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土井 大輔
International Journal of Hydrogen Energy, 91, p.1245 - 1252, 2024/11
被引用回数：0Hydrogen is a major nonmetallic impurity in the coolant of sodium-cooled fast reactors (SFRs) during normal operation. A higher hydrogen concentration than the gas-liquid equilibrium has been transiently detected in the gas space of actual SFR plants. The presence of several sodium compounds can increase hydrogen generation; however, a thorough understanding of the thermal behavior of candidate reactions is lacking. Herein, thermal analysis reveals the hydrogen release behavior of sodium hydride. Mass spectrometry indicates hydrogen generation with decreasing sample mass, indicating thermal decomposition. Detailed kinetic analysis based on master plot methods indicates that the hydrogen release reaction occurred through a mechanism involving random nucleation and growth of nuclei. Furthermore, the reaction rate was newly formulated based on a kinetic model function representing the above mechanism and the Arrhenius-type reaction rate constant comprising an activation energy of 119.0 
0.8 kJ mol
and a frequency factor of 1.8 
10
s. These findings will enable the numerical simulation of the hydrogen release behavior in SFRs.
土井 大輔
Proceedings of 29th International Conference on Nuclear Engineering (ICONE 29) (Internet), 7 Pages, 2022/08
In sodium-cooled fast reactors (SFRs), hydrogen is a major nonmetallic impurity in the coolant during normal operation. A higher hydrogen concentration than the gas-liquid equilibrium had been transiently detected in the gas space of the actual SFR plant. However, the chemical reactions that caused hydrogen generation, which involve several sodium compounds, have not been identified. Furthermore, the thermal behavior of these hydrogen release reactions has not been thoroughly investigated. In this study, the hydrogen release behavior of sodium hydride, which could be involved in all of these reactions, was clarified by two experimental methods dealing with different sample quantities. In the thermal analysis with a semi-micro sample of about 1mmol, the hydrogen generation was demonstrated by mass spectrometry as the sample mass decreased, suggesting thermal decomposition. A monomodal hydrogen release curve similar to the thermal analysis result was obtained in the heating experiment with a macro amount sample of about 1mol. These experimental results showed consistent activation energies within the standard error. Therefore, it was elucidated that the ideal reaction behavior obtained by thermal analysis could be sufficiently extrapolated to the reaction behavior occurring in a larger amount of sample. These findings provide fundamental insights into the thermal decomposition of sodium hydride and are indispensable for analyzing hydrogen release behavior in other hydrogen release reactions involving sodium hydride.
中村 武彦; 山崎 利; 傍島 眞
JAERI-M 94-029, 99 Pages, 1994/03
原研では、NSRRを用いた第I期および第II期実験として軽水発電炉の燃料棒の反応度事故時の挙動を調べる実験を行っている。この実験に続き、高速炉燃料をナトリウム冷却条件でパルス照射する第III期実験を計画し、現在、ナトリウムを実験用カプセルに充填するためのナトリウム純化ループの建設および試作実験カプセルの製作を行っている。NSRRでは実験燃料を破損させるに十分な高い過出力を実験燃料に与えるためには、NSRR炉心からの中性子を十分に減速させる必要がある。従来の軽水炉燃料実験では、軽水を冷却材/減速材として利用して来たが、ナトリウム冷却条件で行う高速炉燃料実験ではポリエチレンあるいは水素化ジルコニウムを使う必要がある。これらの減速材の性能を炉内実験で調べ、軽水と同等の能力がある事を確認した。また、温度特性実験ではいずれの減速材も300
Cまでは分解等によるガス発生も小さく問題なく使用出来る事が分った。
