GdEuZrCeO_7烧绿石陶瓷核废物固化体的制备及化学稳定性

选择镧系元素Eu、Ce分别模拟高放废物中的三价和四价锕系核素,以硝酸盐和氧化物为原料,分别采用普通烧结法和液相烧结法制备了GdEuZrCeO_7烧绿石陶瓷核废物固化体。利用XRD、SEM-EDS对固化体的物相组成、微观结构和化学组成进行了测试表征,研究了烧结方法、烧结温度和烧结助剂对固化体物相组成、晶粒大小以及致密性的影响,并采用PCT静态浸出法研究了固化体的化学稳定性。结果表明:GdEuZrCeO_7烧绿石陶瓷固化体的物相结构为无序缺陷萤石型结构;较高的烧结温度有利于固化体结晶度和致密性的提高,液相烧结和添加烧结助剂对固化体致密性的提高并不明显;PCT结果说明固化体具有较好的化学稳定性,元素的归一化浸出率总体处于10~(-7)～10~(-4) g·m~(-2)·d~(-1)范围。     

地聚合物基多相陶瓷高放废液固化体固化机理与浸出性能

高放废物中放射性核素组成复杂，而陶瓷固化存在核素选择性强的问题。为实现同时固化裂变产物及锕系核素的目的，基于可陶瓷化地聚合物设计原理，将模拟高放废液与偏高岭土、矿粉、硅灰、纳米氧化锆混合后，加入模数为1.5的钾水玻璃作为激发剂制备高放废液多相陶瓷固化基材，该基材在常温下成型硬化后，再以1 100℃高温热处理方式转化为地聚合物基多相陶瓷高放废液固化体。采用静态浸出方法研究固化体的抗浸出性能，同时采用XRD、SEM-EDS、XPS等测试技术探究地聚合物陶瓷化机制、核素固化机理及Ce元素氧化价态。结果表明，该固化基材在固化模拟核素时，以化学形式与物理形式两种方式同时固化：一是大量进入烧结形成的白榴石(立方)、氧化锆(四方)、锆英石晶格或形成陶瓷相；二是少量被玻璃相包裹。其中Cs、Sr均匀分布，Ce、Nd在玻璃相中富集。该固化基材在同时固化不同价态与离子半径的核素时具有优异的抗浸出性能，Cs、Sr的28 d归一化元素浸出率低至10^-2 g/(m²·d),Ce、Nd的28 d归一化元素浸出率低至10^-4～10^-5     

铈模拟放射性废物固化体的物理化学性质

以稀土元素Ce作为示踪核素,采用铝热剂自蔓延高温合成技术固化了粒度≤200μm的模拟核废物土壤,通过密度测定和扫描电子显微镜、X射线荧光光谱、X射线衍射、电感耦合等离子发射光谱分析,研究了不同Ce含量的固化体的组成结构和核素浸出率。结果表明：在CeO2质量分数大于1%的情况下,示踪核素Ce主要是以CeAl11O18和Ce2SiO5的矿物晶体的形态存在于固化产物中。产物为无定形态玻璃和陶瓷体的混合物,体积密度超过3.0 g/cm3。固化体中示踪核素Ce的28 d平均浸出速率为10-5～10-6 g/（m2.d）,比一般硼硅酸盐玻璃固化体中稀土元素的浸出速率低1～2个数量级。固化体中Ca、Si和Al的28d浸出速率约为10-3g/（m2.d）,Fe的28d浸出率约为10-4g/（m2.d）。     

铝热剂SHS合成模拟核废物固化产物的组成结构分析

以Fe2O3为氧化剂,采用铝热剂(Al与Fe2O3的质量比为1:3)自蔓延高温合成(self-propagating high temperature synthesis,SHS)技术制备模拟核废物砂土固化产物,研究了不同模拟示踪核素在固化产物中的存在状态。通过扫描电镜、显气孔率测试、密度分析、X射线衍射分析等分析了固化产物的表面形貌和组成结构。结果表明:采用SHS技术固化砂土,固化产物为无定形玻璃和晶体颗粒构成的混合物,密度为2.60～3.05g/cm3,其中晶体成分主要是α-Al2O3,约占晶体质量的49.4%～63.6%,其他为示踪核素Ce,Sr,Ba,Er与SiO2结合生成的Ce2SiO5,BaSrSi2O6和Er2SiO5,各约占晶体质量的12.0%～18.7%。     

温度对模拟高放玻璃固化体显微结构和抗浸出性能的影响

以模拟北山地下水为浸泡剂,采用静态浸出试验法(MCC-1),研究了温度(40～150℃)对模拟高放废液硼硅酸盐玻璃固化体显微结构和抗浸出性能的影响.结果表明:玻璃固化体浸泡42 d后,在90℃及以上温度出现了蜂窝状的页硅酸盐和铝硅酸盐矿物,在150℃还新生成了白色板状BaSO4晶体;Si、B、Cs和U元素的归一化浸出率(LR)在28 d后趋于平稳,且随着温度升高浸出率逐渐升高;基于B元素浸出速率的表观活化能约为27.8 kJ/mol;玻璃固化体在90℃模拟地下水浸泡28 d后的LRSi、LRB、LRCs、LRU分别为1.45×10-1、1.39×10-1、2.48×10-1、1.3×10-1g/(m2·d).     

