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Suzuki, Eriko; Takase, Gaku; Nakajima, Kunihisa; Nishioka, Shunichiro; Hashimoto, Naoyuki*; Isobe, Shigehito*; Osaka, Masahiko
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR 2019) (Internet), 4 Pages, 2019/05
In order to acquire the knowledge of the Cs chemisorption behaviour in the lower temperature region, the Cs chemisorbed compounds and the surface reaction rates were investigated by conducting the Cs chemisorption tests onto stainless steel at 873 and 973 K. As a result, The cesium ferrate compounds were revealed to be formed at this temperatures. It was seen that the dependences of surface reaction rate constant on this temperature were different from that at the higher temperature region. This behaviour leads to the conclusion that the Cs chemisorption model in the low temperature region should be newly constructed.
Pshenichnikov, A.; Kurata, Masaki; Nagae, Yuji; Yamazaki, Saishun
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR 2019) (Internet), 4 Pages, 2019/05
Hidaka, Akihide; Himi, Masashi*; Addad, Y.*
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR 2019) (Internet), 4 Pages, 2019/05
no abstracts in English
Furusawa, Akinori; Nishimura, Akihiko; Takenaka, Yusuke; Muramatsu, Toshiharu
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR 2019) (Internet), 4 Pages, 2019/05
The aim of this work presented here is to demonstrate the potential of our method for remote controllable systematization, of testing reinforced concrete based on ultrasonic guided-wave on rebar. In order to investigate how the deteriorated phenomena has the effects on the ultrasonic guided-wave propagating on the rebar, following experiments are conducted. Test pieces used for the experiments are made of bare steel rod and cylindrically pored mortar to be representing the actual reinforced concrete. Irradiating the end face of the rod with nanosecond pulsed laser makes the ultrasonic guided-wave induced, at the other end face, the guided wave signal is measured with ultrasonic receiver. One test piece is with no damage and the other is deteriorated test piece. The deterioration is made by electrolytic corroded method. The guided-wave signal from the deteriorated test piece is measured with respect to each energization time, the change in the waveform is investigated. Analyzing the results from the experiments above, it is found that the deterioration of rebar has remarkable effects on the guided-wave signal. The signal from test piece with no damage has strong peak at both specific frequency and lower region, on the other hand, signals from deteriorated test piece has only at the specific frequency depending on the diameter of the steel rod. Finally, discussion concerning with the experimental results and future perspective for remote controllable systematization of our method is carried out.
Shirasu, Noriko; Suzuki, Akihiro*; Nagae, Yuji; Kurata, Masaki
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR 2019) (Internet), 4 Pages, 2019/05
High temperature interaction tests between UO
and Zr were performed at around 2173 K, to make clear the UO/ 
-Zr(O) interaction and the mechanism of degradation, for developing the improved models for advanced severe accident analysis codes. A Zr plate was inserted in a UO crucible, and heat treated at 2173 K in stream of Ar. After the heat-treatment, the samples were subjected to surface microanalysis. The middle region of Zr sample shows streak-like structures which are extended towered the top. It is confirmed that the streak-like structures were mainly consist of U from the EDX results, and the structures revealed that the U-rich phase was liquid during the heat-treatment. It seems that the U-rich liquid grew selectively toward the area where the oxygen concentration was low.
Nakayoshi, Akira; Ikeuchi, Hirotomo; Kitagaki, Toru; Washiya, Tadahiro; Bouyer, V.*; Journeau, C.*; Piluso, P.*; Excoffier, E.*; David, C.*; Testud, V.*
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR 2019) (Internet), 4 Pages, 2019/05
Takahatake, Yoko; Koma, Yoshikazu
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR 2019) (Internet), 4 Pages, 2019/05
Tanifuji, Yuta; Kawabata, Kuniaki
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR 2019) (Internet), 4 Pages, 2019/05
Liu, J.; Dotsuta, Yuma; Kitagaki, Toru; Kozai, Naofumi; Yamaji, Keiko*; Onuki, Toshihiko
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR 2019) (Internet), 2 Pages, 2019/05
To decommission the Fukushima Daiichi Nuclear Power Plant (FDNPP), it is necessary to estimate the current status of fuel debris and predicate the possible change under various condition. Some microorganisms may enter the plant due to the seawater injection after accident and future defueling activity. In this study, microbial influence on fuel debris under aerobic condition was experimentally investigated. By culturing some bacteria in the presence of simulant fuel debris in liquid medium, the microbial degradation of fuel debris was observed.
