摘要
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MOX （Mixed oxide）乏燃料主要由锕系氧化物和少量裂片元素氧化物组成，乏燃料的处理最主要的目的就是回收乏燃料中的锕系元素。锕系氧化物中的在高温熔盐中的溶解度较小，分离步骤较为复杂，本文以铀氧化物作为锕系氧化物的代表，研究了氧化铀（U3O8和UO3）与裂变元素氧化物在NaOH熔体中的溶解性，为进行分离回收铀氧化物提供理论基础。主要研究如下：
(1). 在723 K~973 K温度范围内，研究了2.5 wt.%的U3O8或UO3在NaOH 熔体的溶解。在NaOH熔体中同时加入U3O8和UO3，随着温度的增加，溶解反应加快；XRD表征和热力学计算表明，UO3在NaOH熔体中溶解一步生成Na4UO5；而U3O8在NaOH熔体中溶解，有氧气时会有中间产物Na4UO4生成，最后生成Na4UO5，而在无氧条件下会生成Na4UO4和Na4UO5两种产物。ICP-AES 测试结果显示含UO3熔体中的铀元素含量为8.17 wt.%，U3O8的为7.99 wt.%，说明U3O8未溶解完全。对溶解产物进行表征，发现Na4UO4和Na4UO5水洗干燥后都为无定型的Na2U2O7。
腊梅花的功效与作用(2). 在773 K~823 K温度范围，在NaOH熔体中用循环伏安法和方波伏安法研究了加入U3O8前后氧化还原峰的变化，发现在循环伏安和方波伏安的电化学窗口内未检测到铀氧根的氧化还原峰。根据HSC软件计算了673 K~973 K时在NaOH熔体中加入U3O8和UO3，可能发生反应的理论分解电压。发现溶解产物Na4UO5的理论分解电压比NaOH的理论分解电压更负，在NaOH的电化学窗口内无法检测到UO54+的氧化还原信号。
(3). 在673 K~873 K温度范围，研究了Na2O2的加入对U3O8和UO3在NaOH 熔体中溶解的影响，从溶解现象和反应的热力学分析看出，加入Na2O2能加快U3O8和UO3的溶解反应；不同比例的Na2O2:U3O8会生成不同的产物，确定在质量比为1:1时会生成Na4UO5，而在质量比小于1:1摩尔比大于1:1时会有Na4UO4生成；在NaOH熔体中加入质量比为1:1的Na2O2和U3O8或UO3时，随着温度的增高，对U3O8的溶解反应作用更明显；通过XRD的表征结果发现在有氧和无氧条件下加入Na2O2溶解反应的最终产物都是Na4UO5。通过ICP-AES测试结果发现，加入Na2O2能使U3O8进一步溶解，而Na2O2的加入对UO3的溶解影响不大。
(4). 在723 K~823 K温度范围，研究了U3O8和裂片元素（Sr、Ba、RE）氧化物在NaOH熔体中溶解情况。通过溶解现象和XRD表征结果发现加入BaO、
SrO的NaOH熔体分层不明显，产物为无定型结构；而加入稀土氧化物的NaOH 熔体都分为两层，稀土氧化物都沉积在底部；加入U3O8和BaO或SrO共同溶解时发现Na4UO5沉在底部。用ICP-AES测试熔体上层中的各种裂片元素的含量，发现在NaOH熔体中BaO的溶解度数量级为0.1 wt.%、SrO的溶解度数量级为1 wt.%；而几种稀土氧化物在NaOH熔体几乎不溶解。在NaOH熔体中随着温度的增加，BaO、SrO、Sm2O3、CeO2溶解度增加，Nd2O3、La2O3的溶解度降低。
360插件关键词：U3O8；裂片元素；Na2O2；溶解反应；溶解度
Abstract
MOX (Mixed oxide) spent fuel is mainly compod of actinides and a small amount of fission product oxides. The main purpo of spent fuel reprocessing is to recover actinides from spent fuels. The solubility of actinide oxides in high-temperature molten salts is small, and their paration steps are relatively complex. Thus, in this paper, uranium oxides were taken as the reprentatives of actinide oxides to investigate the solubility of uranium oxides (U3O8and UO3) and fission product oxides in NaOH melt, providing a theoretical basis for the paration and recovery of uranium oxides. The main studies are as follows:
(1). The dissolution behaviors of 2.5 wt.% U3O8and UO3in NaOH melt was studied at 723 K~973 K. When U3O8and UO3were added into NaOH melt, the dissolution rate incread with the increa of temperature. XRD characterization and thermodynamic calculation show that UO3dissolved in NaOH melt in one step to produce Na4UO5, while Na4UO4was first formed and then Na4UO5was produced when U3O8 dissolved in a NaOH melt at the prence of oxygen; but both Na4UO4 and Na4UO5were formed in the abnce of oxygen. ICP-AES results showed that uranium content in UO3-NaOH melt was 8.17 wt.% and that 7.99 wt. % in U3O8-NaOH melt, indicating that U3O8was not completely dissolved. XRD results indicated that amorphous Na2U2O7 was obtained after washi
ng and drying of Na4UO4 and Na4UO5.
