Potential application of a nanocomposite:HCNFe@polymer for effective removal of Cs (I) from nuclear waste

This study highlights new opportunities for the preparation of Cobalt Hexacyanoferrate(CoHCNF)@poly aniline nanocomposite as an adsorbent to efficiently remove Cs (I) ions from water. A chemical co-precipitation method was utilized to prepare CoHCNFe@poly aniline nanocomposite nanostructure. The TEM and SEM images of the product showed that it consists of semi-spherical particles with sizes ranging from 50 to 500 nm. Experimental parameters affecting Cs (I) sorption such as pH, adsorbent dosage, contact time, initial concentration of metal ion and temperature were studied. The maximum adsorption capacity (q) for cesium ions obtained from the Langmuir model at room temperature and 60 °C were 92.12 and 181.81 mg g⁻¹ respectively. It is clear that this adsorbent has effective removal properties for adsorption of Cs(I) from radioactive waste compared with other adsorbents.The kinetic data were analyzed by the pseudo-first-order and the pseudo-second-order kinetic models; consequently, the pseudo-second-order model was the best to describe the adsorption of Cs (I) ions. The equilibrium data were fitted to the three isotherm models: Freundlich, Langmuir and Dubinin–Radushkevich (D–R), and as a result the Langmuir model produced the best fit for the experimental data. Thermodynamic parameters showed that the adsorption of Cs (I) ions onto the nanocomposite was endothermic and spontaneous. The mechanism of Cs (I) ions sorption was discussed.     

聚锑酸离子交换剂吸附锶的热力学

采用自制的聚锑酸无机离子交换剂对锶的吸附性能进行了研究。实验结果表明,在温度为293～323 K和所研究的锶浓度范围内,聚锑酸对锶吸附平衡符合Langmuir和Freundlich吸附等温方程;Freundlich吸附等温线和等量吸附焓表明,聚锑酸对锶吸附是一个吸热过程;计算出了锶在聚锑酸上的吸附焓、自由能和熵变;该聚锑酸离子交换剂对锶的吸附是物理吸附和化学吸附共同作用的结果,并对吸附行为作了合理解释。     

集成缓冲材料对锶的长期阻滞效应

缓冲材料作为高放废物处置库中多重屏障体系的最后一道人工屏障,其对放射性核素的阻滞性能将直接影响到处置库的长期稳定性和安全性。以具有低渗透性和良好的膨胀自愈性的膨润土作为集成缓冲材料的基材,以沸石和黄铁矿作为矿物添加剂,三者按照质量比为63∶27∶10均匀混合构成集成缓冲材料B7ZP,并采用恒定源扩散实验分析了锶在干密度为1.70g/cm~3试样中的扩散特性,结果表明,B7ZP缓冲材料对锶具有良好的阻滞性能,其表观扩散系数为3.30×10~(-12) m~2/s。同时,以多孔介质污染物迁移理论为依据,建立了锶在集成缓冲材料B7ZP中迁移的对流-弥散-吸附多场耦合方程,并应用Matlab软件分析了不同的时间尺度、渗流速率、表观扩散系数和阻滞因子等因素下集成缓冲材料B7ZP对锶的长期阻滞性能,为高放废物处置库的缓冲材料设计和长期阻滞性能评价提供科学依据。     

Eu(Ⅲ)在白云石上的吸附行为

采用静态吸附法研究了Eu(Ⅲ)在塔木素粘土岩主要成分白云石上的吸附行为,探讨了时间、温度、pH值、离子强度、固液比、Eu(Ⅲ)初始浓度、腐殖酸等因素对吸附的影响。结果表明:Eu(Ⅲ)在白云石上的吸附强烈依赖于溶液pH值。当pH<7时,Eu(Ⅲ)的吸附率随溶液离子强度的增加而减小,表明Eu(Ⅲ)在白云石上的吸附以离子交换为主;当pH>7时,则以内层表面配位反应为主。腐殖酸的加入和温度的升高均会促进Eu(Ⅲ)的吸附,其吸附是一个自发吸热的过程,且较好地符合准二级动力学和Freundlich吸附模型,揭示该过程以化学吸附和非均相吸附为主。上述研究结果还表明白云石在塔木素粘土岩吸附Eu(Ⅲ)的过程中非主导作用,这更好地理解了白云石在塔木素粘土岩吸附Eu(Ⅲ)过程中的贡献,为我国高放废物地质处置库选址及安全性评价提供参考。     

The ion exchange phase in corrosion of nuclear waste glasses

The diffusion-controlled ion exchange phase in the corrosion of nuclear waste borosilicate glasses has been examined using the Doremus’ model accounting for interdiffusion and exchange of the cations in the glass with protons from the water. Ion exchange is the principal radionuclide release mechanism for conditions when glass network hydrolysis is suppressed, such as in silica-saturated solutions when ion exchange may persist over geological time scales. In dilute aqueous solutions ion exchange controls the initial cation release and can dominate for tens and many hundreds of years if temperatures are low at low and neutral pH. Ion exchange rates are shown to have inverse square root time dependences, an Arrhenius-controlled temperature relationship and a 10^−0.5pH dependence with the pH of the contacting water. Due to radioactive decay the radionuclide releases from nuclear waste glasses are limited to certain upper values, which can be calculated based on available experimental data.     

