Radiolysis Products Research Articles

The role of porosity in H2/He production ratios in fracture fluids from the Witwatersrand Basin, South Africa

Abiotic H2 produced in the Precambrian lithospheric crust is a key substrate at the base of the metabolic chain of chemosynthetic and photosynthesis-independent microbial communities, significant to our understanding of life on early Earth and other planets. H2 cycling processes are also relevant to recent hydrogen exploration efforts and engineered subsurface environments such as radioactive waste disposal sites. In the lithospheric crust, H2 is produced through water-rock reactions (serpentinisation) and radiolysis; the latter directly linked to He through radioelement decay (U, Th). The Witwatersrand Basin in South Africa is an ideal place to study the radiolytic production pathway in particular, because of the low abundance of ultramafic and mafic minerals and therefore low potential for serpentinisation reactions. Gas samples and gas flow rate data (n = 12) were collected from the surface of exploration boreholes tapping the Witwatersrand and Ventersdorp Supergroups. The samples were predominantly composed of CH4 (65–99%), N2 (3–27%), He (0.1–15%), and trace amounts of C2+ hydrocarbons. Notably, H2 in these samples was below detection limit, despite the presence of He - providing a critical indicator of processes removing H2 from the system. Using a Bayesian modelling approach, we test the hypothesis that the observed fluids are generated in-situ, driven by radioelement decay and subsequent microbial methanogenesis, and controlled by porosity of the host rock. The observed data is consistent with this hypothesis, and can be accounted for by a variation in porosity between 0.3 and 2.2% (typical values to Precambrian basement) across the different sampling sites. These He-rich hydrocarbon gases observed at the surface originate from a hydrogeological system that is porosity-constrained and isolated from externally-sourced fluids. Radioelement decay is the primary process driving the generation of H2 and therefore energy production in this subsurface system, utilised by hydrogenotrophic methanogens at the base of the deep carbon cycle. Microbial utilisation is the key mechanism for H2 consumptions and, conversely, preservation, suggesting that conditions favourable to commercial H2 discoveries are likely constrained to hypersaline environments where microbial activity is inhibited. The model results under the proposed hypothesis (consistent N2/H2 ratio between different boreholes) raises the possibility that N2, which often co-occurs with He-rich deep fluids, is also produced through radiolysis, and future work is needed to fully evaluate this hypothesis.

Enhancement of Physico-chemical and Biological Activities of Antibiotic Cephradine by Gamma Irradiation

Radiation based sterilization is a common tool for microbial inactivation in different products on a commercial scale. The objective of the current study was to determine the effect of gamma radiation on cephradine antibiotic in the solid-state to enhance its biological response. Cephradine drug in powder form was treated with different doses (25, 50, 75, 100 and 125 kGy) of the cobalt-60 source in a Gamma cell-220 at a current rate of 8.5 gray/h. The effect of radiation doses on antibiotic was assessed with the help of different analytical techniques such as FT-IR, UV, XRD, SEM and HPLC. The UV spectra of radiated cephradine show some changes in the absorption peak by increasing the intensity of radiations while only slight changes were observed in the other peaks. The crystallinity of antibiotics was tested by the XRD and SEM, it shows a little morphological change. The FT-IR data disclosed significant changes in the absorption bands. The HPLC analysis showed reports an insignificant change which revealed that the radiolytic products are not formed. The radiated cephradine exposes a remarkable antibacterial activity against bacteria; indicating the enhancement of a biological response. In summary, a slight change was observed in cephradine drug with the radiation but the drug was chemically stable.
 

EVIDENCE OF RADIOCATALYTIC ACTION OF BENTONITE CLAY IN PETROLEUM FORMATION: THE ROLE OF DEHYDRATION REACTION IN HYDROCARBONS GENERATION

The aim of this research is to investigate the changes of Gunashli crude oil’s hydrocarbons generation on the surface of nanostructured sodium-bentonite clay from Alpoid deposit , irradiated with ionizing rays. Generated carbenium ions due to the acidity (H*+AlO3) of bentonite take part in the transformation process of hydrocarbons. Indeed, they can have an effect on the radiolytic H2 production under irradiation. Original pore water radiolysis in this system was investigated.

