Electron Beam Radiolysis Research Articles

Identification and time evolution of thionyl chloride (SOCl2) radiolysis products

Abstract Innovative solutions are needed to reduce the amount of high-level waste generated by used nuclear fuel recycling strategies to support the widespread adoption of sustainable nuclear fission energy technologies. To this end, a new sulfur chloride-based process has been developed to recycle zirconium alloy-based materials, which make up a significant fraction of high-level radioactive waste. To support the continued development of this process, we present new data on the potential reaction pathways over time of the products arising from the gamma and electron beam radiolysis of neat thionyl chloride (SOCl2). Interrogation of the gamma irradiated liquid by Raman spectroscopy provided more conclusive identification of the SOCl2 degradation products, specifically sulfur dichloride (SCl2), molecular chlorine (Cl2), sulfur dioxide (SO2), and sulfuryl chloride (SO2Cl2). In comparison, the high dose rate (∼107 Gy s−1) electron beam irradiations formed significantly more degradation products. For both cobalt-60 gamma and electron beam irradiations, the observed degradation products were found to evolve as a function of time post-irradiation via the same reaction pathways, with indication of a solvent regeneration mechanism. These findings are fortuitous for process development, as such a mechanism would be beneficial for process longevity and cost effectiveness.

On the electron beam-induced degradation of vinyl ester thermosets

We have demonstrated that electron beam radiolysis induces scissions of the C-O-C bonds along the backbone of the chains of unsaturated polyester thermosets of different compositions based on dicyclopentadiene, isophthalic acid, epoxy vinyl ester, and terephthalic acid. The radiolysis is imminent irrespective of the degree of crosslinking in the thermosets both in neat resins and in the presence of solvents. Electron Paramagnetic Resonance (EPR) results show the formation of the alkoxyl radicals and C-centered radicals as the primary intermediate products of the C-O-C scissions. While the alkoxyl radicals of these resins exhibit very good stability even six months after the irradiation, the C-centered radicals decay very rapidly via their reactions with oxygen that is available either as adsorbed in the resins, dissolved in solvents or from the environment. The radiolytically produced •OH radicals in the unsaturated-ester aqueous solutions play a major role in inducing scissions on the backbone of the polymer chains. The solvated electrons (es) from organic solvents, such as dimethyl sulfoxide and isopropyl alcohol, also induce direct scission of the C-O-C bonds, giving rise to the formation of alkoxyl radicals and C-centered radicals. However, a considerable fraction of es is scavenged by the dissolved O2 to produce O2−. Despite the radiation-induced scissions, irradiation of the resins at a dose level of 1000 kGy results in an increase of the glass transition temperature, Tg. This is due to the simultaneous radiation-induced polymerization of the vinyl monomers, toluene, and styrene that are present in the resins. The increase in Tg is observed in all the resins except for the terephthalic polyester resin in aqueous solution, in which the absence of these monomers results in Tg decreasing sharply with irradiation. This work demonstrates that ionizing radiation triggers continuous free radical-chain reactions that lead to the formation of recyclable oligomers.

Understanding Complex Electron Radiolysis in Saline Solution by Big Data Analysis.

In this article, we developed a new method to analyze the complex chemical reactions induced by electron beam radiolysis based on big data analysis. At first, we built an element transport network to show the chemical reactions. Furthermore, the linearity between the species was quantified by Pearson correlation coefficient analysis. Based on the analysis, the mechanism of the high linearity between the special species pairs was interpreted by the element transport roadmap and chemical equations. The time variation of the pH of the solution and bubble formation in the solution were analyzed by simulation and data analysis. The simulation indicates that O2 and H2 can easily oversaturate and form bubbles. Finally, the radiolysis of high-energy electrons in pure water was analyzed as a reference for the radiolysis of high-energy electrons in saline solution. This work provides a new method for investigating a high-energy electron radiolysis process and for simplifying a complex chemical reaction based on quantitative analysis of the species variation in the reaction.

