Establishment of neutron spectrum evaluation method for irradiation facility in equilibrium core of JRR-3 silicide fuel

Nakamura, Takemi; Ogasawara, Reira; Ushijima, Hiroki; Okada, Yuji; Yamaguchi, Atsushi; Horiguchi, Hironori; Hirane, Nobuhiko

JAEA-Technology 2026-008, 39 Pages, 2026/07

JAEA-Technology-2026-008.pdf:2.55MB

Irradiation studies targeting thermal neutrons to fast neutrons are being conducted at the JRR-3 research reactor, and to accurately evaluate the irradiation effect, it is necessary to consider the influence of the neutron spectrum. Fuels and cadmium wires used as combustible absorbers are burned by reactions with neutrons because the JRR-3 is a high-power 20MW reactor, and the fuel shuffling and replacement are performed periodically to ensure uniform burnup and long-term operation. Since it is necessary to accurately reproduce the burnup history both temporally and spatially, it is difficult to evaluate the neutron spectrum with high accuracy through computational analysis. Hence, we investigated a method that can easily and accurately evaluate neutron spectra at irradiation facility in equilibrium core of JRR-3 silicide fuel and verified the validity of the evaluation results. This method uses data of initial guess spectrum and response functions for each irradiation field calculated using MCNP code, reaction rate measured from neutron fluence monitors such as Au-Al and Ni wire to perform unfolding using SAND-II. We conducted characteristic measurements from fiscal year 2023 to 2025 and performed unfolding using actual measured values from neutron fluence monitors for seven cycles. As a result, in all cases, the C/E ratio of the reaction rate was 1.000, indicating good convergence, and the difference from the unfolding and measured neutron flux was within 0.3% for hydraulic irradiation facility HR-1, within 0.8% for pneumatic irradiation facility PN-2, and 0% for vertical irradiation facility RG-2. This suggests that the results of the unfolded spectrum are valid. The application of this method can meet a wide range of user needs, and it is expected to greatly contribute to the advancement of irradiation research with improved reliability of the JRR-3 irradiation field.

Structure and properties of amorphous magnesium carbonate, a key material for geological storage of carbon dioxide

Kyono, Atsushi*; Yamamoto, Genichiro*; Yoneda, Yasuhiro; Okada, Satoru*

Isotope News, (783), p.23 - 27, 2022/10

Mineral traps are attracting attention as an underground storage method for carbon dioxide. Carbon dioxide laden groundwater reacts with basalt to form magnesite. The formed magnesium carbonate phase varies in many ways, but we tried to clarify the structure because all of them pass through amorphous magnesium carbonate. Pair distribution function using high-energy X-ray diffraction revealed that amorphous magnesium carbonate has a structure similar to that of hydromagnesite. It can be said that it is a safe sequestration method as a carbon dioxide storage technology.

Thermally altered subsurface material of asteroid (162173) Ryugu

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Takagi, Yasuhiko*; Nakamura, Tomoki*; Hiroi, Takahiro*; Matsuoka, Moe*; et al.

Nature Astronomy (Internet), 5(3), p.246 - 250, 2021/03

https://doi.org/10.1038/s41550-020-01271-2

Here we report observations of Ryugu's subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. However, the strength and shape of the OH feature still suggests that the subsurface material experienced heating above 300 C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 C at the estimated excavation depth of 1 m, even if the semimajor axis is reduced to 0.344 au. This supports the hypothesis that primary thermal alteration occurred due to radiogenic and/or impact heating on Ryugu's parent body.

scattering length from photoproduction on the proton near the reaction threshold

Ishikawa, Takatsugu*; Fujimura, Hisako*; Fukasawa, Hiroshi*; Hashimoto, Ryo*; He, Q.*; Honda, Yuki*; Hosaka, Atsushi; Iwata, Takahiro*; Kaida, Shun*; Kasagi, Jirota*; et al.

Physical Review C, 101(5), p.052201_1 - 052201_6, 2020/05

https://doi.org/10.1103/PhysRevC.101.052201

Magnetization dynamics and its scattering mechanism in thin CoFeB films with interfacial anisotropy

Okada, Atsushi*; He, S.*; Gu, B.; Kanai, Shun*; Soumyanarayanan, A.*; Lim, S. T.*; Tran, M.*; Mori, Michiyasu; Maekawa, Sadamichi; Matsukura, Fumihiro*; et al.

Proceedings of the National Academy of Sciences of the United States of America, 144(15), p.3815 - 3820, 2017/04

http://doi.org/10.1073/pnas.1613864114

Model magnet development of D1 beam separation dipole for the HL-LHC upgrade

Nakamoto, Tatsushi*; Sugano, Michinaka*; Xu, Q.*; Kawamata, Hiroshi*; Enomoto, Shun*; Higashi, Norio*; Idesaki, Akira; Iio, Masami*; Ikemoto, Yukio*; Iwasaki, Ruri*; et al.

