化学形态分析软件CHEMSPEC及其应用

放射性核素在地质层中的吸附和迁移行为与其所处的化学形态密切相关．为了预测在处置库受损情况下放射性核素的时间和空间分布，需要建立化学形态分析与水力学计算相耦合的数学模型及计算软件．为此，我们编写了化学形态分析软件CHEMSPEC．本文在简要介绍该软件的原理和程序结构后，着重介绍该程序为防止质量平衡方程组迭代求解过程的发散所采取的措施，提出用“预报－校正法”处理沉淀－溶解平衡的算法，以及用“冻结”和“解冻”氧化态的策略处理包含氧化还原反应和沉淀反应的化学平衡的计算．本文用4个典型例子说明CHEMSPE在现阶段能解决些什么问题．最后讨论了存在的问题和尚待完成的工作．

Chemical speciation code CHEMSPEC and its applications

The adsorption and migration behavior of a radionuclide in geological media heavily depend on its chemical forms in a given chemical environment. In order to predict the temporal and spatial distribution of radionuclides around the disposal site when its canister is damaged, it is necessary to develop coupled chemical speciation-solute transport models and relevant software. For that reason, we wrote a new chemical speciation program CHEMSPEC. In this paper, the principles and structure of CHEMSPEC were briefly described, and the strategy and algorithms that were used in this code are interpreted in some detail, such as the adopted measures to prevent the divergence in iteratively solving mass balance equations, the ＂predictor-corrector＂ algorithm for calculation of the number and quantities of formed solid species, and the alternatively use of ＂freezing＂ and ＂defreezing＂ oxidation states in handling of co-existent redox and precipitation equilibria. Four examples are given to illustrate CHEMSPEC＇s features and capabilities.