Thermal conductivity measurement of uranium-plutonium mixed oxide doped with Nd/Sm as simulated fission products

Horii, Yuta; Hirooka, Shun; Uno, Hiroki*; Ogasawara, Masahiro*; Tamura, Tetsuya*; Yamada, Tadahisa*; Furusawa, Naoya*; Murakami, Tatsutoshi; Kato, Masato

Journal of Nuclear Materials, 588, p.154799_1 - 154799_20, 2024/01

https://doi.org/10.1016/j.jnucmat.2023.154799

The thermal conductivities of near-stoichiometric (U,Pu,Am)O doped with NdO/SmO, which is major fission product (FP) generated by a uranium-plutonium mixed oxides (MOX) fuel irradiation, as simulated fission products are evaluated at 1073-1673 K. The thermal conductivities are calculated from the thermal diffusivities that are measured using the laser flash method. To evaluate the thermal conductivity from a homogeneity viewpoint of Nd/Sm cations in MOX, the specimens with different homogeneity of Nd/Sm are prepared using two kinds of powder made by ball-mill and fusion methods. A homogeneous Nd/Sm distribution decreases the thermal conductivity of MOX with increasing Nd/Sm content, whereas heterogeneous Nd/Sm has no influence. The effect of Nd/Sm on the thermal conductivity is studied using the classical phonon transport model (A+BT). The dependences of the coefficients A and B on the Nd/Sm content (C and C, respectively) are evaluated as: A(mK/W)=1.70 10 + 0.93C + 1.20C, B(m/W)=2.39 10.

Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex, 2; Neutron scattering instruments

Nakajima, Kenji; Kawakita, Yukinobu; Ito, Shinichi*; Abe, Jun*; Aizawa, Kazuya; Aoki, Hiroyuki; Endo, Hitoshi*; Fujita, Masaki*; Funakoshi, Kenichi*; Gong, W.*; et al.

Quantum Beam Science (Internet), 1(3), p.9_1 - 9_59, 2017/12

https://doi.org/10.3390/qubs1030009

The neutron instruments suite, installed at the spallation neutron source of the Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex (J-PARC), is reviewed. MLF has 23 neutron beam ports and 21 instruments are in operation for user programs or are under commissioning. A unique and challenging instrumental suite in MLF has been realized via combination of a high-performance neutron source, optimized for neutron scattering, and unique instruments using cutting-edge technologies. All instruments are/will serve in world-leading investigations in a broad range of fields, from fundamental physics to industrial applications. In this review, overviews, characteristic features, and typical applications of the individual instruments are mentioned.

SENJU; A New time-of-flight single-crystal neutron diffractometer at J-PARC

Ohara, Takashi; Kiyanagi, Ryoji; Oikawa, Kenichi; Kaneko, Koji; Kawasaki, Takuro; Tamura, Itaru; Nakao, Akiko*; Hanashima, Takayasu*; Munakata, Koji*; Moyoshi, Taketo*; et al.

Journal of Applied Crystallography, 49(1), p.120 - 127, 2016/02

https://doi.org/10.1107/S1600576715022943

Emergency monitoring of environmental radiation and atmospheric radionuclides at Nuclear Science Research Institute, JAEA following the accident of Fukushima Daiichi Nuclear Power Plant

Okura, Takehisa; Oishi, Tetsuya; Taki, Mitsumasa; Shibanuma, Yukio; Kikuchi, Masamitsu; Akino, Hitoshi; Kikuta, Yasuaki; Kawasaki, Masatsugu; Saegusa, Jun; Tsutsumi, Masahiro; et al.

JAEA-Data/Code 2012-010, 37 Pages, 2012/05

JAEA-Data-Code-2012-010.pdf:2.28MB

Due to the accident at Fukushima Daiichi Nuclear Power Plant caused by the 2011 off the Pacific coast of Tohoku Earthquake occurred at 11th March 2011, the emergency environmental radiation monitoring was conducted at Nuclear Science Research Institute, Japan Atomic Energy Agency (JAEA). This report provides the monitoring results of ambient -ray dose rate and atmospheric radioactivity concentration until the beginning of June 2011. Some anthropogenic radionuclides such as Cs-134, Cs-137, I-131, I-132, Te-132, Xe-133 and others were detected from air samples. The atmospheric radioactivity concentrations varied with some peaks corresponded with that of ambient -ray dose rate after 15th March 2011. Composition of each peak showed various characteristic. Internal exposure caused by inhalation was estimated from the observed atmospheric radioactivity.