放射性废液中钚的耐辐射真菌吸附分离研究

快速、高效、经济地清除放射性污染是核应急处置、污染场址修复的重点研究内容。从放射性污染土壤中提取、遴选出3种耐辐射真菌F3、F7和F16,研究了其对钚的吸附分离性能。3种真菌在弱酸性(pH=0.0~4.2)溶液中对钚均有较强的吸附,吸附率随溶液pH值的增大而升高。25℃下,10 m L pH值1.0溶液中10 ng/m L的钚几乎可被3种真菌完全吸附(吸附率95%),实测F3、F7和F16对钚的平衡吸附容量分别为(11 747±539)、(17 890±757)、(11 946±477)ng/g(干菌),平衡时间约为30 min。吸附过程符合准二级动力学模型和Langmuir等温吸附模型,主要受体扩散、粒内扩散等过程控制。以0.5 mol/L的Na HCO3为解吸剂,可定量回收吸附于微生物上的钚;用3种真菌吸附回收放化实验室高盐度放射性废液中的钚,全程回收率大于99%。     

无机锶吸附剂的制备及其应用

为了去除放射性溶液中的90Sr,采用高锰酸钾和氯化锰的水溶液在pH=10~12、60℃的水浴中反应制备了一种MnO2吸附材料,并用X射线衍射法对其进行了初步分析和表征,该样品为α-MnO2和γ-MnO2的混合晶相。采用静态实验对该吸附剂进行研究,并将其与9种常见的天然锶吸附材料进行比较。结果表明:该吸附剂对90Sr的吸附效果明显好于常用天然吸附材料;其对90Sr的吸附速率非常快,约20min即可吸附平衡,且具有较高的理论饱和吸附容量(Q≈0.52mmol/g)和吸附分配系数(Kd),其典型Kd≈104 mL/g;随着硝酸浓度增加90Sr的Kd值迅速降低,当c(HNO3)=0.01mol/L时,Kd≈6×103 mL/g,而当c(HNO3)=0.1mol/L时,Kd值仅为6mL/g,降低了3个数量级;Na+、K+的含量对Kd值的影响较小,随其浓度增加Kd值缓慢降低,但Co2+、Ca2+对锶的Kd值具有较大的影响,随离子浓度增加Kd值快速减小。该吸附剂对模拟和真实放射性废液的90Sr动态去除实验结果表明,其对锶具有很好的吸附性能,可用于去除放射性废水中的90Sr。     

Removal of Co2+ from radioactive wastewater by polyvinyl alcohol (PVA)/chitosan magnetic composite

Cobalt is one of the toxic radioactive elements and the removal of Co²⁺ from radioactive wastewater has received increasing attention in recent years. In this paper, polyvinyl alcohol (PVA)/chitosan magnetic composite was prepared and used for Co²⁺ removal. The effect of initial pH, contact time and initial Co²⁺ concentration on Co²⁺ adsorption was investigated. The kinetics, thermodynamic and isotherms of Co²⁺ sorption onto the composite were determined. The results showed that pseudo second-order equation could be used to describe the Co²⁺ removal process. The maximum sorption capacity was calculated to be 14.39 mg/g at pH 6.0 and 30 °C using the Langmuir model. The analysis of FTIR and SEM-EDAX were performed before and after Co²⁺ sorption onto the PVA/chitosan magnetic beads, revealing that the functional groups –NH₂ and –OH played main role in Co²⁺ sorption process. PVA/chitosan magnetic composite is promising adsorbent for removing Co²⁺ radioactive wastewater.     

