后处理稳态萃取铀、钚的计算机模拟研究

【作者】 李永；

【导师】 吕忠诚； 王孝荣；

【作者基本信息】 中国原子能科学研究院 ， 应用数学， 2005， 硕士

【摘要】 液-液萃取过程广泛地应用于核燃料后处理以及稀有和有色金属的分离、纯化、浓缩等生产过程中。萃取工艺研究中重要的是得到具体萃取机理的基础上,用单因素循环法设计实验方案、进行实验的具体测定,利用微处理机制得到反映萃取平衡分配的半理论模型和平衡PH值关系的经验模型。建立稳妥、可靠和适用的数学模型是萃取过程的模拟和分析的前提和基础。 萃取过程中,物质在两相之间的转移或传递是一个可逆过程。用TBP-煤油从硝酸水溶液中萃取铀时,在硝酸铀酰分子从水相转入有机相的同时,有机相中的硝酸铀酰分子也在向水相转移。起初,单位时间内向有机相转移的量比向水相转移的量大,因此有机相中的铀浓度不断增高。但随着有机相铀浓度的增高,铀从有机相转入水相的速度也不断加快。当单位时间内转入有机相的量和转入水相的量相等时,两相中的铀浓度就不再变化,也就是达到了萃取平衡。如果体系中含有钚,钚在萃取反应中会和铀竞争自由TBP。 本文是在吕忠诚老师和王孝荣老师的指导下,在放化所九五工作的基础上,编写程序并与之相结合,使得计算机技术用于后处理流程优化设计方面的程序开发和应用研究,逆流萃取计算结果更符合实验数据。本文在萃取机理分析的基础上,用迭代计算法同时关联平衡分配系数和物料平衡的关系式,并在萃取串级模拟中检验数学模型。通过对参数的调整对1A槽中铀、钚、硝酸的萃取行为进行模拟、分析和预测,并与实验相对照,结果证明这种研究方法对萃取的机理和萃取工艺的研究方法上有一定的指导意义。 其意义在于利用计算机这种工具,和实验相结合并指导实验的进行,通过对实验流程予以一定程度的优化:在一定程度上减少一些不必要的实验工作量;减少放射性操作人员所受剂量;减少资源的浪费;为今后的实验工作增加一种手段。 现有的萃取模拟计算程序对1A槽TBP萃取铀、钚、硝酸的模拟计算有较好的计算结果,在下一步的研究工作中,可对萃取反应动力学加以考虑,加以时间常数对动态过程进行模拟计算。同时进一步根据实验数据对分配比的经验公式加以调整,更多还原

【Abstract】 This work is based on the result of Department of Radiochemistry in 1995-2000 and we start our second development and optimize PUREX flowsheet combining with computer technology. Through adjusting original parameters, we can simulate, and predict the stage concentration profile of uranium, plutonium, and nitric acid in the 1A batchwise counter-current mixer-settlers. The reported data were analyzed to determine its solvation number and an empirical model was developed for estimation of its distribution coefficients under PUREX condition. The simulated profiles were compared with the experimental stage profiles and a satisfactory agreement was obtained.The necessary input data are known such as uranium, plutonium and the acid original concentration in the aqueous phase as well as in the organic phase, feed flowrate and its stage number for each stage. The calculations are carried out according to the extraction equilibrium and the extraction reaction for each stage at first, and then the calculations are repeated till the material balance of uranium, plutonium is realized within an acceptable error between the feed and the outlets. At one time the results are exported on the screen in term of concentrations of uranium, plutonium, and nitric acid for each stage.In conclusion the work is to make use of computer as a new tool to instruct the experiment. And the purpose is to optimize the flow of the experiment in order to reduce some unnecessary experiment workload in some extent. On the other hand, it can also help to reduce the dose to the users and cut down the waste of the resource. Finally, based on it we can supply an alternative tool for the experiment.更多还原