Study on the extraction of U(IV) relevant to PUREX process

The paper presents a radiokinetic study on the appearance and growth of^*Fe₂S₃,^*Fe(OH)₃,^*Fe₂(C₂O₄)₃,^*Fe(IO₃)₃ crystals in a colloidal medium of agar and gelatine. The values of the diffusion constants through gels of⁵⁵⁺⁵⁹Fe³⁺ radioactive cations and of the rate of global growth process of these crystals in agar or gelatine were calculated using the experimental data. A new method for the determination of the starting time for the complex nucleation process was proposed. The formation rate of crystals under study decreases in the order:^*Fe(OH)₃>^*Fe(IO₃)₃>^*Fe₂S₃>^*Fe₂(C₂O₄)₃, in agar medium and^*Fe(OH)₃>^*Fe(IO₃)₃>^*FeC₂O₄)₃>^*FeS₃, in gelatine medium.     

Generation of HNO2 by bubbling NO in HNO3 system and its application in the PUREX process

This work is aimed at studying HNO₂ generation by bubbling NO in HNO₃ solution. The formation and decomposition of HNO₂ depend on the 2NO+HNO₃+H₂O3HNO₂ reaction. During the HNO₂ generation, the HNO₃ concentration was kept constant. The influence of HNO₃ concentration, temperature, NaNO₃ concentration and NO bubbling rate was studied. Its possible application in the PUREX process was evaluated.     

Kinetics of reductive stripping of Pu(IV) in the tributylphosphate-kerosene/nitric acid-water system using dihydroxyurea

The kinetics of the reductive stripping of plutonium(IV) by dihydroxyurea (DHU) in 30% TBP/kerosene-HNO₃ system was studied with a constant interfacial area cell. The stripping rate of plutonium(IV) increases with the increase of the stirring speed of two phases and the interfacial area. The activation energy of this process is 28.4 kJ/mol. Under the given experimental conditions, the mass transfer of Pu is not controlled by redox reaction, but controlled by molecular diffusion from the organic phase to organic film layer and from the aqueous film layer to aqueous phase. The rate equation of reductive stripping (process is controlled by diffusion) was obtained as: r ₀ = k′[Pu(IV)]₀[DHU]_a ^0.16[HNO₃]_a ^−0.34. The rate constant k′ is (5.0±0.4)·10⁻² (mol/L)^0.18·min⁻¹ at 18.0°C.     

Mathematical modeling of the co-decontamination process in PUREX

Journal of Radioanalytical and Nuclear Chemistry - A mathematical model of co-decontamination process (1A) containing U(VI), Pu(IV), Zr(IV), and Ru(III) was developed with a high-performance...     

A new internal conversion electron spectrometer and its application to determine the240Pu to239Pu isotope ratio

An internal conversion electron spectrometer with high energy resolution has been constructed by using a windowless Si(Li) detector. After its characteristics were examined fundamentally, it was applied to determine the²⁴⁰Pu to²³⁹Pu isotope ratio. As a result, the energy resolution realized was demonstrated to be satisfactory.     

The behavior of technetium in technetium-scrubbing stage of PUREX process

Technetium decontamination factor as a function of the acidity, flow ratio, scrubbing stage number was investigated by counter-current cascade experiments or mixer-settler batch tests. Results showed that the acidity of the scrubbing acid has little influence on the decontamination factor of technetium when the acidity was kept in the range of 4.5–6 M. The most effective method to increase the decontamination factor is to lower the feed-to-acid flow ratio. Keeping other condition same the factor increased to 10.3 from 3.1 when feed-to-acid ratio changed to 4 from 5.6. The loss of uranium and plutonium can be recovered through a re-extraction technology.     

Determination of dissolved TBP in PUREX process aqueous streams using ICP-AES

A method for the determination of dissolved tri butyl phosphate (TBP) in PUREX process aqueous streams by atomic emission spectrometry with inductively coupled plasma has been evolved. The phosphorous emission lines of 213.618 and 214.914 nm have been chosen and the possibility of determining dissolved TBP in these lines has been explored. Since presence of uranium which is inevitable in the process solution, and also present in macro level, the spectral and matrix interference of uranium on the determination of phosphorous has been investigated. The precision of the method was characterized by RSD of <5 % with a detection limit of 0.06 and 0.24 mg/L for phosphorous which in turn corresponds to detection limit of 0.5 and 2 mg/L for dissolved TBP in lines 213.618 and 214.914 nm respectively.     

