带附加供料流的准理想级联的优化

某些同位素分离任务(比如回收铀的浓缩、轻杂质的净化等)需要借助带附加供料流的级联来完成。这类级联的设计目标之一是针对已知的目标组分的精料和贫料丰度,确定级联的结构参数,即确定级联总级数、主供料级以及附加供料级位置。为对该类级联进行理论设计,建立了准理想级联的数学优化模型。优化问题的目标函数为级联中总的物质流量,通过罚函数法把约束条件下的多变量优化问题转化为无约束优化问题,并用单纯形法对后者进行求解。利用该优化方法对浓缩回收铀的级联进行了计算。     

单纯形法在准理想级联优化中的应用

已知目标组分的精料和贫料丰度,确定准理想级联的结构,即确定级联流量分布、级联总级数以及供料级位置,是约束条件下的多变量优化问题。通过罚函数法把约束条件下的多变量优化问题转化为无约束优化问题,并用单纯形法对后者进行了求解。利用该优化方法对浓缩回收铀的级联进行了计算。     

浓缩回收铀的M级联的近似算法

浓缩回收铀最有效的级联形式是带附加供料流的级联,它以天然铀为主供料,回收铀为附加供料。基于回收铀浓缩的特殊性,提供一种用于浓缩回收铀的带附加供料流的M级联的近似算法。数值计算表明,近似算法与工程优化算法得到的结果非常接近,最大相对偏差不超过0.1%。近似算法相对于工程优化算法更简单、方便和快速。     

带附加流的多组分矩形级联的稳态算法

提供一种带附加流的多组分矩形级联的稳态算法,该算法基于对级联主方程的准线性化,通过对级联分离因子逐渐逼近来加速收敛过程。数值计算表明,由稳态法和瞬态法得到的计算结果吻合完好,但稳态法相对于瞬态法能大为缩短计算时间,适合于计算带附加流的矩形级联或其它诸如阶梯形级联等更为复杂的级联。     

多组分同位素分离级联的优化

以级联中总流量最小为优化标准,以目标同位素贫料浓度和决定级联流离量分布的参数M~*为优化参量,对多组分同位素分离的准理想级联进行了二维优化。优化结果表明,把目标同位素浓缩到某一给定的浓度值,存在一个目标同位素贫料浓度值和M~*值的最佳组合,在该组合下,级联的总流量最小。     

存在损耗的多组分级联的改进模型

本工作建立了损耗同时存在于级联各级供料流、精料流与贫料流中的多组分级联的数学模型,提出了求解该类级联方程的数值方法。各级组分分流比不变的多组分级联称为准理想级联,得到了计算存在损耗的准理想级联中相对产品流、相对贫料流、级联中总物质流量以及产品流和贫料流中组分丰度的解析表达式。     

带扩展流的矩形级联

本文建立了适用于分离中间组分同位素的扩展型(扩展流在贫料段)矩形级联数学模型,该级联模型由两部分不同流量的矩形级联构成,有4股外部流,即供料流,精料取料流、贫料取料流和附加取料流。推导了有附加取料流时的计算方程,并利用一种基于对级联主控制方程准线性化法的稳态计算方法得到数值解。同时,用该级联模型对WF₆的中间组分W-184进行级联计算,研究证明带扩展流的矩形级联在相同流量下可比常规矩形级联获取更高丰度的中间组分,为实际较重中间组分同位素生产和级联建设提供了理论支持。     

带附加供料离心净化级联的优化

通过向离心级联附供载荷气体实现微量杂质的净化时,为充分发挥级联性能,提升级联经济性,需对带附加供料离心净化级联进行优化。本文根据现有离心机模型和相关单机实验结果,以级联总离心机数最少为优化目标,以级联长度、各级离心机数和重馏分压强及载荷气体供料量为优化变量,利用二进制编码遗传算法完成了离心净化级联的优化计算,并通过回收铀浓缩产品中~(99) Tc的去除和高纯WF_6制备中杂质的净化两个算例的计算验证了优化算法的适用性。计算结果表明,遗传算法可有效地求解离心净化级联的优化问题,具有较好的适用性。     

回收铀分离级联计算

乏燃料中回收铀的再利用能节省天然铀资源.轻水堆回收铀的分离必须综合考虑铀235的浓缩、铀232的稀释及因铀236引起的燃耗深度损耗的补偿.基于多组分同位素分离级联理论,提出了分离回收铀的几种不同的级联方案.对各种级联方案进行了理论计算.计算结果表明,利用运载气体的双级联方案为最佳的级联方案.     

