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Am
)O
at high temperaturesMatsumoto, Taku; Arima, Tatsumi*; Inagaki, Yaohiro*; Idemitsu, Kazuya*; Kato, Masato; Morimoto, Kyoichi; Sunaoshi, Takeo*
Journal of Nuclear Science and Technology, 52(10), p.1296 - 1302, 2015/10
Times Cited Count：6 Percentile：45.92(Nuclear Science & Technology)The oxygen potentials of (PuAm)O were measured at 1873K, 1773K and 1473K by gas equilibrium method. It was shown that following the reduction of Am at the O/M ratio above 1.96, Pu was reduced at the O/M ratio below 1.96.
-PuO-ZrO pseudo-ternary systemMorimoto, Kyoichi; Hirooka, Shun; Akashi, Masatoshi; Watanabe, Masashi; Sugata, Hiromasa*
Journal of Nuclear Science and Technology, 52(10), p.1247 - 1252, 2015/10
Times Cited Count：4 Percentile：33.25(Nuclear Science & Technology)As a part of decommissioning plan of the damaged reactors at Fukushima Daiichi Nuclear Power Plant, some strategies for removing of debris from the reactors are discussed. In these considerations, it is necessary to predict a melt progression during the severe accident based on theoretical evidences. Melting temperature is one of the most important thermal characteristics to analyse a melt progression during the severe accident. In this study, the melting temperatures of specimens of U, Pu and Zr mixed oxide prepared as simulated debris were measured by the thermal arrest technique. From the results of this measurement, the influences of Pu
and Zr contents on the melting temperature of the simulated debris were evaluated.
and (U,Zr)O solid solution using MoCl
Sato, Takumi; Shibata, Hiroki; Hayashi, Hirokazu; Takano, Masahide; Kurata, Masaki
Journal of Nuclear Science and Technology, 52(10), p.1253 - 1258, 2015/10
Times Cited Count：6 Percentile：45.92(Nuclear Science & Technology)In order to explore the applicability of the chlorination by MoCl as a potential pretreatment technique for waste treatment of fuel debris by pyrochemical methods, chlorination experiments of UO and (U
Zr)O simulated fuel debris were carried out in two steps: the first one is a chlorination reaction by homogeneous heating, the second one is a volatilization of molybdenum by-product by heating under temperature gradient condition. Most of UO and (UZr)O powder were converted to UCl
or UCl and ZrCl mixture at 573 K, respectively. In the case of (UZr)Osintered particle, most of sample was converted to the chlorides because the products evaporated and be separated from sample surface at 773 K, while only the surface of the sample disk was converted to the chlorides at 573 and 673 K. Most of molybdenum by-product and ZrCl were separated from UCl by volatilization at 573 K.
C and 304L-type stainless steel materials used in BWRs in JapanShibata, Hiroki; Sakamoto, Kan*; Ouchi, Atsushi*; Kurata, Masaki
Journal of Nuclear Science and Technology, 52(10), p.1313 - 1317, 2015/10
Times Cited Count：16 Percentile：79.46(Nuclear Science & Technology)Chemical interactions between S.S. and BC may lead to the melting of control rods and subsequent relocation of control rod materials in the early stage of severe accident. The liquid products interact with the surroundings such as control rod blades, Zircaloy channel boxes and fuel rods, which may accelerate the fuel bundle degradation. Previous studies on the chemical interactions between S.S. and BC have been performed using the BC powders or pellets. However, almost all of control rods of BWR in Japan consist of granular BC filled in S.S. tubes. In the present study, the chemical reaction tests were carried out using the materials adopted in BWR in Japan, namely granular BC and 304L type S.S. and it was concluded that the kinetics of chemical interaction between S.S. and granular BC is clearly different from that between S.S. and pellet or powder BC.