Batch process monitoring and its application to polymerization systems

Slight changes in raw material properties or operating conditions during critical periods of operation of batch and semi-batch polymerization reactors may have a strong influence on reaction mechanism and impact final product quality. Online process monitoring, fault detection, fault diagnosis, and product quality prediction in real-time ensure safe reactor operation and warn operators about excursions from normal operation that may lead to deterioration in product properties. Multivariate statistical process monitoring and quality prediction using multiway principal components analysis and multiway partial least squares have been successful in detecting abnormalities in process operation and product quality. When abnormal process operation is detected, fault diagnosis tools are used to determine the source cause of the deviation. Illustrative case studies are presented via simulated polyvinyl acetate polymerization.     

Improved procedure for Pu/Am,and U isotope analysis in fecal samples

Journal of Radioanalytical and Nuclear Chemistry - Herein, we describe an improved procedure for 238Pu, 240Pu, 241Am, and natural U quantitation in fecal samples and validate it by analyzing...     

Synthesis of magnetic chitosan/graphene oxide nanocomposites and its application for U(VI) adsorption from aqueous solution

Journal of Radioanalytical and Nuclear Chemistry - The performance of a magnetic chitosan/graphene oxide composites (MCGO) have been investigated for the adsorption processes of U(VI) ions from...     

Synthesis of polyaniline/graphene composite and its application in zinc-rechargeable batteries

Journal of Solid State Electrochemistry - Polyaniline, polyaniline/graphene composites were synthesized by a novel in situ chemical oxidative polymerization method including two oxidants. The...     

U and Pu separation with U/TEVA resin: Influence of some parameters on chromatographic cycle performances

Journal of Radioanalytical and Nuclear Chemistry - Due to unexpected Pu behavior using the U/TEVA resin and the most-recognized reagents, some key separation stages need to be studied for the...     

In-line determination of U,Pu and Np in process streams by energy-dispersive X-ray fluorescence analysis (EDXRF)

A -ray source of 300 keV was used in order to excite the fluorescent K-radiation of the heavy elements which is only weakly absorbed in the walls of metal tubes. Thus, uranium can be determined quantitatively in solutions within tubes in the concentration range form 5 mg/l to 100 g/l. The influences of the energy and the activity of the radiation source, the geometrical arrangement, the thickness of the wall and the wall material have been investigated.     

Development of a urea-adduct process for recovery of n-alkane based diluent from spent PUREX/UREX solvent

Urea-adduct process is commercially used to selectively separate n-alkanes from industrial hydrocarbon mixtures. Authors have explored application of this method for recovery of n-alkane based diluents from spent PUREX/UREX solvent. Traditionally this separation is performed by vacuum distillation, an energy-intensive process. The proposed method is simple and does not involve either exotic chemicals or complex processing steps. Application of urea-adduct process for recovery of diluent from spent solvent is reported here possibly first time in literature. Physical properties such as densities, viscosities and vapour pressure for irradiated organic solutions were also measured and reported.     

Sol-Gel Microsphere Pelletisation Process for Fabrication of (U,Pu)O2, (U,Pu)C and (U,Pu)N Fuel Pellets for the Prototype Fast Breeder Reactor in India

A “dust-free” sol-gel microsphere pelletisation (SGMP) process has been developed for fabrication of (U,Pu)O₂, (U,Pu)C and (U,Pu)N fuel pellets containing around 15% plutonium for the forthcoming prototype fast breeder reactor (PFBR) in India. The objective was to produce homogeneous sintered pellets of ∼85% T.D. with a predominantly open-pore structure. Hydrated gel-microspheres of UO₃+PuO₂ and UO₃+PuO₂+C have been prepared from nitrate solutions of uranium and plutonium by the “ammonia internal gelation” process, using hexamethylene tetramine (HMTA) as an ammonia generator and silicone oil at 90±1°C as gelation bath. For oxide fuel pellets, the hydrated UO₃+PuO₂ gel-microspheres were calcined at around 700°C in Ar+8% H₂ atmosphere to produce “non-porous”, “free-flowing” and coarse (around 400 micron) microspheres which could be directly pelletised at 550 MPa to green pellets. The mixed oxide pellets were subjected either to low temperature (∼1100°C) oxidative sintering (LTS) in N₂+air containing ∼1500 ppm O₂ or to high temperature (1650°C) sintering, (HTS) in Ar+8% H₂. For monocarbide and mononitride pellets, hydrated gel-microspheres of UO₃+PuO₂+C were subjected to carbothermic synthesis in vacuum (∼1 Pa) and flowing nitrogen (flow rate: 1.2 m³/h) in the temperature range of 1450–1550°C respectively. The monocarbide and mononitride microspheres thus produced were relatively hard and required higher compaction pressure (∼1200 MPa) for making reen pellets which could be sintered to 85% T.D. in Ar+8% H₂ at 1700°C. The sintered oxide, monocarbide and mononitride pellets had a “blackberry” “open” pore microstructure with fine grain size. The microspheres retained their individual identity in the sintered pellets because during sintering densification took place mainly within and not between the microspheres.     

