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論文

Structural and compositional characteristics of Fukushima release particulate material from Units 1 and 3 elucidates release mechanisms, accident chronology and future decommissioning strategy

Martin, P. G.*; Jones, C. P.*; Bartlett, S.*; Ignatyev, K.*; Megson-Smith, D.*; 佐藤 志彦; Cipiccia, S.*; Batey, D. J.*; Rau, C.*; 末木 啓介*; et al.

Scientific Reports (Internet), 10, p.22056_1 - 22056_17, 2020/12

 被引用回数:1 パーセンタイル:6.79(Multidisciplinary Sciences)

The structural form and elemental distribution of material originating from different Fukushima Daiichi Nuclear Power Plant reactors (Units 1 and 3) is hereby examined to elucidate their contrasting release dynamics and the current in-reactor conditions to influence future decommissioning challenges. Complimentary computed X-ray absorption tomography and X-ray fluorescence data show that the two suites of Si-based material sourced from the different reactor Units have contrasting internal structure and compositional distribution. The known event and condition chronology correlate with the observed internal and external structures of the particulates examined, which suggest that Unit 1 ejecta material sustained a greater degree of melting than that likely derived from reactor Unit 3. In particular, we attribute the near-spherical shape of Unit 1 ejecta and their internal voids to there being sufficient time for surface tension to round these objects before the hot (and so relatively low viscosity) silicate melt cooled to form glass. In contrast, a more complex internal form associated with the sub-mm particulates invoked to originate from Unit 3 suggest a lower peak temperature, over a longer duration. Using volcanic analogues, we consider the structural form of this material and how it relates to its environmental particulate stability and the bulk removal of residual materials from the damaged reactors. We conclude that the brittle and angular Unit 3 particulate are more susceptible to further fragmentation and particulate generation hazard than the round, higher-strength, more homogenous Unit 1 material.

論文

International network of nuclear structure and decay data evaluators

Dimitriou, P.*; Basunia, S*; Bernstein, L.*; Chen, J.*; Elekes, Z.*; Huang, X.*; Hurst, A.*; 飯村 秀紀; Jain, A. K.*; Kelley, J.*; et al.

EPJ Web of Conferences, 239, p.15004_1 - 15004_4, 2020/09

BB2020-0008.pdf:0.34MB

 被引用回数:0 パーセンタイル:0.1(Nuclear Science & Technology)

評価済み核構造データファイル(Evaluated Nuclear Structure Data File: ENSDF)は、原子核構造と崩壊に関する様々な実験データを全ての核種について集めて、それらの実験データの評価値を与えてある世界唯一のデータファイルである。ENSDFは定期的に更新されており、そのための評価作業は各国の評価者で分担している。評価作業を速やかに行うために、IAEAの援助の下に評価者の国際的なネットワークが組織されている。この発表では、ネットワークの最近の活動のうち、ENSDFの処理コードの開発、測定が必要とされているデータのリストの作成、インターネット版核図表の利用の拡充などについて報告する。また、核構造・崩壊データの需要が増大しているにもかかわらず、評価者が減っている問題についても述べる。

論文

$$alpha$$-decay branching ratio of $$^{180}$$Pt

Cubiss, J. G.*; Harding, R. D.*; Andreyev, A. N.; Althubiti, N.*; Andel, B.*; Antalic, S.*; Barzakh, A. E.*; Cocolios, T. E.*; Day Goodacre, T.*; Farooq-Smith, G. J.*; et al.

Physical Review C, 101(1), p.014314_1 - 014314_4, 2020/01

 被引用回数:5 パーセンタイル:51.79(Physics, Nuclear)

$$^{180}$$Ptの基底状態から娘核$$^{176}$$Osの基底状態への$$alpha$$崩壊分岐比を0.52(5)%と、過去の値と比較してより高精度で再決定した。$$^{180}$$PtはCERN-ISOLDE実験施設において$$^{180}$$Hgを単離し、その$$beta$$崩壊孫核種として生成した。今回の結果を用いて導出した$$alpha$$崩壊の換算崩壊幅は、中性子欠損Pt同位体の$$alpha$$崩壊幅の系統性について新しい描像を与えることとなった。

論文

Electromagnetic properties of low-lying states in neutron-deficient Hg isotopes; Coulomb excitation of $$^{182}$$Hg, $$^{184}$$Hg, $$^{186}$$Hg and $$^{188}$$Hg

Wrzosek-Lipska, K.*; Rezynkina, K.*; Bree, N.*; Zieli$'n$ska, M.*; Gaffney, L. P.*; Petts, A.*; Andreyev, A. N.; Bastin, B.*; Bender, M.*; Blazhev, A.*; et al.