“碱-矿渣-粉煤灰-煅烧高岭土”水合陶瓷固化模拟中放α废液

以钕和铈作为放射性铀和钚的模拟核素,采用碱激发和水热法制备了模拟中放α废液"碱-矿渣-粉煤灰-煅烧高岭土"水合陶瓷固化体。研究了固化体的结构组成、力学性能、抗侵蚀性和化学稳定性。结果表明:固化体的主要晶相组成为方沸石和NaPl沸石;在水热条件下,固化体中掺入模拟中放α废液后有利于沸石晶相的形成。抗压强度测试表明,固化体中废物包容量达到40%左右时仍能满足水泥固化体抗压强度的要求。固化体经硫酸盐介质和地下水侵蚀28 d后,其抗压强度损失较少,外观没有裂纹和龟裂,说明固化体具有较好的的抗硫酸盐和地下水侵蚀性能。另外,静态浸出测试结果表明,Nd和Ce的浸出率在10~(-8)~10~(-6)cm/d范围,说明固化体具有优良的化学稳定性。     

镁热剂/铝热剂体系SHS法固化处理无钙焙烧铬渣

采用Al-Fe_2O_3(铝热剂)和Mg-Fe_2O_3(镁热剂)2种自蔓延高温合成体系(SHS)对无钙焙烧铬渣(COPR)进行固化处理,并通过浸出毒性试验对自蔓延产物的无害化效果进行评估。研究结果表明:2种反应体系均可实现铬渣的高效无害化,其中铝热剂体系和镁热剂体系铬渣含量分别高达80%和85%,其自蔓延产物浸取浓度ρ(总铬)和ρ(六价铬)分别低于4.5、1.5 mg·L~(-1),符合生活垃圾填埋场污染控制标准GB 16889—2008,可进行填埋处置。在SHS反应过程中,六价铬还原率均高于90%,还原后的六价铬主要以非晶形式弥散分布于自蔓延产物中,且部分铬离子参与MgAlCrO_4尖晶石等矿物的形成,铬元素同时以物理和化学固定化的形式存在于自蔓延产物中。     

Fe2O3对含铈钙钛矿玻璃陶瓷物相结构及化学稳定性的影响

本文以典型SiO₂-B₂O₃-CaO-Na₂O-TiO₂硼硅酸盐玻璃为基础玻璃,采用热处理析晶法制备含铈钙钛矿玻璃陶瓷固化体。通过DSC、XRD、FTIR、SEM-EDS、ICP等测试方法研究了不同Fe₂O₃含量对该固化体物相结构及化学稳定性的影响。结果表明,随着Fe₂O₃的掺入,CeO₂晶体衍射峰强度逐渐减弱,钙钛矿(CaTiO₃)晶粒分布的均匀程度呈先升高后降低的趋势,所有元素的归一化浸出率呈先降低后升高的趋势。当Fe₂O₃含量为6%(质量分数)时,CeO₂晶体消失,晶粒的分布最为均匀,所有元素的归一化浸出率最低。28 d后,所有样品中元素的归一化浸出率(g·m^-2·d^-1)均低于10^-3数量级,这表明所制备的玻璃...     

钛酸盐陶瓷固化Sr2+核素的SHS热力学

探索采用燃烧合成(SHS)技术制备包容锶核素(Sr2 )的钛酸盐陶瓷固化体,根据自蔓延高温合成热力学分析,计算钛酸盐固化体的绝热燃烧温度Tad大于临界绝热燃烧温度,说明反应能自发进行并合成致密的CaTiO3固化体。     

基于核废物固化应用的铁磷酸盐材料研究进展

铁磷酸盐材料是一类新型的核废物固化材料,铁磷酸盐玻璃具有较高的化学稳定性和较低的熔融温度,独居石、磷灰石等是固化核素优选的晶体,铁磷酸盐玻璃陶瓷固化兼有玻璃基体对多种元素的包容性和陶瓷固化对特定放射性核素抗辐射能力的优势。综述了铁磷酸盐玻璃、陶瓷及玻璃陶瓷的特点及其在高放废物固化方面的研究现状及进展,比较了用于核废物固化的铁磷酸盐固化体的体系及特点。     

