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論文

Transport model comparison studies of intermediate-energy heavy-ion collisions

Walter, H.*; Colonna, M.*; Cozma, D.*; Danielewicz, P.*; Ko, C. M.*; Kumar, R.*; 小野 章*; Tsang, M. Y. B*; Xu, J.*; Zhang, Y.-X.*; et al.

Progress in Particle and Nuclear Physics, 125, p.103962_1 - 103962_90, 2022/07

原子核-原子核衝突や原子核の状態方程式の研究において、反応計算モデルは重要なツールとなり、世界中で開発が進んでいる。本論文は、原子力機構のJQMD-2.0を含め、現在開発中の複数のコード開発者の協力により、これらコードを同じ条件で比較することで共通点や差異を明らかにしたプロジェクトTransport Model Evaluation Project (TMEP)を総括したものである。参加したコードはBoltzmann-Uehling-Uhlenbeck(BUU)法に基づく13のコードと、Quantum Molecular Dynamics (QMD)法に基づく12のコードであった。プロジェクトでは、Au原子核同士を衝突させてその終状態を観測する現実的な計算や、一辺が640nmの箱に核子を詰めて時間発展させる仮想的な計算を行った。その結果、BUU法コードとQMD法コードは計算原理が異なるため、計算の設定に関係なく系統的な差異が生じることが明らかになった。その一方で、同じ方法を採用するコード間の比較では、時間発展を細かく計算することでコード間の差は埋まっていき、一定の収束値を持つことが示された。この結果は今後開発される同分野のコードのベンチマークデータとして有用なものであるだけでなく、原子核基礎物理学の実験や理論研究の標準的な指針としても役に立つことが期待される。

論文

Multipole polaron in the devil's staircase of CeSb

新井 陽介*; 黒田 健太*; 野本 拓也*; Tin, Z. H.*; 櫻木 俊輔*; Bareille, C.*; 明比 俊太朗*; 黒川 輝風*; 木下 雄斗*; Zhang, W.-L.*; et al.

Nature Materials, 21(4), p.410 - 415, 2022/04

Low-energy electronic structures of CeSb which shows multiple phase transitions known as devil's staircase were examined by combination of laser angle-resolved photoemission, Raman and neutron scattering spectroscopies. A new type of electron-boson coupling between the mobile electrons and quadrupole CEF-excitations of the 4f orbitals was found. The coupling is exceedingly strong and exhibits anomalous step-like enhancement during the devil's staircase transition, unveiling a new type of quasiparticle, named multipole polaron.

論文

Metalloid substitution elevates simultaneously the strength and ductility of face-centered-cubic high-entropy alloys

Wei, D.*; Wang, L.*; Zhang, Y.*; Gong, W.; 都留 智仁; Lobzenko, I.; Jiang, J.*; Harjo, S.; 川崎 卓郎; Bae, J. W.*; et al.

Acta Materialia, 225, p.117571_1 - 117571_16, 2022/02

Recently-developed high-entropy alloys (HEAs) containing multiple principal metallic elements have ex-tended the compositional space of solid solutions and the range of their mechanical properties. Here we show that the realm of possibilities can be further expanded through substituting the constituent metals with metalloids, which are desirable for tailoring strength/ductility because they have chemical interactions and atomic sizes distinctly different from the host metallic elements. Specifically, the metalloid substitution increases local lattice distortion and short-range chemical inhomogeneities to elevate strength, and in the meantime reduces the stacking fault energy to discourage dynamic recovery and encourage defect accumulation via partial-dislocation-mediated activities. These impart potent dislocation storage to improve the strain hardening capability, which is essential for sustaining large tensile elongation. As such, metalloid substitution into HEAs evades the normally expected strength-ductility trade-off, enabling an unusual synergy of high tensile strength and extraordinary ductility for these single-phase solid solutions.

