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Kokubun, Yuji; Nakada, Akira; Seya, Natsumi; Nagaoka, Mika; Koike, Yuko; Kubota, Tomohiro; Hirao, Moe; Yoshii, Hideki*; Otani, Kazunori*; Hiyama, Yoshinori*; et al.
JAEA-Review 2023-052, 118 Pages, 2024/03
JAEA-Review-2023-052.pdf:3.67MB
Based on the regulations (the safety regulation of Tokai Reprocessing Plant, the safety regulation of nuclear fuel material usage facilities, the radiation safety rule, the regulation about prevention from radiation hazards due to radioisotopes, which are related with the nuclear regulatory acts, the local agreement concerning with safety and environment conservation around nuclear facilities, the water pollution control law, and by law of Ibaraki Prefecture), the effluent control of liquid waste discharged from the Nuclear Fuel Cycle Engineering Laboratories of Japan Atomic Energy Agency has been performed. This report describes the effluent control results of the liquid waste in the fiscal year 2022. In this period, the concentrations and the quantities of the radioactivity in liquid waste discharged from the reprocessing plant, the plutonium fuel fabrication facilities, and the other nuclear fuel material usage facilities were much lower than the limits authorized by the above regulations.
Ninomiya, Kazuhiko*; Kubo, Kenya*; Inagaki, Makoto*; Yoshida, Go*; Chiu, I.-H. ; Kudo, Takuto*; Asari, Shunsuke*; Sentoku, Sawako*; Takeshita, Soshi*; Shimomura, Koichiro*; et al.
Scientific Reports (Internet), 14, p.1797_1 - 1797_8, 2024/01
Times Cited Count：0The amount of C in steel, which is critical in determining its properties, is strongly influenced by steel production technology. We propose a novel method of quantifying the bulk C content in steel non-destructively using muons. This revolutionary method may be used not only in the quality control of steel in production, but also in analyzing precious steel archaeological artifacts. A negatively charged muon forms an atomic system owing to its negative charge, and is finally absorbed into the nucleus or decays to an electron. The lifetimes of muons differ significantly, depending on whether they are trapped by Fe or C atoms, and identifying the elemental content at the muon stoppage position is possible via muon lifetime measurements. The relationship between the muon capture probabilities of C/Fe and the elemental content of C exhibits a good linearity, and the C content in the steel may be quantitatively determined via muon lifetime measurements. Furthermore, by controlling the incident energies of the muons, they may be stopped in each layer of a stacked sample consisting of three types of steel plates with thicknesses of 0.5 mm, and we successfully determined the C contents in the range 0.20 - 1.03 wt% depth-selectively, without sample destruction.
Ca cast doubt on a doubly magic 
CaChen, S.*; Browne, F.*; Doornenbal, P.*; Lee, J.*; Obertelli, A.*; Tsunoda, Yusuke*; Otsuka, Takaharu*; Chazono, Yoshiki*; Hagen, G.*; Holt, J. D.*; et al.
Physics Letters B, 843, p.138025_1 - 138025_7, 2023/08
Times Cited Count：1 Percentile：0.02(Astronomy & Astrophysics)Gamma decays were observed in 
Ca and 
Ca following quasi-free one-proton knockout reactions from 
Sc. For Ca, a 
ray transition was measured to be 1456(12) keV, while for Ca an indication for a transition was observed at 1115(34) keV. Both transitions were tentatively assigned as the 
decays. A shell-model calculation in a wide model space with a marginally modified effective nucleon-nucleon interaction depicts excellent agreement with experiment for 
level energies, two-neutron separation energies, and reaction cross sections, corroborating the formation of a new nuclear shell above the N = 34 shell. Its constituents, the 
and 
orbitals, are almost degenerate. This degeneracy precludes the possibility for a doubly magic Ca and potentially drives the dripline of Ca isotopes to 
Ca or even beyond.
Osawa, Takahito; Nagasawa, Shunsaku*; Ninomiya, Kazuhiko*; Takahashi, Tadayuki*; Nakamura, Tomoki*; Wada, Taiga*; Taniguchi, Akihiro*; Umegaki, Izumi*; Kubo, Kenya*; Terada, Kentaro*; et al.
