Non-infringement of U.S. patent by the Japan Atomic Energy Agency's proposed silicon carbide fuel matrix for HTGR

Fukaya, Yuji; Asano, Kazuhito; Sato, Hiroyuki; Ohashi, Hirofumi; Sakaba, Nariaki

JAEA-Review 2026-015, 10 Pages, 2026/06

JAEA-Review-2026-015.pdf:0.96MB

The Japan Atomic Energy Agency (JAEA) is developing SiC matrix fuel as a fuel to improve oxidation resistance. It is a simple manufacturing method called the slurry method, in which raw materials are dissolved in water, molded, and sintered, and are designed to pursue manufacturability in consideration of mass production. On the other hand, there is a patent in the U.S. for SiC matrix fuel, and it was expressed that there is a risk that the JAEA's SiC matrix fuel technology may infringe this patent, and it should be confirmed. In that case of infringement, it could become an obstacle to the social implementation of that technology. Therefore, in order to determine whether the SiC-based fuel for HTGR proposed by the JAEA would constitute a patent infringement against the aforementioned U.S. patent, JAEA requested a formal infringement evaluation from a major U.S. patent law firm. As a result, it was determined that the SiC-based fuel for high-temperature gas reactors proposed by the JAEA does not constitute a patent infringement against the aforementioned U.S. patent. This removed obstacles to the future deployment of the SiC matrix fuel proposed by the JAEA for high temperature gas-cooled reactors.

Spontaneous magnetization curve of -iron at high pressures determined using neutron diffraction

Aoki, Katsutoshi*; Takano, Masahiro*; Fukuyama, Ko*; Kagi, Hiroyuki*; Machida, Akihiko*; Saito, Hiroyuki*; Hattori, Takanori; Sano, Asami; Funakoshi, Kenichi*

Physical Review B, 113(18), p.184440_1 - 184440_6, 2026/05

https://doi.org/10.1103/vdnz-y1nk

The temperature dependence of the magnetic moment of bcc -iron was investigated over the range 300-950 K at pressures of approximately 2 and 6 GPa by neutron powder diffraction. The Fe isotope, whose neutron scattering length is approximately half that of naturally abundant Fe, was employed to enhance the relative contribution of magnetic scattering. Curie temperatures () were determined to be 946(30) K, 838(50) K and 740(40) K at 2.1, 6.0 and 6.7 GPa, respectively, defining a magnetic phase boundary described by (K) = 1043 - 49(7) + 1.3(1.2). Upon heating at 6.7 GPa, the structural transition was observed to follow the magnetic transition. This transition sequence indicates that the magnetic phase boundary lies on the low-temperature side of the phase boundary. Accordingly, the transition corresponds to a structural transformation from paramagnetic bcc to paramagnetic fcc iron.

Negligible hydrogen solubility in FeS under high-pressure and high-temperature conditions; Implications for hydrogen storage in planetary cores

Takano, Masahiro*; Kagi, Hiroyuki*; Mori, Yuichiro*; Kobayashi, Hiroki*; Aoki, Katsutoshi*; Takahashi, Yoshio*; Ijichi, Yuta*; Kakizawa, Sho*; Tsujino, Noriyoshi*; Higo, Yuji*; et al.

ACS Earth and Space Chemistry (Internet), 15 Pages, 2026/00

https://doi.org/10.1021/acsearthspacechem.5c00326

Iron monosulfide (FeS) is an important sulfide phase in planetary materials and has been proposed as a potential host of hydrogen in planetary interiors. However, hydrogen solubility in FeS at high pressure and temperature remains debated. In this study, hydrogen incorporation in the NiAs-type FeS phase (FeS V) was reexamined using synchrotron X-ray absorption spectroscopy, in situ X-ray and neutron diffraction, and first-principles calculations. The experimental results indicate that the volume expansion observed under hydrogen-saturated conditions is explained by the reduction of Fe to Fe and a decrease in the value of Fe-deficient FeS, rather than hydrogen incorporation into the lattice. These results suggest that hydrogen incorporation in FeS is extremely limited, with an upper bound of approximately 200 ppm up to 30 GPa.