論文

Suppression of vacancy formation and hydrogen isotope retention in irradiated tungsten by addition of chromium

Wang, J.*; 波多野 雄治*; 外山 健*; 鈴土 知明; 檜木 達也*; Alimov, V. Kh.*; Schwarz-Selinger, T.*

Journal of Nuclear Materials, 559, p.153449_1 - 153449_7, 2022/02

タングステン(W)マトリックス中のクロム(Cr)添加が空孔形成と水素同位体吸蔵に及ぼす影響を調べるために、W-0.3Cr合金サンプルに6.4MeV Feイオンを523-1273Kの温度範囲で照射した。これらの弾き出し損傷サンプルを673KでD$$_{2}$$ガスにさらした。Wマトリックスに0.3%のCrを添加すると、特に高温照射後の純Wと比較して重水素の吸蔵が大幅に減少した。1073Kで照射されたW-0.3Cr合金の陽電子寿命は、照射されていないものとほぼ同じであった。これらの事実は、0.3%のCr添加によって空孔タイプの欠陥の形成が抑制されたことを示している。

論文

Benchmark analysis of ductile fracture simulation for circumferentially cracked pipes subjected to bending

熊谷 知久*; 三浦 靖史*; 三浦 直樹*; Marie, S.*; Almahdi, R.*; 真野 晃宏; Li, Y.; 勝山 仁哉; 和田 義孝*; Hwang, J.-H.*; et al.

Journal of Pressure Vessel Technology, 144(1), p.011509_1 - 011509_18, 2022/02

延性材料の破壊挙動を予測するため、いくつかの延性破壊シミュレーション手法が提案されている。ただし、これらの手法には実機器への適用性に関する懸念がある。本研究では、パラメータの決定を含めたシミュレーション手法の予測能力を確認するため、実機器を想定した破壊試験に関する2つの問題を設定し、ベンチマーク解析を実施した。1つ目の問題は、周方向の表面亀裂及び貫通亀裂を有する配管に対する単調曲げ荷重負荷試験、2つ目の問題は、周方向貫通亀裂を有する配管に対する繰り返し曲げ荷重負荷試験である。ベンチマークの参加機関は、独自に選択した手法によって延性亀裂進展挙動を予測した。用いられた手法は、ボイド率基準を有するGurson-Tvergaard-Needleman(GTN)モデルに基づく有限要素法(FEM)、応力三軸度により修正される破壊ひずみ基準また破壊エネルギー基準に基づくFEM、Jまたは$$Delta$$J基準に基づく拡張FEM及び弾塑性粒子法等である。単調曲げ荷重負荷試験に関しては、すべての手法によるシミュレーションの結果が配管の変形と亀裂進展の挙動を精度よく再現し、シミュレーション手法の実機器への適用性が確認された。一方、繰り返し曲げ荷重負荷試験におけるこれらの挙動については、ほとんどの手法で再現できなかった。今後材料の繰り返し硬化特性等を考慮したパラメータの決定手法についてさらなる検討が必要であることを確認した。

論文

Ten years after the NPP accident at Fukushima; Review on fuel debris behavior in contact with water

Grambow, B.; 二田 郁子; 柴田 淳広; 駒 義和; 宇都宮 聡*; 高見 龍*; 笛田 和希*; 大貫 敏彦*; Jegou, C.*; Laffolley, H.*; et al.

Journal of Nuclear Science and Technology, 59(1), p.1 - 24, 2022/01

 被引用回数:0 パーセンタイル:0.37(Nuclear Science & Technology)

Following the NPP accident, some hundred tons of nuclear fuel elements of 3 damaged nuclear reactor units were partly molten with even larger masses of steel and concrete structures, creating a big mass of corium and fuels debris. Since ten years, this heat generating mass has been cooled permanently by millions of m$$^{3}$$ of water flowing over them. Knowledge on the interaction of this solid mass with water is crucial for any decommissioning planning. Starting from analyses of the evolutions of the accident in the 3 reactor cores and associated fuel debris formations and some additional isotopic and physiochemical information of debris fragments collected in soils of Fukushima, we review the temporal evolution of the chemistry and leached radionuclide contents of the cooling water. Measured concentration ratios of the actinides and fission products in the water where compared to reported results of laboratory leaching studies with either spent nuclear fuel or simulated fuel debris under a variety of simulated environmental conditions.