Mohamad, A.*; Nakajima, Kunihisa; Suzuki, Eriko; Miwa, Shuhei; Osaka, Masahiko; Oishi, Yuji*; Muta, Hiroaki*; Kurosaki, Ken*
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR 2019) (Internet), 4 Pages, 2019/05
In the accident of Fukushima Daiichi Nuclear Power Station, formation of a volatile SrCl could have occurred by the sea-water injection into the core. This can cause the release of non-volatile group Sr from the fuel to induce chemical reactions with reactor structural materials, such as stainless steel and Zircaloy (Zry) cladding. Such reactions could cause the changes in distribution of Sr in the reactor. Chemical reactions between Sr species and Zry were therefore investigated experimentally. As the result, it can be said that Sr vapor species were chemically trapped right after the release from fuel. This trapping effect of Sr by Zry-cladding implies a possibility of preferable Sr retention in the oxide phase of debris.
Imoto, Jumpei; Miwa, Shuhei; Osaka, Masahiko
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR 2019) (Internet), 4 Pages, 2019/05
Boron (B) oxidative vaporization processes from the representative alloys of Fe-B and Zr-B formed in the mixed melt of BWR control material boron carbide, stainless steel and Zircaloy were experimentally investigated toward the construction of B release model under severe accident. The results show that B oxidative vaporization from ZrB would proceed in the formation of ZrO and BO
due to the oxidation of ZrB, followed by the formation of volatile H-B-O vapor species by the reaction of BO with steam. On the other hand, for FeB and FeB, the B oxidative vaporization processes would proceed in the same manner. Complex Fe-B-O compounds formation in addition to amorphous BO were observed by the oxidation of FeB and FeB. Then the B vaporization would occur by the formation of volatile H-B-O compound by the reaction of BO, which were derived from both oxidation of FeB and decomposition of Fe-B-O compounds.
Hanari, Toshihide; Kawabata, Kuniaki
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR 2019) (Internet), 4 Pages, 2019/05
In this paper, we propose a method for improving a visibility of a reconstructed 3D model from images that were photographed at Fukushima Daiichi Nuclear Power Station (NPS). The process of the proposed method consists of pre-processing for correcting a quality of the images, Structure from Motion (SfM) and post-processing for generating a 3D model. We describe the results of the 3D structural reconstruction utilizing plural images recorded by an underwater Remotely Operated Vehicle (ROV) inside the Primary Containment Vessel (PCV). We discussed about the experimental results and confirmed that the proposed method reconstructed major structure in the PCV based on the images.
Nishimura, Akihiko; Yoshida, Minoru*; Yamada, Tomonori; Arakawa, Ryoki
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR 2019) (Internet), 3 Pages, 2019/05
JAEA support the development of remote sensing robotic system in the Naraha Remote Technology Development Center. A water tank is used as a mockup facility of nuclear reactor vessel. A compact seismic vibrometer based on an optical fiber interferometer is applied. A specially designed robotic system is also tested for installing the sensor unit. The experiment is prepared to clarify the transfer function of the water tank, using vibration noise of ground motion.
Hinai, Hiroshi; Sato, Daisuke; Shibata, Atsuhiro; Myodo, Masato; Koma, Yoshikazu; Nomura, Kazunori
no journal, ,
We have been analyzing and characterizing the contaminated water generated in Fukushima Daiichi Nuclear Power Station (NPS) and secondary waste of the contaminated water treatment system for investigation of their waste management. As one of the contaminated water treatment system, Decontamination Device was operated from June until September 2011. The operation of this device generated secondary waste of sludge that have a high dose rate. In this device, the contaminated water was mixed with several reagents to remove some radioactive nuclides. As the result, the sludge was generated as a complex of chemically stable substances. This sludge has been stored in a concrete pit and is required to transport to another place of the site and treat for further storage. For the purposes and upcoming disposal, a small amount of the sludge was analyzed for its radioactivity, particle size distribution and others. For radiochemical analysis, the sludge was successfully dissolved into solutions and was measured for its radioactivity composition; the main nuclides were Sr-90 and Cs-137. The concentration of Sr-90 (6.6E7 [Bq/cm
]) was about 10 times higher than that of Cs-137 in the sludge. And small amount of Pu-238 as alpha-ray emitting nuclide was determined. The sludge mainly contained small particles of 10 micro meter or less in diameter. The rate of sedimentation and behavior of mixing also investigated.
