Effect of temperature on radiolytically generated hydrogen yield from actual nuclear fuel-derived solution

Toigawa, Tomohiro; Hotoku, Shinobu; Kumagai, Yuta; Abe, Yuma*; Oyama, Kanichi*; Fukaya, Hiroyuki; Tsubata, Yasuhiro; Ban, Yasutoshi; Kida, Takashi; Hasegawa, Satoshi*; et al.

Journal of Nuclear Science and Technology, 63(8), p.969 - 975, 2026/08

https://doi.org/10.1080/00223131.2026.2637453

The effect of temperature on hydrogen generated from radiolysis was investigated to determine the safety implications in nuclear fuel reprocessing. Radiolytic hydrogen production poses a risk due to its flammability, especially when it accumulates in confined spaces without ventilation. Herein, generation of radiolytic hydrogen from an actual nuclear fuel-derived solution is investigated. Compared to previous studies using a plutonium nitric acid solution, this study evaluates radiolytic hydrogen yield under more realistic conditions, reflecting post-irradiation fuel composition. G-values of H are determined at multiple temperatures, and the impact of alpha, beta, and gamma radiation doses is evaluated using PHITS-based simulations. Findings from this study confirmed a reduction in hydrogen yield due to scavenging effects of high-concentration nitric acid and metal ions dissolved in the solution, and temperature dependence appeared to be minor. A weak decreasing trend of G-values with temperature under agitated conditions might be related to hydrogen consumption by palladium species.

J-PARC LINAC 50 Hz operation verification study

Kondo, Yasuhiro; Chimura, Motoki; Cicek, E.*; Fukui, Yuji*; Futatsukawa, Kenta*; Fuwa, Yasuhiro; Goto, Rikuto*; Hirano, Koichiro; Ishikawa, Masaki*; Ito, Takashi; et al.

Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.124 - 129, 2026/03

https://www.pasj.jp/web_publish/pasj2025/proceedings/PDF/FRO6/FRO601.pdf

Various upgrade plans of the J-PARC linac are underway, and repetition-rate doubling project is one of the most important part. Currently, the linac supplies a 400~MeV H ion beam to the 3~GeV synchrotron (RCS) at a repetition rate of 25~Hz. However, to deliver the beam to both RCS and proton-beam irradiation facility under planning, it is necessary to raise the repetition rate from 25~Hz to 50~Hz. Prior to construction of the beamline to the irradiation facility, we conducted a verification of the 50~Hz operation of all the linac apparatus simultaneously within the current operational limits in May 2025. And also, the verification of the 50~Hz operation of the particle counter system, which is one of the most important safety device of the J-PARC accelerator, was conducted. As a result, any significant problems were not found out, and it is now ready for the upcoming 50~Hz-beam acceleration demonstration. This paper describes this details of the demonstration of the 50~Hz operation, without beam acceleration, of the J-PARC linac.

Progress in linac beam commissioning for high-intensity operations for J-PARC power upgrades

Liu, Y.*; Otani, Masashi*; Miyao, Tomoaki*; Nakazawa, Yuga*; Shibata, Takanori*; Nammo, Kesao*; Fang, Z.*; Futatsukawa, Kenta*; Fukui, Yuji*; Mizobata, Satoshi*; et al.

Proceedings of 16th International Particle Accelerator Conference (IPAC25) (Internet), p.855 - 857, 2025/11

https://doi.org/10.18429/JACoW-IPAC2025-TUAD1

Stabilization of post-experiment nuclear materials in Plutonium Fuel Research Facility

Sato, Takumi; Otobe, Haruyoshi; Morishita, Kazuki; Marufuji, Takato; Ishikawa, Takashi; Fujishima, Tadatsune; Nakano, Tomoyuki

JAEA-Technology 2023-016, 41 Pages, 2023/09

JAEA-Technology-2023-016.pdf:2.74MB

This report summarizes the results of the stabilization treatments of post-experiment nuclear materials in Plutonium Fuel Research Facility (PFRF) from August 2018 to March 2021. Based on the management standards for nuclear materials enacted after the contamination accident that occurred at PFRF on June 6, 2017, the post-experiment nuclear materials containing plutonium (Pu): samples mixed with organic substances that cause an increase in internal pressure due to radiolysis (including X-ray diffraction samples mixed with epoxy resin and plutonium powder which caused contamination accidents), carbides and nitrides samples which is reactive in air, and chloride samples which may cause corrosion of storage containers, were selected as targets of the stabilization. The samples containing organic materials, carbides and nitrides were heated in an air flow at 650 C and 950 C for 2 hours respectively to remove organic materials and convert uranium (U) and Pu into oxides. U and Pu chlorides in LiCl-KCl eutectic melt were reduced and extracted into liquid Cd metal by a reaction with lithium (Li) -cadmium (Cd) alloy and converted to U-Pu-Cd alloy at 500 C or higher. All of the samples were stabilized and stored at PFRF. We hope that the contents of this report will be utilized to consider methods for stabilizing post experiment nuclear materials at other nuclear fuel material usage facilities.