Estimation of permeability and Forchheimer coefficient for non-uniform packed beds

Sano, Yoshihiko*; Ota, Kensuke*; Kuwahara, Fujio*; Uesawa, Shinichiro; Yoshida, Hiroyuki

Nihon Kikai Gakkai Netsu Kogaku Konfuarensu 2025 Koen Rombunshu, 1 Pages, 2025/10

To estimate the thermal behavior of fuel debris inside the Primary Containment Vessels (PCVs) of TEPCO's Fukushima Daiichi nuclear power station, a simulation method has been developed using the JUPITER code with porous medium models. However, it has been found that the selection of models and parameters according to the internal structure of the porous media significantly affects the accuracy of simulation results, highlighting the need for appropriate model selection strategies. In this study, we investigated methods for calculating macroscopic model constants that characterize flow behavior in porous media. These properties are influenced not only by the volume ratio of solid and gas phases but also by the structural features of the porous media. Focusing on packed beds composed of particles with varying diameters, we conducted numerical simulations to evaluate permeability and Forchheimer coefficient across diverse structural configurations. Based on the results, we propose a method for appropriately determining these parameters according to the structure of the packed bed, thereby contributing to the improvement of the porous media heat transfer and flow model.

Neutron diffraction study of the crystal and magnetic structures of antiferromagnetic manganese deuteride at high temperatures and high pressures

Machida, Akihiko*; Saito, Hiroyuki*; Aoki, Katsutoshi*; Komatsu, Kazuki*; Hattori, Takanori; Sano, Asami; Funakoshi, Kenichi*; Machida, Shinichi*; Sato, Toyoto*; Orimo, Shinichi*

Physical Review B, 111(22), p.224413_1 - 224413_6, 2025/06

https://doi.org/10.1103/yf8k-cy61

The crystal and magnetic structures of antiferromagnetic Mn deuterides formed by hydrogenating Mn metal at high temperature and high pressure, fcc -MnDx and hcp -MnDx, were investigated by in-situ neutron powder diffraction. Deuterium atoms partially occupied the octahedral interstitial positions of the fcc and hcp metal lattices. The site occupancies increased rapidly with decreasing temperature from 700 to 450 K and remained down to 300 K. Nel temperature of 543(10) K was determined for -MnD. For -MnD, saturation magnetic moment and Nel temperature were determined to be 0.82(1) and 347(3) K, respectively. The Nel temperatures determined for -MnD and -MnD are consistent with those predicted by the respective Slater-Pauling curves proposed in previous studies. The updated Nel temperatures provide insights into the development of more accurate Slater-Pauling curves based on electronic band structure calculations.

Addendum: Site occupancy of interstitial deuterium atoms in face-centred cubic iron

Machida, Akihiko*; Saito, Hiroyuki*; Sugimoto, Hidehiko*; Hattori, Takanori; Sano, Asami; Endo, Naruki*; Katayama, Yoshinori*; Iizuka, Riko*; Sato, Toyoto*; Matsuo, Motoaki*; et al.

Nature Communications (Internet), 15, p.8861_1 - 8861_2, 2024/10

https://doi.org/10.1038/s41467-024-52736-1

In our previous article (Nature Commun. 5, 5063 (2014)), the site occupancies of D atoms dissolved in an fcc Fe metal lattice were investigated via Rietveld refinement of neutron powder diffraction patterns collected at 988 K and 6.3 GPa. The fcc metal lattice has two interstitial sites available for accommodating D atoms: octahedral and tetrahedral sites. The Rietveld refinement revealed that D atoms occupied mainly the octahedral sites with occupancy of 0.532 and slightly the tetrahedral sites with occupancy of 0.056. Subsequent density-functional-theory (DFT) calculations by Antonov (Phys. Rev. Mater. 2019)) showed that the occupation energy on the tetrahedral site was significantly higher than that on the octahedral site; the tetrahedral site occupation was unlikely to occur even at temperatures as high as 988 K. We reexamined the site occupancies of D-atom by Rietveld refinement including extinction correction. As a result, the octahedral occupancy was increased to 0.60 and the tetrahedral occupancy was reduced to zero. The occupation of only the octahedral site for D atom is consistent with the DFT calculation, although in contrast to the previous results.