Oxygen chemical diffusion in hypo-stoichiometric MOX

Kato, Masato; Morimoto, Kyoichi; Tamura, Tetsuya*; Sunaoshi, Takeo*; Konashi, Kenji*; Aono, Shigenori; Kashimura, Motoaki

Journal of Nuclear Materials, 389(3), p.416 - 419, 2009/06

https://doi.org/10.1016/j.jnucmat.2009.02.018

Plutonium and uranium mixed oxide (MOX) has been developed to use as a core fuel of the fast reactor. The oxygen to metal ratio (O/M) of the MOX fuel is an important parameter to control the FCCI. The oxygen potential and the oxygen diffusion coefficient of the MOX are essential data to understand the oxygen behaviour in MOX. The oxygen potentials of the MOX were measured with accuracy as a function of O/M and temperatures in the previous work. In this work the oxygen chemical diffusion coefficient in (PuU)O and (PuU)O were investigated using thermo gravimetric technique. The kinetics of the reduction processes of (PuU)O and (PuU)O were measured by TG-DTA method. The oxygen chemical diffusion coefficients have been estimated from the reduction curves. It was concluded that the oxygen chemical diffusion coefficient in (PuU)O is a smaller than that of (PuU)O.

Characterization of electrode/electrolyte interface using X-ray reflectometry and LiNiCoO epitaxial film electrode synthesized by pulsed laser deposition method

Hirayama, Masaaki*; Sakamoto, Kazuyuki*; Hiraide, Tetsuya*; Mori, Daisuke*; Yamada, Atsuo*; Kanno, Ryoji*; Sonoyama, Noriyuki*; Tamura, Kazuhisa; Mizuki, Junichiro

Electrochimica Acta, 53(2), p.871 - 881, 2007/12

https://doi.org/10.1016/j.electacta.2007.07.074

An experimental technique was developed for detecting structure changes at the electrode/electrolyte interface of lithium cell using synchrotron X-ray reflectometry and two-dimensional model electrodes with a restricted lattice plane. The electrode was constructed with an epitaxial film of LiNiCoO synthesized by the pulsed laser deposition method. These films provided an ideal reaction field suitable for detecting structure changes at the electrode/electrolyte interface during the electrochemical reaction. The X-ray reflectometry indicated a formation of a thin-film layer at the LiNiCoO (1 1 0)/electrolyte interface during the first charge-discharge cycle, while the LiNiCoO (0 0 3) surface showed an increase in the surface roughness without forming the surface thin-film layer.

Evaluation of thermal physical properties for fast reactor fuels; Melting point and thermal conductivities

Kato, Masato; Morimoto, Kyoichi; Komeno, Akira; Nakamichi, Shinya; Kashimura, Motoaki; Abe, Tomoyuki; Uno, Hiroki*; Ogasawara, Masahiro*; Tamura, Tetsuya*; Sugata, Hiromasa*; et al.

JAEA-Technology 2006-049, 32 Pages, 2006/10

JAEA-Technology-2006-049.pdf:19.46MB
JAEA-Technology-2006-049(errata).pdf:0.32MB

Japan Atomic Energy Agency has developed a fast breeder reactor(FBR), and plutonium and uranium mixed oxide (MOX) having low density and 20-30%Pu content has used as a fuel of the FBR, Monju. In plutonium, Americium has been accumulated during long-term storage, and Am content will be increasing up to 2-3% in the MOX. It is essential to evaluate the influence of Am content on physical properties of MOX on the development of FBR in the future. In this study melting points and thermal conductivities which are important data on the fuel design were measured systematically in wide range of composition, and the effects of Am accumulated were evaluated. The solidus temperatures of MOX were measured as a function of Pu content, oxygen to metal ratio(O/M) and Am content using thermal arrest technique. The sample was sealed in a tungsten capsule in vacuum for measuring solidus temperature. In the measurements of MOX with Pu content of more than 30%, a rhenium inner capsule was used to prevent the reaction between MOX and tungsten. In the results, it was confirmed that the melting points of MOX decrease with as an increase of Pu content and increase slightly with a decrease of O/M ratio. The effect of Am content on the fuel design was negligible small in the range of Am content up to 3%. Thermal conductivities of MOX were evaluated from thermal diffusivity measured by laser flash method and heat capacity calculated by Nuemann- Kopp's law. The thermal conductivity of MOX decreased slightly in the temperature of less than 1173K with increasing Am content. The effect of Am accumulated in long-term storage fuel was evaluated from melting points and thermal conductivities measured in this study. It is concluded that the increase of Am in the fuel barely affect the fuel design in the range of less than 3%Am content.

