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.

Decommissioning report for Wastewater Treatment Facility (Part 2); Chapter on contamination inspection section

Yamamoto, Keisuke; Nakagawa, Takuya; Shimojo, Hiroto; Kijima, Jun; Miura, Daiya; Onose, Yoshihiko*; Namba, Koji*; Uchida, Hiroaki*; Sakamoto, Kazuhiko*; Ono, Chika*; et al.

JAEA-Technology 2024-019, 211 Pages, 2025/02

JAEA-Technology-2024-019.pdf:35.35MB

The uranium enrichment facilities at the Nuclear Fuel Cycle Engineering Laboratories of Japan Atomic Energy Agency (JAEA) were constructed sequentially to develop uranium enrichment technology with centrifugal separation method. The developed technologies were transferred to Japan Nuclear Fuel Limited until 2001. And the original purpose has been achieved. Wastewater Treatment Facility, one of the uranium enrichment facilities, was constructed in 1976 to treat radioactive liquid waste generated at the facilities, and it finished the role in 2008. In accordance with the Medium/Long-Term Management Plan of JAEA Facilities, interior equipment installed in this facility had been dismantled and removed since November 2021 to August 2023. This report summarizes the findings obtained through the work related to the contamination inspection methods cancellation the controlled area of Wastewater Treatment Facility from September 2023 to March 2024.

Magnetic-field-induced polarization flop in multiferroic TmMnO

Fukunaga, Mamoru*; Sakamoto, Yuma*; Kimura, Hiroyuki*; Noda, Yukio*; Abe, Nobuyuki*; Taniguchi, Koji*; Arima, Takahisa*; Wakimoto, Shuichi; Takeda, Masayasu; Kakurai, Kazuhisa; et al.

Physical Review Letters, 103(7), p.077204_1 - 077204_4, 2009/08

https://doi.org/10.1103/PhysRevLett.103.077204

Investigation on the temperature dependence of G value of H in Reprocessing solutions, 6; Consideration on the temperature dependence of G value of H in plutonium nitrate solution

Abe, Yuma; Kumagai, Yuta; Hotoku, Shinobu; Inoue, Masao*; Suzuki, Sachiko*; Toigawa, Tomohiro; Watanabe, Masayuki; Nakano, Masanao*; Oyama, Kanichi*; Tamauchi, Yoshikazu*

no journal, , 

Hydrogen is generated from aqueous solutions containing radioactive materials through radiolysis of water. Because of the wide variety of solution properties treated in reprocessing plants and the difficulty of conducting experiments with radioactive materials, few studies have taken into account the properties of the solutions actually used. In particular, there are very few studies on the effects of agitation by bubbling, etc. and on temperature dependence. In this study, hydrogen generation was measured in Pu nitrate solution with and without agitation and at different temperatures, and G-values were calculated. Under the test conditions where the solution was agitated (bubbling agitation or boiling), the G-value increased by about 20 to 30% compared to that under static conditions at room temperature. Under the stirring condition, there was no clear trend of increase/decrease of G-values with increasing temperature. From these results, it is considered that the G-value of Pu nitrate solution increases with stirring and that there is no significant temperature dependence in the stirred condition. The reason for the observed temperature dependence of the hydrogen G-values in this study, which gives different from that of the nitric acid solution in the validation experiment, may be due to the difference in the composition and reaction behavior of the radicals produced by radiolysis between Co-60 gamma-rays and alpha-rays from Pu due to the difference in LET.

Investigation on the temperature dependence of G value of H in Reprocessing Solutions, 7; Measurement of hydrogen generation test using high active liquid waste

Hotoku, Shinobu; Fukaya, Hiroyuki; Kumagai, Yuta; Inoue, Masao*; Suzuki, Sachiko*; Ban, Yasutoshi; Kida, Takashi; Watanabe, Masayuki; Abe, Yuma*; Tamauchi, Yoshikazu*

no journal, , 

In order to evaluate the amount of hydrogen generated by radiolysis of water from the high active liquid waste in the reprocessing process, In this study a spent fuel solution was used and tests were conducted under the conditions of the solution temperature and the presence or absence of agitation and analyzed of the components in spent fuel solution. In this presentation, it is report on the outline of the test and the results obtained in the test.

Corrosion behavior of Ni-based alloy in molten FLiNaK salt as a fundamental research on molten salt reactors

Ogasawara, Koji*; Sekiguchi, Yuma*; Terai, Takayuki*; Kawamura, Hiroshi*; Tsuchiya, Kunihiko; Watanabe, Takashi*

no journal, , 

no abstracts in English

Migration dynamics of radiocesium in the river systems of the Fukushima Prefecture and surrounding areas

Ochiai, Shinya*; Nagao, Seiya*; Nakanishi, Takahiro; Tsuruta, Tadahiko; Misono, Toshiharu; Watanabe, Shun*; Suzuki, Kyuma*; Tomihara, Seiichi*

no journal, , 

We investigated the controlling factors of radiocesium derived from the nuclear accident in each river systems in Fukushima Prefecture and the surrounding area. Dissolved Cs concentration / Cs deposition ratio tended to be higher in the Tone River and lower in the Natsui River than in the Abukuma River. Dissolved Cs concentration generally decreases exponentially, but the half-life is shorter in the Natsui River and longer in the Tone River than in the Abukuma River.