Purex流程共去污工艺稳态趋近过程计算机模拟

乏燃料后处理Purex流程中的铀钚共去污工艺（1A）是整个化学分离过程的关键环节之一，该工艺计算机模拟计算对1A进行流程优化和安全分析具有重要意义。     

后处理工艺Purex流程计算机模拟研究现状及展望

利用与Purex流程相关的基础数据,开展Purex流程计算机模拟研究并形成模拟程序,能够开展工艺条件分析和工艺优化工作,具有重要的应用价值。国外对于此类研究开展的较早,在分配比模型研究上形成了以Richardson模型为代表的半理论模型;混合澄清槽和脉冲萃取柱的计算机模拟也分别在全混模型和扩散模型的基础上开展了大量的研究工作,形成了较多的模拟程序。我国开展此类研究稍晚,仅在分配比模型和混合澄清槽模拟方面开展了部分研究工作,与国外存在较大的差距。     

基于拟Newton算法的Purex流程计算机模拟程序

在多级逆流萃取MESH方程基础上,基于拟Newton算法编写了用于模拟Purex萃取流程的计算机程序,使用SEPHIS分配比模型,分别以1A、2D槽工艺条件为例,计算了其各级出口的U、Pu酸浓度。程序计算结果与实验浓度剖面符合很好。相对于已有的一些计算机模拟程序,该程序具有适用性广、收敛性强的特点。     

锝在Purex流程共去污段（1A槽）的走向

研究了在不同铀-锆-锝比条件下,硝酸浓度对Tc(Ⅶ)在30％TBP-OK中分配系数的影响,锝在1A槽中的萃取行为及走向。实验结果表明1A槽中1AF为2mol/L和3mol/LHNO3介质时,锝进入1AP的比例分别为14.4％和27.0％。当1AF料液经加热预处理后,以3mol/LHNO3进料时,99.8％的锝进入了1AP。     

Purex流程1A槽中Pu(Ⅵ)行为的计算机模拟

在乏燃料后处理Purex流程中,共去污循环的安全稳定运行是整个生产过程的关键之一。Pu(Ⅵ)在TBP中的分配系数比Pu(Ⅳ)的低而易导致钚流失。文章采用计算机模拟1A萃取槽中UO²⁺₂、HNO₃、Pu⁴⁺、PuO²⁺₂的运行。计算结果表明,Pu(Ⅵ)的流失是造成钚收率降低的主要因素之一,提高Pu(Ⅵ)的收率能够有效提高钚产品的收率。当1AF中ρ(U)＝225g/L、c(HNO₃)＝3.0mol/L、ρ(Pu)＝2.20g/L,1AS中c(HNO₃)＝3.0mol/L,1AX为30％TBP/煤油,流比1AF∶1AS∶1AX＝1.25∶0.75∶3.00时,为使1A萃取槽中钚的收率不低于99.9%,应控制1AF料液中Pu(Ⅵ)量（占总Pu百分数）不超过7%。     

Purex流程的改进Ⅰ.共去污单元锆、钌净化工艺

通过单级实验,研究了不同铀饱和度、酸度、温度条件下30%TBP对锆、钌的萃取规律,在此基础上确定了提高1A净化锆、钌的工艺,并进行了台架实验验证。研究结果表明：提高铀饱和度、温度和酸度有助于降低钌在30%TBP中的分配比;在30%TBP中,高铀饱和度条件下,锆分配比受铀饱和度的影响远大于水相硝酸浓度的影响;温度对锆的分配比影响不显著。当1A槽采用4mol/L硝酸进料、4mol/L硝酸洗涤时,45℃条件下,铀、钚的回收率达99.98%,钌的去污系数约达到10⁵。     

稳态计算法分析Purex流程中U/Pu分离工艺铀酸分布

研究了Purex流程中U／Pu分离段还原剂从一端加入时铀酸分布的稳态计算方法。计算结果与串级实验结果吻合较好。在所选几种工艺条件下，对铀酸分布进行了计算，并根据计算结果对Purex流程中采用水溶性还原剂时U／Pu分离工艺条件进行了分析。     

Purex流程1A工艺单元锝萃取行为研究

通过计算机模拟研究了不同燃耗和不同工艺条件下,硝酸、锆、铀、钚和锝在Purex流程1A中的萃取行为,获得了相应萃取行为数据,测定了不同硝酸浓度下锝锆共存时锝的分配比D₍Tc(Zr))、锆的分配比D_Zr以及锝的分配比D_Tc,再结合1A中硝酸、锆、铀和钚萃取行为数据,解析锝的萃取行为。结果表明,萃取段锝因锆锝共萃进入有机相,洗涤段锝因铀锝共萃和钚锝共萃留在有机相,相比于硝酸浓度变化对锝萃取的影响,洗涤段铀锝共萃和钚锝共萃的作用更重要。     

Purex流程1A工艺单元锝萃取行为研究

通过计算机模拟研究了不同燃耗和不同工艺条件下,硝酸、锆、铀、钚和锝在Purex流程1A中的萃取行为,获得了相应萃取行为数据,测定了不同硝酸浓度下锝锆共存时锝的分配比 DTc(Zr)、锆的分配比DZr以及锝的分配比 DTc,再结合1A中硝酸、锆、铀和钚萃取行为数据,解析锝的萃取行为.结果表明,萃取段锝因锆锝共萃进入有机相...     