含钴废渣硫酸化焙砂浸出液中钴、铁、锰分离研究

对某锌厂含钴废渣硫酸化焙砂浸出液进行了钴与铁、锰分离工艺研究。研究表明 ,焙砂用水浸出时延长时间为 3.5h,可使大量铁以黄铁矾的形式除去 ,再控制溶液 p H3～ 3.5,温度 1 0 0°C,时间 1 h的条件下 ,采用针铁矿法除铁 ,铁的去除率可达 99.5% ,然后控制溶液 p H4～ 4.5,温度1 0 0°C,用 1 0 % ( NH4 ) 2 S2 O8溶液氧化 Mn2 + 为沉淀而除去 ,锰的去除率为 99.8% ,同时还可氧化Fe2 +达到深度除铁的目的 ,铁的总去除率达 99.9%。在此过程中 ,钴的损失率仅为 2 .5% ,取得了令人满意的结果     

Durability of Zirconium-Containing Ceramic Waste Forms in Water

The durability of three ceramic waste forms containing Zr as a constituent is examined at 90° and 150°C in HCl or deionized water. The three ceramic waste forms examined are: (A) 10-mol%-Y₂O₃-stabilized ZrO₂, (B) La₂Zr₂O₇ with a pyrochlore structure, and (C) CaZrO₃ with a perovskite structure. Each form contains an appropriate amount of Ce, Nd, and Sr to simulate the leaching behavior of actinides, lanthanides, and alkaline-earth fission products from highlevel nuclear waste. Two forms, (A) 10-mol%-Y₂O₃-stabilized ZrO₂ and (B) La₂Zr₂O₇ with a pyrochlore structure, show excellent durability in HCl and deionized water. For example, leach rates of all constituents in the La₂Zr₂O₇ waste form are less than about 10⁻⁴ g·m⁻²·d⁻¹ at 150°C for a leach time of 32 d in deionized water.     

Thermodynamic Considerations of Covalency in Trivalent Actinide-(poly)aminopolycarboxylate Interactions

The complexation thermodynamics of trivalent actinides with (poly)aminopolycarboxylates (APCs) are reviewed to assess aspects of covalency and selectivity in actinide-amine interactions. The preferential interaction of APC ligands with trivalent actinides over trivalent actinides has been interpreted to suggest that the amine donors on the APC ligand are able to interact covalently with the actinides. This potentially covalent interaction could allow APC ligands to serve as a thermodynamic probe for covalency in actinide interactions. This review considers enthalpic binding signatures associated with actinide-APC systems, linear free energy relationships that compare the chemistry of comparably sized trivalent lanthanides and actinides and, through examination of the TALSPEAK system, evaluation of a separation system where understanding the chemistry of the heaviest actinides could be relevant. An overarching observation of this review is the lack of thermodynamic data that would be instructive in describing the chemistry of a broader part of the actinide series.     

A COUNTER CURRENT EXPERIMENT FOR THE SEPARATION OF TRIVALENT ACTINIDES AND LANTHANIDES BY THE SETFICS PROCESS

ABSTRACT

The SETFICS process, a variation of TRUEX process, was developed for the recovery of Am and Cm from acidic waste solution and the separation of actinides (III) and light lanthanides. The process uses the general TRUEX solvent as the extracting reagent and a DTPA-sodium nitrate solution for selective stripping of actinides(III). The basic flow sheet is composed of four steps: extraction-scrubbing; acid stripping; actinide(III) stripping; and lanthanide stripping.

To demonstrate the usefulness of the SETFICS process, a counter current experiment was conducted using a real TRUEX product solution. Americium and curium were successfully recovered with a solution of 0.05 M DTPA-4 M NaNO₃ (pH 2.0). Although the actinide(III) product solution contained Sm and Eu, the decontamination factor of ¹⁴⁴Ce/²⁴¹Am was 72, and most of the light lanthanides, specifically La, Ce, Pr, Nd, were removed. At least 80 % of the lanthanides were separated from the Am and Cm end products. In order to minimize the acidity in the actinide(III) stripping step, the nitric acid which extracted with the trivalent metals was previously removed with a solution of 0.5 M NaNO₃ (pH 2.0) in the “acid stripping” step.     