用于多组分分离的中间取料矩形级联的优化设计

多组分同位素混合物的某一中间组分通常在分离级联的中间某级达到峰值,但一般的级联均采用从级联组两端取出产品和废料的工艺。为得到丰度较高的中间组分产品,最好在级联中间取料。本工作研究矩形级联中使用中间取料方式以提高级联分离的中间组分丰度。通过数值模拟计算和数值优化,研究了级联两端取料量和级联供取料位置等参数对中间取料中目标组分丰度的影响。采用单参数分析,估计了级联各参数的取值范围以及它们对目标组分丰度的影响。通过优化计算,在供料丰度和流量不变、产品流量不变的情况下,得到了可以生产更高丰度中间组分产品的级联。     

Special features of the enrichment of components with intermediate mass in a quasi-ideal cascade

An approximate approach is described, making it possible to estimate without solving nonlinear equations describing the mass transfer of a multicomponent mixture in a quasi-ideal cascade, the maximum concentration of the intermediate target component which can be obtained in the product flux from the cascade. Asymptotic formulas are obtained for the range of existence of the solutions of the system of equations which relates the external and internal parameters of the cascade. The approach developed is illustrated by examples of a process of separation of a natural mixture of krypton isotopes in a quasi-ideal cascade for admissible concentrations of the target intermediate component in the product and waste flows. __________ Translated from Atomnaya énergiya,Vol. 100, No. 1, pp. 51–56, January, 2005.     

Analytical calculation of the content of uranium isotopes in a cascade with two feed flows,two product flows,and one waste flow

The problem of estimating the ^232,234,236U content in the product flows of an optimal cascade is examined. Relations are found for studying the characteristics of the concentration variations along the cascade for various ratios of the feed flows. It is shown that an effective procedure is to obtain from the intermediate product of the cascade a diluent for high-enrichment uranium. __________ Translated from Atomnaya énergiya, Vol. 102, No. 4, pp. 241–244, April, 2007.     

Plant designing of ion exchange chemical uranium enrichment and its non-proliferation aspects

The chemical uranium enrichment using ion exchanger had been developed mainly in Japan, but now only the academic studies have been continued at Tokyo Tech. For the purpose of revaluation as the alternative production process of the low enriched uranium for nuclear power plants, the plant design and the non-proliferation aspects of redox ion exchange chemical uranium enrichment (Redox Ion Exchange Method) were studied.The conceptual design of a commercial enrichment plant with a scale of 1400 tSWU/Y was newly performed based on data reported. It is composed of seven enrichment units with two enrichment columns with an inner diameter of 6.5 m and a height of 11 m and redox systems. It is evaluated as having the site area of 97,200 m² including the vacancy to double the production with subsidiary sections of pre-treatment and post-treatment of uranium or the like, a construction cost is 218 billion Japanese yen(JPY), and a cost per enrichment work is 18,000 JPY/kgSWU. As for the nuclear proliferation resistance of this process, it is suggested that the production of highly enriched uranium for weapon use is difficult from the view point of nuclear fission criticality and the lengthy equilibrium time mentioned as following. It is difficult to operate the enrichment plant for the production of highly enriched uranium of 50 wt% of ²³⁵U or higher, because the effective neutron multiplication factor (k_eff) in the enrichment columns becomes 1 or above depending on the enrichment conditions. And the required time for the production of highly enriched uranium of 90 wt% of ²³⁵U is estimated 10 thousands days or more, this means substantially impossible to get highly enriched uranium under the safeguard of IAEA by the Redox Ion Exchange Method.The Redox Ion Exchange Method is suggested to be a promising candidate for an alternative enrichment process to obtain low enriched uranium in the range 3-5 wt% ²³⁵U for nuclear power plant in the world. Furthermore, for the future prospective fuel cycle without UF₆, new front-end system coupled with uranium from seawater and chemical enrichment is proposed.