Calculation Model Of The Co-decontamination And Separation Process In PUREX

PUREX process is currently the only commercial process for spent fuel reprocess-ing.In this thesis,the calculation model of the key co-decontamination and separation process in PUREX is established.It can provide a useful reference for selection of the process parameters,decreasing the number of experiments,reducing the costs of ex-periments and shortening the time of experiments finally.Therefore,there is a great significance of mathematical modeling method of PUREX process.The main results and innovations are as follows:1.The Iteration of Extraction Equilibrium algorithm(ITEE)for calculating the ex-traction problem has been created.This algorithm has the advantage of high efficiency and robustness.Most importantly,it can obtain the only all positive solution set.The ITEE algorithm can effectively solve the problems of extraction balance in complex situation.So it has a relatively multiple applications in various extraction systems such as PUREX process.2.The 1A mathematical model has been created.By simplified the elements of 1A process,an extraction model containing four elements of U,Pu,Zr,and Ru is con-structed.Based on the continuous mixer-settler model,the 1A mathematical model is finally created.And it has been used to explore the influence of acidity and feed stage on trends of the four metal elements through typical Pressurized Water Reactor spent fuel and typical Fast Breeder Reactor spent fuel.The relative response rates of U,Pu,Zr and Ru to acidity,the overall trend of the extraction of these four elements towards different feed stages and the differences in the extraction of two kind fuel feeds when changing the acidty and feed stage are obtained through 1A mathematical model.In addition,the extraction model in the 1A mathematical model is expandable,which the extraction reaction of other elements can be added in.There is an importantly practical significance of this mathematical model for the optimization of process parameters and the prediction of 1A process in PUREX.3.The 1B mathematical model has been created.This mathematical model uses HAN(NH3OH+)as the reducing agent of Pu(Ⅳ).The redox reaction model is estab-lished by the chemistry mechanism of reduction of Pu(Ⅳ)which is solved by the BDF(Backward-differentiation Formulas)algorithm.At the same time,based on the empirical formula,an extraction model is established which is solved by the iterative method.In addition,the redox reaction and the extraction process can be simultaneously described through establishment of the mass transfer model.Based on the continuous mixer-settler model and the above models,the 1B mathematical model is finally cre-ated.And it has been used to evaluate the effect of secondary stripping on the separation efficiency between uranium and plutonium.The 1B mathematical model can be used to optimize process parameters of the 1B process and predict the separation efficiency of U and Pu,being of important practical significance.