The effect of radiolysis and thermally stimulated acid hydrolysis on tributyl phosphate and its solutions in ISOPAR-M

The radiolytic and post-radiation thermochemical (at 90–170 °C) transformations of tri-n-butyl phosphate (TBP) and its 30% solution into Isopar-M during pre-radiation and post-radiation acidification with nitric acid have been investigated. The assortment of nitrogen-containing products of TBP oxidation during gamma radiolysis, electron beam radiolysis, and thermally stimulated acid hydrolysis is similar. Specific products of radiolysis are TBP dimer and alkyl adducts of dibutyl phosphate, and specific products of thermolysis are ethylbenzene and xylenes. It was shown that, in contrast to 100% TBP, where radiolysis and hydrolysis have approximately the same additive effect on the degradation of TBP, hydrolysis in a 30% solution leads to the degradation of nitrogen-containing radiolysis products and additional formation of dibutyl phosphate and monobutyl phosphate. Temperatures above 110 °C during post-radiation thermolysis intensify the formation of highly volatile compounds from radiolysis products (up to 17 wt% at 170 °C), which increases the fire and explosion hazard of using extraction mixtures.

Dynamic Processes of Nanobubbles: Growth, Collapse, and Coalescence

Abstract Nanobubbles are typically classified as gas/vapor phase cavities in an aqueous solution with a characteristic length of approximately 100 nanometers (nm). The theoretical lifetime of these nanobubbles has been estimated to be less than ∼1 μs at a diameter of 100 nm based upon the Young-Laplace pressure, but experimental observations have been reported that indicate that they may exist for many hours, or even days. These nanobubbles can be generated by a number of different methods, such as solvent exchange, pressure and/or temperature variations, chemical reactions, or through the electron beam radiolysis of water. The imaging methods utilized to observe these nanobubbles have evolved from low temporal resolution/high spatial resolution, using atomic force microscopy (AFM); or low spatial resolution/high temporal resolution, using optical microscopy (X-rays); or finally, high spatial/high temporal resolution using more recent electron microscopy techniques. A review of the various methods utilized in the nucleation of nanobubbles and the different imaging technologies utilized, along with a summary of the most recent experimental and theoretical investigations of the dynamic behavior and processes of these nanobubbles, including nanobubble growth, nanobubble collapse, and nanobubble coalescence, are presented, discussed and summarized.

Radiolysis-Induced Crystallization of Sodium Chloride in Acetone by Electron Beam Irradiation.

In situ liquid cell transmission electron microscopy (LC-TEM) is an innovative method for studying the processes involved in the formation of crystals in liquids. However, it is difficult to capture early stages of crystallization because of the small field of view and the unfavorable changes in sample composition resulting from electron-beam radiolysis. Nevertheless, if the radiolysis required to induce the crystallization of a sample could be controlled in LC-TEM, this would be advantageous for observing the crystallization process. Here, we examined this possibility by using a mixture of sodium chlorate (NaClO3) and acetone in the LC-TEM. The electron beam induced the formation of dendritic crystals in a saturated acetone solution of NaClO3; moreover, these crystals consisted of sodium chloride (NaCl), rather than NaClO3, suggesting that chloride ions (Cl−), which were not present in the initial solution, were generated by radiolysis of chlorate ions ${\rm \lpar ClO}_3^- \rpar$. As a result, the solution then supersaturated with NaCl because its solubility in acetone is much lower than that of NaClO3. The combination of radiolysis and a solvent in which a solute is much less soluble is potentially useful for establishing crystallization conditions for materials that are difficult to crystallize directly in LC-TEM experiments.

