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Journal Articles

Radiolysis of boiling water

Yang, S.*; Katsumura, Yosuke*; Yamashita, Shinichi*; Matsuura, Chihiro*; Hiroishi, Daisuke*; Lertnaisat, P.*; Taguchi, Mitsumasa

Radiation Physics and Chemistry, 123, p.14 - 19, 2016/06

 Times Cited Count:2 Percentile:23.29(Chemistry, Physical)

$$gamma$$-radiolysis of boiling water has been investigated. The G-value of H$$_{2}$$ evolution was found to be very sensitive to the purity of water. In high-purity water, both H$$_{2}$$ and O$$_{2}$$ gases were formed in the stoichiometric ratio of 2:1; a negligible amount of H$$_{2}$$O$$_{2}$$ remained in the liquid phase. The G-values of H$$_{2}$$ and O$$_{2}$$ gas evolution depend on the dose rate: lower dose rates produce larger yields. To clarify the importance of the interface between liquid and gas phase for gas evolution, the gas evolution under Ar gas bubbling was measured. A large amount of H$$_{2}$$ was detected, similar to the radiolysis of boiling water. The evolution of gas was enhanced in a 0.5 M NaCl aqueous solution. Deterministic chemical kinetics simulations elucidated the mechanism of radiolysis in boiling water.

Oral presentation

Probabilistic safety analysis on the reprocessing plant at Rokkashomura, 12; Experimental study on the effect suppressing hydrogen emission from concentrated high level liquid waste, 1

Kodama, Takashi*; Nakano, Masamichi*; Matsuoka, Shingo*; Matsuura, Chihiro*; Ito, Yasuo*; Kurosu, Katsuya*; Shiraishi, Hirotsugu; Katsumura, Yosuke*

no journal, , 

It has been known that although a considerable amount of hydrogen is produced radiolytically in the high level liquid waste, only small part is emitted into the gas phase when the liquid depth is large. We report here the results of an experimental study which shows that the liquid-depth effect is caused not by the reaction between hydrogen and radicals, as has been previously suggested, but by Pd-catalyzed reaction between hydrogen and nitric acid. The method for evaluating the magnitute of the effect is also proposed.

Oral presentation

The Inhibitory effect of hydrogen release from high active liquid waste, 2; Mechanism of solution depth effect

Kodama, Takashi*; Nakano, Masanao*; Hayashi, Yoshiaki*; Matsuoka, Shingo*; Ito, Yasuo*; Matsuura, Chihiro*; Shiraishi, Hirotsugu; Katsumura, Yosuke*

no journal, , 

We have reported in the previous meeting that the accumulation of radiolytically produced hydrogen in high-level liquid waste is suppressed owing to some oxidation reaction catalyzed by Pd in the solution. In this report, we present the results of a hydrogen bubbling experiment with mock high-level liquid waste, made to clarify the species involved in the reaction. Analysis was made on nitrous acid and nitric acid in the solution, and also on nitrogen oxide in the outlet gas. It was found that although the concentration of nitrous acid present in the solution is small, nitrogen oxide, consisting mostly of NO, is detected in the gas at concentration corresponding to the decrease of nitric acid in the solution. The amount of the produced nitrogen oxide matched roughly with an estimated amount of reacted hydrogen, confirming that nitric acid is the oxidant.

Oral presentation

The Inhibitory effect of hydrogen release from high active liquid waste, 3; Estimation of the hydrogen concentration of upper space of tank

Kodama, Takashi*; Nakano, Masanao*; Hayashi, Yoshiaki*; Matsuoka, Shingo*; Ito, Yasuo*; Matsuura, Chihiro*; Shiraishi, Hirotsugu; Katsumura, Yosuke*

no journal, , 

We report here an evaluation for hydrogen concentration that may be attained in the upper space of the high-level liquid waste tank when the gas sweeping function happens to be lost. The parameters are the rate of radiolytic production of hydrogen, the rate of Pd-catalyzed hydrogen consuming reaction, and the solubility of hydrogen. For the first, a literature value on nitric acid solution was used, while for the second and third, experimental estimate was made in the present study with mock high-level liquid waste. All data have been taken at ambient temperature. For simplicity, it was assumed that both the gas and the liquid are homogeneous, and that the two phases are in equilibrium regarding hydrogen concentration. These led to an estimate of 0.6% for the hydrogen concentration in the gas phase, a value smaller than the lower limit of explosion.