Oxygen Potentials of Plutonium and Uranium Mixed Oxide

Kato, Masato; Aono, Shigenori; Tamura, Tetsuya*; Konashi, Kenji*

Journal of Nuclear Materials, 344, p.235 - 239, 2005/00

https://doi.org/10.1016/j.jnucmat.2005.04.048

The oxygen potentials of (PuU)O near stoichiometric region were measured by thermogravimetric technique which was used to establish the equilibrium between the oxide phases and H/HO system gas. The experimental results of (PuU)O give a consistent picture variation in Po with O/M and the temperature with other works. The relationship between the partial oxygen pressure and X in MOwas evaluated by the lattice defect theory. The relation in hypo-stoichiometric region is xPo near stoichiometric composition, and changes to xPo with a decrease in O/M.

Development of low decontaminated MOX fuel containing MA II; Sintering property and phase stability of MOX containing Np, Am and FPs

Kato, Masato; ; ; *; Tamura, Tetsuya*; Sunaoshi, Takeo*; *

JNC TN8400 2003-014, 151 Pages, 2003/05

JNC-TN8400-2003-014.PDF:11.66MB

JNC has been developing low decontaminated MOX fuel containing Miner Actinide (MA) for advanced FBR. It is very important for the fuel development to investigate sintering properties and physical properties of the fuel. In this paper, the influence of oxygen partial pressure during sintering on sintering behavior and migration of MA and FPs in MOX pellets containing Np/Am and simulated FP have been studied. The results of the examination are as follows. (1)The pellets sintered in atmosphere of high oxygen partial pressure have homogeneous composition and large grain size. Additive Ln elements promote homogenization and restrain grain growth in the pellets. (2)O/M ratio of the sintered pellets could be controlled to 1.95 by heat treatment of appropriate temperature, time and oxygen partial pressure. Phase separation was observed in the pellets with O/M=1.95. (3)Pu-Am-Ln compounds precipitated in the pellets with Ln. The form of precipitation of Pu-Am-Ln compounds changed depending on sintering conditions. (4)Y and Zr were distributed homogeneously in the pellet not depending on the sintering condition and it is considered that Ru, Rh and Pd are precipitated with metallic particle or alloy of this particles.

Oxygen potential of (Pu,U)O I -Oxygen potential measurement of UO and (PuU)O

Kato, Masato; Tamura, Tetsuya*; Endo, Hideo

JNC TN8400 2002-020, 76 Pages, 2003/03

JNC-TN8400-2002-020.pdf:2.1MB

The ratio of oxygen to metal is one of important fuel specifications on UO and MOX fuels, because it effect on irradiation behavior. Oxygen potential of oxide fuels have been measured by various methods on the purpose of optimization of irradiation behavior and fabrication condition. In this repot the oxygen potential of UO and (PuU)O was measured by thermal gravimetry and differential thermal analysis (TG-DTA). Measurements of oxygen potential were carried out at 800C, 1000C and 1200C in Ar/H/HO mixture gas flow. Ratio of O/M was obtained from the weight change of the sample according to the partial oxygen pressure that was controlled by H/HO ratio in atmosphere. The partial oxygen pressure in atmosphere was measured by stabilized zyrconia oxygen sensor. The experimental results agree approximately to the other works. Thermodynamic data, Go, Ho, So, were evaluatedfrom the experimental data. The oxygen potential of UO, (Pu,U)O and PuO was modeled by lattice defect theory using the data of the literature and this work. The resulting equation well reproduce the large amount of oxygen potential-temperature-composition data for the Pu-U oxide system.