論文

Long decay length of magnon-polarons in BiFeO$$_{3}$$/La$$_{0.67}$$Sr$$_{0.33}$$MnO$$_{3}$$ heterostructures

Zhang, J.*; Chen, M.*; Chen, J.*; 山本 慧; Wang, H.*; Hamdi, M.*; Sun, Y.*; Wagner, K.*; He, W.*; Zhang, Y.*; et al.

Nature Communications (Internet), 12(1), p.7258_1 - 7258_8, 2021/12

Magnons can transfer information in metals and insulators without Joule heating, and therefore are promising for low-power computation. The on-chip magnonics however suffers from high losses due to limited magnon decay length. In metallic thin films, it is typically on the tens of micrometre length scale. Here, we demonstrate an ultra-long magnon decay length of up to one millimetre in multiferroic/ferromagnetic BiFeO$$_{3}$$(BFO)/La$$_{0.67}$$Sr$$_{0.33}$$MnO$$_{3}$$ (LSMO) heterostructures at room temperature. This decay length is attributed to a magnon-phonon hybridization and is more than two orders of magnitude longer than that of bare metallic LSMO. The long-distance modes have high group velocities of 2.5 km$$^{-1}$$ as detected by time-resolved Brillouin light scattering. Numerical simulations suggest that magnetoelastic coupling via the BFO/LSMO interface hybridizes phonons in BFO with magnons in LSMO. Our results provide a solution to the long-standing issue on magnon decay lengths in metallic magnets and advance the bourgeoning field of hybrid magnonics.

論文

The $$^{59}$$Fe(n,$$gamma$$)$$^{60}$$Fe cross section from the surrogate ratio method and its effect on the $$^{60}$$Fe nucleosynthesis

Yan, S. Q.*; Li, X. Y.*; 西尾 勝久; Lugaro, M.*; Li, Z. H.*; 牧井 宏之; Pignatari, M.*; Wang, Y. B.*; Orlandi, R.; 廣瀬 健太郎; et al.

Astrophysical Journal, 919(2), p.84_1 - 84_7, 2021/10

 被引用回数:0

The long-lived $$^{60}$$Fe (with a half-life of 2.62 Myr) is a crucial diagnostic of active nucleosynthesis in the Milky Way galaxy and in supernovae near the solar system. The neutron-capture reaction $$^{59}$$Fe(n,$$gamma$$)$$^{60}$$Fe on $$^{59}$$Fe (half-life=44.5 days) is the key reaction for the production of $$^{60}$$Fe in massive stars. This reaction cross section has been previously constrained by the Coulomb dissociation experiment, which offered partial constraint on the E1 $$gamma$$-ray strength function but a negligible constraint on the M1 and E2 components. In this work, for the first time, we use the surrogate ratio method to experimentally determine the $$^{59}$$Fe(n,$$gamma$$)$$^{60}$$Fe cross sections in which all the components are included. We derived a Maxwellian-averaged cross section of 27.5$$pm$$3.5 mb at $$kT$$ = 30 keV and 13.4$$pm$$1.7 mb at $$kT$$ = 90 keV, roughly 10%-20% higher than previous estimates. We analyzed the impact of our new reaction rates in nucleosynthesis models of massive stars and found that uncertainties in the production of $$^{60}$$Fe from the $$^{59}$$Fe(n,$$gamma$$)$$^{60}$$Fe rate are at most 25$$%$$. We conclude that stellar physics uncertainties now play a major role in the accurate evaluation of the stellar production of $$^{60}$$Fe.