Oral presentation

Possibility of production and condensation of hydrogen from boiling water under irradiation in the Fukushima Daiichi F4 fuel storage pool

Yamashita, Shinichi; Hirade, Tetsuya; Matsuura, Chihiro*; Iwamatsu, Kazuhiro; Taguchi, Mitsumasa; Katsumura, Yosuke*

no journal, , 

Fukushima Daiichi Nuclear Power Plant Unit-4 was under an inspection on the day of Tohoku earthquake, and all of the fuels were cooled in the fuel storage pool. However, the explosion occurred only four days after the cooling of the pool stopped. Later, the pool was investigated and it was clarified that the fuels were not so damaged and the water was not contaminated with radioisotopes. There are several explanations of the cause of the explosion. We picked up one possibility that the radiolysis of the water was the source of the hydrogen and that the vapor condensation could make the high hydrogen density behind the cold roof or walls, and investigated by an experiment of boiled water radiolysis by $$gamma$$-rays. The results can explain some of the typical things happened on the explosion of Unit-4.

Oral presentation

Radiolysis of boiling water and hydrogen enrichment; A Mystery of the hydrogen explosion at No.4 reactor in Fukushima Daiichi Nuclear Power Station

Katsumura, Yosuke; Yamashita, Shinichi; Hirade, Tetsuya; Matsuura, Chihiro*; Iwamatsu, Kazuhiro*; Taguchi, Mitsumasa

no journal, , 

no abstracts in English

Oral presentation

Radiolysis of boiling water

Katsumura, Yosuke*; Matsuura, Chihiro*; Yamashita, Shinichi; Hirade, Tetsuya; Iwamatsu, Kazuhiro; Taguchi, Mitsumasa

no journal, , 

We successfully obtained the experimental results of large amount of production of hydrogen gas by boiling water radiolysis. Moreover, G(H$$_{2}$$) for boiling sea water was larger than G(H$$_{2}$$) for boiling pure water. We also identified that the yields of hydrogen production for water with gas babbling even at the room temperature could be as high as at that for the boiling water.

Oral presentation

Hydrogen evolution in the radiolysis of boiling water and non-homogenous distribution

Katsumura, Yosuke*; Matsuura, Chihiro*; Yamashita, Shinichi; Hirade, Tetsuya; Iwamatsu, Kazuhiro; Taguchi, Mitsumasa

no journal, , 

Relevant to the nuclear accident at Fukushima Dai-ichi Nuclear Power Station, a radiolysis study of boiling water irradiated with Co-60 $$gamma$$ rays has been conducted. The evolution of hydrogen gas was clearly detected under boiling condition, while an extremely small amount of gas formation was found under the stable condition without boiling even at 97$$^{circ}$$C. The G(H$$_{2}$$) of 0.37 was obtained under boiling condition. It was found that solution of 3.5% NaCl, similar to seawater, enhances the evolution, and the value of 0.7 was obtained. On the contrary, the O$$_{2}$$ gas formation was much lower than that of H$$_{2}$$, suggesting the formed H$$_{2}$$O$$_{2}$$ is not decomposed and remained in liquid. In addition, it was found that the evolved hydrogen is distributed selectively at the inner surface of the container under boiling condition. Gas injection experiments were also done without irradiation to clarify the behavior of hydrogen in the container.

Oral presentation

Neutron scattering studies on trinuclear Zn-Ln-Zn single-molecule magnets

Kofu, Maiko; Kajiwara, Takashi*; Kawamura, Seiko; Kikuchi, Tatsuya*; Nakajima, Kenji; Matsuura, Masato*; Shibata, Kaoru; Nagao, Michihiro*; Yamamuro, Osamu*

no journal, , 

no abstracts in English

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