European Physical Journal A, 55(8), p.130_1 - 130_23, 2019/08

 被引用回数:11 パーセンタイル:73.85(Physics, Nuclear)

The neutron-deficient mercury isotopes serve as a classical example of shape coexistence, whereby at low energy near-degenerate nuclear states characterized by different shapes appear. The electromagnetic structure of even-mass $$^{182-188}$$Hg isotopes was studied using safe-energy Coulomb excitation of neutron-deficient mercury beams delivered by the REX-ISOLDE facility at CERN. The population of 0$$^{+}_{1,2}$$, 2$$^{+}_{1,2}$$, and 4$$^{+}_{1}$$ states was observed in all nuclei under study. Reduced $$E2$$ matrix elements coupling populated yrast and non-yrast states were extracted, including their relative signs. These are a sensitive probe of shape coexistence and may be used to validate nuclear models. The experimental results are discussed in terms of mixing of two different configurations and are compared with three different model calculations: the Beyond Mean Field model, the Interacting Boson Model with configuration mixing and the General Bohr Hamiltonian. Partial agreement with experiment was observed, hinting to missing ingredients in the theoretical descriptions.

論文

Neutron-hole states in $$^{131}$$Sn and spin-orbit splitting in neutron-rich nuclei

Orlandi, R.; Pain, S. D.*; Ahn, S.*; Jungclaus, A.*; Schmitt, K. T.*; Bardayan, D. W.*; Catford, W. N.*; Chapman, R.*; Chipps, K. A.*; Cizewski, J. A.*; et al.

Physics Letters B, 785, p.615 - 620, 2018/10

 被引用回数:7 パーセンタイル:53.13(Astronomy & Astrophysics)

Low-lying neutron-hole states in $$^{131}$$Sn were populated via the $$^{132}$$Sn(d,t) reaction at Oak Ridge National Laboratory. The triton angular distributions were compared to DWBA calculations and revealed spectroscopic factors compatible with a single-hole nature of the states populated. The data permit to determine the spin-orbit splitting of the strongly bound $$d_{3/2}$$ and $$d_{5/2}$$ neutron orbits below the shell gap, which was compared to the splitting of the weakly bound 3$$p$$ and 2$$f$$ orbits above the gap. The comparison revealed a smaller energy splitting of the 3$$p$$ orbits. All splittings were reproduced using Woods-Saxon calculations, and the lower splitting of the 3$$p$$ orbits was explained to arise from the large radial extent of the wavefunction and small value of the amplitude at the surface. This result is important to understand at a fundamental level the spin-orbit interaction, and its effects on neutron-rich nuclei.

論文

EXILL; A High-efficiency, high-resolution setup for $$gamma$$-spectroscopy at an intense cold neutron beam facility

Jentschel, M.*; Blanc, A.*; de France, G.*; K$"o$ster, U.*; Leoni, S.*; Mutti, P.*; Simpson, G.*; Soldner, T.*; Ur, C.*; Urban, W.*; et al.

Journal of Instrumentation (Internet), 12(11), p.P11003_1 - P11003_33, 2017/11

 被引用回数:38 パーセンタイル:85.29(Instruments & Instrumentation)

A highly efficient array of high-purity germanium (HPGe) detectors was developed and operated at the cold neutron beam facility PF1B of the Institut Laue-Langevin (ILL) to carry out nuclear structure studies, via measurements of $$gamma$$-rays following neutron-induced capture and fission reactions. The setup consisted of a collimation system producing a pencil beam with a thermal capture equivalent flux of about 10$$^8$$ns$$^{-1}$$cm$$^{-2}$$ at the target position and negligible neutron halo. The target was surrounded by an array of eight to ten anti-Compton shielded EXOGAM Clover detectors, four to six anti-Compton shielded large coaxial GASP detectors and two standard Clover detectors. For a part of the campaign the array was combined with 16 LaBr$$_{3}$$:(Ce) detectors from the FATIMA collaboration.

