Radiolysis Products Research Articles

Radiolysis of pyridine in solid water

We irradiated the complex organic molecule pyridine and mixtures of pyridine and water in the solid phase (thin icy films) at 12 K at different beam lines of the GANIL facility (ARIBE: 90 keV $$\hbox {O}^{\mathrm {6+}}$$ , SME: $$650\, \hbox {MeV Zn}^{\mathrm {26+}})$$ . The destruction of the initial molecule and the appearance of radiolytic products were followed by in-situ infrared absorption spectroscopy as a function of the projectile fluence with the CASIMIR experimental set-up of CIMAP. We measured the destruction cross section as a function of pyridine concentration. A clear dependence on the percentage of pyridine in $$\hbox {H}_{\mathrm {2}}\hbox {O}$$ was found: the destruction cross sections are significantly higher for small concentration, i.e. pure pyridine is more radioresistant than pyridine diluted in water ice at 12 K. Thus, the presence of water environment significantly modifies the radiation resistance of the initial complex organic molecules: it enhances radiosensitivity and destruction of pyridine, with implications for radiobiology and astrochemistry.

Migration of polymer additives and radiolysis products from irradiated PET/PE films into a food simulant

The commercial application of food irradiation has raised increasing concern regarding the migration of chemical hazards from irradiated food packaging materials which may threaten food safety and human health. In this study, polymer additives and radiolysis products that migrated from irradiated PET/PE films into a fatty food simulant (95% ethanol) were identified using a UHPLC-QTOF/MS method. Based on the identification results, six additives were selected and their migration behaviors were evaluated under the effect of gamma and electron beam irradiation at a dose of 10 kGy. No significant change in migration levels was observed after irradiation treatment in additives with superior resistance to irradiation (e.g., fatty acid amides). Migration levels of additives vulnerable to irradiation (e.g., antioxidants and disubstituted glycerides) exhibited a decrease, which varied between the different types of irradiation treatments. Decrease in the concentration of phosphite antioxidant (Irgafos 168) was associated with increase in the concentration of its oxidized product (Irgafos 168-ox) that was induced by irradiation. In addition, migration levels of additives were affected by partitioning between the polymer and the food simulant. A high migration level was observed in antioxidants that were predominantly present in the food simulant (due to migration) rather than in the polymer before irradiation treatment. The findings of the present study provide insights into future studies on chemical migration from packaging materials into irradiated food.

Quantitative estimation of track segment yields of water radiolysis species under heavy ions around Bragg peak energies using Geant4-DNA

We evaluate the track segment yield G′ of typical water radiolysis products (eaq−, ·OH and H2O2) under heavy ions (He, C and Fe ions) using a Monte Carlo simulation code in the Geant4-DNA. Furthermore, we reproduce experimental results of ·OH of He and C ions around the Bragg peak energies (< 6 MeV/u). In the relatively high energy region (e.g., > 10 MeV/u), the simulation results using Geant4-DNA have agreed with experimental results. However, the G-values of water radiolysis species have not been properly evaluated around the Bragg peak energies, at which high ionizing density can be expected. Around the Bragg peak energy, dense continuous secondary products are generated, so that it is necessary to simulate the radical–radical reaction more accurately. To do so, we added the role of secondary products formed by irradiation. Consequently, our simulation results are in good agreement with experimental results and previous simulations not only in the high-energy region but also around the Bragg peak. Several future issues are also discussed regarding the roles of fragmentation and multi-ionization to realize more realistic simulations.

The sputtering of radiolytic O2 in ion irradiated H2O-ice

Charged particle bombardment alters the physical and chemical properties of extraterrestrial icy surfaces by simultaneously producing radiolytic products and sputtered material. To better understand these phenomena, we measure the total sputtering yield of H2O-ice induced by 0.5–5 keV Ar+ at temperatures between 40 and 120 K, using microbalance gravimetry as our analytical tool. In addition, we also estimate the sputtered flux of radiolytic products formed during irradiation and in both cases find good agreement with comparable laboratory studies. At 120 K, we find that the O2/H2O sputtered ratio increases nearly linearly with the ion range suggesting that the ions are stopping at depths where O2 is still efficiently being produced below the surface. Furthermore, we find that although theoretical models appear to over predict our O2 sputtering yields by about a factor of three, we can make a small adjustment to this model, which improves the agreement between the model and the laboratory data significantly. This empirical adjustment may have implications for models of energetic processing that occurs on extraterrestrial icy surfaces, such as Europa, where low-energy ions are thought to be the primary source producing O2 from sputtering of the surface H2O-ice.