ACS Earth and Space Chemistry (Internet), 7(4), p.699 - 711, 2023/04
Times Cited Count：4 Percentile：93.95(Chemistry, Multidisciplinary)The concentrations of carbon and other major elements in asteroid samples provide very important information on the birth of life on the Earth and the solar-system evolution. Elemental analysis using muonic X-rays is one of the best analytical methods to determine the elemental composition of solid materials, and notably, is the only method to determine the concentration of light elements in bulk samples in a non-destructive manner. We developed a new analysis system using muonic X-rays to measure the concentrations of carbon and other major elements in precious and expectedly tiny samples recovered from the asteroid Ryugu by spacecraft Hayabusa2. Here we report the development process of the system in 4 stages and their system configurations, The analysis system is composed of a stainless-steel analysis chamber, an acrylic glove box for manipulating asteroid samples in a clean environment, and Ge semiconductor detectors arranged to surround the analysis chamber. The performance of the analysis system, including the background level, which is crucial for the measurement, was greatly improved from the first stage to the later ones. Our feasibility study showed that the latest model of our muonic X-ray analysis system is capable of determining the carbon concentration in Hayabusa2's sample model with an uncertainty of less than 10 percent in a 6-day measurement.
Katata, Genki*; Yamaguchi, Takashi*; Watanabe, Makoto*; Fukushima, Keitaro*; Nakayama, Masataka*; Nagano, Hirohiko*; Koarashi, Jun; Tateno, Ryunosuke*; Kubota, Tomohiro
Atmospheric Environment, 298, p.119640_1 - 119640_12, 2023/04
Times Cited Count：1 Percentile：58.15(Environmental Sciences)
100 MeV/nucleonPohl, T.*; Sun, Y. L.*; Obertelli, A.*; Lee, J.*; G
mez-Ramos, M.*; Ogata, Kazuyuki*; Yoshida, Kazuki; Cai, B. S.*; Yuan, C. X.*; Brown, B. A.*; et al.
Physical Review Letters, 130(17), p.172501_1 - 172501_8, 2023/04
Times Cited Count：5 Percentile：92.42(Physics, Multidisciplinary)We report on the first proton-induced single proton- and neutron-removal reactions from the neutron deficient 
O nucleus with large Fermi-surface asymmetry at 100 MeV/nucleon. Our results provide the first quantitative contributions of multiple reaction mechanisms including the quasifree knockout, inelastic scattering, and nucleon transfer processes. It is shown that the inelastic scattering and nucleon transfer, usually neglected at such energy regime, contribute about 50% and 30% to the loosely bound proton and deeply bound neutron removal, respectively.
Nakada, Akira; Kanai, Katsuta; Kokubun, Yuji; Nagaoka, Mika; Koike, Yuko; Yamada, Ryohei*; Kubota, Tomohiro; Hirao, Moe; Yoshii, Hideki*; Otani, Kazunori*; et al.
JAEA-Review 2022-079, 116 Pages, 2023/03
JAEA-Review-2022-079.pdf:2.77MB
Based on the regulations (the safety regulation of Tokai Reprocessing Plant, the safety regulation of nuclear fuel material usage facilities, the radiation safety rule, the regulation about prevention from radiation hazards due to radioisotopes, which are related with the nuclear regulatory acts, the local agreement concerning with safety and environment conservation around nuclear facilities, the water pollution control law, and by law of Ibaraki Prefecture), the effluent control of liquid waste discharged from the Nuclear Fuel Cycle Engineering Laboratories of Japan Atomic Energy Agency has been performed. This report describes the effluent control results of the liquid waste in the fiscal year 2021. In this period, the concentrations and the quantities of the radioactivity in liquid waste discharged from the reprocessing plant, the plutonium fuel fabrication facilities, and the other nuclear fuel material usage facilities were much lower than the limits authorized by the above regulations.
island of inversion; First study of low-lying bound excited states in 
V and 
VElekes, Z.*; Juh
sz, M. M.*; Sohler, D.*; Sieja, K.*; Yoshida, Kazuki; Ogata, Kazuyuki*; Doornenbal, P.*; Obertelli, A.*; Achouri, N. L.*; Baba, Hidetada*; et al.
