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Nakano, Masanao; Fujii, Tomoko; Nagaoka, Mika; Inoue, Kazumi; Koike, Yuko; Yamada, Ryohei; Yoshii, Hideki*; Otani, Kazunori*; Hiyama, Yoshinori*; Kikuchi, Masaaki*; et al.
JAEA-Review 2019-045, 120 Pages, 2020/03
Based on the regulations (the safety regulation of Tokai Reprocessing Plant, the safety regulation of nuclear fuel material usage facilities, the radiation safety rule, the regulation about prevention from radiation hazards due to radioisotopes, which are related with the nuclear regulatory acts, the local agreement concerning with safety and environment conservation around nuclear facilities, the water pollution control law, and by law of Ibaraki Prefecture), the effluent control of liquid waste discharged from the Nuclear Fuel Cycle Engineering Laboratories of Japan Atomic Energy Agency has been performed. This report describes the effluent control results of the liquid waste in the fiscal year 2018. In this period, the concentrations and the quantities of the radioactivity in liquid waste discharged from the reprocessing plant, the plutonium fuel fabrication facilities, and the other nuclear fuel material usage facilities were much lower than the limits authorized by the above regulations.
Saito, Yoshimoto*; Hirano, Shinichi*; Nagaoka, Toru*; Amano, Yuki
Ecological Genetics and Genomics, 12, p.100042_1 - 100042_9, 2019/10
Culture-independent molecular techniques enable us to analyze microflora in various environments. Many uncultured prokaryotes have been detected by the molecular methods from extreme environments, including anaerobic, no light, high-pressure, and high temperature. Recently, microbial eukaryotes were also detected in deep-sea environments, suggesting that microbial eukaryotes can adapt to a wider range of environments than previously thought. Here, we performed a culture-independent analysis of eukaryotes from approximately -250 m depth in the Horonobe Underground Research Laboratory at Horonobe, Japan. Our results indicate that fungi are the dominant eukaryotic flora in deep sedimentary rocks of Horonobe. We detected a wide range of species, including Zygomycete, Basidiomycete, and Ascomycete fungi from the rocks. This study is the first report of eukaryotic diversity in deep subsurface sedimentary rocks.
Nakano, Masanao; Fujita, Hiroki; Mizutani, Tomoko; Nagaoka, Mika; Inoue, Kazumi; Koike, Yuko; Yamada, Ryohei; Yoshii, Hideki*; Hiyama, Yoshinori*; Otani, Kazunori*; et al.
JAEA-Review 2018-028, 120 Pages, 2019/02
Based on the regulations (the safety regulation of Tokai Reprocessing Plant, the safety regulation of nuclear fuel material usage facilities, the radiation safety rule, the regulation about prevention from radiation hazards due to radioisotopes, which are related with the nuclear regulatory acts, the local agreement concerning with safety and environment conservation around nuclear facilities, the water pollution control law, and by law of Ibaraki Prefecture), the effluent control of liquid waste discharged from the Nuclear Fuel Cycle Engineering Laboratories of Japan Atomic Energy Agency has been performed. This report describes the effluent control results of the liquid waste in the fiscal year 2017. In this period, the concentrations and the quantities of the radioactivity in liquid waste discharged from the reprocessing plant, the plutonium fuel fabrication facilities, and the other nuclear fuel material usage facilities were much lower than the limits authorized by the above regulations.
Nakano, Masanao; Fujita, Hiroki; Nagaoka, Mika; Inoue, Kazumi; Koike, Yuko; Yoshii, Hideki*; Hiyama, Yoshinori*; Otani, Kazunori*; Kikuchi, Masaaki*; Sakauchi, Nobuyuki*; et al.
JAEA-Review 2017-037, 119 Pages, 2018/03
Based on the regulations (the safety regulation of Tokai Reprocessing Plant, the safety regulation of nuclear fuel material usage facilities, the radiation safety rule, the regulation about prevention from radiation hazards due to radioisotopes, which are related with the nuclear regulatory acts, the local agreement concerning with safety and environment conservation around nuclear facilities, the water pollution control law, and bylaw of Ibaraki Prefecture), the effluent control of liquid waste discharged from the Nuclear Fuel Cycle Engineering Laboratories of Japan Atomic Energy Agency has been performed. This report describes the effluent control results of the liquid waste in the fiscal year 2016. In this period, the concentrations and the quantities of the radioactivity in liquid waste discharged from the reprocessing plant, the plutonium fuel fabrication facilities, and the other nuclear fuel material usage facilities were much lower than the limits authorized by the above regulations.
Nakano, Masanao; Fujita, Hiroki; Kono, Takahiko; Nagaoka, Mika; Inoue, Kazumi; Yoshii, Hideki*; Otani, Kazunori*; Hiyama, Yoshinori*; Kikuchi, Masaaki*; Sakauchi, Nobuyuki*; et al.
JAEA-Review 2017-001, 115 Pages, 2017/03
Based on the regulations (the safety regulation of Tokai reprocessing plant, the safety regulation of nuclear fuel material usage facilities, the radiation safety rule, the regulation about prevention from radiation hazards due to radioisotopes, which are related with the nuclear regulatory acts, the local agreement concerning with safety and environment conservation around nuclear facilities, the water pollution control law, and bylaw of Ibaraki prefecture), the effluent control of liquid waste discharged from the Nuclear Fuel Cycle Engineering Laboratories of Japan Atomic Energy Agency has been performed. This report describes the effluent control results of the liquid waste in the fiscal year 2015. In this period, the concentrations and the quantities of the radioactivity in liquid waste discharged from the reprocessing plant, the plutonium fuel fabrication facilities, and the other nuclear fuel material usage facilities were much lower than the limits authorized by the above regulations.