锶在土壤中的吸附动力学

用动态法测定了锶在核废物处置预选场址土壤中的平衡吸附容量,研究了水相pH值、流速、土壤粒度和锶溶液的初始质量浓度对土壤吸附锶的影响。水相pH值、流速、溶液的初始质量浓度越大,土壤平衡吸附容量越大;土壤粒度越小,土壤平衡吸附容量越大。用常用的吸附动力学方程对实验数据进行了拟合,并对吸附机理进行了探讨。实验结果表明,该放射性废物处置预选场址土壤对锶的最大吸附率为48.8％,吸附性能较差。     

Estimation of the radiation dose equivalent for the hypothetical submergence of a sea-transport package of low-level radioactive waste

Japanese Electric Power Utilities plans to transport low-level radioactive waste (LLW) in CSD-C (36 canisters) and CSD-B packages (10 canisters) by sea from France to Japan. In this study, we carried out assessments of the dose to the public from a hypothetical release of radioactive materials from submerged LLW packages into the sea. The estimated dose equivalents from the CSD-C and CSD-B packages were 2.8 × 10^?8 and 7.9 × 10^?9 mSv year^?1, respectively, for the near shore case. For the deep sea case, the estimated dose equivalents were 8.6 × 10^?8 and 5.8 × 10^?8 mSv year^?1, respectively. These estimated results were much smaller than those found in a previous study of Type-B packages (spent fuel, high level waste, and mixed oxide fuel) and the ICRP recommendation (1 mSv year^?1).     

聚丙烯酰胺-咪唑类聚离子液体凝胶的辐射合成及其对铀和碘的吸附

采用γ射线辐射引发技术制备了一类聚丙烯酰胺-咪唑类聚离子液体凝胶(PAm-C_nvim_2Br_2)。当吸收剂量为5kGy时,得到了凝胶分数超过95%的聚离子液体凝胶,其溶胀度可由吸收剂量控制。合成的PAmC_nvim_2Br_2可以从碳酸盐溶液中吸附铀最大吸附量约130mg/g,或从碘化钠溶液中吸附碘离子最大吸附量约160mg/g,吸附过程符合Langmuir模型。红外与XPS分析表明,吸附过程遵循离子交换的反应机理。PAmC_nvim_2Br_2凝胶对铀及碘有很好的吸附、解吸性能,有望用于含有铀和碘的放射性废水处理。     

Conceptual Design of Large Boxes for the Packaging of Intermediate and Low Level Radioactive Waste

Abstract

United Kingdom Nirex Limited (Nirex) is developing standard containers for the packaging of radioactive waste for disposal in a deep underground repository. Waste Package Specifications have been produced for each standard package to provide the essential link between waste package design and the design of the deep repository. Previous studies carried out by Nirex identified the dimensions and key features of standard boxes for decommissioning intermediate level waste and for low level waste: the 4 m ILW box, 4 m LLW box·and 2 m LLW box. Nirex has now produced conceptual designs for these boxes.     

微陶材料对铀的吸附特性

采用多种方法对微陶材料进行了表征,分别采用静态法和动态法研究了溶液pH、吸附时间、铀初始浓度、吸附剂用量、解吸流速、吸附剂粒度等因素对微陶材料吸附铀的影响;探究了微陶材料对模拟放射性废水的处理能力。实验结果表明,扫描电镜显示微陶材料底部为层状结构,能谱显示其表面主要成分为铝元素,还有少量(质量分数6.00%)的铁元素;XRD结果显示微陶材料表面无明显Fe的衍射峰;红外光谱显示微陶材料对铀进行了吸附;当pH=5、吸附时间为1h、铀初始质量浓度为100μg/L、微陶材料用量为50mg时,微陶材料对铀的吸附率达到95%以上;动态法中流速和粒度对吸附影响较小;微陶材料对铀的吸附等温线符合Freundlich吸附等温模型;采用准二级反应动力学模型描述微陶材料对铀的吸附,吸附过程主要为化学吸附;微陶材料对模拟放射性废水中铀的吸附率均在90%以上,对锶、铯也有一定的吸附能力。     

一维普鲁士蓝/硅藻土复合材料对Cs+的吸附

含137Cs的放射性废水处理在核能及核技术应用中具有重要意义。以表面活性剂十六烷基三甲基溴化钾和十二烷基磺酸钠为模版,合成了一维结构的普鲁士蓝并将其附着在硅藻土表面,制备成一维普鲁士蓝/硅藻土复合材料;在不同的温度、吸附时间、pH值下,分别探究了一维普鲁士蓝/硅藻土复合材料对Cs⁺的吸附性能,并研究了溶液中其他阳离子对吸附的影响。结果表明：一维普鲁士蓝/硅藻土对Cs⁺的吸附能力随温度（293～318 K）的升高而增加（从42.4 mg/L到61.6 mg/L）,其吸附行为符合Langmuir等温线和准二级动力学方程。     

Radwaste Management and Transport in the Republic of Croatia — Present Status and Main Issues

Abstract

Radioactive waste in Croatia is generated from various nuclear applications as well as from the Kr?ko NPP (a joint venture Slovenian and Croatian facility). The national programme on radioactive waste management is aimed at straightening existing infrastructure in the field, establishing a new and more transparent system of responsibilities as well as developing new legislation. The siting of the LLW/ILW repository in the Repubic of Croatia is one of the most important steps in the whole radioactive waste management cycle. A review of the main activities, the role of institutions involved and some on-going projects which cover the present situation in the field of radioactive waste management in Croatia are presented.     

