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Journal Articles

Incommensurately modulated crystal structure of $$alpha$$'(O'3)-type sodium cobalt oxide Na$$_{x}$$CoO$$_{2}$$ (${it x}$ $$sim$$ 0.78)

Miyazaki, Yuzuru*; Igawa, Naoki; Yubuta, Kunio*

Acta Crystallographica Section B; Structural Science, Crystal Engineering and Materials (Internet), 77(3), p.371 - 377, 2021/06

 Times Cited Count:0 Percentile:0.02(Chemistry, Multidisciplinary)

Crystal structure of $$alpha$$'(O'3)-type layered sodium cobalt oxide Na$$_{x}$$CoO$$_{2}$$ (${it x}$ $$sim$$ 0.78) was analyzed using the (3+1)-dimensional superspace approach to the neutron diffraction data. The crystal structure is described based on the superspace group ${it C}$2 = ${it m}$(${it p}$0${it q}$)00, wherein the positions of Na atoms are most significantly modulated in the monoclinic ${it a}$-direction to form an ordered arrangement. Such a positional modulation causes a quasi-periodic shift of Na atoms from the centers of the NaO$$_{6}$$ polyhedra between undulated CoO$$_{2}$$ sheets, changing the form of the NaO$$_{6}$$ polyhedron from an octahedral coordination (O) to a trigonal prismatic one (P). Where the Na atoms are most significantly shifted, the neighboring Na atoms are located at almost touching distances and yielding Na-deficient sites. As a result, a typical sequence of NaO$$_{6}$$ octahedra with -O-O-O-P-$${it V}$$$$_{mathrm Na}$$-P- along the a-axis is realized.

Journal Articles

Multiple wavelengths texture measurement using angle dispersive neutron diffraction at WOMBAT

Xu, P. G.; Liss, K.-D.*

Quantum Beam Science (Internet), 5(2), p.11_1 - 11_14, 2021/06

JAEA Reports

Annual report of Department of Research Reactor and Tandem Accelerator, JFY2018 (Operation, utilization and technical development of JRR-3, JRR-4, NSRR, Tandem Accelerator, RI Production Facility and Tritium Process Laboratory)

Department of Research Reactor and Tandem Accelerator

JAEA-Review 2020-074, 105 Pages, 2021/03

JAEA-Review-2020-074.pdf:3.72MB

The Department of Research Reactor and Tandem Accelerator is in charge of the operation, utilization and technical development of JRR-3 (Japan Research Reactor No.3), JRR-4 (Japan Research Reactor No.4), NSRR (Nuclear Safety Research Reactor), Tandem Accelerator, RI Production Facility and TPL (Tritium Process Laboratory). This annual report describes the activities of our department in fiscal year of 2018. We carried out the operation and maintenance, utilization, upgrading of utilization techniques, safety administration and international cooperation. Also contained are lists of publications, meetings, granted permissions on laws and regulations concerning atomic energy, outcomes in service and technical developments and so on.

JAEA Reports

Annual report of Department of Research Reactor and Tandem Accelerator, JFY2017 (Operation, utilization and technical development of JRR-3, JRR-4, NSRR, Tandem Accelerator, RI Production Facility and Tritium Process Laboratory)

Department of Research Reactor and Tandem Accelerator

JAEA-Review 2020-073, 113 Pages, 2021/03

JAEA-Review-2020-073.pdf:3.87MB

The Department of Research Reactor and Tandem Accelerator is in charge of the operation, utilization and technical development of JRR-3 (Japan Research Reactor No.3), JRR-4 (Japan Research Reactor No.4), NSRR (Nuclear Safety Research Reactor), Tandem Accelerator, RI Production Facility and Tritium Process Laboratory. This annual report describes the activities of our department in fiscal year of 2017. We carried out the operation and maintenance, utilization, upgrading of utilization techniques, safety administration and international cooperation. Also contained are lists of publications, meetings, granted permissions on laws and regulations concerning atomic energy, outcomes in service and technical developments and so on.