Hirano, Shinichi*; Nagaoka, Toru*; Ise, Kotaro; Amano, Yuki; Matsumoto, Norio*
Zairyo To Kankyo, 64(12), p.535 - 539, 2015/12
To obtain the knowledge about the corrosion ability and its mechanism as a target the soil environment microorganisms, lake mud was cultured with metallic iron. As a result, corrosion of carbon steel was observed with sulfate reduction and methane producing activity in brackish medium with lactate as substrate. Inhibition test of SRB and MPA suggested that SRB plays a major role for this corrosion, and MPA enhanced corrosion activity by the coexistence of SRB.
Hirano, Shinichi*; Nagaoka, Toru*; Matsumoto, Norio*; Amano, Yuki
no journal, ,
In this presentation, we will introduce case studies of microbial effects on engineering barrier systems in geological disposal systems. The results of the metal corrosion experiments using mixtures of Kunigel V1 and sand as a buffer material and anaerobic metal reducing microbial consortium will be presented in this talk.
Nagaoka, Toru*; Hirano, Shinichi*; Matsumoto, Norio*; Amano, Yuki
no journal, ,
Amano, Yuki; Beppu, Hikari*; Ono, Hirokazu; Taniguchi, Naoki; Hirano, Shinichi*; Matsumoto, Norio*; Nagaoka, Toru*
no journal, ,
Hirano, Shinichi*; Nagaoka, Toru*; Matsumoto, Norio*; Amano, Yuki
no journal, ,
no abstracts in English
Nagaoka, Toru*
no journal, ,
Spent nuclear fuel (SF) and other high-level radioactive wastes (HLW) from nuclear energy production must be stored safely for at least 100,000 years. The safety requirements for HLW and SF disposal call for metallic containers to remain intact for a long period of time. Microbial activity in bentonite buffer materials in deep geological repository is of concern for microbiologically influenced corrosion which could affect the longevity of metallic containers. In this lecture, laboratory examinations of microbial abundance and activities in compacted bentonite buffer materials will be introduced.
Sena, C.*; Molinero, J.*; Nagaoka, Toru*; Ajima, Shuji*; Ito, Tsuyoshi; Sasaki, Yoshito; Asano, Takahiro; Yoshikawa, Hideki
no journal, ,
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.
Nagaoka, Toru*; Hirano, Shinichi*; Matsumoto, Norio*; Amano, Yuki
no journal, ,
Nagaoka, Toru*; Hirano, Shinichi*; Kosaba, Takumi*; Amano, Yuki; Mochizuki, Akihito
no journal, ,
In-situ corrosion experiment of carbon steel coupons embedded in compacted bentonite were conducted in the subsurface environment at the Horonobe underground Research Laboratory. The experiment was carried out at the 250 m depth using boreholes. To simulate a small schale of geological disposal condition, compacted bentonite coupons in the test cells were made of 100% bentonite material (Kunigel V1) with different dry densities (1.0, 1.4, 1.6, 1.8 g/cm). After the installation, the test cells were collected after a certein period of time and measured the number of viable bacteria and analyzed microbial community stracture based on 16S rRNA gene. The carbon steel coupons were subjected to weight impairment measurements and analysis of corrosion products. The results showed that the weight of carbon steel coupons in compacted bentonite decreased at all conditions, but the amount of weight-loss tended to be greater at lower dry densities. The weight-loss was particularly large at the lowest dry density of 1.0 g/cm
, and corrosion was suppressed at dry densities of 1.4 g/cm
and higher. The corrosion rate tended to decrease in the later stages of the test compared to the early stages of the test. To evaluate the effect of microorganisms on the corrosion behavior, the number of viable bacteria in the collected bentonite samples was measured. The results showed that the number of aerobic bacteria tended to decrease with increasing dry density. In addition, 16S rRNA gene analysis showed that the composition of the microflora at high drying density was similar to that in the initial bentonite, while the microflora at low drying density was significantly altered. These findings suggest that microorganisms may be active in compacted bentonite at low dry density and promote corrosion.
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.
Hirano, Shinichi*; Nagaoka, Toru*; Kosaba, Takumi*; Amano, Yuki; Mochizuki, Akihito
no journal, ,
The effects of microbial corrosion induced by microorganisms have been reported for rapid corrosion and localized corrosion that occurs in environments that are not susceptible to chemical corrosion. In geological disposal projects where radioactive waste is buried deep underground, it is considered that radioactive waste should be encapsulated in an engineered barrier (overpack (metal disposal container), buffer material) and buried underground to ensure the confinement of the radioactive waste. Since a variety of microorganisms exist in the deep subsurface, it is necessary to consider the corrosive effects of microorganisms on the metal disposal container when evaluating the confinement performance of the engineered barriers. However, there have been limited studies on corrosion by microorganisms in the subsurface. Therefore, the objective of this study was to search for the presence of microorganisms causing iron corrosion in deep groundwater at the Horonobe Underground Research Laboratory and to evaluate their corrosion activity. Microorganisms in the groundwater collected from the Horonobe Underground Research Laboratory were cultured under anaerobic conditions with carbon steel coupons. As a result, methane gas was detected in some of the groundwater culture solutions, and a prefectural weight loss and localized surface thinning of the carbon steel specimens were observed. Analysis of the microbiota in the groundwater after incubation revealed an increase in the proportion of Methanobacterium spp. in the samples with corrosive activity, so further accumulation culture was conducted using iron granules to obtain Methanobacterium isolates. Based on the results of 16S rRNA gene sequence analysis of the isolate, we designated it as Methanobacterium sp. strain H04.
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.
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.
Nagaoka, Toru*; Hirano, Shinichi*; Matsumoto, Norio*; Amano, Yuki
no journal, ,
no abstracts in English