Purex流程中所氚的行为研究

研究了氚在Ｐｕｒｅｘ流程中的行为，测量了氚和ＨＮＯ３在３０％ＴＢＰ－煤油和水相之间的分配比，研究了γ辐照和铀浓度对氚分配的影响及辐照对氚在有机相中保留的影响，萃取有有机相中氚的洗涤实验表明，洗涤是一种氚在两相间重新分配的简单过程，对氚在一循环中的行为进行了台架实验，结果表明１Ａ混合－澄清槽（６级萃取，９级洗涤）中对氚的去污系数在１０＾４以上，并且氚主要集中１Ａ的萃取段，残留在１ＡＰ中的氚易在附加的     

Numerical Simulation of Neptunium Extraction Behavior in Co-decontamination Stage for Late Split Purex System

Numerical simulation of neptunium concentration profiles is carried out in order to understand the extraction behavior of neptunium in the co-decontanimation stage which decontaminates through two extraction banks before the uranium and plutonium partitioning steps. Simulation results show that leaking of neptunium to the waste stream at the second extraction bank is caused by reduction from Np(VI) to Np(V) unextracted by TBP in the presence of nitrous acid of 10^?3 mol/l. It is found that the prevention of the reduction reaction from Np(VI) to Np(V) is effective for the recovery of neptunium with uranium and plutonium into the product stream. Two methods for the recovery of neptunium are suggested; i) to decrease residence time in the acid adjustment vessel located between first and second extraction banks, ii) to diminish nitrous acid in the aqueous phase by hydrazine. Simulation results show that the recovery of neptunium with uranium and plutonium is improved from 40 to 60% and kom 40 to 70% by the first and the second methods, respectively.     

Purex流程铀钚分离工艺单元数学模型研究

在铀钚分离工艺单元单级数学模型和混合澄清槽瞬态数学模型的基础上,建立了以U(Ⅳ)-N₂H₄为还原反萃剂、混合澄清槽为萃取设备的Purex流程铀钚分离工艺单元数学模型,开发了计算机模拟程序,并使用台架实验数据对程序的可靠性进行了验证。结果表明,模拟程序的计算值和实验值符合良好。在此基础上,利用模拟软件对铀钚分离工艺单元的工艺参数进行了计算分析,结果表明：1BX₁加入位置、1BS和1BX₂酸度对钚反萃率无太大影响,但1BX₁加入位置和补萃级数对钚中去铀系数SF_U/Pu有一定影响。     

K边界技术在Purex流程中的应用

利用现有混合式K边界／X荧光测量装置在Purex流程中进行了应用研究。根据Purex流程样品分析要求，进行了装置硬件改造调试、数据分析软件改进，并完成了条件实验及大量样品的测量分析，为实现U、Pu物料衡算提供了可靠依据。     

Purex流程中有机无盐试剂的应用分析

文章较系统地讨论了已报道的有机无盐试剂的热力学和动力学研究结果，分析了这些试剂用于Purex流程的可能性，并对今后相应的研究工作提出了建议。     

Determination of Optimal Process Variables for Two-Cycle Purex Process

The large and complicated system that is the Purex process is decomposed into units possessing common functions. Then, using the concentration plofile determined by linear search, the inputs, the outputs and the concentration profiles of all the individual units can be determined systematically. Using this approach, Powell's method and multilevel control theory is applied to the Purex process design problem, which is thereby reduced to a problem of optimization. Numerical calculations are carried out, resulting in optimal process variables well within the range of practicability. These process variables are calculated without taking into consideration such relevant but difficult factors as criticality and the instability of Pu solutions. These factors could, however be accounted for by adding appropriate penalty terms to the performance index. The computer program devised for the present calculations is given the code name POSER (Program for Optimization of Solvent Extraction Process).     

Precipitation Formation of Zirconium-Dibutyl Phosphate Complex in Purex Process

Dibutyl phosphate (DBP) was added to 30% TBP-70% dodecane solvent (DBP concentration, 30–1,150mg/l). These samples were used to investigate distribution behavior of Zr from a 3 M nitric acid solution (Zr concentration, 60–4,000 mg/l). The experimental results show that the Zr distribution depended mainly on the total DBP/Zr mole ratio. Below DBP/Zr=2, the Zr distribution to the organic phase became larger as the DBP/Zr mole ratio increased. Above DBP/Zr=2, the Zr distribution factor was saturated. Moreover, colloidal precipitation at the interface between organic and aqueous phases was observed above DBP/Zr=2.

Then in order to characterize the precipitation, 3 M nitric acid solution containing Zr ion was directly reacted with DBP and the obtained products were analyzed by ¹³C, ³¹P and ¹⁴N NMR spectroscopy. The measured NMR spectra indicated that the products were polymers having four kinds of bonding structures. One was a hydrogen bonded structure and the others were Zr bridged structures with two to four DBP molecules coordinated per Zr atom. The Zr bridged structure with four DBP molecules was thought to make the biggest contribution to precipitate formation.