論文

$$beta$$-delayed fission of $$^{230}$$Am

Wilson, G. L.*; 武山 美麗*; Andreyev, A. N.; Andel, B.*; Antalic, S.*; Catford, W. N.*; Ghys, L.*; 羽場 宏光*; He${ss}$berger, F. P.*; Huang, M.*; et al.

Physical Review C, 96(4), p.044315_1 - 044315_7, 2017/10

 被引用回数:6 パーセンタイル:46.71(Physics, Nuclear)

The exotic decay process of $$beta$$-delayed fission has been studied in the neutron-deficient isotope $$^{230}$$Am at RIKEN, Japan. The $$^{230}$$Am nuclei were produced in the complete fusion reaction $$^{207}$$Pb($$^{27}$$Al,4n)$$^{230}$$Am and separated by using the GARIS gas-filled recoil ion separator. A lower limit for the $$beta$$-delayed fission probability larger than 0.30 was deduced, which so far is the highest value among all known nuclei exhibiting this decay mode.

論文

Collectivity in the light radon nuclei measured directly via Coulomb excitation

Gaffney, L. P.*; Robinson, A. P.*; Jenkins, D. G.*; Andreyev, A. N.; Bender, M.*; Blazhev, A.*; Bree, N.*; Bruyneel, B.*; Butler, P.*; Cocolios, T. E.*; et al.

Physical Review C, 91(6), p.064313_1 - 064313_11, 2015/06

 被引用回数:8 パーセンタイル:50.48(Physics, Nuclear)

Radioactive ion beams of $$^{202,204}$$Rn were studied by means of low-energy Coulomb excitation at REX-ISOLDE, CERN. The electric-quadrupole (E2) matrix elements connecting the first excited 2$$^+$$ to the ground state of these nuclei was extracted, which permits to determine the collectivity of these isotopes, which in both cases is deduced to be weak, as expected from the low-lying level-energy scheme. Comparisons were also made with beyond-mean-field model calculations and the magnitude of the transitional quadrupole moments are well reproduced.

論文

Single-neutron orbits near $$^{78}$$Ni; Spectroscopy of the N=49 isotope $$^{79}$$Zn

Orlandi, R.; M$"u$cher, D.*; Raabe, R.*; Jungclaus, A.*; Pain, S. D.*; Bildstein, V.*; Chapman, R.*; De Angelis, G.*; Johansen, J. G.*; Van Duppen, P.*; et al.

Physics Letters B, 740, p.298 - 302, 2015/01

 被引用回数:28 パーセンタイル:86.67(Astronomy & Astrophysics)

Single-neutron states in $$^{79}$$Zn have been populated using the reaction $$^{78}$$Zn(d,p) at REX-Isolde, CERN. The analysis reveals that the lowest excited states in $$^{79}$$Zn lie at approximately 1 MeV, and involve neutron orbits above the N=50 shell gap. A 5/2$$^{+}$$ configuration was assigned to the 983-keV state. Comparison with large-scale shell model calculations supports a robust neutron N=50 shell closure for $$^{78}$$Ni. These data constitute an important step towards the understanding the magicity of $$^{78}$$Ni and the structure of nuclei in the region.

論文

$$B(E2;2^+_1rightarrow 0^+_1)$$ value in $$^{90}$$Kr

R$'e$gis, J.-M.*; Jolie, J.*; Saed-Samii, N.*; Warr, N.*; Pfeiffer, M.*; Blanc, A.*; Jentschel, M.*; K$"o$ster, U.*; Mutti, P.*; Soldner, T.*; et al.