Synthesis of isoxazoline N-oxides and its application in the formal synthesis of dehydroclausenamide

A protocol for the synthesis of isoxazoline N-oxides and its application in the formal synthesis of dehydroclausenamide are described. Sulfonium salt 1 reacts with substituted nitroalkenes smoothly to generate isoxazoline N-oxides in high to excellent yields with dr higher than 99/1. Its asymmetric version has been developed by using cinchona alkaloid-derived ammonium salts 6a and 6b instead of sulfonium salt 1 and higher than 96% ee values are achieved. This method has also been successfully applied to the formal synthesis of dehydroclausenamide.     

Chemical separation and ICP-AES determination of 22 metallic elements in U and Pu matrices using cyanex-923 extractant and studies on stripping of U and Pu

Comprehensive studies have been carried out on the extraction behavior of uranium and plutonium matrices using cyanex-923 extractant. The near total extraction of U/Pu and quantitative separation of 22 metallic elements at trace levels has been established using inductively coupled plasma-atomic emission spectrometry (ICP-AES). The studies carried out on back extraction of U/Pu from organic phase have established the near total recovery of these matrices into the aqueous phase using 1 M Na(2)CO(3) and saturated oxalic acid, respectively.     

Denitration of simulated high-level liquid waste by formic acid for the connection of PUREX process with TRPO process

Journal of Radioanalytical and Nuclear Chemistry - Denitration of simulated high level liquid waste (HLLW) by formic acid was performed for the connection of Plutonium Uranium Recovery by...     

Synthesis of N,N-Ac,Boc laurylthio sialoside and its application to O-sialylation

The combination of the 5-N-tert-butoxycarbonyl (Boc) group of laurylthio sialoside and cyclopentyl methyl ether (CPME) as a solvent enhanced the reactivity and α-selectivity of the sialyl donor during sialylation. Selective deprotection of the N-Boc group of sialoside, including an acid-sensitive isopropylidene function, was successfully achieved by Yb(OTf)₃-SiO₂. Transformation of N,N-Ac,Boc into an N-acetylglycolyl group of sialoglycoside was easily performed via selective N-deacylation of the mixed Ac-N-Boc carbamate, subsequent Boc group removal, and acylation.     

Ni/Mo/N催化剂合成及其在噻吩存在体系下苯加氢反应中的应用(英文)

Ni/Mo/N间隙型催化剂具有高的加氢活性及良好耐硫性, 可应用于煤液化油加氢精制高性能喷气燃料. N原子由于只占据晶格间隙位置, 在进入Ni/Mo过程中会因不占据晶格中的特定晶位, 容易从金属晶格溢出导致无法形成稳定的Ni/Mo/N间隙型催化剂. 为此, 本文利用前驱体晶型控制的方式来实现Ni/Mo/N催化剂合成. 采用络合物分解一步法, 考察了不同结晶过程和老化时间对合成的Ni/Mo/N催化剂用于苯加氢反应活性影响, 并采用X射线衍射、X射线光电子能谱和透射电镜-能量色散X射线光谱对催化剂结构组成进行表征. XRD分析结果显示, 钼酸铵[(NH4)6Mo7O24·4H2O]、乙酸镍[Ni(CH3COO)2·4H2O]和六亚甲基四胺(HMT)添加顺序、结晶过程和老化时间直接影响催化剂组成, 并决定Ni/Mo/N晶相的形成. 结晶过程慢速搅拌速度和短老化时间有利于合成含Ni2Mo3N, Mo2C和Ni晶相的高活性Ni/Mo/N间隙型催化剂, 使苯加氢制环己烷模型反应苯的最大转化率达93%, 环己烷选择性为100%. 含0.01 wt%噻吩的存在使苯转化率由72%降至50%, XPS分析结果表明, 催化剂表面形成的MoS2是催化剂活性降低的重要因素.