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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.
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.
Tashiro, Shinsuke; Matsumoto, Tetsuya; Kataoka, Osamu; Amano, Yuki; Abe, Hitoshi; Yamane, Yuichi; Yoshida, Kazuo; Ishikawa, Jun; Uchiyama, Gunzo; Ueda, Yoshinori*; et al.
no journal, ,
Measurements on the release ratios of aerial radioactive materials from mocked fuel reprocessing liquid waste under its boiling to dryness process were performed using labo-scaled experiments. Test sample, dissolved 27 elements into nitric acid and arranged to 2M acidity, was heated up to 300 
C under the constant air ventilation. Steam, gaseous and airborne materials were collected or absorbed at the condenser, the air filter and the washing bottles. The accumulated release ratios of mocked FP elements from samples were determined using ICP-MS. From the accumulated release ratios determined from the condensed samples, the major release of Cs and Ru could be involved the release of mist and gaseous RuO
, respectively. Besides, accumulated release ratios of Ru was about 10 to 1000 times higher than Cs, differed from the literature using fuel reprocessing liquid waste. Its differences could be influenced the nitrous acid, which was reduced the generation of RuO.
Tomiyama, Masahiro; Yasuda, Takeshi; Tsutagi, Koichi; Yoshino, Yasuyuki; Shirato, Yoji; Nakamura, Yoshinobu; Kinuhata, Hiroshi*; Kodama, Takashi*; Nakano, Masanao*; Tamauchi, Yoshikazu*; et al.
no journal, ,
no abstracts in English
Kinuhata, Hiroshi*; Kodama, Takashi*; Nakano, Masanao*; Tamauchi, Yoshikazu*; Matsuoka, Shingo*; Tomiyama, Masahiro; Yasuda, Takeshi; Tsutagi, Koichi; Yoshino, Yasuyuki; Shirato, Yoji; et al.
no journal, ,
no abstracts in English
Tashiro, Shinsuke; Matsumoto, Tetsuya; Kataoka, Osamu; Amano, Yuki; Abe, Hitoshi; Yamane, Yuichi; Yoshida, Kazuo; Ishikawa, Jun; Uchiyama, Gunzo; Ueda, Yoshinori*; et al.
no journal, ,
The release behavior of radioactive materials from high-level radioactive liquid wastes (HLW) from reprocessing plants under an accidents of boiling to dryness of HLW condition has been studied. The influences of FP concentration in the simulated HLW on the release ratio of FP from the waste were measured in the laboratory-scaled experiments using non-radioactive simulated HLW which was prepared by dissolving 27 FP elements into nitric acid and adjusted to 2 M acidity. The simulated HLW was heated up to 300C under the constant air ventilation condition. The accumulated release ratios of FP elements from samples were determined using ICP-MS analysis. It was found that the accumulated release ratio of Ru was decreased with the increase of the initial Ru concentration in the simulated HLW. However, those of Cs and Nd were not influenced by the initial concentrations of them.
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.
in Reprocessing solutions, 8; Consideration on the temperature dependence and evaluation of the absorbed dose of G value of H in High active liquid wastes.Abe, 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.