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and zircalloy-2廣岡 瞬; 赤司 雅俊; 内田 哲平; 森本 恭一; 加藤 正人
Materials Research Society Symposium Proceedings, Vol.1444, p.97 - 101, 2012/09
被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)As a part of severe accident research in LWRs, physical and chemical properties of corium formed by meltdown of the reactor core have been studied. The corium consists of two kinds of phases, Zr-rich phase and U-rich phase. The U-rich phase has fluorite structure and Zr-rich phase has monoclinic structure which transforms to tetragonal and fluorite structure with temperature. These phase transformations with temperature change cause volume change and cracks. In this study, the corium was prepared from Zry-2 and UO, and thermal expansion was measured. Then, volume change with phase transformation was analyzed from the results.
神戸 振作; 酒井 宏典; 徳永 陽
Materials Research Society Symposium Proceedings, Vol.1444, p.165 - 168, 2012/09
被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)
波超伝導体では、超伝導クーパー対は磁気揺らぎによって誘起されている。実際、反強磁性磁気揺らぎエネルギーと超伝導転移温度は、高温超伝導体を含む波超伝導体で相関がある。この相関に加え、
電子系の新奇超伝導体では、磁気異方性と超伝導対称性に相関が見られる。反強磁性新奇超伝導にはXY型揺らぎが有利であり、強磁性新奇超伝導にはISING揺らぎが有利である。ここではXY型磁気異方性の起源について軌道角運動量とFermi面の観点から議論する。
米野 憲; 加藤 正人; 廣岡 瞬; 砂押 剛雄*
Materials Research Society Symposium Proceedings, Vol.1444, p.85 - 89, 2012/09
被引用回数：10 パーセンタイル：96.94(Materials Science, Multidisciplinary)Oxygen potentials of PuO were measured at temperatures of 1473-1873 K by thermo-gravimetry. The oxygen potentials were determined by 
analysis as functions of oxygen-to-metal ratio and temperature. The measurement data were analyzed on the basis of defect chemistry and an approximate equation was derived to represent the relationship among temperature, oxygen partial pressure, and deviation 
in PuO.
and zircalloy-2加藤 正人; 内田 哲平; 廣岡 瞬; 赤司 雅俊; 米野 憲; 森本 恭一
Materials Research Society Symposium Proceedings, Vol.1444, p.91 - 96, 2012/09
被引用回数：1 パーセンタイル：54.99(Materials Science, Multidisciplinary)Pellets of UO react with zircalloy (Zry) cladding to form corium in severe accident of LWRs. It is important to know thermal and chemical properties of corium to analyze fuel behavior in severe accident and to treat corium in post-accident. However, their data are limited. In this work, corium was prepared from UO and Zry-2, and its melting temperature and thermal conductivity were investigated as a parameter of U content. In the heating curves in the melting temperature measurement, thermal arrests were clearly observed. The solidus temperatures of 75%U, 50%U and 25%U-sample were determined to be 2622
C, 2509C and 2540C, respectively, which were consistent with solidus temperature reported in the UO-ZrO system. The melted samples were taken from W-capsule and sliced in a plate. Thermal diffusivity of the plate sample was measured. The data were lower than that of UO.