Intruder configurations in Ne at the transition into the island of inversion; Detailed structure study of Ne

Wang, H.*; Yasuda, Masahiro*; Kondo, Yosuke*; Nakamura, Takashi*; Tostevin, J. A.*; Ogata, Kazuyuki*; Otsuka, Takaharu*; Poves, A.*; Shimizu, Noritaka*; Yoshida, Kazuki; et al.

Physics Letters B, 843, p.138038_1 - 138038_9, 2023/08

https://doi.org/10.1016/j.physletb.2023.138038

Detailed -ray spectroscopy of the exotic neon isotope Ne has been performed using the one-neutron removal reaction from Ne. Based on an analysis of parallel momentum distributions, a level scheme with spin-parity assignments has been constructed for Ne and the negative-parity states are identified for the first time. The measured partial cross sections and momentum distributions reveal a significant intruder p-wave strength providing evidence of the breakdown of the N = 20 and N = 28 shell gaps. Only a weak, possible f-wave strength was observed to bound final states. Large-scale shell-model calculations with different effective interactions do not reproduce the large p-wave and small f-wave strength observed experimentally, indicating an ongoing challenge for a complete theoretical description of the transition into the island of inversion along the Ne isotopic chain.

Japan's contribution to international development of nuclear and radiation education, 2; Instructor training program for human resource development in Asian countries entrusted from MEXT

Nakano, Yoshihiro; Suzuki, Takashi; Irie, Tsutomu; Kato, Hiroshi

Nihon Genshiryoku Gakkai-Shi ATOMO, 63(11), p.757 - 759, 2021/11

https://doi.org/10.3327/jaesjb.63.11_757

no abstracts in English

Corrigendum: Beam range estimation by measuring bremsstrahlung (2012 Phys. Med. Biol. 57 2843)

Yamaguchi, Mitsutaka; Torikai, Kota*; Kawachi, Naoki; Shimada, Hirofumi*; Sato, Takahiro; Nagao, Yuto; Fujimaki, Shu; Kokubun, Motohide*; Watanabe, Shin*; Takahashi, Tadayuki*; et al.

Physics in Medicine & Biology, 61(9), p.3638 - 3644, 2016/05

https://doi.org/10.1088/0031-9155/61/9/3638

no abstracts in English

Proton order-disorder phenomena in a hydrogen-bonded rhodium--semiquinone complex; A Possible dielectric response mechanism

Mitsumi, Minoru*; Ezaki, Kazunari*; Komatsu, Yuki*; Toriumi, Koshiro*; Miyato, Tatsuya*; Mizuno, Motohiro*; Azuma, Nobuaki*; Miyazaki, Yuji*; Nakano, Motohiro*; Kitagawa, Yasutaka*; et al.

Chemistry; A European Journal, 21(27), p.9682 - 9696, 2015/06

https://doi.org/10.1002/chem.201500796

NHEJ repair rather than HR repair is the primary function to target to enhance radiosensitization at high LET values

Takahashi, Akihisa*; Kubo, Makoto*; Igarashi, Chie*; Yoshida, Yukari*; Funayama, Tomoo; Kobayashi, Yasuhiko; Nakano, Takashi*

JAEA-Review 2014-050, JAEA Takasaki Annual Report 2013, P. 82, 2015/03

https://doi.org/10.11484/jaea-review-2014-050

DNA double-strand breaks (DSBs) induced by ionizing radiation pose a major threat to cell survival. The cell can respond to the presence of DSBs, through two major repair pathways: Homologous recombination (HR) and non-homologous end-joining (NHEJ). Higher levels of cell death are induced by high-LET radiation when compared to low-LET radiation, even at the same doses because of less effective or more inefficient DNA repair. In this study, we examine the effects of radiation with different LET values on DNA DSB repair and radiosensitivity. Wild-type cells and HR deficient (but NHEJ proficient) cells exhibited the high RBE values at LET values of 108 keV/ m. The RBE value for each cell type decreased with increasing LET values over 200 keV/m. Although NHEJ proficient cells had an almost constant SER value, NHEJ deficient cells showed a high SER value when compared to NHEJ proficient cells, even with increasing LET values.

The Behavior of radiolytically produced hydrogen in a high-level liquid waste tank of a reprocessing plant; Hydrogen concentration in the ventilated tank air

Kinuhata, Hiroshi*; Shirato, Yoji; Tomiyama, Masahiro; Kodama, Takashi*; Nakano, Masanao*; Yasuda, Takeshi; Tsutagi, Koichi; Yoshino, Yasuyuki; Nakamura, Yoshinobu; Tamauchi, Yoshikazu*; et al.

Nuclear Technology, 189(2), p.122 - 132, 2015/02

https://doi.org/10.13182/NT14-11

We reported that H formed in simulated high-level liquid waste (SHLLW) by Co -irradiation is consumed due to the catalytic effect of the Pd ion, and derived equations to learn the gas-phase H concentration in a tank in case of a sweeping air function loss. In order to confirm that such quantitative treatment is applicable to actual high-level liquid waste (HLLW), we measured the H concentration in the ventilated air of HLLW tanks of the Tokai Reprocessing Plant and compared it with that derived from the SHLLW results.