Matsumoto, Yoshinobu*; Do, Thi-Mai-Dung*; Inoue, Masao; Nagaishi, Ryuji; Ogawa, Toru
Journal of Nuclear Science and Technology, 52(10), p.1303 - 1307, 2015/10
Times Cited Count：4 Percentile：33.25(Nuclear Science & Technology)Effects of zirconium oxides and oxidation products of zircaloy-4 on water radiolysis were investigated to predict the hydrogen generation from the water-immersed debris after a severe accident of a nuclear power plant. Observed yields of hydrogen in water containing the oxides were measured as a function of their weight fractions. Assuming that energies of Co-60 
-ray deposited to water and the oxides brought about the water radiolysis to generate hydrogen independently, the radiolysis showed an additional term of hydrogen generation due to the energy deposition to the oxides. This term seemed to be dependent on the specific surface area or particle size of oxides, but not on the crystal structure of oxides in our experimental results. The oxides in distilled water gave the strong enhancement of term. The enhancement tended to saturate with increasing the weight fraction of oxides and was not apparent in the seawater.
Tanaka, Kosuke; Sato, Isamu; Hirosawa, Takashi; Kurosaki, Ken*; Muta, Hiroaki*; Yamanaka, Shinsuke*
no journal, ,
Thermophysical properties of Ba(Pu
Am
)O
were examined and compared with data for BaPuO and other Ba and Sr ternary oxide compounds.
Akutsu, Yoko; Tanaka, Kosuke; Osaka, Masahiko
no journal, ,
I studied the new fuel for fast reactors which assumed molybdenum an inert matrix. The purpose of this study is to grasp the dissolution behavior in wet reprocessing. Therefore I produced a molybdenum compound of various kinds of composition that simulated Mo CERMET fuel. I carried out a examination using this and evaluated the characteristics such as sintering and dissolution rates.
studied by 
O-NMRTokunaga, Yo; Nishi, Tsuyoshi; Nakada, Masami; Ito, Akinori*; Sakai, Hironori; Kambe, Shinsaku; Homma, Yoshiya*; Honda, Fuminori*; Aoki, Dai*; Walstedt, R. E.*
no journal, ,
We will present the result of our recent NMR study performed to elucidate the origin of magnetic phase transition near 
K in AmO. To avoid complexities arising from sample aging associated with the alpha decay of 
Am, all measurements have been performed within 40 days after sample synthesis. Even during such a short period, however, a rapid change of NMR line shape has been observed at 1.5 K, suggesting that the ground state of AmO is very sensitive to disorder. We have also confirmed the loss of O NMR signal intensity over a wide temperature range below 
, and more than half of oxygen nuclei are undetectable at 1.5 K. This behavior reveals the persistence of slow and distributed spin fluctuations down to temperatures well below . The results are all indicative of short-range, spin-glass-like character for the magnetic transition in this system.
Iwata, Yoshihiro; Ito, Chikara; Sekine, Takashi; Osaka, Masahiko
no journal, ,
no abstracts in English
Takai, Toshihide; Nakajima, Kunihisa; Furukawa, Tomohiro; Osaka, Masahiko
no journal, ,
Improvement of the serve accident analysis code is important to evaluate the distribution of the released fission products (FPs) in the reactor more precisely from the view point of both the removal preparation of the fuel debris in the Fukushima Daiichi Nuclear Power Station and improved source term evaluation. The development of the calculation model, which can evaluate the effect of atmosphere and the chemical reaction between the released FPs and control rod material (BC) at elevated temperature, is important for this purpose. The measurement technique of the equilibrium vapor pressure using a high temperature mass spectrometer was under development to expand the thermodynamic database of the simulated FPs, because the chemical equilibrium analysis plays an important role to clarify the effect of chemical reactions. In this study, the apparatus was developed for the equilibrium vapor pressure measurements, and then the reliability of measurement results was evaluated.
-ray spectrometryIshimi, Akihiro; Katsuyama, Kozo; Miwa, Shuhei; Osaka, Masahiko
no journal, ,
The passive -ray spectrometry is under development as one of the non-destructive measurement for nuclear material accountancy for the fuel debris in the Fukushima-Daiichi Nuclear Power Station. In this technology, the amounts of nuclear materials are derived from the determined -emitting fission products by the -spectrometry by using predetermined relationships between FPs and the nuclear materials considering burnup, and so on. Based on the results of TMI-2 accident, Eu and Ce were selected as the candidate nuclides which are expected to accompany to nuclear material. The accompanying behavior of Ce to the nuclear material was investigated by the high temperature heating test and the chemical equilibrium calculation. This test was carried out under the simulated condition of severe accident that the irradiated fuel was liquefied by the high temperature reaction with molten zircaloy. Ce was found to exist in high concentration at the boundary of reaction layer between unreacted fuel and molten zircaloy.
