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Spectroscopic study of Pu(IV) oxidation to Pu(VI) in 3 mol/dm$$^{3}$$ nitric acid at 373 K

373Kの3mol/dm$$^{3}$$硝酸中におけるPu(IV)からPu(VI)への分光学的研究

伴 康俊; 森田 泰治

Ban, Yasutoshi; Morita, Yasuji

373Kの3mol/dm$$^{3}$$(M)硝酸中におけるPu(IV)の吸光スペクトルを薄膜ヒータの付いた分光用石英セルを用いて測定した。373Kでの加熱によってPu(IV)はPu(VI)に酸化され、Pu(IV)及びPu(VI)の濃度は加熱時間とともにそれぞれ減少及び増加した。加熱時間394分におけるPu(IV)のPu(VI)への酸化割合は37%であり、Pu(III)及びPu(V)に特徴的な吸光ピークは観察されなかった。373Kの3M硝酸中におけるPu(IV)の酸化反応式は-d[Pu(IV)]$$_{t}$$/d$$t$$=$$k_{1}^{'}$$[Pu(IV)]$$_{t}$$-$$k_{2}^{'}$$[Pu(VI)]$$_{t}$$で表わされた。ここで、[Pu(IV)]$$_{t}$$及び[Pu(VI)]$$_{t}$$は加熱時間t分におけるPu(IV)及びPu(VI)の濃度である。Pu(IV)の見かけの酸化反応速度定数($$k_{1}^{'}$$)、及びPu(VI)の見かけの還元反応速度定数($$k_{2}^{'}$$)としてそれぞれ2.3$$times$$10$$^{-3}$$min$$^{-1}$$及び3.4$$times$$10$$^{-3}$$min$$^{-1}$$を得た。

Optical absorption spectra of Pu(IV) in 3 mol/dm$$^{3}$$ (M) nitric acid at 373 K were measured using an optical quartz cell equipped with a thin-film heater. Pu(IV) was oxidized to Pu(VI) by heating at 373 K, and the concentrations of Pu(IV) and Pu(VI) gradually decreased and increased, respectively, with the heating time. The ratio of Pu(IV) oxidized to Pu(VI) was 37% at a heating time of 394 min, and no Pu(III) or Pu(V) characteristic peaks were observed throughout the experiment. The oxidation rate of Pu(IV) in 3 M nitric acid at 373 K could be described by the equation -d[Pu(IV)]$$_{t}$$/d$$t$$ =$$k_{1}^{'}$$[Pu(IV)]$$_{t}$$-$$k_{2}^{'}$$[Pu(VI)]$$_{t}$$, where [Pu(IV)]$$_{t}$$ and [Pu(VI)]$$_{t}$$ were the concentrations of Pu(IV) and Pu(VI) at a heating time of t min. The apparent rate constants for Pu(IV) oxidation ($$k_{1}^{'}$$) and Pu(VI) reduction ($$k_{2}^{'}$$) at 373 K were calculated to be 2.3$$times$$10$$^{-3}$$min$$^{-1}$$ and 3.4$$times$$10$$^{-3}$$min$$^{-1}$$, respectively.

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パーセンタイル:74.11

分野:Chemistry, Inorganic & Nuclear

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