Controlling radiolysis chemistry on the nanoscale in liquid cell scanning transmission electron microscopy.

When high-energy electrons from a scanning transmission electron microscope (STEM) are incident on a liquid, the vast majority of the chemical reactions that are observed are induced by the radiolysis breakdown of the liquid molecules. In the study of liquids, the radiolysis products of pure water are well known, and their rate of formation for a given flux of high-energy electrons has been studied intensively over the last few years for uniform TEM illumination. In this paper, we demonstrate that the temporal and spatial distribution of the electron illumination can significantly affect the final density of radiolysis products in water and even change the type of reaction taking place. We simulate the complex array of possible spatial/temporal distributions of electrons that are accessible experimentally by controlling the size, the scan rate and the hopping distance of the electron probe in STEM mode and then compare the results to the uniformly illuminated TEM mode of imaging. By distributing the electron dose both spatially and temporally in the STEM through a randomised "spot-scan" mode of imaging, the diffusion overlap of the radiolysis products can be reduced, and the resulting reactions can be more readily controlled. This control allows the resolution of the images to be separated from the speed of the induced reaction (which is based on beam current alone) and this facet of the experiment will allow a wide range of chemical reactions to be uniquely tailored and observed in all liquid cell STEM experiments.

ОЦЕНКА ВОЗМОЖНОСТИ ОЧИСТКИ СТОЧНЫХ ВОД ОТ ФАРМАЦЕВТИЧЕСКИХ ПРЕПАРАТОВ РАДИАЦИОННЫМ МЕТОДОМ

To assess the possibility of using radiation purification of aqueous solutions from contained pharmacological preparations by spectrophotometry, high-performance liquid chromatography and chemical analysis, the effect of the absorbed dose of ionizing radiation on the concentration of analytes in solutions was studied. The values of the radiation-chemical yield of destruction of the investigated pharmaceutical preparations, the formation of peroxide products of radiolysis were determined, and the values of absorbed doses sufficient for the complete decomposition of the substances under consideration were calculated. It was shown that at initial concentrations of ketoprofen of 1,1•10-4 M and diclofenac of 0,5•10-4 M, the values of absorbed doses required for their complete decomposition are 2,4 kGy and 0,85 kGy, respectively. The obtained values indicate the possibility of using radiation technology for the purification of aqueous solutions from those pharmaceutical preparations. Further research can clarify the necessary doses for sufficient destruction of various groups of drugs in concentrations found in wastewater

Formation of Luminescing High-Temperature Ceramics upon Exposure to Powerful High-Energy Electron Flux

It is shown that MgF2 and YAG:Ce ceramics is synthesized with a high rate from the charge with low bulk density irradiated by powerful flux of electrons with energy of 1.4 MeV. High efficiency of synthesis is caused by the formation of radiolysis products stimulating solid- and gas-phase reactions in the charge upon exposure to powerful radiation fluxes.

A Study of the Radiolysis Products of the Tri-n-Butyl-Phosphate–Isopar-M–HNO3 System before and after Regeneration with Carbonates of Organic Bases

By measuring the hydrodynamic characteristics (viscosity, density of extraction mixture, and interfacial tension) and determining the composition of degradation products by the IR, CMS, and nuclear magnetic resonance methods, the efficiency of using solutions of methylamine and guanidine carbonates at the stage of intracycle regeneration was evaluated. It has been experimentally proven that, when using these solutions, the same efficiency is achieved as when using a sodium bicarbonate solution. The main products of radiation destruction of the 30% Tri-n-butyl-phosphate in Isopar-M extraction mixture irradiated after saturation with nitric acid are determined: dibutyl phosphoric and monobutyl phosphoric acids, carboxylic acids, ketones, carbonyl compounds, and hydrocarbons.

