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Iimoto, Takeshi*; Shimada, Kazumasa; Hashimoto, Makoto; Nagai, Haruyasu; Hohara, Shinya*; Murakami, Kenta*
Nihon Genshiryoku Gakkai-Shi ATOMO
, 66(7), p.356 - 360, 2024/07
no abstracts in English
Sakon, Atsushi*; Nakajima, Kunihiro*; Takahashi, Kazuki*; Hohara, Shinya*; Sano, Tadafumi*; Fukaya, Yuji; Hashimoto, Kengo*
EPJ Web of Conferences, 247, p.09009_1 - 09009_8, 2021/02
In graphite-reflected thermal reactors, even a detector placed far from fuel region may detect a certain degree of the correlation amplitude. This is because mean free path of neutrons in graphite is longer than that in water or polyethylene. The objective of this study is experimentally to confirm a high flexibility of neutron detector placement in graphite reflector for reactor noise analysis. The present reactor noise analysis was carried out in a graphite-moderated and -reflected thermal core in Kyoto University Critical Assembly (KUCA). BF
proportional neutron counters (1" dia.) were placed in graphite reflector region, where the counters were separated by about 35cm and 30cm -thick graphite from the core, respectively. At a critical state and subcritical states, time-sequence signal data from these counters were acquired and analyzed by a fast Fourier transform (FFT) analyzer, to obtain power spectral density in frequency domain. The auto-power spectral density obtained from the counters far from the core contained a significant degree of correlated component. A least-squares fit of a familiar formula to the auto-power spectral density data was made to determine the prompt-neutron decay constant. The decay constant was 63.3
14.5 [1/s] in critical state. The decay constant determined from the cross-power spectral density and coherence function data between the two counters also had a consistent value. It is confirmed that reactor noise analysis is possible using a detector placed at about 35cm far from the core, as we expected.
Yonomoto, Taisuke; Mineo, Hideaki; Murayama, Yoji; Hohara, Shinya*; Nakajima, Ken*; Nakatsuka, Toru; Uesaka, Mitsuru*
Nihon Genshiryoku Gakkai-Shi ATOMO, 63(1), p.73 - 77, 2021/01
no abstracts in English
Uozumi, Yusuke*; Sawada, Yusuke*; Mzhavia, A.*; Nogamine, Sho*; Iwamoto, Hiroki; Kin, Tadahiro; Hohara, Shinya*; Wakabayashi, Genichiro*; Nakano, Masahiro*
Physical Review C, 84(6), p.064617_1 - 064617_11, 2011/12
Times Cited Count：21 Percentile：73.74(Physics, Nuclear)Deuteron production from intermediate-energy proton-nucleus interactions was investigated through experiments and model calculations, mainly to develop a theoretical model by elucidating the mechanism of cluster production. Spectral double-differential cross sections were measured for inclusive (
, 
) reactions on five targets in the periodic table, namely 
C, 
Al, 
V, 
Nb, and 
Au, at beam energies of 300 and 392 MeV. The cross sections were determined in almost the entire outgoing energy range from the highest down to 30 MeV and at laboratory angles from 20
to 104. To interpret the measured spectra, we proposed a new model that includes the nucleon correlations of the initial- and final-state interactions to describe cluster knockout and pickup within the intranuclear cascade model. The results of the model calculations showed reasonable agreements with those of the experiments. Moreover, the model indicated reasonable predictive power for the (, 
He
), (, 
), and (
, ) reactions measured elsewhere.
Se as a probe of neutron capture for the s-process branch-point nucleus 
Makinaga, Ayano*; Hohara, Shinya*; Utsunomiya, Hiroaki*; Goko, Shinji*; Kaihori, Takeshi*; Akimune, Hidetoshi*; Yamagata, Tamio*; Goriely, S.*; Toyokawa, Hiroyuki*; Harano, Hideki*; et al.
