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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
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)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.
Toigawa, Tomohiro; Hotoku, Shinobu; Kumagai, Yuta; Abe, Yuma*; Oyama, Kanichi*; Fukaya, Hiroyuki; Ban, Yasutoshi; Kida, Takashi; Hasegawa, Satoshi*; Nakano, Masanao*; et al.
Journal of Nuclear Science and Technology, 63(3), p.322 - 327, 2026/03
Times Cited Count：2 Percentile：41.98(Nuclear Science & Technology)The effect of temperature on hydrogen production generated from radiolysis was investigated to determine the associated implications for nuclear fuel reprocessing safety. The hydrogen yield from radiolysis of plutonium nitric acid solution was measured at temperatures up to the boiling temperature of the solution. The results showed no notable temperature dependence even under boiling conditions. The impact of solution agitation on hydrogen production was also assessed, which revealed minor differences in the hydrogen yield between static and agitated conditions at room temperature. These findings suggest that high temperatures or boiling the solution do not considerably enhance hydrogen generation, and provide crucial information for accurately modeling hydrogen risks under severe accidents.
in Reprocessing solutions, 8; Consideration on the temperature dependence and evaluation of the absorbed dose of G value of H in High active liquid wastesAbe, Yuma*; Kumagai, Yuta; Toigawa, Tomohiro; Hotoku, Shinobu; Fukaya, Hiroyuki; Watanabe, Masayuki; Oyama, Kanichi*; Hasegawa, Satoshi*; Nakano, Masanao*; Tamauchi, Yoshikazu*
no journal, ,
We evaluated hydrogen production G-value in high-level liquid waste from the results of hydrogen production test at elevated temperatures and the absorbed dose of the solution calculated by using an ionizing radiation transport code. The temperature effect on the radiolytic hydrogen production was discussed based on the evaluated G-values.
in Reprocessing Solutions, 5; Experimental apparatus and its validation test for measuring radiolytic H production from aqueous plutonium nitrate solutionKumagai, Yuta; Oyama, Kanichi*; Sato, Tomonori; Ishijima, Yasuhiro; Taguchi, Mitsumasa*; Watanabe, Masayuki; Abe, Yuma; Nakano, Masanao*; Tamauchi, Yoshikazu*
no journal, ,
Radiolysis of water generates H gas. The radiolytic H production inevitably goes on when an aqueous solution contains radioactive nuclides such as plutonium nitrate solution in the nuclear fuel reprocessing. In order to obtain experimental data for the H safety assessment, we carried our measurements of H production from the aqueous plutonium nitrate solution at elevated temperatures. In this presentation, we will talk about experimental apparatus and results of a validation test of the apparatus using Co-60 gamma source.
in Reprocessing solutions, 6; Consideration on the temperature dependence of G value of H in plutonium nitrate solutionAbe, 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.