Nitta, Ayako; Hinai, Hiroshi; Shibata, Atsuhiro; Nomura, Kazunori; Oki, Keiichi; Koma, Yoshikazu
no journal, ,
Liu, X.; Machida, Masahiko; Saito, Kimiaki; Tanimura, Naoki*
no journal, ,
To extract the space dependent ecological half-lives from car-borne survey data, a linear sparse model with LASSO regularization and Bayesian background has been developed. The model has been applied to analysis the KURAMA data in Fukushima Prefecture in 2011-2016. The fitting results are in reasonably good agreement with previous works, and could be studied other space dependent factors.
Mizokami, Masato*; Suzuki, Akihiro*; Maeda, Koji; Ito, Kenichi*; Sato, Ikken; Mizokami, Shinya*
no journal, ,
Some radioactive material samples were taken inside the PCV of Fukushima Daiichi Units 1-3. TEPCO is working for sample collection, transport, and detailed examinations at hot cells using SEM, TEM and ICP-MS. Uranium-bearing micro-particles were analysed using SEM and Emit was confirmed that particles derived from fuel can be categorized into two groups. One is believed to have been separated from hot corium by hydrodynamic processes, while the other showed characteristics suggesting evaporation from hot corium and condensation afterward. The former particles might have compositional features common to the major part of fuel debris. Both groups possibly cause alpha contamination (actinide behavior) in the reactor building.
production under gamma irradiationCantarel, V.; Arisaka, Makoto; Yamagishi, Isao
no journal, ,
The present study aimed at completing previous results on geopolymer H production under irradiation, taking into account physical phenomena such as gas diffusion. Experimental data showed the consumption of hydrogen by the wasteform itself under irradiation provided hydrogen diffusion was slow enough or the sample large enough. Sample with the same water content and same internal chemistry were shown to have very different effective radiolytic yield by modification of the sample dimensions (100 times smaller for a 40 cm long cylinder compared to the powder of the same sample). A simple model taking in account only hydrogen gas diffusion in the sample, its production and a pseudo first order reaction for the H consumption allowed to predict correctly the effective experimental hydrogen production. A strong dependency between H production, wasteform dimensions and sample permeation properties was highlighted and understood. This difference in our vision of hydrogen production opens new horizons for active waste immobilization.
Miyabe, Masabumi; Oba, Masaki; Akaoka, Katsuaki; Wakaida, Ikuo
no journal, ,
Remote analysis of highly radioactive materials including actinide elements and fission products is a necessary technology for decommissioning of the Fukushima Daiichi Nuclear Power Plant. However, due to the intense radioactivity, it is difficult for the analysis engineer to directly handle the analytical samples, and the application of traditional radiochemical analysis is considered to be difficult. Therefore, we are developing a remote analytical technique by combining atomic absorption spectrometry and laser ablation technique requiring no sample pretreatment. When a solid sample is irradiated with a intense laser pulse, part of the surface materials evaporates and is decomposed into monoatomic species to form an ablation plume. When another laser beam tuned to the resonance frequency of the isotope of interest is intersected with the plume, the isotope ratio can be determined from the comparison of the absorbance for each isotope since only the isotope atoms absorb the laser light. In order to reduce the effects of the Doppler effect and the Stark effect to realize sensitive and isotope-selective analysis, it is necessary to optimize the experimental conditions. Thus, we measured the absorption spectra with various experimental conditions, and investigate variations in the spectral line-width and the absorbance. The experimental conditions for higher sensitivity were determined from the laser-induced fluorescence image of the plume observed at various observation timing. By evaluating the analytical performance of U and Pu using the obtained optimum conditions, it was demonstrated that this analytical technique is applicable to the isotope analysis of decommissioning related substances.
Meier, R.; Kitagaki, Toru; Onuki, Toshihiko*
no journal, ,
During severe accident scenarios, actinides can volatilize and subsequently react with ferrous metal in different parts of the reactors. Their behavior and potential release to the environment needs to be investigated. To this end, this study investigates high temperature reactions of actinides with ferrous metals. A focused light was used as a heating device and the heated materials were analysed by SEM-EDS and XRD to acquire information about the formed phases and specific sorption phenomena on steel surface. This study provides fundamental information about the distribution and chemical properties of actinide compounds potentially formed in the damaged reactor vessel, as well as their vapor and aerosol behavior, for the planned decommissioning of the Fukushima NPPs.