Synthesis of a Magnetic Composite Resin and Its Cobalt Removal Characteristics in Aqueous Solution

A series of stepwise procedures to prepare a new organic-inorganic composite magnetic resin with phenolsulphonic-formaldehyde and freshly formed iron ferrite was established, based upon wet-and-neutralization method for synthesizing iron ferrite and pearl-polymerization method for synthesizing rigid bead-type composite resin. The ion exchange and sorption characteristics of the composite resin prepared by the above method at various conditions were experimentally disclosed. The composite resin prepared shows stably high removal efficiency to Co(II) species in aqueous solution in a wide range of solution pH. The overall isotherm is qualitatively explained by the generalized adsorption isotherm concept proposed by McKinley. The standard enthalpy change derived from van't Hoff equation conforms to the typical range for chemisorption or ion exchange. The selectivity of the PSF-F (phenolsulphonic formaldehyde-iron ferrite) composite resin to Co(II) species and other competing chemicals (i.e. Na₂EDTA, Ca(II) and Na) was compared. It is anticipated that the composite resin can also be used for column-operation with process-control by applying external magnetic field, since the rigid bead-type composite resin shows magnetic-susceptibility due to its paramagnetic inorganic constituent (i.e. iron ferrite).     

Removal of radionuclide Sr2+ ions from aqueous solution using synthesized magnetic chitosan beads

Strontium-90 is one of the main fission products, existing in the radioactive wastes produced in nuclear power plant. In this paper, a novel magnetic chitosan beads were synthesized, characterized and applied for removal of Sr²⁺ ions from aqueous solution. The SEM analysis indicated that the magnetic beads were in regular spherical geometry with about 1 mm diameter. The XRD and EDS analysis revealed that the chitosan beads were magnetic and can be used for the magnetic separation. The influencing factors of Sr²⁺ sorption onto magnetic chitosan beads were studied, including contact time, initial pH value, initial Sr²⁺concentration and sorbent dosage. The maximum adsorption capacity (q_m) of Sr²⁺ was calculated to be 11.58 mg/g using the Langmuir isotherm. The kinetic data were analyzed by intra particle diffusion model. The FT-IR study revealed that –NH₂ was mainly involved in Sr²⁺ sorption by magnetic chitosan beads.     

Analysis of Sorption Behavior of Cesium and Iodide Ions on Pumice Tuff

In the reliable safety assessment of radioactive waste disposal, the understanding and modeling of the sorption behavior onto the host rock under various groundwater conditions are indispensable. The influence of pH, ionic strength, and the initial concentrations of Cs and I on the sorption of Cs and I on tuff and pumice isolated from the original pumice tuff rock was investigated. For both rocks, the proton concentration has little effect on the K_d values forCs in the pH range 3–10. As the ionic strength of the solution increases in the presence of sodium perchlorate as a matrix ion, the K_d value of cesium apparently decreases, reflecting the competition of the electrolyte Na⁺ with thespecific sorption of Cs⁺ on the negatively charged sites. In contrast, no significant dependence of ionic strength on the K_d of anionic iodine was found. A simple surface complexation model without considering electrostatic works was applied to simulate the sorption of ions on rocks, and the model parameters were determined. The K_d values at the given chemical conditions were estimated using the parameters and compared with the ones in the literature.     

钛硅酸钠（Na2Ti2O3SiO4·2H2O）对Cs的吸附热力学分析

钛硅酸钠(Crystalline Sillicotitanate, CST)对铯（Cs）的吸附热力学分析是研究钛硅酸钠吸附铯机理的重要途径之一。本工作通过研究不同温度下CST与不同浓度CsNO₃溶液反应,测定反应前后Cs⁺的浓度变化,得到了一系列参数。结果显示,不同的反应温度对应不同的饱和吸附量,当温度为298.15 、313.15和328.15 K时,饱和吸附量分别为212.8、217.4和232.6 mg/g。分别用Langmuir方程和Freundlich方程对实验数据进行拟合,结果表明,此吸附过程更符合Langmuir等温吸附。在不考虑温度对吸附焓和吸附熵影响的前提下,计算得到吸附焓ΔH=21.28 kJ/mol,ΔS=89.18 J/K/mol以及ΔG<0。以上结果表明,CST对Cs的吸附过程是一个自发进行、既有物理吸附又有化学吸附的吸热反应。