JAEA Reports

Annual report of Department of Research Reactor and Tandem Accelerator, JFY2016 (Operation, utilization and technical development of JRR-3, JRR-4, NSRR, Tandem Accelerator, RI Production Facility and Tritium Process Laboratory)

Department of Research Reactor and Tandem Accelerator

JAEA-Review 2020-072, 102 Pages, 2021/03

JAEA-Review-2020-072.pdf:3.86MB

The Department of Research Reactor and Tandem Accelerator is in charge of the operation, utilization and technical development of JRR-3 (Japan Research Reactor No.3), JRR-4 (Japan Research Reactor No.4), NSRR (Nuclear Safety Research Reactor), Tandem Accelerator, RI Production Facility and Tritium Process Laboratory). This annual report describes the activities of our department in fiscal year of 2016. We carried out the operation and maintenance, utilization, upgrading of utilization techniques, safety administration and international cooperation. Also contained are lists of publications, meetings, granted permissions on laws and regulations concerning atomic energy, outcomes in service and technical developments and so on.

Journal Articles

Feasibility study on tritium recoil barrier for neutron reflectors of research and test reactors

Kenzhina, I.*; Ishitsuka, Etsuo; Ho, H. Q.; Sakamoto, Naoki*; Okumura, Keisuke; Takemoto, Noriyuki; Chikhray, Y.*

Fusion Engineering and Design, 164, p.112181_1 - 112181_5, 2021/03

Tritium release into the primary coolant during operation of the JMTR (Japan Materials Testing Reactor) and the JRR-3M (Japan Research Reactor-3M) had been studied. It is found that the recoil release by $$^{6}$$Li(n$$_{t}$$,$$alpha$$)$$^{3}$$H reaction, which comes from a chain reaction of beryllium neutron reflectors, is dominant. To prevent tritium recoil release, the surface area of beryllium neutron reflectors needs to be minimum in the core design and/or be shielded with other material. In this paper, as the feasibility study of the tritium recoil barrier for the beryllium neutron reflectors, various materials such as Al, Ti, V, Ni, and Zr were evaluated from the viewpoint of the thickness of barriers, activities after long-term operations, and effects on the reactivities. From the results of evaluations, Al would be a suitable candidate as the tritium recoil barrier for the beryllium neutron reflectors.

Journal Articles

Triple axis spectrometers of JAEA

Osakabe, Toyotaka

Hamon, 31(1), p.14 - 17, 2021/02

no abstracts in English

Journal Articles

Introduction to SANS-J and PNO

Kumada, Takayuki; Motokawa, Ryuhei; Nakagawa, Hiroshi; Oba, Yojiro; Sekine, Yurina

Hamon, 31(1), p.5 - 6, 2021/02

no abstracts in English

Journal Articles

SUIREN (polarized neutron reflectometer)

Takeda, Masayasu

Hamon, 31(1), p.18 - 19, 2021/02

no abstracts in English

Journal Articles

Evaluation of tritium release into primary coolant for research and testing reactors

Kenzhina, I.*; Ishitsuka, Etsuo; Okumura, Keisuke; Ho, H. Q.; Takemoto, Noriyuki; Chikhray, Y.*

Journal of Nuclear Science and Technology, 58(1), p.1 - 8, 2021/01

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

The sources and mechanisms for the tritium release into the primary coolant in the JMTR and the JRR-3M containing beryllium reflectors are evaluated. It is found that the recoil release from chain reaction of $$^{9}$$Be is dominant and its calculation results agree well with trends derived from the measured variation of tritium concentration in the primary coolant. It also indicates that the simple calculation method used in this study for the tritium recoil release from the beryllium reflectors can be utilized for an estimation of the tritium release into the primary coolant for a research and testing reactors containing beryllium reflectors.

