakazawa, Toshiyuki*; Yamada, Norikazu*; Yui, Mikazu
Radiochimica Acta, 98(9-11), p.703 - 709, 2010/11
Times Cited Count：3 Percentile：24.08(Chemistry, Inorganic & Nuclear)Diffusion and sorption behaviors of Eu in sedimentary rock were investigated in the presence of humic substance in the present study. Sedimentary rock obtained from Horonobe URL test site in Hokkaido, Japan, (accessible pore diameter is around several to several ten nanometer) was used. The Diffusion behaviors of Eu were examined based on reservoir depletion method coupled with analysis of inner distribution of the radioactive elements in the rock. Time sequence of concentration of each radioactive element as well as the humic substance in the reservoir was obtained as a function of concentration and molecular size of humic substance. Coexistence of humic substance reduced the depletion of Eu in the reservoir, indicating complexation between the radioactive elements and the humic substance. On the contrary, obvious decrease of humic substance in the reservoir was not observed in the system. This observation suggests that the radioactive elements became hard to diffuse into the sedimentary rock due to an increase of their size through complexation with the humic substance. The sorption of Eu was reduced with increase of the humic substance although the sorption of the humic substance was not influenced by the existence of Th or Eu. The diffusion and sorption of Eu were found to be reduced in the presence of humic substance.
Yamada, Fumitaka*; Yamachi, Hiroshi*; Sato, Toshinori; Funatsu, Takahiro*; Shimizu, Norikazu*
no journal, ,
no abstracts in English
Yamachi, Hiroshi*; Yamada, Fumitaka*; Sato, Toshinori; Funatsu, Takahiro*; Shimizu, Norikazu*
no journal, ,
no abstracts in English
Yamaguchi, Kohei; Oda, Chie; Nakazawa, Toshiyuki*; Yamada, Norikazu*; Takase, Toshio*
no journal, ,
In this research, the batch immersion experiment and the flow-through column experiment of granite and the artificial highperalkaline pore water were conducted, and the main geochemistry reaction was examined. A change with the lapse of time of the saturation index was calculated by the chemical equilibrium computation based on the batch immersion experiment result. The secondary mineral with the possibility of precipitation in the liquid phase based on the calculation result was extracted, and the combination was examined. In addition, the combination of these secondary minerals was applied to the flow-through column experiment result, and the liquid phase composition after the flow-through and the secondary mineral's spatial distribution were compared with geochemistry calculation (PHREEQC) result. As a result, it has been understood to have to understand the main geochemistry reaction paying attention at the precipitation rate of the secondary mineral in the future.
Mihara, Morihiro; Honda, Akira; Kamei, Gento; Nakazawa, Toshiyuki*; Yamada, Norikazu*
no journal, ,
no abstracts in English
Nakazawa, Toshiyuki*; Yamada, Norikazu*; Mihara, Morihiro; Honda, Akira; Kamei, Gento
no journal, ,
no abstracts in English
Seida, Yoshimi; Tachi, Yukio; Kitamura, Akira; Takahashi, Hiroaki; Nakazawa, Toshiyuki*; Yamada, Norikazu*
no journal, ,
no abstracts in English
Yamaguchi, Kohei; Oda, Chie; Nakazawa, Toshiyuki*; Yamada, Norikazu*; Takase, Toshio*
no journal, ,
High alkaline pore water runs out from a large amount of cementitious material used for the TRU waste disposal to the host rock, and there is a possibility that the migration characteristic of the nuclide. Here, the applicability of a chemical model in the environment with water flow was evaluated by the viewpoint of the solution composition and the precipitation composition by conducting the experiment that passed high alkaline solution to the column. As a result, a change with the lapse of time of the concentration was able to be reproduced almost for the solution composition. Moreover, the precipitation of Al was not able to be reproduced though Ca and Si were able to be wide in the column. The thermodynamics data of the secondary mineral including Al, the maintenance of the precipitation rate, and the applicability examination to the experiment result etc. are profitable as future tasks.
Mihara, Morihiro; Kamei, Gento; Nakazawa, Toshiyuki*; Yamada, Norikazu*
no journal, ,
To evaluate effects of nitrate on nuclide migration parameter, we performed solubility experiments of Np(IV), Tc(IV) and Se(0) with nitrated ion. The significant enhancements of the solubility were not observed since oxidization of nitrate ion. The dependency of solubility of Np(IV) with concentration of nitrate ion was simulated using modified stability constant and ion strength correction.
Nakazawa, Toshiyuki*; Yamada, Norikazu*; Mihara, Morihiro
no journal, ,
We performed solubility experiments for Pd and Nb to evaluate the effect of ammonia on the solubilities. Published solubility data of Pd were under the alkaline condition. Therefore, solubility experiments were carried out under neutral condition. Solubities of Nb were not increased, however those of Pd were increased.
Nakazawa, Toshiyuki*; Shimoda, Satoko*; Yamada, Norikazu*; Tachi, Yukio; Seida, Yoshimi*; Yui, Mikazu
no journal, ,
To set reliable parameters for the performance assessment (PA) of geological disposal, it is necessary to establish a reliable method for experimental evaluation and model prediction of sorption and diffusion in compacted bentonites. The through-diffusion and reservoir depletion experiments coupled with multiple curve analyses, including tracer depletion, breakthrough, and depth concentration curves were developed and applied for some systems including key radionuclides and geochemical conditions.