IEEE Transactions on Applied Superconductivity, 25(3), p.4000505_1 - 4000505_5, 2015/06

https://doi.org/10.1109/TASC.2014.2361404

Recently, development of superconducting magnet system with high radiation resistance has been demanded for application in accelerator facilities such as CERN LHC. In order to realize superconducting magnet system with high radiation resistance, it is necessary to develop electrical insulator with high radiation resistance because the electrical insulator is made of organic materials whose radiation resistance is inferior to that of inorganic materials. We developed a glass fiber reinforced plastic with bismaleimide-triazine resin. The developed material showed excellent radiation resistance; the material evolved gases of 510 mol/g and maintained flexural strength of 640MPa (90% of initial value).

High power laser developments with femtosecond to nanosecond pulse durations for laser shock science and engineering

Kiriyama, Hiromitsu; Mori, Michiaki; Suzuki, Masayuki*; Daito, Izuru*; Okada, Hajime; Ochi, Yoshihiro; Tanaka, Momoko; Sato, Masatoshi*; Tamaoki, Yoshinori*; Yoshii, Takehiro*; et al.

Reza Kenkyu, 42(6), p.441 - 447, 2014/06

http://ci.nii.ac.jp/naid/40020137371

We describe three specific high power laser systems that are being developed in our laboratory for many applications in high field science, nonlinear optics and material processing. We report on a femtosecond petawatt-class Ti:sapphire chirped-pulse amplification laser system that can produce a pulse energy of 20 J of 40 fs pulse duration, a picosecond high intensity Yb:YAG chirped-pulse amplification laser system that can generate a pulse energy of 100 mJ of 0.5 ps pulse duration, and a nanosecond high repetition rate Nd:YAG laser system that can provide an average power of 360 W with a pulse duration of 30 ns delivered at a 1 kHz repetition rate. We discuss the basic design aspects and present the results from our experimental investigations of these laser systems.

Polarization-selectable cavity locking method for generation of laser Compton scattered -rays

Kosuge, Atsushi; Mori, Michiaki; Okada, Hajime; Hajima, Ryoichi; Nagashima, Keisuke

Optics Express (Internet), 22(6), p.6613 - 6619, 2014/03

https://doi.org/10.1364/OE.22.006613

Nowadays, generation of energy-tunable, monochromatic -rays is needed to establish a nondestructive assay method of nuclear fuel materials. The -rays are generated by collision of laser photons stored in a cavity and relativistic electrons. We propose a configuration of an enhancement cavity capable of performing polarization control fabricated by a combination of a four-mirror ring cavity with a small spot inside a cavity and a three-mirror of reflective optics as an image inverter for polarization-selectable -rays. The image inverter introduces a phase shift of specific polarization which can be used to generate an error signal to lock an optical cavity at a resonance condition.

Ultra-intense, high spatio-temporal quality petawatt-class laser system and applications

Kiriyama, Hiromitsu; Shimomura, Takuya; Mori, Michiaki; Nakai, Yoshiki*; Tanoue, Manabu; Kondo, Shuji; Kanazawa, Shuhei; Pirozhkov, A. S.; Esirkepov, T. Zh.; Hayashi, Yukio; et al.

Applied Sciences (Internet), 3(1), p.214 - 250, 2013/03

https://doi.org/10.3390/app3010214

This paper reviews techniques for improving the temporal contrast and spatial beam quality in an ultra-intense laser system that is based on chirped-pulse amplification (CPA). We describe the design, performance, and characterization of our laser system, which has the potential for achieving a peak power of 600 TW. We also describe applications of the laser system in the relativistically dominant regime of laser-matter interactions and discuss a compact, high efficiency diode-pumped laser system.

Event structure and double helicity asymmetry in jet production from polarized collisions at = 200 GeV

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Y.*; Al-Bataineh, H.*; Alexander, J.*; Aoki, K.*; Aphecetche, L.*; Armendariz, R.*; et al.

Physical Review D, 84(1), p.012006_1 - 012006_18, 2011/07

https://doi.org/10.1103/PhysRevD.84.012006

We report on the event structure and double helicity asymmetry () of jet production in longitudinally polarized collisions at = 200 GeV. Photons and charged particles were measured by the PHENIX experiment. Event structure was compared with the results from PYTHIA event generator. The production rate of reconstructed jets is satisfactorily reproduced with the next-to-leading-order perturbative QCD calculation. We measured = -0.0014 0.0037 at the lowest bin and -0.0181 0.0282 at the highest bin. The measured is compared with the predictions that assume various distributions.