Physical Review C, 106(6), p.064321_1 - 064321_10, 2022/12
Times Cited Count：2 Percentile：0.02(Physics, Nuclear)The low-lying level structure of V and V was investigated for the first time. The neutron knockout reaction and inelastic proton scattering were applied for V while the neutron knock-out reaction provided the data for V. Four and five new transitions were determined for V and V, respectively. Based on the comparison to our shell-model calculations using the Lenzi-Nowacki-Poves-Sieja (LNPS) interaction, three of the observed rays for each isotope could be placed in the level scheme and assigned to the decay of the first 11/2
and 9/2 levels. The (
,
) excitation cross sections for V were analyzed by the coupled-channels formalism assuming quadrupole plus hexadecapole deformations. Due to the role of the hexadecapole deformation, V could not be unambiguously placed on the island of inversion.
neutron orbital and the 
shell closure in 
CaEnciu, M.*; Liu, H. N.*; Obertelli, A.*; Doornenbal, P.*; Nowacki, F.*; Ogata, Kazuyuki*; Poves, A.*; Yoshida, Kazuki; Achouri, N. L.*; Baba, Hidetada*; et al.
Physical Review Letters, 129(26), p.262501_1 - 262501_7, 2022/12
Times Cited Count：4 Percentile：46.35(Physics, Multidisciplinary)The one-neutron knockout from Ca was performed at 230 MeV/nucleon combined with prompt spectroscopy. The momentum distributions corresponding to the removal of 
and 
neutrons were measured. The cross sections are consistent with a shell closure at the neutron number , found as strong as at 
and 
in Ca isotopes from the same observables. The analysis of the momentum distributions leads to a difference of the root-mean-square radii of the neutron 
and orbitals of 0.61(23) fm, in agreement with the modified-shell-model prediction of 0.7 fm suggesting that the large root-mean-square radius of the orbital in neutron-rich Ca isotopes is responsible for the unexpected linear increase of the charge radius with the neutron number.
Shibata, Taiju; Nishihara, Tetsuo; Kubo, Shinji; Sato, Hiroyuki; Sakaba, Nariaki; Kunitomi, Kazuhiko
Nuclear Engineering and Design, 398, p.111964_1 - 111964_4, 2022/11
Times Cited Count：2 Percentile：53.91(Nuclear Science & Technology)Japan Atomic Energy Agency (JAEA) has been promoting the research and development (R&D) of High Temperature Gas-cooled Reactor (HTGR). R&D on reactor technologies is carried out by using High Temperature engineering Test Reactor (HTTR). The HTTR was resumed without significant reinforcements in 2021. On January 2022, a safety demonstration test under the OECD/NEA LOFC project was carried out. JAEA is promoting R&D on a carbon-free hydrogen production by thermochemical water splitting Iodine-Sulfur process (IS process). JAEA conducts design study for various HTGR systems toward commercialization. A new test program about demonstration of hydrogen production by the HTTR was launched. Steam methane reforming hydrogen production system was selected for the first demonstration by 2030.
Nakamura, Hironori*; Hayakawa, Satoshi*; Shibata, Akihiro*; Sasa, Kyohei*; Yamano, Hidemasa; Kubo, Shigenobu
Proceedings of 12th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS12) (Internet), 7 Pages, 2022/10
In order to evaluate long-term coolablity of the debris-bed with decay heat, a three-dimensional calculation method coupled with the debris bed module was developed in this study. The coupled code calculation results show that natural circulation of the coolant between the hot pool and the cold pool is established through the four intermediate heat exchangers after the activation of the dipped direct heat exchangers. The cold pool with the debris-bed is continually cooled not only by the natural circulation flow, but also by heat transfer to the hot pool through the plenum separation plate between the hot pool and the cold pool. The effect of the three-dimensional flow field around the core catcher on the temperature in the debris-bed is about 20K under the current calculation condition.