Adsorption Study of Main Gas Products from Water Radiolysis on 4A Zeolite by Numerical Simulations

This work is motivated by the results obtained during a study on the tritiated water adsorbed in zeolite [L. Frances et al., J. Phys. Chem. C, 119, 28462 (2015)]. The decomposition of water by radiolysis leads to the production of dioxygen and dihydrogen as main stable products. By studying the evolution of their quantities of matter, one can note an increase in a first stage, followed by a decrease after a few hundred days of storage until complete disappearance. This interesting process depends on the water loading ratios, expressed in mass percentage, lying between 4%, and 19%; such a phenomenon is not observed in saturated zeolite. Our goal is to determine, through numerical simulations, how this disappearance, which is associated with the recombination of the radiolysis products, occurs by making a microscopic study on the adsorption of H2O, H2, and O2 molecules on 4A zeolite (Z4A). Computational physics is useful to understand the effects of molecule adsorption on its structure and also to closely examine the molecule-zeolite and molecule-molecule interactions. Indeed, different simulation methods are used from static to dynamic studies employing both quantum and classical tools with the periodical structure of Z4A. To summarize, the adsorption of molecules from the radiolysis of water are studied according to different points of view (quantum and classical) using various numerical simulation tools, such as density functional theory for ab initio structural optimization and energy calculation, Monte Carlo to study the distribution of the adsorbed molecules in the zeolite, and molecular dynamics to follow the evolution of the system (molecule + zeolite) over time depending on the temperature, in order to extract as much information as possible (structurally, statistically, energy, electronically) to understand the main problematic of this work: How do stable molecules issued from radiolysis recombine in Z4A?

Radiolysis induced degradation of 1,3-dichlorobenzene and 4-chlorophenol in aqueous solution

1,3-dichlorobenzene (1,3-DClB) degradation was studied to obtain radiolytic product yields (Gtotal = 0.546 μmol/J) and degradation in aerated or oxygen-free aqueous solutions, saturated with either N2O or N2O containing K3Fe(CN)6. In the four environments, several peaks were observed in the chromatograms, corresponding to byproducts, with more oxidized products produced in N2O saturated solutions. The absorbed dose necessary for the removal of 1,3-DClB increased with increasing solute concentrations in aerated solution. Further, 4-chlorophenol (4-ClP) degradation was investigated in a 0.3 mmol/dm3 solution by gamma radiolysis in the presence and absence of oxygen. The results showed that 4-ClP degrades more rapidly in a N2O environment, demonstrated by quantification of product concentrations in different doses, the value of Chemical oxygen demand, and a kinetics study. Hydroquinone, a radiolytic product, is very resistant to degradation. The dose necessary for the complete degradation of a 4-ClP solution containing air reached 9 kGy; however, in N2O saturated solution only 4.5 kGy were necessary for that purpose. The kinetics have a similar behavior in the two compounds, being pseudo-first-order. Importantly, the number of chlorine atoms in the molecule determined the chemical oxygen demand, as this determination was easy in 4-ClP but not possible in 1,3-DClB.

Endogenic and Exogenic Contributions to Visible-wavelength Spectra of Europa’s Trailing Hemisphere

Abstract The composition of Europa’s trailing hemisphere reflects the combined influences of endogenous geologic resurfacing and exogenous sulfur radiolysis. Using spatially resolved visible-wavelength spectra of Europa obtained with the Hubble Space Telescope, we map multiple spectral features across the trailing hemisphere and compare their geographies with the distributions of large-scale geology, magnetospheric bombardment, and surface color. Based on such comparisons, we interpret some aspects of our spectra as indicative of purely exogenous sulfur radiolysis products and other aspects as indicative of radiolysis products formed from a mixture of endogenous material and magnetospheric sulfur. The spatial distributions of two of the absorptions seen in our spectra—a widespread downturn toward the near-UV and a distinct feature at 530 nm—appear consistent with sulfur allotropes previously suggested from ground-based spectrophotometry. However, the geographies of two additional features—an absorption feature at 360 nm and the spectral slope at red wavelengths—are more consistent with endogenous material that has been altered by sulfur radiolysis. We suggest irradiated sulfate salts as potential candidates for this material, but we are unable to identify particular species with the available data.