Use of β Radiation to Localize the Binding Sites of Mercury Ions and Platinum-Containing Ligand in DNA

Composite sequence-specific ligands with DNA-damaging groups may dramatically increase the efficacy of radiotherapy. The most promising damage sensitizers are the atoms of heavy elements, in which electrons are emitted from upper orbitals and a multiply charged positive ion forms when an electron is kicked out from lower orbitals. The biophysical mechanisms of DNA damage produced by these sensitizers are far from fully understood. In this work, high-performance polyacrylamide gel electrophoresis (PAGE) in denaturing gel was used to investigate the nature of DNA cleavage on exposure to β radiation for complexes of heavy atom-containing ligands with DNA restriction fragments. It was demonstrated for the first time that DNA in complexes with Pt-bis-netropsin or mercury salts is cleaved in the vicinity of the heavy atom in the presence of radioactive isotopes emitting β particles of different energies. In the presence of 1 M glycerol, the cleavage of the DNA sugar-phosphate backbone was almost entirely due to a neutralization of the multiply charged Auger ion and was not associated with the Auger electron electron-beam radiolysis. Based on the observations, a relatively simple technique was proposed for precise localization of binding sites for various DNA ligands containing a heavy atom. Analysis of the end groups at the cleavage point and the nature of damage to the complementary DNA chain made it possible to speculate about the mechanisms of direct influence of irradiation on a heavy atom.

In situ transmission electron microscopy observation of ZnO polar and non-polar surfaces structure evolution under electron beam irradiation

Using in situ transmission electron microscopy, we investigated the dynamic reconstruction and evolution of ZnO polar and non-polar surfaces under high-energy electron beam irradiation. Electron beam radiolysis creates oxygen vacancies and a Zn rich (0001) surface. Positive polar charges at the (0001) surface expel loosely bonded Zn ions to diffuse away from the (0001) polar surface. As a result, mass loss was observed around the (0001) surface. Dehydration by the electron beam breaks the charge balance on the (0001¯) polar surface. The negative charges on the (0001¯) surface suppress the radiolysis effect and further absorb Zn ions to the surface to neutral the polar charges. The ideal stacking sequences of Zn ions in hexagonal ZnO structure can be considered as ABAB… along its c axis, while the absorbed individual Zn ion on the (0001¯) surface occupies the C site to form three bonds with surface O ions beneath, instead of one bond in the ideal structure. With more Zn ion absorption and surface oxidization, new nanocrystals grow up from the (0001¯) polar surface. New nanocrystals nucleated at the (011¯0) non-polar surface are driven by the electric field of the polar charges as well, for the Zn ions were always observed to absorb on the negatively charged [0001¯] end of the newly formed (011¯0) surface layer.

EB-radiolysis of carbamazepine: in pure-water with different ions and in surface water

The electron beam (EB) radiolysis characteristics of carbamazepine (CBZ) in pure-water with different ions and that in surface water were studied in this paper. It suggested that the ·OH, ·H and e aq − all played roles on CBZ EB degradation, and the ·OH played the vital role. Acidic solution was favorable for CBZ degradation, while alkaline environment inhibited it. HSO4 – and SO3 2− enhanced the CBZ degradation, but CO3 2−, NO2 −, NO3 − NH4 + and Cl− inhibited. In surface water, the EB-radiolysis was an effective way to degrade CBZ; and CBZ might evolve in three different ways during EB radiation: reduction by e aq − and ·H (intermediate 10,11-dihydrocarbamazepine (I)), oxidization by ·OH (intermediates 10,11-dihydro-10-11-expoxycarbamazepine (II) and 2(3)-hydroxycarbamazepine (III)) and hydration into 10,11-dihydro-10-hydroxycarbamazepine (IV) and finally the intermediates were all mineralized into CO2, H2O, N2 and NH4 +. All the results contribute to study the EB-radiolysis of pharmaceuticals in surface water.

Nanoparticles synthesis by electron beam radiolysis

Abstract Electron beam (EB) irradiation is a useful method to generate stable silver nanoparticles without the interference of inherent impurities generated from chemical reactions. Our experiments were carried out using linear electron beam accelerators with two different EB absorbed dose rates: 2 kGy min−1 and 7–8 kGy s−1, and with different absorbed dose levels. The optimum conditions for silver nanoparticles (AgNPs) generation by radiolysis, or by radiolysis combined with chemical reduction, were established. In order to obtain a good yield for AgNPs synthesized by radiolysis, a high dose rate is required, resulting in a rapid production process. At low absorbed dose rates, the utilization of a stabilization agent is advisable. By modifying the experimental conditions, the ratio between the chemical and radiolytic reduction process can be adjusted, thus it is possible to obtain nanoparticles with tailored characteristics, depending on the desired application.