Proceedings of Science (Internet), 28, p.239_1 - 239_4, 2010/12
no abstracts in English
Iwamoto, Hiroki; Imamura, Minoru*; Koba, Yusuke*; Fukui, Yoshinori*; Wakabayashi, Genichiro*; Uozumi, Yusuke*; Kin, Tadahiro; Iwamoto, Yosuke; Hohara, Shinya*; Nakano, Masahiro*
Physical Review C, 82(3), p.034604_1 - 034604_8, 2010/09
Times Cited Count：13 Percentile：61.47(Physics, Nuclear)We investigate proton-production double-differential cross sections (DDXs) for 300- and 392-MeV proton-induced reactions on O, V, Tb, Ta, Au, Pb, and Bi. Emitted proton energies are measured with stacked scintillator spectrometers by the 
- technique. Experimental results are compared with the intranuclear cascade (INC) and quantum molecular dynamics models. Although both models can reproduce spectral DDXs, there is a difference at the most forward and backward angles. The cause of these differences is discussed in terms of the refraction caused by the nuclear potential. Angular distributions of the present data are well accounted for by the Kalbach systematics plus INC one-step calculations. The quasi-free-scattering contribution increases with decreasing target mass and increasing emission energy.
Se; Implications for the s-process branching at SeMakinaga, Ayano*; Utsunomiya, Hiroaki*; Goriely, S.*; Kaihori, Takeshi*; Goko, Shinji*; Akimune, Hidetoshi*; Yamagata, Tamio*; Toyokawa, Hiroyuki*; Matsumoto, Tetsuro*; Harano, Hideki*; et al.
Physical Review C, 79(2), p.025801_1 - 025801_8, 2009/02
Times Cited Count：26 Percentile：79.12(Physics, Nuclear)Photoneutron cross sections were measured for Se immediately above the neutron separation energy with quasimonochromatic 
-ray beams to experimentally constrain the E1 strength function for Se. Two sets of the strength function and the level density that equally meet the experimental constraint predict largely different neutron capture cross sections for Se. Based on the Maxwell-averaged cross sections of the latest compilation complemented with the predicted cross sections for Se, we calculated 
N values of the main s-process component using a phenomenological model and deduced empirical abundances of the weak s-process component.
Se; Implications for the s-process thermometerMakinaga, Ayano*; Utsunomiya, Hiroaki*; Kaihori, Takeshi*; Yamagata, Tamio*; Akimune, Hidetoshi*; Goriely, S.*; Toyokawa, Hiroyuki*; Matsumoto, Tetsuro*; Harano, Hideki*; Harada, Hideo; et al.
Nuclear Physics A, 805(1-4), p.564 - 566, 2008/06
Photoneutron cross sections were measured for Se near the neutron threshold energy with quasi-monochromatic rays. Using the Se(,
) cross section as experimental constraints on the E1 strength function, we estimate the neutron capture rates for Se. The solar abundance ratio of s-only nuclides Kr and 
Kr are analyzed in terms of the s-process branching at Se within the local approximation. The corresponding temperature and neutron density regimes are discussed in the light of the s-process scenario in massive stars.
Sm(,n) cross section with laser-Compton scattering rays and the photon difference methodHara, Kaoru; Harada, Hideo; Kitatani, Fumito; Goko, Shinji*; Hohara, Shinya*; Kaihori, Takeshi*; Makinaga, Ayano*; Utsunomiya, Hiroaki*; Toyokawa, Hiroyuki*; Yamada, Kawakatsu*
Journal of Nuclear Science and Technology, 44(7), p.938 - 945, 2007/07
Times Cited Count：48 Percentile：93.16(Nuclear Science & Technology)no abstracts in English
SmHara, Kaoru; Harada, Hideo; Kitatani, Fumito; Goko, Shinji*; Hohara, Shinya*; Kaihori, Takeshi*; Makinaga, Ayano*; Utsunomiya, Hiroaki*; Toyokawa, Hiroyuki*; Yamada, Kawakatsu*; et al.