Radiation-Driven Chemistry in Molten Salts

A variety of molten salts are proposed as liquid fuels or coolants in a new fleet of molten salt nuclear reactors that would have operational and safety advantages over present reactor systems. The molten salt will be exposed to high radiation levels under these conditions, therefore understanding the chemical effects of radiolysis on the molten salt fuel or coolant is essential to reliable, efficient and sustainable reactor operation. This understanding begins with identifying the primary salt radiolysis products and characterizing their reactivities, in pure salt and also under conditions that represent loading with fuel (actinides), fission products and corrosion products. These reactions form subsequent products that determine the chemical evolution of the molten salt fuel over the duration of its lifetime in the reactor. To obtain predictive insight into this radiation-driven chemical evolution, we investigate these reactions by performing pulse radiolysis transient absorption spectroscopy at the BNL Laser-Electron Accelerator Facility using a high-temperature sample configuration. Examples will be given of how the composition of the molten salt determines the identities and reactivities of the primary radiolysis products, and we will follow their reactions with metal ions that are representative of the reactor fuel environment. This work was supported as part of the Molten Salts in Extreme Environments Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science. Figure 1

Reaction Kinetics of Zn2+ with Radiolysis Products in Molten LiCl-KCl Eutectic

A thorough understanding of radiation effects on molten salt media is necessary to support the design, development, and deployment of molten salt reactor, using either fuel salt or solid fuel with salt as the coolant. Fundamental issues include the determination of the initial yields and reactivity of the primary radiolytic species, i.e., the solvated electron (esolv –), chlorine atom (Cl•), and dichloride radical anion (Cl2 •–) as their reactivity varies depending on the environment such as the salt cation and temperature. Here we report on the reaction kinetics for esolv – and Cl2 •– in molten LiCl-KCl eutectic doped with Zn2+ ions. Electron pulse radiolysis absorption spectroscopy was used to observe the transient behavior of esolv – and Cl2 •– on the nanosecond to microsecond time scale. Experiments were performed using the Brookhaven National Laboratory Laser-Electron Accelerator Facility (LEAF)1 and utilizing a recently developed high-temperature sample holder.2 Decay kinetics of of esolv – and Cl2 •– in 9.41 mM ZnCl2 in LiCl-KCl are shown in the figure. esolv – and Cl2 •– decays in different time scale due to different reaction kinetics and decay speed increase as temperature.This work was supported as part of the Molten Salts in Extreme Environments Energy Frontier Research Center, funded by the U.S. Department of Energy (US-DOE), Office of Science, Basic Energy Sciences, at BNL, INL and ORNL under contracts DE-SC0012704, DE-AC07-05ID14517 and DE-FC02-04ER15533, respectively. The Laser Electron Accelerator Facility of the BNL Accelerator Center for Energy Research is supported by the US-DOE Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences under contract DE-SC0012704. Wishart, J. F.; Cook, A. R.; Miller, J. R.; Rev. Sci. Instrum., 2004, 75 (11), 4359.Phillips, W. C.; Layne, B.; Gakhar, R.; Horne, G. P.; Ramos-Ballesteros, A.; Iwamatsu, K.; LaVerne, J. A.; Pimblott, S. M.; Wishart, J. F.; Rev. Sci. Instrum., 2019, in peer review. Figure 1

On the reactivity of aqueous radiolysis products towards carbon black used in in-situ radiation-synthesis of catalytic nanoparticles in graphite electrodes

Enhanced electrochemical performance of graphite electrodes can be achieved by incorporation of catalytic nanoparticles. One promising method for incorporation is in-situ radiation-synthesis where the radiolysis of water is used to drive the process of particle formation on carbon black. A potential problem is the direct reaction between radiolysis products and carbon black. In this work the reactivities of radiolytically produced HO·, (CH3)2C·OH, e-aq and H2O2 towards carbon black were investigated at room temperature with a dose rate 0.124 Gy s−1. HO· was found to react with carbon black with a rate constant of 20 ± 5 m s−1. For (CH3)2C·OH the corresponding value is 0.8 ± 0.1 m s−1. The reactivity of e-aq towards carbon black is negligible compared to that of (CH3)2C·OH. At concentrations <0.05 mmol L−1, H2O2 can react with carbon black with a rate constant of (6.7 ± 0.4) × 10−10 m s−1 mainly due to adsorption. At higher H2O2 concentrations catalytic decomposition producing HO· is also observed. It was also observed that the presence of carbon black increases the radiolytic formation of H2O2. In addition, the impact of carbon black reactivity on the radiation-synthesis of nanoparticles is discussed with an example from the literature.