Radiation Stability of Cations in Ionic Liquids. 4. Task-Specific Antioxidant Cations for Nuclear Separations and Photolithography

Three families of "task-specific" antioxidant organic cations that include designated sites to facilitate deprotonation following electronic excitation and ionization have been introduced. The deprotonation from the excited state is reversible, leading to minimal damage of the cation, whereas the deprotonation from the oxidized cation yields persistent aroxyl and trityl radicals. This protection improves radiation stability of ionic compounds in 2.5 MeV electron beam radiolysis. Apart from the use of such cations as structural components of room temperature ionic liquid (IL) diluents for nuclear separations, their ionic compounds involving bases of superacids are well suited for use as chemically amplified acid generator resists in electron beam lithography and extreme ultraviolet photolithography.

Radiation Stability of Cations in Ionic Liquids. 1. Alkyl and Benzyl Derivatives of 5-Membered Ring Heterocycles

In order to use hydrophobic room temperature ionic liquids (ILs) as diluents in nuclear separations for advanced fuel cycles, it is desirable to reduce the breakdown of the constituent ions caused by ionizing radiation. In this series, we survey radiation stability for different classes of organic cations used to formulate ILs. While radiolysis of 1-alkyl-3-methylimidazolium cations has been extensively studied, there have not been complementary studies of 1-benzyl derivatives of these cations nor organic cations that are derived from 5-membered ring heterocycles other than imidazole, such as 1,2,4-triazole and thiazole. In part 1, we establish the fragmentation pathways for such cations and quantify product yields for 2.5 MeV electron beam radiolysis of these aromatic cations. Radiolytic reduction of 1-benzyl cations derived from imidazole and 1,2,4-triazole is shown to cause the elimination of benzyl radicals from their electron adducts, whereas this elimination does not occur in the thiazole derivatives due to stabilization of the excess electron as a dimer radical cation. No such elimination occurs in the corresponding 1-alkyl derivatives, but there is significant C-N and C-C bond fragmentation in the aliphatic arms. As such bond dissociation reactions are irreversible, there is significant loss of 1-alkyl cations during the radiolysis. For 1-benzyl derivatives, this electronic excitation causes fragmentation of the C-N bonds in the benzyl arms with the release of the corresponding base and the benzyl carbocation that can subsequently attack this base or add to another cation. Such systems exhibit more predictable fragmentation patterns and yield well-defined products; some of the systems also exhibit increased radiation resistance. The C-N bond fragmentation in the reduced cations can be further suppressed through the use of appropriate electron scavengers, including acids and aromatic imide anions. The observed trends are rationalized using density functional theory calculations, and the implications of these results for the design of IL diluents are examined.

