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=2.2
10
exp[-65
10
/(
)][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 = 2.2
10
exp[-65
10
/(
)][Np(V)]
, where
and [Np(V)]
indicate the gas constant and Np(V) concentration at time
, respectively.