EUR-22794-EN, p.65 - 68, 2007/00
Neutron capture cross sections of the unstable nuclei 
Sm (t
=90yr) are the fundamental data for the nuclear transmutation, since the Sm is one of radioactive fission products in the nuclear waste. On the other hand, the branching point nucleus Sm is important for characterizing the slow neutron capture process (s-process) nucleosynthesis in the AGB stars. The cross sections of the inverse Sm(,n)Sm reaction were measured with the laser-Compton scattering (LCS) rays at 8.3-12.4 MeV. Quasi-monochromatic beams of LCS photons irradiated an enriched Sm
O
sample. The emitted neutrons were detected with a 4
neutron detector consisting of 20 He proportional counters embedded in a polyethylene moderator. The Au(,n) reaction cross sections were also measured as a standard. In the data analysis, the (,n) cross sections are deduced with two methods. The present data for Sm and Au are compared with the previous data compiled in the IAEA document and the calculation with a nuclear reaction code TALYS. The neutron capture cross sections for Sm in the keV-MeV energy range are evaluated with the present photonuclear data for Sm as constraint in the statistical model calculations.
Zr using laser inverse Compton 
raysHohara, Shinya*; Goko, Shinji*; Makinaga, Ayano*; Kaihori, Takeshi*; Toyokawa, Hiroyuki*; Utsunomiya, Hiroaki*; Hara, Kaoru; Kitatani, Fumito; Harada, Hideo; Matsumoto, Tetsuro*; et al.
JAEA-Conf 2006-009, p.66 - 69, 2006/11
no abstracts in English
Hara, Kaoru; Harada, Hideo; Kitatani, Fumito; Goko, Shinji*; Hohara, Shinya*; Kaihori, Takeshi*; Makinaga, Ayano*; Utsunomiya, Hiroaki*; Toyokawa, Hiroyuki*; Watanabe, Yukinobu*
no journal, ,
Neutron capture cross sections of the unstable nuclei 
Cl (t=3.0
10
yr) and Sm (t=90 yr) are the fundamental data for the nuclear transmutation. The cross sections of the inverse 
Cl(,n)Cl and 
Sm(,n)Sm reaction were measured with the laser-Compton scattering (LCS) rays at 10.4-12.0 MeV and 8.3-12.4 MeV, respectively. Quasi-monochromatic beams of LCS photons irradiated a natural NaCl sample and an enriched SmO sample. The emitted neutrons were detected with a 4 neutron detector. The energy distribution of LCS beam was measured with a 120 
Ge detector or the high-resolution high-energy photon spectrometer (HHS). The present data for Cl, Sm, and Au are compared with the previous data compiled in the IAEA document and the calculation with a nuclear reaction code TALYS.
Hohara, Shinya*; Sono, Hiroki; Koyamada, Takumi*; Yonomoto, Taisuke
no journal, ,
While it is known that the risks of research reactors are smaller than those of commercial power reactors in terms of thermal output and amount of radioactive material contained therein, not many nuclear experts understand the actual state of regulations for research reactors. In order to rationally confirm the safety of nuclear facilities with different risks, the idea of a Graded Approach (GA), which requires that "the strictness of regulations be commensurate with the risk," is emphasized by domestic and international regulatory agencies. In this special session, we will review the actual state of regulations for research reactors, organize the issues from the perspective of GA, and deepen the discussion.
Sm(,n) reaction and s-processHara, Kaoru; Kitatani, Fumito; Harada, Hideo; Utsunomiya, Hiroaki*; Kaihori, Takeshi*; Goko, Shinji*; Hohara, Shinya*; Makinaga, Ayano*; Toyokawa, Hiroyuki*; Watanabe, Yukinobu*
no journal, ,
no abstracts in English
Zr(,n)
Zr cross sectionHohara, Shinya*; Goko, Shinji*; Makinaga, Ayano*; Kaihori, Takeshi*; Hara, Kaoru; Kitatani, Fumito; Toyokawa, Hiroyuki*; Matsumoto, Tetsuro*; Harano, Hideki*; Harada, Hideo; et al.