Yamano, Hidemasa; Kubo, Shigenobu; Tokizaki, Minako*; Nakamura, Hironori*
Proceedings of International Conference on Topical Issues in Nuclear Installation Safety; Strengthening Safety of Evolutionary and Innovative Reactor Designs (TIC 2022) (Internet), 12 Pages, 2022/10
Specific design features of advanced sodium-cooled fast reactors (SFRs) designed in Japan are a passive reactor shutdown system, a passive decay heat removal system (DHRS), and an in-vessel retention (IVR) concept against an anticipated transients without scram (ATWS) in design extension condition (DECs). The present paper describes numerical analysis methodologies for event sequences studied in Japan and some numerical analyses of DECs to show the effectiveness of the passive shutdown system against a typical ATWS and severe accident mitigation measures for the IVR of molten core. For the passive shutdown capability, the numerical analysis has demonstrated the effectiveness of a self-actuated shutdown system against a severe ATWS event, for which the temperature response time was separately evaluated by a computational fluid dynamics (CFD) code. A recently developed debris-bed cooling analysis methodology coupled with a CFD code and a debris-bed module has successfully simulated a three-dimensional coolant flow field near the debris bed with the passive DHRS capability in order to demonstrate the debris-bed coolability on a core catcher.
Ohshima, Hiroyuki; Morishita, Masaki*; Aizawa, Kosuke; Ando, Masanori; Ashida, Takashi; Chikazawa, Yoshitaka; Doda, Norihiro; Enuma, Yasuhiro; Ezure, Toshiki; Fukano, Yoshitaka; et al.
Sodium-cooled Fast Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.3, 631 Pages, 2022/07
This book is a collection of the past experience of design, construction, and operation of two reactors, the latest knowledge and technology for SFR designs, and the future prospects of SFR development in Japan. It is intended to provide the perspective and the relevant knowledge to enable readers to become more familiar with SFR technology.
Ca; Spectroscopy of 
K, Ca, and 
CaKoiwai, Takuma*; Wimmer, K.*; Doornenbal, P.*; Obertelli, A.*; Barbieri, C.*; Duguet, T.*; Holt, J. D.*; Miyagi, Takayuki*; Navrtil, P.*; Ogata, Kazuyuki*; et al.
Physics Letters B, 827, p.136953_1 - 136953_7, 2022/04
Times Cited Count：4 Percentile：52.69(Astronomy & Astrophysics)no abstracts in English
Nakano, Masanao; Nakada, Akira; Kanai, Katsuta; Nagaoka, Mika; Koike, Yuko; Yamada, Ryohei; Kubota, Tomohiro; Yoshii, Hideki*; Otani, Kazunori*; Hiyama, Yoshinori*; et al.
JAEA-Review 2021-040, 118 Pages, 2021/12
JAEA-Review-2021-040.pdf:2.48MB
Based on the regulations (the safety regulation of Tokai Reprocessing Plant, the safety regulation of nuclear fuel material usage facilities, the radiation safety rule, the regulation about prevention from radiation hazards due to radioisotopes, which are related with the nuclear regulatory acts, the local agreement concerning with safety and environment conservation around nuclear facilities, the water pollution control law, and by law of Ibaraki Prefecture), the effluent control of liquid waste discharged from the Nuclear Fuel Cycle Engineering Laboratories of Japan Atomic Energy Agency has been performed. This report describes the effluent control results of the liquid waste in the fiscal year 2020. In this period, the concentrations and the quantities of the radioactivity in liquid waste discharged from the reprocessing plant, the plutonium fuel fabrication facilities, and the other nuclear fuel material usage facilities were much lower than the limits authorized by the above regulations.
Cl isotopesLinh, B. D.*; Corsi, A.*; Gillibert, A.*; Obertelli, A.*; Doornenbal, P.*; Barbieri, C.*; Chen, S.*; Chung, L. X.*; Duguet, T.*; Gmez-Ramos, M.*; et al.
Physical Review C, 104(4), p.044331_1 - 044331_16, 2021/10
Times Cited Count：5 Percentile：46.8(Physics, Nuclear)no abstracts in English
Nagano, Hirohiko; Nakayama, Masataka*; Katata, Genki*; Fukushima, Keitaro*; Yamaguchi, Takashi*; Watanabe, Makoto*; Kondo, Toshiaki*; Atarashi-Andoh, Mariko; Kubota, Tomohiro*; Tateno, Ryunosuke*; et al.