Journal Articles

A New convention for the epithermal neutron spectrum for improving accuracy of resonance integrals

Harada, Hideo; Takayama, Naoki; Komeda, Masao

Journal of Physics Communications (Internet), 4(8), p.085004_1 - 085004_17, 2020/08

A new convention of epithermal neutron spectrum is formulated for improving accuracy of resonance integrals. The new type function is proposed as an approximating function of epithermal neutron spectrum based on calculations by the state-of-art Monte Carlo code MVP-3. Bias effects on determination of resonance integrals due to utilizing approximating functions of the traditional types and the new type are compared. The other bias effect is also investigated, which is caused by neglecting position dependence of a neutron spectrum inside an irradiation capsule. For demonstrating the bias effects due to these assumptions on neutron spectrum quantitatively in a practical case, the thermal neutron-capture cross section and resonance integral of $$^{135}$$Cs measured at a research reactor JRR-3 are re-evaluated. A superior property of the proposed new convention is discussed. The experimental method is proposed to determine the new shape factor $$beta$$ introduced in the convention by a combinational use of triple flux monitors ($$^{197}$$Au, $$^{59}$$Co and $$^{94}$$Zr), and its analytical methodology is formulated.

Journal Articles

$$f$$-electron states of NpPd$$_5$$Al$$_2$$ and the isostructural family; Heavy fermion superconductivity accompanied by valence crossover

Metoki, Naoto

Kotai Butsuri, 55(7), p.285 - 296, 2020/07

Electron states are the main theme of "solid-state physics", which is essential for microscopic understanding of multipoles and superconductivity, etc. Rare earths (4$$f$$) and actinides (5$$f$$) provide variety of interesting states realized with competing interactions between the increasing number of $$f$$ electrons. Since crystal field splitting of many-body $$f$$ electron system is smaller than the bandwidth, (1) high resolution experiments are needed, (2) essentially no clear spectrum with well defined peaks is expected in itinerant Ce and U compounds, and (3) Np and Pu is strictly regulated. Therefore, systematic research on magnetic excitations by neutron scattering experiments of localized compounds and rare earth iso-structural reference is useful. We describe the $$f$$ electron states of heavy electron compounds NpPd$$ _5$$Al$$_2$$ and actinide and rare earth based iso-structural family.

Journal Articles

Residual stress distribution in water jet peened type 304 stainless steel

Hayashi, Makoto*; Okido, Shinobu*; Suzuki, Hiroshi

Quantum Beam Science (Internet), 4(2), p.18_1 - 18_12, 2020/06

Journal Articles

Application of neutron, 1; Neutron stress measurement in the research reactor JRR-3

Suzuki, Hiroshi

Hozengaku, 19(1), p.24 - 28, 2020/04

no abstracts in English

Journal Articles

The $$f$$-electron state of the heavy fermion superconductor NpPd$$_5$$Al$$_2$$ and the isostructural family

Metoki, Naoto; Aczel, A. A.*; Aoki, Dai*; Chi, S.*; Fernandez-Baca, J. A.*; Griveau, J.-C.*; Hagiwara, Masato*; Hong, T.*; Haga, Yoshinori; Ikeuchi, Kazuhiko*; et al.

JPS Conference Proceedings (Internet), 30, p.011123_1 - 011123_6, 2020/03

Rare earths (4$$f$$) and actinides (5$$f$$) provide variety of interesting states realized with competing interactions between the increasing number of $$f$$ electrons. Since crystal field splitting of many-body $$f$$ electron system is smaller than the bandwidth, (1) high resolution experiments are needed, (2) essentially no clear spectrum with well defined peaks is expected in itinerant Ce and U compounds, and (3) Np and Pu is strictly regulated. Therefore, systematic research on magnetic excitations by neutron scattering experiments of localized compounds and rare earth iso-structural reference is useful. We describe the $$f$$ electron states of heavy electron compounds NpPd$$_5$$Al$$_2$$ and actinide and rare earth based iso-structural family.

Journal Articles

What should we learn from the back numbers of HAMON ?