Physical Review C, 90(6), p.067301_1 - 067301_4, 2014/12

 被引用回数:23 パーセンタイル:80.1(Physics, Nuclear)

A smooth onset of collectivity in $$^{88,92,94,96}$$Kr has been determined from reported $$B(E2;2^+_1rightarrow 0^+_1)$$ and E(2$$^+_1$$) values. This is in contrast to the sudden onset in even-even Zr, Mo, and Sr isotopes. Our objective was to complete the systematics by determining the $$B(E2;2^+_1rightarrow 0^+_1)$$ value in $$^{90}$$Kr, which was produced by cold-neutron-induced fission of $$^{235}$$U. The lifetime of the 2$$^+_1$$ state in $$^{90}$$Kr was measured via the electronic $$gamma - gamma$$ timing technique using the EXILL and FATIMA spectrometers. Based on the measured mean lifetime of $$tau$$ = 15(10) ps, the $$B(E2;2^+_1rightarrow 0^+_1)$$ value of 13$$^{+26}_{-5}$$ W.u. in $$^{90}$$Kr is determined for the first time and the smooth onset of deformation in the even-even Kr isotopes beyond neutron number N=50 is confirmed.

論文

Origin of the phonon Hall effect in rare-earth garnets

森 道康; Spencer-Smith, A.*; Sushkov, O. P.*; 前川 禎通

Physical Review Letters, 113(26), p.265901_1 - 265901_7, 2014/12

 被引用回数:48 パーセンタイル:87.69(Physics, Multidisciplinary)

The phonon Hall effect has been observed in the paramagnetic insulator, Tb$$_{3}$$Gd$$_{5}$$O$$_{12}$$. A magnetic field applied perpendicularly to a heat current induces a temperature gradient that is perpendicular to both the field and the current. We show that this effect is due to resonant skew scattering of phonons from the crystal field states of superstoichiometric Tb$$^{3+}$$ ions. This scattering originates from the coupling between the quadrupole moment of Tb$$^{3+}$$ ions and the lattice strain. The estimated magnitude of the effect is consistent with experimental observations at T=5 K, and can be significantly enhanced by increasing temperature.

論文

ENDF/B-VII.1 nuclear data for science and technology; Cross sections, covariances, fission product yields and decay data

Chadwick, M. B.*; Herman, M.*; Oblo$v{z}$insk$'y$, P.*; Dunn, M. E.*; Danon, Y.*; Kahler, A. C.*; Smith, D. L.*; Pritychenko, B.*; Arbanas, G.*; Arcilla, R.*; et al.

Nuclear Data Sheets, 112(12), p.2887 - 2996, 2011/12

 被引用回数:2048 パーセンタイル:100(Physics, Nuclear)

原子力科学・技術の利用分野ための評価済み核データライブラリーENDF/B-VII.1を公開した。米国核データ評価委員会が中心となって評価・整備したこの最新ライブラリーは、前バージョン(ENDF/B-VII.0)公開以後に得られた原子核理論や実験に関する知見を反映した中性子断面積,共分散,核分裂収率や崩壊データ等を格納している。ライブラリーの主な更新内容は、核種数の拡大、共分散データの拡充、R行列理論に基づく軽核の共鳴パラメータ評価、中重核やアクチノイドデータの改訂等である。核外輸送コードMCNPによるベンチマーク解析を行った結果、臨界予測性能等のパフォーマンスが向上した。

論文

Cross-shell excitations near the "island of inversion"; Structure of $$^{30}$$Mg

Daecon, A. N.*; Smith, J. F.*; Freeman, S. J.*; Janssens, R. V. F.*; Carpenter, M. P.*; Hadinia, B.*; Hoffman, C. R.*; Kay, B. P.*; Lauritsen, T.*; Lister, C. J.*; et al.

