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Nuclear Fuel Materials
Published in C. K. Gupta, Materials in Nuclear Energy Applications, 1989
Fuel making by co-precipitation is an attractive alternative to the mechanical blending process. A process flow diagram is shown in Figure 37. Chemically co-precipitated oxides based on simultaneous precipitation of ADU and Pu(OH)4 from nitrate solutions are more easily sinterable and can readily form a solid solution during sintering. A clear advantage would have emerged if uranium and plutonium really co-precipitate. This does not take place in practice, since uranium is hexavalent and plutonium is usually tetravalent. They are precipitated readily and at the same time, but do not form mixed crystals. Precipitation with ammonia yields separate crystals of ADU and Pu(OH)4. Precipitation with oxalate is not suitable for co-precipitated fuel, since uranyl oxalate is rather soluble.
Analysis and Design of Photoreactors
Published in James J. Carberry, Arvind Varma, Chemical Reaction and Reactor Engineering, 2020
Eliana R. de Bernardez, María A. Clariá, Alberto E. Cassano
The uranyl oxalate photochemical decomposition is a well-known chemical actinometer. Chemists have found that the rate of oxalic acid decomposition is proportional to the local volumetric rate of energy absorption, where the proportionality factor is the overall quantum yield. It represents a good example of a photochemical reaction that can be modeled using an overall kinetics. To find the relationship between the oxalic acid exit conversion and the volumetric flow rate, we must solve the mass balance equation for the oxalic acid.
Properties of Solids
Published in W. M. Haynes, David R. Lide, Thomas J. Bruno, CRC Handbook of Chemistry and Physics, 2016
W. M. Haynes, David R. Lide, Thomas J. Bruno
Ammonium uranyl oxalate Ammonium uranyl oxalate trihydrate Sodium bromide Sodium bromate Sodium cyanide Sodium carbonate Sodium carbonate decahydrate Sodium chloride Sodium chlorate Sodium perchlorate Sodium fluoride Sodium trihydrogen selenite Sodium trideuterium selenite Sodium iodide
Synthesis and crystal structures of two new uranyl coordination compounds obtained in aqueous solutions of 1-butyl-2,3-dimethylimidazolium chloride
Published in Journal of Coordination Chemistry, 2018
Fangyuan Wang, Lei Mei, Weiqun Shi, Taiwei Chu
As a common inorganic ligand, the strong oxidant K2Cr2O7 is used in the redox process to adjust the valence states of Pu and U [15], and the potassium chromate solution is used as both coolant and corrosion inhibitor for spent nuclear fuel (SNF) rod arrays made from Mg–Be alloys [16]. For organic ligands, oxalic acid is ubiquitous in the nuclear fuel separation process and is a common precipitant and chelating agent for Pu(IV) in the plutonium uranium redox extraction (PUREX). During this purification process of plutonium, oxalic acid functions to remove small amounts of uranium and its fission products. Therefore, uranyl chromate and uranyl oxalate complexes have attracted strong research interests and consequently, several uranyl chromate or oxalate coordination compounds have been reported [17–24]. For example, Krivovichev et al. synthesized the first sodium uranyl chromate coordination compound Na4[UO2(CrO4)3] [17]. Siidra et al. obtained a novel mixed-valent uranyl chromate (V, VI) compound (C3NH10)10[(UO2)13(Cr125+O42)(Cr6+O4)(H2O)6](H2O)6 [20]. Xie et al. created a porous 3D framework (TMA)2[(UO2)4(C2O4)4(H4C4O4)] [23].
Syntheses, structures and properties of uranyl oxalate complexes templated by amines
Published in Journal of Coordination Chemistry, 2021
Yin Su, Xueling Qiao, Jiangang He
There are five coordination modes between oxalate and uranyl ions: (a) 1, 2-coordination; (b) 1, 4-coordination; (c) 1, 3-coordination; (d) 1, 4-coordination-2-bridge; (e) four-tooth chelating bridge coordination [1]. The diversity of coordination modes of oxalate itself and the abundant structural features of uranyl oxalate complexes make the uranyl oxalate complexes have a variety of structures. Uranyl hybrid materials have received attention because of their unique characteristics and applications, such as rich topologies, electrical properties, gas storage, drug delivery, optical radiation detector, and catalysis [4–8]. In the past ten years, the research about uranyl oxalate hybrid materials has focused on the following aspects: (1) co-existing ligands, such as acetic acid [9], peroxide ions [10], sulfuric acid and thiocyanate [11]; (2) central metals, such as Cu [12], Eu and Gd [13]; (3) inorganic or organic templates, including Cs [14], K [15] and protonated amines [11, 16, 17]. Especially, protonated amines and anions can form crystalline solids through cation-anion interactions, which is a frequently used method for synthesizing functional solid materials [18–20]. The protonated amine template guides anions to form pore structures of different shapes and sizes, which are attached to the inner wall in the pore channels through hydrogen bonds to fill the gap. Protonated amines play the role of template orientation, gap filling and charge balance, and can be used as a hydrogen bond donor or acceptor to connect the anion skeleton, so that the compound forms high-dimensional 3 D crystal structures [21]. At present, there are very few studies focusing on the influence of protonated amines on structural construction of uranyl oxalate complexes.
A comparative approach of methylparaben photocatalytic degradation assisted by UV-C, UV-A and Vis radiations
Published in Environmental Technology, 2018
Giovanna Doná, João Luiz Andreoti Dagostin, Thiago Atsushi Takashina, Fernanda de Castilhos, Luciana Igarashi-Mafra
The photon flux was determined actinometrical using the uranyl oxalate method. Photon flux rates equal to 6.588 × 10−7, 3.435 × 10−7, 6.703 × 10−8 einstein L−1s1 were obtained for the UV-C, UV-A, and Vis radiations, respectively.