Radiation Stability of Cations in Ionic Liquids. 3. Guanidinium Cations

Due to their superb structural versatility, guanidinium cations find increasing use as constituent ions in room temperature ionic liquids (ILs). This versatility allows fine-tuning of hydrophobicity, which is an important concern for the use of ILs as diluents for metal ion separations. However, the presence of six C-N bonds in such cations poses a question, whether the guanidinium based ILs can be considered as diluents for nuclear separations, given that the radiation emitted by the decaying radionuclides can break these relatively weak bonds over the use cycle of the solvent. As nothing is presently known about the radiolytic stability of the guanidinium cations, we addressed this question using 2-dialkylamino-1,3-dimethylimidazolidine based cations (R = Et, Pr, and Bu) as a representative model for the entire class of such cations, and assessed their stability in 2.5 MeV electron beam radiolysis. Electron paramagnetic resonance spectroscopy, nuclear magnetic resonance spectroscopy, and mass spectrometry have been used to establish chemical mechanisms for radiation damage in guanidinium cations. Our conclusion is that radiation stability of these cations is not significantly different from that of more familiar aliphatic and aromatic IL cations. In fact, these cations yield exceptionally stable radicals, and fragmentation occurs only in their radiolytically generated excited states. The predominant chemical pathway for the cation decomposition is the elimination of their aliphatic arms, with radiolytic yields of 0.65 to 1.06 to 1.46 per 100 eV from R = Et to R = Bu, respectively. The total loss of the parent cation was estimated as 2.62, 1.65, and 1.98 species per 100 eV. While this attrition is not negligible, it is comparable to other organic cations that have fewer fissile C-N bonds. Many of the products are either modified guanidinium ions or protonated bases that are not expected to interfere with radionuclide separations.

Reduction of Carbonate Electrolytes and the Formation of Solid-Electrolyte Interface (SEI) in Lithium-Ion Batteries. 2. Radiolytically Induced Polymerization of Ethylene Carbonate

Extensive polymerization of ethylene carbonate (EC) leading to the formation of oligomers with masses up to 1 to 2 kDa in electron beam radiolysis is demonstrated using electrospray ionization mass spectrometry and nuclear magnetic resonance. This polymer has a different structure and morphology than the linear chain copolymer of ethylene oxide and EC that is generated in anionic polymerization of intact EC molecules. This radiolytically generated polymer exhibits chain branching and pendant carbonate groups, and it can form a 3D organic network that is additionally cross-linked through lithium ions. Such a morphology is consistent with the occurrence of anionic and radical polymerization that involve the products of recombination and disproportionation of secondary radicals generated in one-electron reduction of EC. Our examination of this chemistry suggests that the same polymer is likely to occur in electrochemical reduction of EC. The formation of this polymeric network qualitatively accounts for some of unexplained properties of the solid-electrolyte interface (SEI) occurring in electrochemical cells with EC-based electrolyte, including common lithium batteries.

Analysis and Review of Chemical Reactions and Transport Processes in Pulsed Electrical Discharge Plasma Formed Directly in Liquid Water

Electrical discharges formed directly in liquid water include three general cases where (a) streamer-like plasma channels form in, but do not span, the electrode gap, (b) spark discharges produce transient plasma channels that span the electrode gap, and (c) arc discharges form plasma channels with relatively longer life times. Other factors including the input energy (from 1 kJ/pulse) as well as solution properties and the rates of energy delivery affect the nature of the discharge channels. An understanding of the formation of chemical species, including the highly reactive hydroxyl radical and more stable molecular species such as hydrogen and hydrogen peroxide, in such plasma requires determination of temporal and spatial variations of temperature, pressure, plasma volume, and electrical characteristics including current, voltage (electric field), and plasma conductivity. In spark and arc discharges analysis of the physical processes has focused on hydrodynamic and thermal characterization, while only a limited amount of work has connected these physical processes to chemical reactions. On the other hand, the most successful model of the chemical reactions in streamer-like discharges relies on simple assumptions concerning the temperature and pressure in the plasma channels, while analysis of the physical processes is more limited. This paper reviews the literature on the mathematical modeling of electrical discharges in liquid water spanning the range from streamer-like to spark and arc discharges, and compares the properties and processes in these electrical discharges to those in electron beam radiolysis and ultrasound.

Electron Beam Radiolysis of Diethyl Phthalate in Aqueous Solutions

Abstract Electron beam radiolysis experiments were undertaken to gain insights into the kinetic mechanisms of diethyl phthalate (DEP) degradation in aqueous solutions. DEP degradation was found to follow pseudo-first-order kinetics. The pseudo-first-order rate constant decayed exponentially with DEP initial concentrations (C0), whereas G values of DEP and C0 followed linear relationship. Addition of sodium carbonate to irradiated DEP solutions reduced DEP decomposition. H2O2 was not favorable for removal of DEP. An effective degradation was achieved in both N2O-saturated and t-BuOH–containing N2-saturated DEP solutions. High removals (>99%) were achieved at 15 kGy without these radical scavengers. Radical scavenging tests indicated that both •OH and e−aq played significant roles in DEP radiolysis. Several intermediates such as monoethyl phthalate, phthalate acid, and short-chain aliphatic carboxylic acids were formed from DEP radiolytic degradation. Finally, DEP was completely mineralized when the absorbe...

