低浓缩铀靶辐照后溶液中铀的化学种态及主要裂变元素的影响

Effect of Low-Enriched Uranium Targets Irradiation on Major Fission Elements and Uranium Speciation

利用化学种态分析软件CHEMSPEC计算了低浓缩铀靶辐照后溶液中铀(U)的化学种态分布及其主要裂变元素对U化学种态的影响。结果表明,在单组分体系中,p H值和铀酰浓度都会显著影响U的化学种态分布。随着铀酰浓度的增大,溶液中将会生成多核配合物;在较高的NO3-浓度下,U在溶液中主要以UO22+和UO2NO3+的形式存在。CO2对不同浓度铀的种态分布影响结果表明,当铀酰浓度较低时,铀的化学种态多以碳酸铀酰的形式存在;当铀酰浓度较高时,铀的化学种态多以氢氧铀酰或柱铀矿沉淀的形式存在。计算发现,当裂片元素Tc、I、Mo的浓度小于0.01 mol·L-1并分别以Tc O4-、I-、Mo O42-的种态存在时,这些裂片元素不改变铀的各化学种态的分布。

The speciation of uranium and effect of major fission products after low-enriched uranium targets being irradiated and solvated were analyzed using the geochemical program CHEMSPEC. The results indicate that the speciation of uranium in water is determined by pH value and the concentration of uranyl, and polynuelear complexes may be generated at high concentration of uranyl. Nitrate anion in the solution may interact with uranyl, and at high concentration of nitrate, uranyl exists as UO22＋ and UO2NO3＋. The presence of CO2 at low concentrations of uranium brings substantial distribution uranyl carbonate, while this is negligible at highconcentration of uranyl due to heavy hydrolysis and aggregation of uranyl. The calculations also show that the major fission products, Tc, I, and Mo, do not affect the speciation of uranium when their concentrations are below 0.01 mol-L-1 and when they exist as Tc04, I-, MoO42-.