Proposal of a Chemical Mechanism for Mini-Beam and Micro-Beam Efficacy

This simulation study proposes a chemical mechanism to define a surrogate to the tumor control during micro- and mini-beam radiation therapy (MBRT). The main focus is proton-MBRT (pMBRT) and the methods developed are applied also to photon-MBRT (xMBRT). MBRT was reported to provide tumor control with reduced side effects when compared to standard dose delivery. The underlying mechanisms leading to a differential response of the normal tissue and the tumor are still unknown. In this work, we propose a chemical mechanism to describe the efficacy of MBRT. The model was developed starting from the observation that pMBRT led to long term survival without significant side effects of rats implanted with a high-grade glioma. We investigated whether the distribution of a generic radiation-induced molecule or radical could be a surrogate to describe the biological effect. The specific mechanisms leading to cell damage were outside the scope of this work. The molecules and radicals were selected according to a set of properties: (i) they should be stable to allow diffusion achieving coverage of the dose-valleys, (ii) they should reach a steady state in production versus removal, (iii) they should be a product of water radiolysis and (iv) they should have oxidizing capacity. A convolution model was developed to assess the property (i) keeping the analysis as general as possible. The tumor coverage was defined widening the interpretation of the ICRU-62 recommendations. The properties (ii) and (iii) were investigated with the TRAX-CHEM software. The property (iv) was used to exclude not relevant chemical species. The results show that hydrogen peroxide fulfills all the requirements. Moreover, the modelling of its temporal and spatial distributions demonstrate that a uniform coverage of the target by this reactive oxygen specie (ROS) can be achieved during the beam-on time. The model was compared and proven to be compatible with two independent photon micro-beam and proton mini-beam animal experiments. We conclude that hydrogen peroxide is a good candidate to describe the mini-beam and micro-beam efficacy. Further experiments are proposed to experimentally benchmark the model and to correlate the hydrogen peroxide concentration to the tumor control probability.

Structure-oriented catalytic radiosensitization for cancer radiotherapy

Given that the outcome of clinical radiotherapy (RT) is closely related to the radiolysis products from the interactions between the radiation and intracellular water, an appropriate catalyst to promote radiolysis may improve the therapeutic efficacy. However, catalysis-based radiosensitization strategy remains under investigated. Herein, we propose a catalytic RT concept and synthesize Janus-like Au-Fe2C nanoparticles (AFCNPs) as the catalytic radiosensitizer to improve the conversion efficiency of free radicals from the water molecules, resulting in a nearly five-fold increase in hydroxyl radicals (OH) with comparison to pure Au nanoparticles under the clinical radiation dose. The theoretical simulation reveals that the catalytic activity of AFCNPs derived from the increase in the electron concentration on the surface of Au, as a result of the electron transfer from the Fe2C moiety with lower work function to the Au moiety with higher work function. As a novel radiosensitization strategy, catalytic RT has shown promising potentials warranting further exploration.

XPS study of external α-radiolytic oxidation of UO2 in the presence of argon or hydrogen

UO2 pellets exposed to 1.85 MBq and 3.30 MBq Am-241 sources with a 30 μm separation in solution were studied under Ar and H2 atmospheres. The 1.85 MBq Am-241 source was shown to have a too low radiolytic production to cause any measurable change in UO2 surface oxidation state. However, a significant oxidation was observed after exposure to the 3.30 MBq source under Ar atmosphere through the production of U(V), as seen from the U4f7/2-peak deconvolution and valence band peak analysis. The H2 atmosphere was shown to suppress the oxidation of the UO2 pellet surface as well as the dissolution in both Milli-Q and NaHCO3 solutions. The dissolved uranium concentration was reduced by a factor 10 under H2 atmosphere as compared to the Ar atmosphere experiments.