Physical Review C, 82(3), p.034305_1 - 034305_7, 2010/09

 被引用回数:23 パーセンタイル:77.2(Physics, Nuclear)

$$^{30}$$Mgは、中性子数20の魔法数が消滅する「逆転の島」と呼ばれている領域の境界にあたり、その詳しい核構造は興味が持たれている。この研究では、アルゴンヌ国立研究所において$$^{30}$$Mgの励起状態を$$^{14}$$C($$^{18}$$O,2$$p$$)反応にて生成し、そこからの脱励起$$gamma$$線を観測することによってエネルギー準位を構築した。その結果、励起エネルギー2-4MeV領域に魔法数消滅が起きないことを前提とした理論計算では得られない状態が複数観測された。モンテカルロ殻模型による大規模計算と比較したところ、これらの状態は、2個の中性子が中性子数20の殻ギャップを超えて励起した状態と対応させることができた。すなわち、$$^{30}$$Mgではかなり低い励起エネルギーに殻ギャップを超えた励起状態が存在することが明らかとなり、「逆転の島」の境界に属することがはっきりした。

論文

Computational infrastructure for nuclear astrophysics

Smith, M. S.*; Lingerfelt, E. J.*; Scott, J. P.*; Nesaraja, C. D.*; Hix, W. R.*; Chae, K.*; 小浦 寛之; Meyer, R. A.*; Bardayan, D. W.*; Blackmon, J. C.*; et al.

AIP Conference Proceedings 847, p.470 - 472, 2006/07

インターネット上で利用可能な天体核物理に関するコンピュータシステムのサイトを再構築した。これは、天体物理のシミュレーションを最新の原子核物理の結果を用いて行うように作成されたシステムで、URL: nucastrodata.orgから無料で利用可能である。Java言語を用いて作成されたシステムであり、Windows, Macintosh, Unixといったプラットホームに依存せず、数回のマウス操作で中性子捕獲反応率、原子核質量等といった核データの可視化や、p過程やr過程といった元素合成計算の結果をアニメーション動画として表示することを平易に行うことが可能である。今回の再構築で特に原子核質量の可視化及びr過程元素合成の動画化のシステムを新たに開発した。

報告書

H12: Examination of safety assessment aims, procedures and results from a wider perspective

Neall, F. B.*; Smith, P. A.*

JNC TY1400 2004-001, 144 Pages, 2004/05

JNC-TY1400-2004-001.pdf:1.58MB

第2次取りまとめの安全評価に対する考察を行った。その結果、第2次取りまとめは、日本における高レベル放射性廃棄物の安全な処分に向けてサイト選定及び処分場建設が実現可能であるという、明確かつ根拠のあるメッセージを提示していることが示された。

論文

Building confidence in radionuclide transport models for fractured rock; The Nagra/JNC Radionuclide Retardation Programme

太田 久仁雄; 梅木 博之; 天野 健治; Smith, P. A.*; Mori, A.*; Cowper, M. M.*

Materials Research Society Symposium Proceedings, Vol.663, p.1033 - 1041, 2001/00

サイクル機構とNagra(スイス放射性廃棄物処分共同組合)では、これまで15年間にわたり、より現実的な核種移行モデルの構築とその信頼性の確認を主目的とした原位置試験研究を実施してきた。とくに、グリムゼル原位置試験場および釜石鉱山において、核種移行の場(透水性割れ目とその近傍)とそこで生じる現象(収着/マトリクス拡散)について、様々な手法を用いて解析的あるいは直接的に評価を行うことにより、核種移行モデルの高度化とそのための技術の開発・確認を図ってきた。本報告では、上記の原位置試験研究の手法と成果の概要、および核種移行モデルの構築とその信頼性の確認のために有効な手法などについて論じる。

口頭

非磁性絶縁体におけるフォノンホール効果の理論

森 道康; Spencer-Smith, A.*; Sushkov, O. P.*; 前川 禎通

no journal, , 

非磁性絶縁体に温度勾配を与え、それと垂直な方向に磁場を加えたとき、両者に垂直な方向に温度勾配が現れる現象をフォノンホール効果と呼ぶ。次の組成式Tb$$_{3}$$Gd$$_{5}$$O$$_{12}$$で表されるTb-Gdガーネット(TGG)で観測されている。測定はバンドギャップより十分に小さい温度(約5K)で行われているため、熱励起された電荷の寄与は考えにくい。また、反強磁性転移温度は0.24Kなので磁気秩序はなく、パイロクロア酸化物で観測されているマグノンの寄与は期待できない。本講演では、TGGで観測されたフォノンホール効果の起源が、過剰に含まれた磁性イオン(Tb$$^{3+}$$)によるフォノンのスキュー散乱によるものである可能性を提案する。Tbイオンの最低エネルギー準位が擬二重項であることを考慮し、簡単のためJ=1を仮定して、磁場(B)下でのフォノンの散乱振幅(kp)を見積もると、B・p$$times$$kに比例する項が残ることがわかる。得られた散乱振幅をフォノンのボルツマン方程式に用いて、熱伝導度の横成分(kxy)を計算し、縦成分(kxx)との比(S=kxy/kxx)を見積もると温度(T)に関してTb$$^{3+}$$に比例する結果が得られた。もし、5K以上の温度依存性を測ることができたなら、フォノンホール効果がより顕著になることが期待される。講演では、ほかの散乱機構の可能性についても議論する。

