NbBr_5及NbOBr_3的在线气相等温色谱研究

On-Line Isothermal Gas Chromatography Experiments With NbBr_5 and NbOBr_3

采用在线等温气相色谱装置对Nb的短寿命同位素的溴化物和氧溴化物在石英柱中的挥发行为进行了研究。以252Cf源自发裂变产物中的短寿命核素99Nb(T1/2=15 s)为研究对象,使用高纯氮气作载气,用溴化钾气溶胶的气喷嘴系统将裂变产物连续快速地传送到色谱装置。通过加入反应气体溴化氢,在900℃的反应区中生成易挥发的化合物。当系统中存在痕量的氧气和水蒸气时,在反应区生成NbBr5和NbOBr3的混合物;除尽氧气和水的条件下,只生成单一产物NbBr5。经过气相色谱分离后,采用活性炭管收集产物并进行在线测量。通过Monte Carlo程序对实验结果进行拟合,得到NbBr5和NbOBr3在石英表面的摩尔吸附焓分别为(-92±5)kJ/mol和(-153±5)kJ/mol。

The retention behaviour of volatile bromide and oxybromide of short-lived isotope of niobium in quartz column was studied using on-line isothermal gas chromatography apparatus.The 99Nb nuclide with a half-life of 15 s was produced by spontaneous fission of californium-252.The fission products were continuously and rapidly transported through the capillary to the isothermal chromatography apparatus using the N2/KBr gas-jet techniques.Volatile molecules are formed at the reaction zone kept at 900 ℃ by adding HBr as reactive gas.Depending on trace amounts of oxygen and water vapour in the system,two species NbBr5 and NbOBr3 are formed.While without oxygen and water vapour,only NbBr5 is formed.After separation,the products were collected by activated charcoal filters and measured synchronously.On the basis of the experimental data and stimulated by the Monte Carlo method,an adsorption enthalpy of（-92±5） kJ/mol for NbBr5 and（-153±5） kJ/mol for NbOBr3 are deduced.