Akashi, Masatoshi; Hirooka, Shun; Watanabe, Masashi; Komeno, Akira; Morimoto, Kyoichi
no journal, ,
Uranium oxide fuels containing GdO had been used to control fuel power in reactors of the Fukushima Daiichi Nuclear Power Plant where the severe accident occurred in 2011. JAEA has been evaluating physical properties of the molten fuel debris in the damaged core. However physical properties of the fuel debris containing Gd are not known, hence it is very difficult to select an appropriate debris removal method. Especially, it is important to know the distribution of Gd in the molten fuels for the evaluation of nuclear criticality safety during removal work. In this study, simulated samples of the molten fuel debris, which consisted of ZrO, UO and GdO, were prepared and their properties, which are density, crystal structure, thermal conductivity, thermal expansion and melting temperature, were investigated. This study includes results obtained under the research program entrusted to International Research Institute for Nuclear Decommissioning including Japan Atomic Energy Agency by Agency for Natural Resources and Energy, Ministry of Economy, Trade and Industry (METI) of Japan.
Usui, Takahiro*; Sawada, Akihiko; Amaya, Masaki; Suzuki, Akihiro*; Chikada, Takumi*; Terai, Takayuki*
no journal, ,
SiC coatings were fabricated on SUS316 and Zircaloy-4 substrate. Hydrogen permeation experiment and oxidation experiment were performed. From hydrogen permeation experiment to SiC coated specimen on SUS316 subsrate, permeability of specimen was smaller in one order in magnitude than that of uncoated. From oxidation experiment on Zircaloy-4 substrate, weight gain and thickness of oxide film decreased. Specimens with thicker coating has less weight gain than that with thinner coating, however, thicker coating was peeled off more than thinner coating after oxidized in 1200
C.
inert matrix fuelMiwa, Shuhei; Osaka, Masahiko
no journal, ,
Oxidation and reduction behaviors of a prototypic MgO-based inert matrix fuels (IMF) containing PuO were experimentally investigated by means of thermogravimetry. A dense disk-shaped prototypic MgO-based IMF containing PuO (MgO-PuO) was prepared by a powder metallurgy method. The oxidation and reduction kinetics and oxygen potentials of the MgO-PuO specimen were determined in the temperature range of 1273 K to 1473 K. The oxidation and reduction rates of the MgO-PuO were found to be notably low compared with those of PuO. On the other hand, the oxygen potentials of the MgO-PuO were the same level as those of PuO as a whole. However, it is of note that the oxygen potentials of MgO-PuO were lower than those of PuO near stoichiometry.
Sudo, Ayako; Nishi, Tsuyoshi; Shirasu, Noriko; Takano, Masahide; Kurata, Masaki
no journal, ,
Although Fe-B-C ternary system is a dominant phase diagram when considering the control blade degradation, phase relation data around eutectic composition were not sufficient. The phase relations of three Fe-B-C samples were analyzed by XRD and SEM/EDX and solidus were determined by DTA. The solidus detected in the present study was maintained at about 1400 K for all three samples, although preliminary calculation using conventional thermodynamic database estimated that solidus varies with roughly 50 K difference. The difference might be originated from the insufficient evaluation on the phase stability of Fe(B,C) in the database. The present results give useful information on improvement of iron-boron-carbon phase diagram.
Ito, Chikara; Ito, Keisuke; Naito, Hiroyuki; Nishimura, Akihiko; Oba, Hironori; Sekine, Takashi; Wakaida, Ikuo
no journal, ,
A high-radiation resistant optical fiber has been developed in order to investigate the interiors of the reactor pressure vessels and the primary containment vessels of the Fukushima Daiichi Nuclear Power Station. We have been developed a radiation resistant optical fiber, which consists of 1,000 ppm hydroxyl doped pure silica core and fluorine doped pure silica clad. The number of the core of image fibers has been increased from 2,000 to 22,000 of the practical use level. The transmissive rate of an infrared image was not affected after the irradiation of 1 MGy. The spatial resolution of the view scope by means of the image fiber was not changed between before and after irradiation. We have proposed the concept of applicability of the probing system that consists of view scope, remote ultimate analysis by laser induced breakdown spectroscopy and radiation monitor using the radiation-resistant optical fibers.
