Development of hydrophobic platinum catalyst for oxidation of tritium in JAEA

原子力機構におけるトリチウム酸化用疎水性触媒技術の発展

岩井 保則; 枝尾 祐希; 浅原 浩雄*; 林 巧

Iwai, Yasunori; Edao, Yuki; Asahara, Hiroo*; Hayashi, Takumi

貴金属触媒によるトリチウム酸化は核融合の分野では酸化後の水蒸気吸着システムと組み合わせ環境へのトリチウム放出を抑制する雰囲気トリチウム除去システムに用いられる基礎的な反応である。電源喪失などの異常事態に対するトリチウム安全性の向上にむけて加熱を要せず室温でトリチウムを酸化できる疎水性触媒の技術が注目されている。疎水性触媒を用いた室温トリチウム酸化触媒塔の設計には疎水性触媒の作成技術の進歩と付随する反応速度の知見が必須である。本報告では室温近傍温度におけるトリチウム酸化の反応速度を評価した。触媒の差を考慮して製造方法が異なる二種類の疎水性触媒を試験に使用した。結果は反応速度は疎水性母材に担持する白金径に強く影響され、反応次数は室温近傍では濃度の0.5乗である。この結果から白金触媒表面でのトリチウム酸化の反応メカニズムの温度による変化を考察した。

Tritium oxidation over noble catalyst is a fundamental reaction in the fusion fields since the system of catalytic reactor for the oxidation of tritium in combination with following tritiated vapor absorber has been applied in tritium handling facilities to control the tritium release into the environment as low as achievable. To enhance tritium safety as much as possible with taking severe accidents such as complete loss of power supply into account, technology of hydrophobic catalyst has been drawing intense interest recently because of its potential application in passive recombiner for tritium oxidation at room temperature. To design a passive recombiner packed with hydrophobic catalyst for tritium oxidation, the development of manufacturing technology for hydrophobic platinum catalyst and the following data on reaction rate are essential. This presentation deals with the reaction rate for tritium oxidation over hydrophobic platinum catalyst at temperatures from room temperature to 343 K. Two kinds of hydrophobic platinum catalysts; supported with styrene-divinylbenzene and with silica were used for this test. The results indicate that (1) the reaction rate is effected by the particle size of platinum, (2) the order of reaction is 0.5 of hydrogen concentration at room temperature. The rate-determining step approximation method is applied for the discussion on the reaction mechanism of tritium oxidation over platinum catalyst.