Kinetics and mechanisms studies on dimethyl phthalate degradation in aqueous solutions by pulse radiolysis and electron beam radiolysis

The kinetics and mechanisms of hydroxyl radical/hydrated electron reactions with dimethyl phthalate (DMP) were investigated using pulse radiolysis and electron beam radiolysis techniques. The bimolecular rate constants for the reaction of hydroxyl radical and hydrated electron with DMP were measured to be 3.4×10 9 M −1 s −1 and 1.6×10 10 M −1 s −1 under pulse radiolysis experiments, respectively. The major products after radiation were elucidated by LC/MS/MS and ion chromatography analysis. It was found that DMP degradation had different mechanisms in oxidative and reductive conditions: hydroxyl radical attacked aromatic ring of DMP leading to the fracture of benzene ring, formed a series of byproducts which were completely mineralized while hydrated electron attacked the ester group of DMP, formed the product of phthalic acid in reductive conditions.

Na2SO4 Monocrystal Nanowires—Aspect Ratio Control and Electron Beam Radiolysis

This paper presents the synthesis of water-dissolvable Na(2)SO(4) nanowires and nanorods by a simple chemical reaction between CuSO(4) and NaBH(4) in ethylene glycol. By adjusting the pH and the monomer concentration, the aspect ratio and size of the Na(2)SO(4) nanowires could be tuned. Na(2)SO(4) nanorods, nanowhiskers, nanowires, and submicrorods were obtained. Optimal chemical potential is believed to be the dominant driving force for the growth of Na(2)SO(4) nanowires during the synthesis. We also demonstrated the Na(2)SO(4) nanotubes obtained by the electron beam radiolysis of Na(2)SO(4) nanowires. The mechanism of selective radiolysis is also investigated.

Electron-beam radiolysis of gaseous alkanes under circulation conditions: Gas-to-liquid transformation

The circulating mode of electron-beam irradiation was used for synthesis of the branched liquid hydrocarbons from the gaseous alkane mixtures, including natural gas and the associated petroleum gas. Atmospheric distillation of resulting liquids was characterized by boiling point range from 36 up to 200–230 °C. The average degree of molecular branching in the synthesized liquids was evaluated on the basis of their antiknock characteristics. The octane values of liquids synthesized from natural gaseous mixtures were above 95. The fractional composition and antiknock characteristics of synthesized liquids suggested the prevalence of C 5–C 11 isomers with highly branched structures. Fractional and isomeric compositions of the liquid products depended on the gas-phase composition, dose rate, and gas-dynamic conditions in the irradiation area.

Modelling molecular weight changes induced in polydimethylsiloxane by gamma and electron beam irradiation

A commercial linear polydimethylsiloxane (PDMS) was subject to gamma irradiation under vacuum and in air, as well as to accelerated electron beam radiolysis (EB). All irradiation treatments were done at room temperature. The molecular weight changes induced by the radiation processes have been investigated using size exclusion chromatography (SEC) with refraction index (RI) and multi angle laser light scattering (MALLS) detectors to obtain the number and weight average molecular weights of the irradiated samples.The analysis of the data indicates that crosslinking reactions predominated over scission reactions in all cases. Gamma irradiation under vacuum was the most efficient process within the analyzed dose range, reaching the gel point earlier. Irradiation in the presence of oxygen induces oxidative effects, both in gamma and EB irradiations. A previously developed mathematical model of the irradiation process that accounts for simultaneous scission and crosslinking and allows for both H and Y crosslinks fitted well the measured molecular weight data.