no journal, ,
no abstracts in English
Tsunoyama, Yuichi*; Satoh, Daiki; Miyamura, Hiroko; Ikuta, Yuko; Onose, Takatoshi*; Tomida, Natsuki*; Hirota, Seiko*; Hohara, Shinya*; Fujishima, Kaori*; Ui, Naoto*; et al.
no journal, ,
The 2nd International Nuclear Science Olympiad (INSO 2025) was held in Malaysia from July 31 to August 5, 2025. INSO is a newly established international science olympiad, launched in 2024, that aims to promote awareness of the peaceful uses of nuclear science and technology. The competition is open to pre-university students under the age of 20 who demonstrate comprehensive knowledge of nuclear science. Each participating country may send up to four student representatives, accompanied by two experts serving as team leaders. Japan made its debut at INSO 2025 by dispatching four high school students (one female second-year and three male third-year students). All members earned medals - one gold, two silver, and one bronze - and two of them also received special awards: the Highest Score in the Experimental Examination Award and the Outstanding Female Participant Award. This presentation reports on the training process that led to these achievements, including the use of online educational materials and an intensive training camp focused on experimental techniques, held at the JAEA Nuclear Science Research Institute. Furthermore, recognizing that radiation safety - a core focus of this academic society - is fundamental to nuclear science and technology, we also propose new initiatives by experts to foster the next generation of talent.
Sm(,n) reaction cross section with laser-Compton scattering raysHara, Kaoru; Kitatani, Fumito; Harada, Hideo; Akimune, Hidetoshi*; Utsunomiya, Hiroaki*; Kaihori, Takeshi*; Goko, Shinji*; Hohara, Shinya*; Makinaga, Ayano*; Yamagata, Tamio*; et al.
no journal, ,
no abstracts in English
SeMakinaga, Ayano*; Utsunomiya, Hiroaki*; Goko, Shinji*; Kaihori, Takeshi*; Harada, Hideo; Kitatani, Fumito; Hara, Kaoru; Toyokawa, Hiroyuki*; Harano, Hideki*; Matsumoto, Tetsuro*; et al.
no journal, ,
no abstracts in English
Takahashi, Kazuki*; Nakajima, Kunihiro*; Sakon, Atsushi*; Hohara, Shinya*; Hashimoto, Kengo*; Fukaya, Yuji; Sano, Tadafumi*
no journal, ,
A Mock-up core for HTTR was configured on the B rack of the Kyoto University Critical Assembly (KUCA), and control rod and center core drop experiments were conducted to obtain time-series data. As a result of performing inverse kinetics analysis on the acquired time-series data, position dependency of each detector was confirmed. Furthermore, in the case with large reactivity worth, such as C1 and the central core, significant differences were found between the analysis results of the integration method and the least squares inverse kinetics method.
analysis for HTTR simulated core in KUCANakajima, Kunihiro*; Sakon, Atsushi*; Takahashi, Kazuki*; Hohara, Shinya*; Hashimoto, Kengo*; Fukaya, Yuji; Sano, Tadafumi*
no journal, ,
Time series data of neutron detector was obtained under Am-Be steady neutron source driven condition and neutron source from fuel in the graphite core system configured on B rack of the Kyoto University Critical Assembly (KUCA), and the reactor noise analysis with Rossi- method was performed. As a result, neutron correlation component could not be observed under Am-Be neutron source driven condition, but a significant correlation component was observed under fuel neutron source driven condition, and prompt neutron decay constant could be determined.
Sakon, Atsushi*; Nakajima, Kunihiro*; Takahashi, Kazuki*; Hohara, Shinya*; Sano, Tadafumi*; Fukaya, Yuji; Hashimoto, Kengo*
no journal, ,
Subcriticality measurement experiment by reactor noise analysis was performed in mock-up core for HTTR configured on B rack of the Kyoto University Critical Assembly (KUCA). The experiments were carried out in low power critical state and in the subcritical state driven by Am-Be neutron source, and the measurements were performed with several neutron detectors at different positions. We analyzed neutron detector time series data acquired by experiment by power spectrum method, and tried to estimate the prompt neutron decay constant of the system.
