Spectroscopic study of Np(V) oxidation to Np(VI) in 3 mol/dm nitric acid at elevated temperatures

3mol/dmの加熱硝酸中におけるNp(V)のNp(VI)への酸化の分光学的研究

伴 康俊 ; 袴塚 保之; 筒井 菜緒 ; ト部 峻一; 萩谷 弘通; 松村 達郎 

Ban, Yasutoshi; Hakamatsuka, Yasuyuki; Tsutsui, Nao; Urabe, Shunichi; Hagiya, Hiromichi; Matsumura, Tatsuro

加熱した3mol/dm硝酸中におけるNpの吸光スペクトルを光路長1cmのウォータージャケット付き分光セルで測定し、Np(VI)のモル吸光係数()を種々の温度で求めた。は温度の上昇と共に減少し、の温度依存性を表す式として=-0.14+85.5 (は温度)を得た。加熱した3mol/dm硝酸中におけるNp(V)のNp(VI)への酸化を上述の分光セルで観察し、Np(V)の酸化はNp(V)の濃度に対する疑一次反応として進行することを示した。さらに、336-362KにおけるNp(V)の酸化反応速度式として-d[Np(V)]/dt=2.210exp[-6510/()][Np(V)] (及び[Np(V)]は気体定数及び時間における[Np(V)]の濃度)を導出した。

Optical absorption spectra of Np in 3 mol/dm nitric acid at elevated temperatures were measured using an optical glass cell with a water jacket having a light path of 1 cm, and molar extinction coefficients of Np(VI), , were obtained at various temperature. The values of was found to decrease with increasing the temperature, and could be described by the equation = -0.14+85.5, where is the temperature. Oxidation of Np(V) to Np(VI) in 3 mol/dm nitric acid at elevated temperatures was observed using the optical glass cell. Oxidation of Np(V) proceeded as pseudo-first order with respect to Np(V) concentration. The rate equation in the temperature range of 336-362 K was obtained as follows: -d[Np(V)]/dt = 2.210 exp[-6510/()][Np(V)], where and [Np(V)] indicate the gas constant and Np(V) concentration at time , respectively.