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'(O'3)-type sodium cobalt oxide Na
CoO
(
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 '(O'3)-type layered sodium cobalt oxide NaCoO ( 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 
2 = 
(
0
)00, wherein the positions of Na atoms are most significantly modulated in the monoclinic 
-direction to form an ordered arrangement. Such a positional modulation causes a quasi-periodic shift of Na atoms from the centers of the NaO
polyhedra between undulated CoO sheets, changing the form of the NaO 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 octahedra with -O-O-O-P-
-P- along the a-axis is realized.
Xu, P. G.; Liss, K.-D.*
Quantum Beam Science (Internet), 5(2), p.11_1 - 11_14, 2021/06
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.
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.
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.
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 
Li(n
,)
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.
Osakabe, Toyotaka
Hamon, 31(1), p.14 - 17, 2021/02
no abstracts in English
Kumada, Takayuki; Motokawa, Ryuhei; Nakagawa, Hiroshi; Oba, Yojiro; Sekine, Yurina
Hamon, 31(1), p.5 - 6, 2021/02
no abstracts in English
Takeda, Masayasu
Hamon, 31(1), p.18 - 19, 2021/02
no abstracts in English
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 
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.
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 
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 
introduced in the convention by a combinational use of triple flux monitors (
Au, 
Co and 
Zr), and its analytical methodology is formulated.
-electron states of NpPd
Al
and the isostructural family; Heavy fermion superconductivity accompanied by valence crossoverMetoki, 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) and actinides (5) provide variety of interesting states realized with competing interactions between the increasing number of electrons. Since crystal field splitting of many-body 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 electron states of heavy electron compounds NpPd
Al and actinide and rare earth based iso-structural family.
Hayashi, Makoto*; Okido, Shinobu*; Suzuki, Hiroshi
Quantum Beam Science (Internet), 4(2), p.18_1 - 18_12, 2020/06
Suzuki, Hiroshi
Hozengaku, 19(1), p.24 - 28, 2020/04
no abstracts in English
-electron state of the heavy fermion superconductor NpPdAl and the isostructural familyMetoki, 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) and actinides (5) provide variety of interesting states realized with competing interactions between the increasing number of electrons. Since crystal field splitting of many-body 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 electron states of heavy electron compounds NpPdAl and actinide and rare earth based iso-structural family.
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.
electron state in the heavy fermion superconductor NpPdAlMetoki, 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 NpPdAl was concluded. The magnetic susceptibility 
can be reproduced by the singlet ground state 
with the main component of 
and the first excited doublet 
dominated by 
at 
,K. The magnetization curve can be explained from the effective local hamiltonian for pseudo spin 
=1 with 
(
) equivalent to the quadrupole operator 
. The specific heat can be described with the Kondo model normalized to give the entropy R
, corresponding to the pseudo triplet state. The derived Kondo temperature 
,K comparable to the level splitting ,K indicates the contribution of the excited doublet to the possible multi-channel Kondo effect.
-electron states of heavy-fermion superconductor NpPdAl and rare-earth- and actinide-based isostructural compoundsMetoki, 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 
and 
- coupling scheme can be realized in the -electron states of the heavy-fermion superconductor NpPdAl and the isostructural family. The rare-earth and actinide elements are under a common strong uniaxial point charge potential with tetragonal point symmetry 
. The systematic development of the -electron states can be understood in the coupling scheme of 
configuration (the number of electrons 
). We can find the corresponding states in - coupling scheme with three -orbitals 
, and 
determined from CePdAl with 
configuration.
Kaneko, Koji
Nihon Kessho Gakkai-Shi, 61(4), p.237 - 242, 2019/12
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 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 2040 
m is required for three orders reduction.