利用分子量分布探讨粉末活性炭对膜生物反应器的影响

采用空间排阻液相色谱法监测了不同粉末活性炭（PAC）投加量下膜生物反应器混合液分子量分布情况,发现当PAC投加量从1 g·L^-1增加到2 g·L^-1时,混合液中分子量大于10×10³的物质会增加;分子量小于0.5×10³及介于3×10³～10×10³的物质含量相当;分子量介于0.5×10³～3×10³的物质显著减少。膜污染速率分别为2.74、3.10 kPa·m^-1,证实了混合液中分子量大于10×10³的有机物是引起膜污染的主要物质。     

Diamides as Actinide Extractants for Various Waste Treatments

Abstract

Substituted propanediamides were studied at Fontenay-aux-Roses for the declassification of nuclear liquid wastes by extraction of all the actinides. Their synthesis has been improved. By optimization of the formula, it is possible to use aliphatic diluents without third-phase formation in contact with nitric acid at 20°C. Addition of oxalic acid allows separation of iron and zirconium from americium and plutonium. In selected conditions, it appears that americium extraction is faster than iron extraction, which could lead to practical applications. Recent studies have shown that diamides can be used to remove the actinides from waste solutions in chloride medium coming from defense facilities. The current knowledge and the projects for using diamides as actinide extractants will be reviewed.     

“TRU-SANEX”: A variation on the EURO-GANEX and i-SANEX processes for heterogeneous recycling of actinides Np-Cm

A novel separation process for recovering transuranic actinides has been tested in centrifugal contactors using a surrogate feed solution. This “TRU-SANEX” (transuranic element-selective actinide extraction) process uses solvent extraction between nitric acid and an organic phase containing 0.2 mol/L N,N,N′,N′-tetraoctyl diglycolamide with 0.5 mol/L N,N′-dimethyl-N,N′-dioctylhexylethoxy-malonamide to co-extract actinides and lanthanides followed by separate sections for plutonium–neptunium and americium–curium stripping. Overall, good performance was achieved with good recoveries of plutonium and americium in the products and only small amounts of cross-contamination between products. Decontamination factors for selected lanthanides in the americium–curium product ranged from ~40 to >1300.     

石墨烯增强复合相变储能材料的热学性能研究

以铁尾矿多孔陶瓷为载体,通过自发浸渗法成功制备出了添加石墨烯的复合相变储能材料,并对该材料热学性能及稳定性进行测试。结果表明：通过改变载体孔隙率,可以制得导热系数为0.41～0.59 W/(m·K)、潜热为69～120 kJ/kg、热学稳定性良好的导热增强复合相变储能材料。通过拟合,复合相变储能材料的导热系数与多孔载体的孔隙率呈线性关系,且经100次热循环后材料熔化潜热和导热系数分别降低了3.2%和16.7%。本研究为固废铁尾矿在蓄热、储能领域的应用提供了新思路。     

Mixed Monofunctional Extractants for Trivalent Actinide/Lanthanide Separations: TALSPEAK-MME

The basic features of an f-element extraction process based on a solvent composed of equimolar mixtures of Cyanex-923 (a mixed trialkyl phosphine oxide) and 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) extractants in n-dodecane are investigated in this report. This system, which combines features of the TRPO and TALSPEAK processes, is based on co-extraction of trivalent lanthanides and actinides from 0.1 to 1.0 M HNO₃ followed by application of a buffered aminopolycarboxylate solution strip to accomplish a Reverse TALSPEAK selective removal of actinides. This mixed-extractant medium could enable a simplified approach to selective trivalent f-element extraction and actinide partitioning in a single process. As compared with other combined process applications in development for more compact actinide partitioning processes (DIAMEX-SANEX, GANEX, TRUSPEAK, ALSEP), this combination features only monofunctional extractants with high solubility limits and comparatively low molar mass. Selective actinide stripping from the loaded extractant phase is done using a glycine-buffered solution containing N-(2-hydroxyethyl)ethylenediaminetriacetic acid (HEDTA) or triethylenetetramine-N,N,N’,N’’,N’’’,N’’’-hexaacetic acid (TTHA). The results reported provide evidence for simplified interactions between the two extractants and demonstrate a pathway toward using mixed monofunctional extractants to separate trivalent actinides (An) from fission product lanthanides (Ln).     

Effect of Iron on Waste-Glass Leaching

The interactive effects between ductile iron and PNL 76–68 borosilicate glass were investigated as a function of time in 90°C static deionized, tuff, and basalt groundwaters. A syn-ergistic effect occurs between the two materials, i. e. iron enhances glass dissolution and glass enhances iron corrosion. An iron silicate precipitate forms, part of which is colloidal in nature. This precipitate effectively removes many of the elements from solution and therefore inhibits the saturation effects which normally cause decreases in elemental removal rates. Thus, the effects of initial solution composition on the glass leach rates are significantly reduced and the relatively high early leach rates normally observed in deionized water are maintained for longer times due to the suppression of saturation effects. This results in more total elemental removal from the glass in all of the groundwaters evaluated. The precipitate and its colloidal form require further characterization.