核临界安全是核工业发展过程中最重要的安全问题之一，其中对临界事故的评价和分析是临界事故后屏蔽设计、应急计划等的基础，因此具有重要的研究意义和工程价值。CAACS是自主开发的溶液系统临界事故分析程序，可计算临界事故的裂变次数、裂变功率、温度随时间变化等。在临界基准实验验证的基础上，利用CAACS对2个真实的临界事故进行分析和计算，并与事故估计值进行对比，结果表明，CAACS的计算结果与事故估计值符合较好，可为后处理厂的工程设计提供临界事故分析的技术手段，为后续的临界瞬态研究打下基础。

Nuclear criticality safety is one of the most important security issues in the process of development of nuclear industry, in which evaluation and analysis of critical accidents is the foundation of shielding design and emergency plan after critical accidents. Therefore it has important research significance and engineering value. CAACS is a program developed to analyze criticality accidents of solution system. It can calculate the number of fission, fission power and temperature change with time of the criticality accident and so on. CAACS has been verified by the benchmark experiments.This paper presents the analysis and calculation of two criticality accidents, and compares the calculated results with the accident estimates. The result shows that, the calculation results of CAACS concur with the accident estimates, the study could provide technical means for the design of fuel reprocessing plants, and also lay a foundation for the subsequent research of critical transient.