Takeda, Masayasu

Hamon, 30(1), p.7 - 8, 2020/02

Safety review of JRR-3 under the New Regulatory Requirements was completed on 7th November 2018. Neutron beam will come back in early 2021 after reinforcement works of the roof of the reactor building, the peripheral structures like a stack, a cooling tower, and the experimental hall. The future of neutron sciences using the research reactor strongly depends on how many impacted researches using JRR-3 are achieved after restarting JRR-3. At this stage, we can learn a lot of things from the back numbers of HAMON.

Journal Articles

Pseudo-triplet 5$$f$$ electron state in the heavy fermion superconductor NpPd$$_5$$Al$$_2$$

Metoki, Naoto; Aoki, Dai*; Griveau, J.-C.*; Otsuki, Junya*

Journal of the Physical Society of Japan, 89(2), p.024707_1 - 024707_6, 2020/02

 Times Cited Count:2 Percentile:54.33(Physics, Multidisciplinary)

The pseudo triplet ground state in the heavy-fermion superconductor NpPd$$_5$$Al$$_2$$ was concluded. The magnetic susceptibility $$chi$$ can be reproduced by the singlet ground state $$Gamma_{t1}$$ with the main component of $$|0rangle$$ and the first excited doublet $$Gamma_{t5}$$ dominated by $$|pm1rangle$$ at $$Delta E=49$$,K. The magnetization curve can be explained from the effective local hamiltonian for pseudo spin $$J$$=1 with $$DJ_z^2$$($$D=Delta E$$) equivalent to the quadrupole operator $$O_{20}$$. The specific heat can be described with the Kondo model normalized to give the entropy R$$ln3$$, corresponding to the pseudo triplet state. The derived Kondo temperature $$T_{rm K}=55$$,K comparable to the level splitting $$Delta E=49$$,K indicates the contribution of the excited doublet $$Gamma_{t5}$$ to the possible multi-channel Kondo effect.

Journal Articles

$$f$$-electron states of heavy-fermion superconductor NpPd$$_5$$Al$$_2$$ and rare-earth- and actinide-based isostructural compounds

Metoki, Naoto

Journal of the Physical Society of Japan, 89(2), p.025001_1 - 025001_2, 2020/02

 Times Cited Count:0 Percentile:0(Physics, Multidisciplinary)

Good correspondence of the $$LS$$ and $$j$$-$$j$$ coupling scheme can be realized in the $$f$$-electron states of the heavy-fermion superconductor NpPd$$_5$$Al$$_2$$ and the isostructural family. The rare-earth and actinide elements are under a common strong uniaxial point charge potential with tetragonal point symmetry $$D_{4h}$$. The systematic development of the $$f$$-electron states can be understood in the $$LS$$ coupling scheme of $$^nf$$ configuration (the number of $$f$$ electrons $$nleq6$$). We can find the corresponding states in $$j$$-$$j$$ coupling scheme with three $$f$$-orbitals $$Gamma_7^{rm; i}, Gamma_7^{rm; ii}$$, and $$Gamma_6$$ determined from CePd$$_5$$Al$$_2$$ with $$^1f$$ configuration.

Journal Articles

Fine structural analysis using single crystal neutron diffraction

Kaneko, Koji

Nihon Kessho Gakkai-Shi, 61(4), p.237 - 242, 2019/12

Journal Articles

Feasibility study of tritium recoil barrier for neutron reflectors

Ishitsuka, Etsuo; Sakamoto, Naoki*

Physical Sciences and Technology, 6(2), p.60 - 63, 2019/12

Tritium release into the primary coolant of the research and test reactors during operation had been studied, and it is found that the recoil release from chain reaction of $$^{9}$$Be is dominant. To reduce tritium concentration of the primary coolant, feasibility study of the tritium recoil barrier for the beryllium neutron reflectors was carried out, and the tritium recoils of various materials were calculated by PHITS. From these calculation results, it is clear that the thickness of tritium recoil barrier depends on the material and 20$$sim$$40 $$mu$$m is required for three orders reduction.

1707 (Records 1-20 displayed on this page)