Soil Science and Plant Nutrition, 67(5), p.606 - 616, 2021/10
Times Cited Count：2 Percentile：19.73(Plant Sciences)We analyzed the relationships between nitrogen deposition (deposition of nitrate and ammonium ions) and soil microbial properties in a cool temperate forest surrounded by normally fertilized pasture grasslands in northern Japan. The aim of the present study was to gain the primary information on soil microbial response to moderately elevated nitrogen deposition (
10 kg N ha
y). We established three experimental plots in the forest edge adjacent to grasslands and other three plots in the forest interior at least 700 m away from the grasslands. During May to November 2018, nitrogen deposition in each plot was measured. In August 2018, litter and soil (0-5 cm depth) samples were collected from all plots to measure net nitrogen mineralization and nitrification rates as indicators of microbial activity, and microbial biomass carbon and nitrogen and various gene abundances (i.e. bacterial 16S rRNA, fungal ITS, bacterial amoA, and archaeal amoA genes) as indicators of microbial abundance and structure. Nitrogen deposition in the forest edge was 1.4-fold greater than that in the forest interior, even while the maximum deposition was 3.7 kg N ha. Nitrogen deposition was significantly correlated to the net nitrogen mineralization and nitrification rates and the 16S rRNA and bacterial amoA gene abundances. Microbial community structures were different between litter and soil samples but were similar between the forest edge and interior. Significant correlations of nitrogen deposition to the soil carbon to nitrogen ratio, and the nitrate and ammonium contents were also observed. Thus, our results show that moderately elevated nitrogen deposition in nitrogen-limited forest edges can stimulate microbial activities and abundances in soils.
X raysOkumura, Takuma*; Azuma, Toshiyuki*; Bennet, D. A.*; Caradonna, P.*; Chiu, I. H.*; Doriese, W. B.*; Durkin, M. S.*; Fowler, J. W.*; Gard, J. D.*; Hashimoto, Tadashi; et al.
Physical Review Letters, 127(5), p.053001_1 - 053001_7, 2021/07
Times Cited Count：13 Percentile：79.44(Physics, Multidisciplinary)We observed electronic X rays emitted from muonic iron atoms using a superconducting transition-edge-type sensor microcalorimeter. The energy resolution of 5.2 eV in FWHM allowed us to observe the asymmetric broad profile of the electronic characteristic 
and 
X rays together with the hypersatellite X rays around 6 keV. This signature reflects the time-dependent screening of the nuclear charge by the negative muon and the 
-shell electrons, accompanied by electron side-feeding. Assisted by a simulation, this data clearly reveals the electronic - and -shell hole production and their temporal evolution during the muon cascade process.
Ca from direct reactionsBrowne, F.*; Chen, S.*; Doornenbal, P.*; Obertelli, A.*; Ogata, Kazuyuki*; Utsuno, Yutaka; Yoshida, Kazuki; Achouri, N. L.*; Baba, Hidetada*; Calvet, D.*; et al.
Physical Review Letters, 126(25), p.252501_1 - 252501_7, 2021/06
Times Cited Count：10 Percentile：69.3(Physics, Multidisciplinary)Direct proton-knockout reactions of Sc were studied at the RIKEN Radioactive Isotope Beam Factory. Populated states of Ca were investigated through -ray and invariant-mass spectroscopy. Level energies were calculated from the nuclear shell model employing a phenomenological inter-nucleon interaction. Theoretical cross sections to states were calculated from distorted-wave impulse approximation estimates multiplied by the shell model spectroscopic factors. Despite the calculations showing a significant amplitude of excited neutron configurations in the ground-state of Sc, valence proton removals populated predominantly the ground-state of Ca. This counter-intuitive result is attributed to pairing effects leading to a dominance of the ground-state spectroscopic factor. Owing to the ubiquity of the pairing interaction, this argument should be generally applicable to direct knockout reactions from odd-even to even-even nuclei.
Ar by the (,2) reactionJuhsz, M. M.*; Elekes, Z.*; Sohler, D.*; Utsuno, Yutaka; Yoshida, Kazuki; Otsuka, Takaharu*; Ogata, Kazuyuki*; Doornenbal, P.*; Obertelli, A.*; Baba, Hidetada*; et al.
Physics Letters B, 814, p.136108_1 - 136108_8, 2021/03
Times Cited Count：5 Percentile：46.8(Astronomy & Astrophysics)The nuclear structure of Ar was studied by the (,2) reaction using -ray spectroscopy for the bound and unbound states. Comparing the results to our shell-model calculations, two bound and six unbound states were established. The low cross sections populating the two bound states of Ar could be interpreted as a clear signature for the presence of significant sub-shell closures at neutron numbers 32 and 34 in argon isotopes.