口頭

Phonon Hall effect in rare-earth garnet

森 道康; Spencer-Smith, A.*; Sushkov, O. P.*; 前川 禎通

no journal, , 

In this talk, we show that the PHE originates from the resonant skew scattering of phonons by quasi-doublet states at superstoichiometric Tb$$^{3+}$$ ions. Phonons interact with the crystal field due to electrostatic interaction of lattice with electric multipole moments of the ion. Thus, one can see that the scattering originates from the coupling of lattice strain and the quadrupole moments of Tb$$^{3+}$$ ions. The phonon Hall angle (S), given by the ratio of off-diagonal and diagonal thermal conductivities divided by the magnitude of the magnetic field, is calculated using Boltzmann transport theory. Obtained magnitude of the effect is in agreement with experiments. We show that S significantly grows with temperature at low temperatures characterized by resonance energy.

口頭

Low-energy states in $$^{79}$$Zn and the structure of $$^{78}$$Ni

Orlandi, R.; M$"u$cher, D.*; Raabe, R.*; Jungclaus, A.*; Pain, S. D.*; Bildstein, V.*; Chapman, R.*; De Angelis, G.*; Johansen, J. G.*; Van Duppen, P.*; et al.

no journal, , 

Single-neutron states in the $$N$$ = 49 isotope $$^{79}$$Zn were populated in the $$^{78}$$Zn(d,p)$$^{79}$$Zn transfer reaction at REX-ISOLDE, CERN. The combined detection of protons ejected in the reaction and of $$gamma$$ rays emitted by $$^{79}$$Zn permitted the identification of the lowest-lying 5/2$$^+$$ and 1/2$$^+$$ excited states. The analysis of proton angular distributions links these states to a significant amount of single-particle strength around 1 MeV, and specifically to the $$nu$$d$$_{5/2}$$ and $$nu$$s$$_{1/2}$$ neutron orbits, which lie above the $$N$$ = 50 neutron shell gap. Comparison with large-scale-shell-model calculations supports a robust $$N$$ = 50 shell-closure for $$^{78}$$Ni. These data constitute a considerable step towards the understanding of the magicity of $$^{78}$$Ni and of the structure of isotopes in the region.

口頭

Neutron hole states in $$^{131}$$Sn studied via the $$^{132}$$Sn(d,t)$$^{131}$$Sn reaction

Orlandi, R.; Pain, S. D.*; Bardayan, D. W.*; Gross, C. J.*; Smith, M. S.*; Jungclaus, A.*; Ahn, S.*; Jones, K. L.*; Pittman, S. T.*; Schmitt, K. T.*; et al.

no journal, , 

Knowledge of single-particle energies in the vicinity of exotic doubly-magic nuclei is of critical importance to understand evolution of nuclear structure. In the present work, the $$^{132}$$Sn(d,t)$$^{131}$$Sn reaction (Q=-1.055 MeV) was studied in inverse kinematics at HRIBF of Oak Ridge National Laboratory. The $$^{132}$$Sn ISOL beam was post-accelerated to an energy of 4.39 MeV/u using the ORNL HRIBF accelerator. The beam (average intensity of $$sim$$1.2e4 pps) impinged on a $$sim$$250 $$mu$$g/cm$$^{2}$$ deuterated polyethylene target, for approximately 4 days. Ejected tritons were detected using the Super ORRUBA array of segmented Si telescopes. Low-lying states in $$^{131}$$Sn were populated in the experiment. Preliminary results will be shown.

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