論文

Temperature effects on local structure, phase transformation, and mechanical properties of calcium silicate hydrates

Im, S.*; Jee, H.*; Suh, H.*; 兼松 学*; 諸岡 聡; 小山 拓*; 西尾 悠平*; 町田 晃彦*; Kim, J.*; Bae, S.*

Journal of the American Ceramic Society, 104(9), p.4803 - 4818, 2021/09

 被引用回数:0 パーセンタイル:0.02(Materials Science, Ceramics)

This study aims to elucidate the effect of heating on the local atomic arrangements, structure, phase transformation, and mechanical properties of synthesized calcium-silicate-hydrate (C-S-H). The alteration in the atomic arrangement of the synthesized C-S-H (Ca/Si = 0.8) and the formation of crystalline phases that occurred in three distinct transformation stages of dehydration (105-200 $$^{circ}$$C), decomposition (300-600 $$^{circ}$$C), and recrystallization (700-1000 $$^{circ}$$C) were investigated via powder X-ray diffraction, $$^{29}$$Si nuclear magnetic resonance spectroscopy, and thermogravimetric analysis. Further, the deformation of the local atomic bonding environment and variations in mechanical properties during the three stages were assessed via pair distribution function analysis based on in-situ total X-ray scattering. The results revealed that the C-S-H paste before heating exhibited a lower elastic modulus in real space than that in the reciprocal space in the initial loading stage because water molecules acted as a lubricant in the interlayer. At the dehydration stage, the strain as a function of external loading exhibited irregular deformation owing to the formation of additional pores induced by the evaporation of free moisture. At the decomposition stage, the structural deformation of the main d-spacing (d $$approx$$ 3.0 ${AA}$) was similar to that of the real space before the propagation of microcracks. At the recrystallization stage, the elastic modulus increased to 48 GPa owing to the thermal phase transformation of C-S-H to crystalline $$beta$$-wollastonite. The results provide direct experimental evidence of the micro- and nanostructural deformation behavior of C-S-H pastes after exposure to high temperature under external loading.

論文

Half-integer Shapiro steps in strong ferromagnetic Josephson junctions

Yao, Y.*; Cai, R.*; Yang, S.-H.*; Xing, W.*; Ma, Y.*; 森 道康; Ji, Y.*; 前川 禎通; Xie, X.-C.*; Han, W.*

Physical Review B, 104(10), p.104414_1 - 104414_6, 2021/09

 被引用回数:0 パーセンタイル:0(Materials Science, Multidisciplinary)

We report the experimental observation of half-integer Shapiro steps in the strong ferromagnetic Josephson junction (Nb-NiFe-Nb) by investigating the current-phase relation under radio-frequency microwave excitation. The half-integer Shapiro steps are robust in a wide temperature range from T = 4 to 7 K. The half-integer Shapiro steps could be attributed to co-existence of 0- and $$pi$$-states in the strong ferromagnetic NiFe Josephson junctions with the spatial variation of the NiFe thickness. This scenario is also supported by the high-resolution transmission electron microscopy characterization of the Nb/NiFe/Nb junction.

論文

Measurement of $$^{237}$$Np and $$^{243}$$Am fission reaction rates in lead region at A-core of KUCA

大泉 昭人; 方野 量太; 児島 亮平; 福島 昌宏; 辻本 和文; Pyeon, C. H.*

KURNS Progress Report 2020, P. 104, 2021/08

加速器駆動未臨界システム(ADS)の研究開発において、マイナーアクチノイド(MA)の核データ検証に資する反応率の実験データの拡充は重要である。本研究では、京都大学臨界実験装置(KUCA)で局所的に構築した鉛と高濃縮ウランの混合装荷領域において、ウラン-235($$^{235}$$U)に対するネプツニウム-237($$^{237}$$Np)及びアメリシウム-243($$^{243}$$Am)の各核分裂反応率比を核分裂計数管で測定した。その結果、$$^{237}$$Np/$$^{235}$$U及び$$^{243}$$Am/$$^{235}$$Uは、それぞれ0.048$$pm$$0.003及び0.042$$pm$$0.004となった。ここで得られた実験結果は、今後核データの検証に用いられる。

論文

New $$alpha$$-emitting isotope $$^{214}$$U and abnormal enhancement of $$alpha$$-particle clustering in lightest uranium isotopes

Zhang, Z. Y.*; Yang, H. B.*; Andreyev, A. N.; Liu, M. L.*; Ma, L.*; 他37名*

Physical Review Letters, 126(15), p.152502_1 - 152502_6, 2021/04

 被引用回数:0 パーセンタイル:0(Physics, Multidisciplinary)

