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Yoshikawa, Takamichi*; Iwasaki, Tomohiko*; Wada, Kotaro*; Suyama, Kenya
Proceedings of American Nuclear Society Topical Meeting on Physics of Reactors (PHYSOR 2006) (CD-ROM), 8 Pages, 2006/09
To examine the procedures of the reprocessing, the vitrification and the geologic disposal, precise burn-up calculation for high burn-up and MOX fuels has been performed for not only PWR but also BWR by using SWAT and SWAT2 codes which are the integrated burn-up calculation code systems combined with the burn-up calculation code, ORIGEN2, and the transport calculation code, SRAC (the collision probability method) or MVP (the continuous energy Monte Carlo method), respectively. The calculation results shows that all of the evaluated items (heat generation and concentrations of Mo and Pt) largely increase and those significantly effect to the current procedures of the vitrification and the geologic disposal. The calculation result by SWAT2 confirms that the bundle calculation is required for BWR to be discussed about those effects in details, especially for the MOX fuel.
Yoshikawa, Takamichi*; Iwasaki, Tomohiko*; Endo, Hideki*; Suyama, Kenya; Shikoda, Keiji*; Yamada, Kohei*; Hamahata, Yoshiki*; Oeda, Shin*
no journal, ,
In order to develop a fuel design system of BWR based on opened calculation codes, a burnup code system SWAT2 using continuous energy Mote Carlo code was revised to include a function of branch calculation. A tool to evaluate lattice constants used in calculation code adopting modern nodal method was also developed and validated by comparison with CASMO.
Amano, Yuki; Nanjo, Isao; Iwatsuki, Teruki; Sasaki, Yoshito; Asano, Takahiro; Terashima, Motoki; Nagaoka, Toru*; Nakamura, Takamichi*; Yoshikawa, Hideki; Aoki, Kazuhiro
no journal, ,
In-situ experiment of redox reaction was conducted to assess the redox buffur capacity of water-rock-microbes system in the subsurface environment at 140 m depth of Horonobe Underground Research Laboratory. Dissolved oxygen was injected into a borehole, and the physico-chemical parameters (i.e. pH, ORP, DO, EC, etc.) and geochemical composition, microbial cell number, and microbial community structure were monitored continuously during the groundwater circulation. DO concentration could not detected after 10 hours from the injection. The concentration of Fe(II) was decreased with time, then the injected oxygen could be consumed by Fe(II). The rate of oxygen consumption during the experiment was 9.64 mg/L/day. The Eh value become stable at -208 mV after 5 days, then it showed that the reducing condition would be recovered quickly after closed condition.
Iwatsuki, Teruki; Sasaki, Yoshito; Ito, Tsuyoshi; Asano, Takahiro; Amano, Yuki; Yoshikawa, Hideki; Nakamura, Takamichi*; Nagaoka, Toru*
no journal, ,
Microbial activities and the reaction processes with groundwater and rock minerals up to 500 m below ground level were studied to infer the redox process and buffer capacity of rock materials for the articifitial disturbance such as facility construction at subsurface. Based on results of observation at in-situ and batch experiments, the geochemical modelling using PHREEQC-2 was carried out to develop the numerical simulation techniques on water-rock-microbe interaction system.
Yoshikawa, Hideki; Ito, Tsuyoshi; Sasaki, Yoshito; Asano, Takahiro*; Nagaoka, Toru*; Nakamura, Takamichi*
no journal, ,
This report shows that PHREEQC-2 code are used to analyzed a laboratory experimental for water-microbe interaction using a microbe collected from groundwater of Horonobe area, in order to evaluate influence by the microbe activity on the chemical composition of the water to contribute to the performance assessment of the disposal of the high-level radioactive waste. As a results, we understood that behavior such as the oxygen consumption could be estimated with the microbe influence.
Amano, Yuki; Iwatsuki, Teruki; Nanjo, Isao; Sasaki, Yoshito; Asano, Takahiro*; Yoshikawa, Hideki; Nagaoka, Toru*; Nakamura, Takamichi*
no journal, ,
In situ experiments for assessment of redox buffer capacity were conducted at 140 m depth of Horonobe Under Research Laboratory, and demonstrated to recover reducing condition from the oxidation condition by "water-rock-microbes" interactions.
Nagaoka, Toru*; Nakamura, Takamichi*; Sasaki, Yoshito; Asano, Takahiro*; Ito, Tsuyoshi*; Amano, Yuki; Iwatsuki, Teruki; Yoshikawa, Hideki
no journal, ,
Laboratory jar experiment was conducted with deep subsurface sedimentary rock and groundwater, in order to assess the response of the geochemical and microbial communities toward redox processes. The redox process was induced by exposure to air and discontinuation to sediment suspension, which simulated the process occurring during operation of nuclear waste repositories. As a results, after discontinuation of air exposure with lactate amendment, redox potentials decreased from ca. +100 mV to -600 m V (vs. Ag/AgCl), and some sequential terminal electron-accepting process (TEAPs) was observed with the reactions of aerobic respiration, iron reduction and hygrogen fermentation. The related species of the microbes along with TEAPs, e.g., Pseudomonas sp. for aerobic respiration and Shewanella sp. for iron reduction, was also detected. These results indicated that the microbial activities would affect the geochemical changes in nuclear repositories.