徳永 陽; 酒井 宏典; 神戸 振作; 中堂 博之; 逢坂 正彦; 三輪 周平; 西 剛史; 中田 正美; 伊藤 昭憲; 本間 佳哉*
Materials Research Society Symposium Proceedings, Vol.1444, p.149 - 158, 2012/00
被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)二酸化アクチノイドは原子力燃料としての応用がよく知られているが、アクチノイド化合物の基礎的な電子物性を系統的に理解するうえでも非常に重要な化合物群である。特に低温では電子特有の強いスピン-軌道相互作用を起源とした多彩な磁気状態が実現することが知られている。われわれはこれまで
O酸素核のNMR測定を通じて微視的観点から系統的な研究を行ってきた。最近ではアメリシウム化合物では初めてとなるNMR測定をAmOにおいて成功している。本講演ではこれまでの二酸化アクチノイドのNMR研究結果についての総括的に議論する予定である。
小川 徹; 沢 和弘
no journal, ,
VHTRのより高い燃焼度,燃料温度は次の2型の被覆粒子燃料の研究開発を促した。(1)従来型のTrisoを強化したもの、(2)ZrC-Triso.従来型のTrisoについてはSiC層のPd腐食と、SiCを通しての
Agの拡散放出のモデル化に注力した。CVD-SiC中の
Agの速い拡散については、自己媒介型のパーコレーション拡散モデルを開発している。同モデルではCVD-SiCの粒界の特殊性に着目した。ZrC被覆粒子燃料は特に従来型Trisoの耐熱限界の1600C以上で優れた特性を示した。ZrC被覆の品質保証のために、ポジトロン消滅スペクトロメトリーの応用を研究中である。ZrC被覆の短所としてRuの拡散係数が比較的大きい点が上げられる。これについても簡単に考察を加えた。
吹留 博一*; 小嗣 真人*; 大河内 拓雄*; 吉越 章隆; 寺岡 有殿; 遠田 義晴*; 木下 豊彦*; 末光 哲也*; 尾辻 泰一*; 末光 眞希*
no journal, ,
We have developed epitaxy of graphene on Si (GOS) and device operation of GOS-based field-effect transistor (GOS-FET). In this paper, we will demonstrate that the stacking, the interface structure, and the electronic properties of GOS can be controlled by tuning surface termination and symmetry of 3C-SiC(111)/Si, with a proper choice of Si substrate and SiC growth conditions. On the Si-terminated 3C-SiC(111)/Si(111) surface GOS is Bernal-stacked with a band splitting, while on the C-terminated 3C-SiC(111)/Si(110) surface GOS is turbostratically stacked without a band splitting. This novel epitaxy techniques enable us to precisely control electronic properties of GOS for the forthcoming devices. Furthermore, it is shown that the macroscopic uniformity of the GOS within a sizable area makes it possible to fabricate a topgate GOS-FET using Si device technologies.
小川 修一*; 山田 嵩壽*; 吉越 章隆; 石塚 眞治*; 渡辺 大輝*; 長谷川 雅考*; 寺岡 有殿; 高桑 雄二*
no journal, ,
Graphene on a diamond layer is required for fabrication of a graphene transistor. It has been reported the graphitization of diamond C(111) surface by annealing in vacuum. The aim of this study is to identify the sp2-bonded carbon layer and to clarify the grafitization mechanism on the diamond C(111) surface. Real-time photoemission spectroscopy using synchrotron radiation and ultraviolet was employed during annealing. The C 1s photoelectron spectra showed two peaks. The high binding energy (HBC) peak is attributed the bulk diamond, and the low binding energy (LBC) peak corresponds to the surface component of diamond C(111)-2
1 structure. The increase of LBC above 1173 K is not due to the increase of surface photoemission, but increase of sp2 component of graphene carbon. The graphitization of diamond was also indicated in C 1s energy loss spectra and ultraviolet spectra. Based on these results, the formation process of graphene on diamond is proposed.
小川 修一*; 山田 貴壽*; 吉越 章隆; 石塚 眞治*; 渡辺 大輝*; 長谷川 雅考*; 寺岡 有殿; 高桑 雄二*
no journal, ,
Diamond has been attracted as a substrate for graphene growth. It has been reported the graphitization of diamond C(111) surface by annealing in vacuum. The aim of this study is to identify the sp
-bonded carbon layer and to clarify the formation mechanism of a graphene layer on the diamond C(111) surface (GOD). In order to achieve this aim, real-time photoemission spectroscopy using synchrotron radiation (SR-XPS) and ultraviolet He I resonance line (UPS) was employed for investigation of vacuum annealing processes of C(111) surface. Graphitization of diamond surface is clearly observed from the analysis of C 1s energy loss spectra. The sp component comes out as a 21 reconstruction structure component goes in by annealing. This is also confirmed by UPS measurement. In the UPS spectra, the surface state peaks derived from dangling bonds can be clearly observed at low temperature. Based on these results, formation processes of GOD is proposed.
芳賀 芳範
no journal, ,
Heavy fermion superconductor is characterized by its heavy conduction electrons condensing in Cooper pairs. Particularly NpPd
Al is one of the recent examples in such materials. It shows superconductivity below 5 K with a large electronic specific heat in the normal state corresponding to the heavy fermion state. We developed a Faraday magnetometer suitable for radioactive material to investigate the magnetization characteristics at low temperature (0.1 K) and high field (15 T). Magnetization of NpPdAl clearly shows discontinuous change at the upper critical field, demonstrating the Pauli-limited first order transition. The present results are discussed in comparison with other rare-earth and actinide based heavy fermion superconductors.