A new $$alpha$$-emitting isotope $$^{214}$$U, produced by the fusion-evaporation reaction $$^{182}$$W($$^{36}$$Ar,4n)$$^{214}$$U, was identified by employing the gas-filled recoil separator SHANS and the recoil-$$alpha$$ correlation technique. More precise $$alpha$$-decay properties of even-even nuclei $$^{216,218}$$U were also measured in the reactions of $$^{40}$$Ar, $$^{40}$$Ca beams with $$^{180,182,184}$$W targets. By combining the experimental data, improved $$alpha$$-decay reduced widths $$delta$$$$^{2}$$ for the even-even Po-Pu nuclei in the vicinity of the magic neutron number ${it N}$ = 126 are deduced. Their systematic trends are discussed in terms of the ${it N}$ $$_{it p}$$ ${it N}$ $$_{it n}$$ scheme in order to study the influence of proton-neutron interaction on $$alpha$$ decay in this region of nuclei. It is strikingly found that the reduced widths of $$^{214,216}$$U are significantly enhanced by a factor of two as compared with the ${it N}$ $$_{it p}$$ ${it N}$ $$_{it n}$$ systematics for the 84 $$leq$$ ${it Z}$ $$leq$$ 90 and ${it N}$ $$<$$ 126 even-even nuclei. The abnormal enhancement is interpreted by the strong monopole interaction between the valence protons and neutrons occupying the $$pi$$1${it f}$ $$_{7/2}$$ and $$nu$$1${it f}$ $$_{5/2}$$ spin-orbit partner orbits, which is supported by the large-scale shell model calculation.

論文

Origin of magnetovolume effect in a cobaltite

Miao, P.*; Tan, Z.*; Lee, S. H.*; 石川 喜久*; 鳥居 周輝*; 米村 雅雄*; 幸田 章宏*; 小松 一生*; 町田 真一*; 佐野 亜沙美; et al.

Physical Review B, 103(9), p.094302_1 - 094302_18, 2021/03

 被引用回数:0 パーセンタイル:0(Materials Science, Multidisciplinary)

層状ペロブスカイトPrBaCo$$_{2}$$O$$_{5.5}$$は、熱膨張のない複合材料を作るために必要な負の熱膨張(NTE)を示す。NTEは、自発的な磁気秩序と密接に関連していることがわかっていた(磁気体積効果: MVE)。今回、われわれは、PrBaCo$$_{2}$$O$$_{5.5}$$の連続的な磁気体積効果が、本質的には不連続であり、大きな体積を持つ反強磁性絶縁体(AFILV)から、小さな体積をもつ強磁性卑絶縁体(FLISV)への磁気電気的相転移に起因することを明らかにした。また、磁気電気効果(ME)は、温度,キャリアドーピング,静水圧,磁場などの複数の外部刺激に対して高い感度を示した。これは、これまでよく知られている対称性の破れを伴う巨大磁気抵抗やマルチフェロイック効果などのMEとは対照的であり、輝コバルト鉱のMEは同一の結晶構造で起こる。われわれの発見は、MEとNTEを実現するための新しい方法を示しており、それは新しい技術に応用されるかもしれない。

論文

Stable double-heavy tetraquarks; Spectrum and structure

Meng, Q.*; 肥山 詠美子*; 保坂 淳; 岡 眞; Gubler, P.; Can, K. U.*; 高橋 徹*; Zong, H. S.*

Physics Letters B, 814, p.136095_1 - 136095_6, 2021/03

 被引用回数:2 パーセンタイル:90.09(Astronomy & Astrophysics)

Bound states of double-heavy tetraquarks are studied in a constituent quark model. Two bound states are found for isospin and spin-parity $$I(J^P) = 0(1^+)$$ in the $$bbbar{u}bar{d}$$ channel. One is deeply bound and compact made of colored diquarks, while the other is shallow and extended as a $$BB^{ast}$$ molecule. The former agrees well with lattice QCD results. A systematic decrease in the binding energy is seen by replacing one of the heavy quarks to a lighter one. Altogether we find ten bound states. It is shown for the first time that hadrons with totally different natures emerge from a single Hamiltonian.