Antioxidant and Gene-Protective Properties of Ethylmethylhydroxypyridine Succinate (Mexidol) in X-Ray Irradiation

The antioxidant formulation ethylmethylhydroxypyridine succinate (Mexidol) effectively neutralizes the radiolysis products of water and oxidative damage to DNA and proteins induced by X-irradiation. This substance was found to affect the formation of long-lived reactive forms of albumins and globulins and their degradation, which is accompanied by generation of hydrogen peroxide and an increase in the duration of oxidative stress after irradiation. Ethylmethylhydroxypyridine succinate has gene-protective and radiomitigating actions in vivo, decreasing the formation of micronuclei in polychromatophilic erythrocytes from red bone marrow in mice after irradiation, and is a potential therapeutic radiomitigating agent for preventing adverse effects due to impairments of redox homeostasis after irradiation.

The effect of aliphatic alcohol additives on the radiolytic degradation of TODGA in Isopar-M

The radiolysis of solutions of TODGA (N,N,N′,N′-tetra-n-octylamide of diglycolic acid) in mixtures of Isopar-M (iso-paraffins C13–C14) with n-nonanol or n-decanol at 500 kGy leads to predominant decomposition of TODGA. The radiation-chemical yield of this process is 0.4–0.5 μmol J−1. The main products of the direct effect of ionizing radiation on TODGA are N,N-dioctylacetamide and 2-hydroxy-N,N-dioctylacetamide. The indirect effect of ionizing radiation is mainly due to reactions with alkoxy radicals and leads to the breaking of the C–N and C–C bonds in the α-position relative to the carbonyl group. An increase in the alcohol content in the solution results in the increase of the variety of radiolytic products, in the enhancement of gas evolution, and in the increase in the yield of TODGA decomposition. The replacement of n-decanol with n-nonanol does not significantly affect the radiolytic stability of the solutions.

Investigations on the unusual aggregation behaviour of tetra(2-ethyhexyl)diglycolamide in n-dodecane medium upon gamma irradiation

The limit of reverse micellar aggregation of amphiphilic ligands in n-dodecane medium, known as the third phase formation, is an undesirable event during the course of solvent extraction. The tetraalkyl diglycolamide (DGA) in n-dodecane (n-DD) is a promising solvent medium for the extraction of trivalent actinides from high-level nuclear waste, but it is susceptible to third phase formation. The DGAs in n-dodecane medium undergo a number of chemical transformations in organic phase, known as the radiolytic degradation products, when it was contacted with nuclear waste. While the effect of radiolytic degradation products on the solvent extraction behaviour of actinides was reasonably understood, the third phase formation and reverse micellar aggregation behaviour of the radiolytically degraded DGAs/n-DD has been not explored so far and unfamiliar to the solvent extraction community. To unravel the effect of radiolytic degradation on the aggregation behaviour(third phase formation) of DGAs in n-DD, the following categories of liquids comprising of (1) 0.2 M solution of tetra(2-ethylhexyl)diglycolamide (TEHDGA) present in n-DD, (2) TEHDGA alone, (3) n-dodecane alone, and (4) 0.2 M TEHDGA/n-DD in the presence of extracted nitric acid, were irradiated to a specified absorbed dose levels (10 kGy to 500 kGy) in a 60Co gamma irradiator. The irradiated liquids were made to a solution of 0.2 M TEHDGA in n-dodecane, if required, and the extraction behaviour of nitric acid in the irradiated organic phase was studied. The organic phase obtained after extraction was subjected to dynamic light scattering studies to explore the aggregation behaviour of TEHDGA in organic phase and compared with those obtained before extraction and irradiation. The results revealed that the formation of polar degradation products upon irradiation minimized the aggregation, and the production of higher homologs of n-paraffins enhanced aggregation. In reality, the formation of nitration and other polar radiolytic degradation products in organic phase, confirmed by FTIR spectroscopy, minimized the aggregation and therefore prevented the third phase formation to a significant extent in the present system.