Stability enhancement by hydrophobic anchoring and a cross-linked structure of a phospholipid copolymer film for medical devices

Uchida, Kazuto*; Masuda, Tsukuru*; Hara, Shintaro*; Matsuo, Yoichi*; Liu, Y.*; Aoki, Hiroyuki; Asano, Yoshihiko*; Miyata, Kazuki*; Fukuma, Takeshi*; Ono, Toshiya*; et al.

ACS Applied Materials & Interfaces, 16(30), p.39104 - 39116, 2024/07

https://doi.org/10.1021/acsami.4c07752

Hydrogenation of silicon-bearing hexagonal close-packed iron and its implications for density deficits in the inner core

Mori, Yuichiro*; Kagi, Hiroyuki*; Aoki, Katsutoshi*; Takano, Masahiro*; Kakizawa, Sho*; Sano, Asami; Funakoshi, Kenichi*

Earth and Planetary Science Letters, 634, p.118673_1 - 118673_8, 2024/05

https://doi.org/10.1016/j.epsl.2024.118673

To investigate silicon effects on the hydrogen-induced volume expansion of iron, neutron diffraction and X-ray diffraction experiments were conducted to examine hcp-FeSi under high pressures and high temperatures. Neutron diffraction experiments were performed on the deuterated hcp-FeSi at 13.5 GPa and 900 K, and at 12.1 GPa and 300 K. By combining the P-V-T equation of state of hcp-FeSi, present results indicate that the hydrogen-induced volume expansion of hcp-FeSi is 10% greater than that of pure hcp iron. Using the obtained values, we estimated the hydrogen content that would reproduce the density deficit in the inner core, which was 50% less than that without the effect of silicon. Possible hydrogen content, , in the inner core and the outer core was calculated to be 0.07 and 0.12-0.15, respectively, when reproducing the density deficit of the inner core with hcp-FeSiHx.

The Hydrogen-bond network in sodium chloride tridecahydrate; Analogy with ice VI

Yamashita, Keishiro*; Nakayama, Kazuya*; Komatsu, Kazuki*; Ohara, Takashi; Munakata, Koji*; Hattori, Takanori; Sano, Asami; Kagi, Hiroyuki*

Acta Crystallographica Section B; Structural Science, Crystal Engineering and Materials (Internet), 79(5), p.414 - 426, 2023/10

https://doi.org/10.1107/S2052520623007199

The structure of a recently-found hyperhydrated form of sodium chloride, NaCl 13H(D)O, has been determined by single-crystal neutron diffraction at 1.7 GPa and 298 K. It has large hydrogen-bond networks and some water molecules have distorted bonding features such as bifurcated hydrogen bonds and five-coordinated water molecules. The hydrogen-bond network has similarities to ice VI in terms of network topology and disordered hydrogen bonds. Assuming the equivalence of network components connected by pseudo symmetries, the overall network structure of this hydrate can be expressed by breaking it down into smaller structural units which correspond to the ice VI network structure. This hydrogen-bond network contains orientational disorder of water molecules in contrast to the known salt hydrates. Here, we present an example for further insights into a hydrogen-bond network containing ionic species.

Effect of gas density and surface tension on liquid film thickness in vertical upward disturbance wave flow

Zhang, H.*; Mori, Shoji*; Hisano, Tsutomu*; Yoshida, Hiroyuki

International Journal of Multiphase Flow, 159, p.104342_1 - 104342_15, 2023/02

https://doi.org/10.1016/j.ijmultiphaseflow.2022.104342