論文

Quasifree neutron knockout reaction reveals a small $$s$$-Orbital component in the Borromean nucleus $$^{17}$$B

Yang, Z. H.*; 久保田 悠樹*; Corsi, A.*; 吉田 数貴; Sun, X.-X.*; Li, J. G.*; 木村 真明*; Michel, N.*; 緒方 一介*; Yuan, C. X.*; et al.

Physical Review Letters, 126(8), p.082501_1 - 082501_8, 2021/02

 被引用回数:10 パーセンタイル:98.7(Physics, Multidisciplinary)

ボロミアン核であり中性子ハロー構造が期待される$$^{17}$$Bに対する($$p$$,$$pn$$)反応実験を行った。断面積の運動量分布を分析することで、$$1s_{1/2}$$$$0d_{5/2}$$軌道の分光学的因子を決定した。驚くべきことに、$$1s_{1/2}$$の分光学的因子は9(2)%と小さいことが明らかになった。この結果は、連続状態を含むdeformed relativistic Hartree-Bogoliubov理論によってよく説明された。本研究の結果によると、現在知られているハロー構造を持つとされる原子核の中で$$^{17}$$Bは$$s$$および$$p$$軌道の成分が最も小さく、$$s$$または$$p$$軌道成分が支配的であることが必ずしもハロー構造の前提条件ではない可能性を示唆している。

論文

Determination of atomistic deformation of tricalcium silicate paste with high-volume fly ash

Jee, H.*; Im, S.*; 兼松 学*; 鈴木 裕士; 諸岡 聡; 小山 拓*; 町田 晃彦*; Bae, S.*

Journal of the American Ceramic Society, 103(12), p.7188 - 7201, 2020/12

 被引用回数:2 パーセンタイル:40.39(Materials Science, Ceramics)

We examined the influence of incorporating high-volume fly ash (FA) on the atomic structure and deformation behavior of calcium silicate hydrates (C-S-H) in tricalcium silicate (C$$_{3}$$H) paste upon exposure to external forces. Atomic structural changes and strains under compressive load were assessed using synchrotron in situ high-energy X-ray scattering-based atomic pair distribution function (PDF) analysis. Three different strain types, namely macroscopic strains, measured by a gauge attached to the specimen, strain in reciprocal space, (Bragg peak shifts), and strain in real space (PDF peak shift), were compared. All monitored and calculated strains for C$$_{3}$$H-FA (50 wt.% FA) paste were compared with those of pure C$$_{3}$$H paste. In the range of $$r$$ $$<$$ 10 ${AA}$, PDF analysis showed that C$$_{3}$$H-FA had a similar atomic structure to synthetic C-S-H followed by pure C$$_{3}$$H paste. The atomic strain of C$$_{3}$$H-FA in real space ($$r$$ $$<$$ 20 ${AA}$) was smaller than that of C$$_{3}$$H under compression, which suggests that the incompressibility of C-S-H on an atomistic scale is enhanced by fly ash incorporation. This may be caused by increased silicate polymerization of C-S-H due to the additional silicate provided by the fly ash.

論文

Radionuclides from the Fukushima Daiichi Nuclear Power Plant in terrestrial systems

恩田 裕一*; 谷口 圭輔*; 吉村 和也; 加藤 弘亮*; 高橋 純子*; 脇山 義史*; Coppin, F.*; Smith, H.*

Nature Reviews Earth & Environment (Internet), 1(12), p.644 - 660, 2020/12

 被引用回数:17 パーセンタイル:81.26(Environmental Sciences)

This review, concerning on findings obtained by detailed field monitoring after the Fukushima Daiichi Nuclear Power Plant accident, covers the initial fallout and vertical movement of radionuclide in the land and forest, and subsequent transport and redistribution through hydrological and geomorphological processes in cropland, urban area, paddy field, and forested area. We discuss the finding of the transport of radionuclides through rivers and new discoveries for hydrological and sediment transport environmental impact in monsoonal regions.