(2) In the temperature range of 773 K~823 K, cyclic voltammetry and square wave voltammetry were performed before and after the addition of U3O8 in NaOH melt. It was found that no redox peaks ascribed to uranium oxygen roots were detected in the electrochemical window. The theoretical decomposition voltages of the products when U3O8 and UO3 added in NaOH melt at 673 K~973 K were calculated employing HSC software. It was found that the theoretical decomposition voltage of Na4UO5was more negative than that of NaOH, and the redox signal of UO54+ could not be detected in the electrochemical window.间开头的成语
(3) The influence of the addition of Na2O2 on the dissolution of U3O8 and UO3 in NaOH melt was studied in the temperature range of 673 K~873 K. According to the dissolution phenomenon and thermodynamic analysis of the reaction, the addition of
Na2O2can accelerate the dissolution reaction of U3O8and UO3. Different ratios of Na2O2:U3O8 can generate different products. Na4UO5 can be generated when the mass ratio was 1:1, while Na4UO4 can be generated when the mass ratio was less than 1:1 and the molar ratio was greater than 1:1. When mass ratio of Na2O2 and U3O8 or UO3 was 1:1, the dissolution of U3O8incread
with the increa of temperature. XRD results showed that the product was Na4UO5. The addition of Na2O2can promote further dissolution of U3O8, however, had little effect on the dissolution of UO3. (4). The dissolution behavior of U3O8 and the fission product oxides (Sr, Ba, RE) in NaOH melt was studied in the temperature range of 723 K~823 K. It was found from dissolution phenomenon and XRD results that the addition of BaO and SrO into NaOH melt has no obvious stratification and the product is amorphous structure. The NaOH melt was divided into two layers after the addition of rare earth oxides, and the rare earth oxides appeared at the bottom. When adding U3O8and BaO or SrO into NaOH melt, Na4UO5was found at the bottom. ICP-AES results indicated that the contents of various fission product elements in the upper layer of melt. It was found that the solubility of BaO and SrO in NaOH melt was 0.1 wt.% and 1 wt. %, respectively. Rare earth oxides are almost insoluble in NaOH melts. With the increa of temperature, the solubility of BaO, SrO, Sm2O3 and CeO2 incread, while that of Nd2O3 and La2O3 decread.
Key words：U3O8; fission element; sodium peroxide; dissolution reaction; solubility
目录
第1章绪论 (1)
1.1 引言 (1)
1.2 MOX乏燃料干法后处理 (2)
1.2.1概述 (2)四步交谊舞
1.2.2铀氧化物的性质 (3)
1.2.3 MOX乏燃料的的研究进展 (6)考上公务员
1.2.4铀氧化物在不同熔盐中溶解度的测定 (9)
1.3 论文的选题意义和主要内容 (10)
1.3.1 选题意义 (10)
1.3.2 研究内容 (11)
第2章实验部分 (12)
2.1 实验试剂和仪器 (12)
根号65等于多少
2.1.1 实验试剂 (12)
2.1.2 实验仪器 (12)
2.2熔体及原料 (13)
2.2.1原料的测定 (13)
2.2.2熔盐体系 (15)
2.3 分析表征方法 (17)
2.4 本章小结 (18)
第3章U3O8和UO3在NaOH溶体中的溶解及反应 (19)
3.1 引言 (19)
3.2 U3O8和UO3在NaOH中的溶解 (19)
3.2.1 U3O8和UO3在NaOH熔体中的溶解现象 (19)
3.2.2 U3O8和UO3在NaOH熔体中溶解反应 (22)
3.2.3 温度对U3O8和UO3在NaOH熔体中溶解反应的影响 (24)
3.2.4溶解反应产物的表征 (30)
3.2.5 U3O8在NaOH熔体中的电化学 (32)
3.3 本章小结 (35)
第4章Na2O2对U3O8和UO3在NaOH熔体中溶解的影响 (37)ui怎么写
4.1 引言 (37)