論文

Author correction; Radionuclides from the Fukushima Daiichi Nuclear Power Plant in terrestrial systems

恩田 裕一*; 谷口 圭輔*; 吉村 和也; 加藤 弘亮*; 高橋 純子*; 脇山 義史*; Coppin, F.*; Smith, H.*

Nature Reviews Earth & Environment (Internet), 1(12), P. 694_1, 2020/12

 被引用回数:0 パーセンタイル:0.29(Environmental Sciences)

The values along the mass depth axes in Figure 4a and 4b were slightly misaligned, and the relaxation mass depth markers shown in Figure 4b and 4c incorrectly located.

論文

HPRL; International cooperation to identify and monitor priority nuclear data needs for nuclear applications

Dupont, E.*; Bossant, M.*; Capote, R.*; Carlson, A. D.*; Danon, Y.*; Fleming, M.*; Ge, Z.*; 原田 秀郎; 岩本 修; 岩本 信之; et al.

EPJ Web of Conferences, 239, p.15005_1 - 15005_4, 2020/09

 被引用回数:0 パーセンタイル:0.19

The OECD-NEA High Priority Request List (HPRL) is a point of reference to guide and stimulate the improvement of nuclear data for nuclear energy and other nuclear applications. The HPRL is application-driven and the requests are submitted by nuclear data users or representatives of the user's communities. A panel of international experts reviews and monitors the requests in the framework of an Expert Group mandated by the NEA Nuclear Science Committee Working Party on International Nuclear Data Evaluation Cooperation (WPEC). After approval, individual requests are divided in two priority categories only, whereas a third category now includes groups of generic requests in a well-defined area (e.g., dosimetry, standard). The HPRL is hosted by the NEA in the form of a relational database publicly available on the web. This contribution provides an overview of HPRL entries, status and outlook. Examples of requests successfully completed will be given and new requests will be described with emphasis on updated nuclear data needs in the fields of nuclear energy, neutron standards, dosimetry, and medical applications.

論文

Main findings, remaining uncertainties and lessons learned from the OECD/NEA BSAF Project

Pellegrini, M.*; Herranz, L.*; Sonnenkalb, M.*; Lind, T.*; 丸山 結; Gauntt, R.*; Bixler, N.*; Morreale, A.*; Dolganov, K.*; Sevon, T.*; et al.

Nuclear Technology, 206(9), p.1449 - 1463, 2020/09

 被引用回数:11 パーセンタイル:98.02(Nuclear Science & Technology)

The OECD/NEA Benchmark Study at the Accident of Fukushima Daiichi Nuclear Power Station (BSAF) project, which started in 2012 and continued until 2018, was one of the earliest responses to the accident at Fukushima Daiichi. The project, divided into two phases addressed the investigation of the accident at Unit 1, 2 and 3 by Severe Accident (SA) codes until 500 h focusing on thermal-hydraulics, core relocation, Molten Corium Concrete Interaction (MCCI) and fission products release and transport. The objectives of BSAF were to make up plausible scenarios based primarily on SA forensic analysis, support the decommissioning and inform SA codes modeling. The analysis and comparison among the institutes have brought up vital insights regarding the accident progression identifying periods of core meltdown and relocation, Reactor Pressure Vessel (RPV) and Primary Containment Vessel (PCV) leakage/failure through the comparison of pressure, water level and CAMS signatures. The combination of code results and inspections (muon radiography, PCV inspection) has provided a picture of the current status of the debris distribution and plant status. All units present a large relocation of core materials and all of them present ex-vessel debris with Unit 1 and Unit 3 showing evidences of undergoing MCCI. Uncertainties have been identified in particular on the time and magnitude of events such as corium relocation in RPV and into cavity floor, RPV and PCV rupture events. Main uncertainties resulting from the project are the large and continuous MCCI progression predicted by basically all the SA codes and the leak pathways from RPV to PCV and PCV to reactor building and environment. The BSAF project represents a pioneering exercise which has set the basis and provided lessons learned not only for code improvement but also for the development of new related projects to investigate in detail further aspects of the Fukushima Daiichi accident.

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