Characteristics and Rates of Microbial Processes in Clays of Different Mineral and Elemental Composition in Relation to Safety Prediction for ESB Clay Materials

Microbial activity in clay barrier materials during radioactive waste disposal can lead to a violation of important physicochemical properties of the barrier system as a whole, thereby reducing the safety of the storage facility. This work evaluates the activity of the microbial complex of five bentonite and two kaolin clays. All clay materials were found to contain microorganisms, mostly with organotrophic aerobic and anaerobic metabolism capable of forming hydrogen sulfide and transforming basic and impurity clay minerals. The activity of microorganisms can increase with the ingress of degradation products of aluminophosphate matrices and cement barriers, as well as radiolysis products. For all clay the rates of microbial processes were shown to exhibit a direct correlation with the content of organic matter, kaolinite, and potassium feldspar, and an inverse correlation with montmorillonite content. A systematic methodological approach is proposed for clay materials and their susceptibility to microbial processes. The approach makes it possible, based on the content of organic matter, biophilic elements in the samples, parameters of the respiratory activity of the microbial complex, the formation of hydrogen sulfide, and other parameters, to assess in advance the possibility of using them in barriers.

Matrix effect in the hydroxyl radical induced degradation of β-lactam and tetracycline type antibiotics

Due to the spread of antibiotic resistant bacteria, elimination of antibiotics from purified wastewater is a highly important task. Purified wastewater contains large variety of organic/inorganic compounds that strongly influence the efficiency of advanced oxidation processes (AOP). In this work, we investigate the radiation-induced degradation of selected antibiotic contaminants (oxacillin and cloxacillin from the β-lactams; tetracycline and chlortetracycline from the tetracyclines) in four matrices: pure water, tap water, synthetic wastewater and purified wastewater received from a wastewater treatment plant. Changes in technically important parameters, such as COD, TOC, BOD, OUR, acute toxicity and antibacterial activity, were investigated at 0.1 mmol dm−3 (40–48 mg dm−3) antibiotic concentration. None of the four antibiotics were biodegradable in any of the four matrices, however, after irradiation with relatively low doses the obtained products were biodegradable. Oxacillin and cloxacillin were not toxic in Vibrio fischeri test, while tetracycline and chlortetracycline showed toxicity that was strongly reduced by the irradiation treatment. Both COD and TOC decreased after irradiation, their ratio shifted towards TOC indicating an increase in the average oxidation state (AOS). The increase in AOS was lower in purified wastewater matrices: this matrix may contain various small, highly oxidized molecules in high concentration, which degrade very slowly in AOP. The antibacterial activity in most of matrices was greatly reduced or completely disappeared at around 2–4 kGy. However, in purified wastewater matrices some antibiotic activity remained even at 4 kGy. Here the degradation of antibiotic is slow (small ΔCOD/dose value) because a large fraction of the reactive radicals is scavenged presumably by small, highly oxidized molecules in the solution. Although the water radiolysis product H2O2 affected some of the bioassays, this phenomenon was absent in purified wastewater. The purified wastewater after ionizing radiation treatment can be safely released into the receiving lakes or rivers.

On the Mechanism of the Steady-State Gamma Radiolysis-Induced Scissions of the Phenyl-Vinyl Polyester-Based Resins.

The major societal problem of polymeric waste necessitates new approaches to break down especially challenging discarded waste streams. Gamma radiation was utilized in conjunction with varying solvent environments in an attempt to discern the efficacy of radiolysis as a tool for the deliberate degradation of model network polyesters. Our EPR results demonstrated that gamma radiolysis of neat resin and in the presence of four widely used solvents induces glycosidic scissions on the backbone of the polyester chains. EPR results clearly show the formation of alkoxy radicals and C-centered radicals as primary intermediate radiolytic products. Despite the protective role of the phenyl groups on the backbone of the radiation-induced polyester chains, the radiolytic-glycosidic scissions predominate. Among the following three solvents used in this study (water, isopropyl alcohol, and dichloromethane), the highest radiolytic yield of glycosidic scission was achieved using water. The •OH radicals produced in the radiolysis of phenyl unsaturated polyester aqueous suspensions very rapidly abstract H atoms from the methylene group, which is followed by a very rapid glycosidic scission. The lowest glycosidic yield was found in the dichloromethane solutions of these polyester resins due to scavenging by the fast electron capture reactions.

A CO2 Cycle on Ariel? Radiolytic Production and Migration to Low-latitude Cold Traps

Abstract CO2 ice is present on the trailing hemisphere of Ariel but is mostly absent from its leading hemisphere. The leading/trailing hemispherical asymmetry in the distribution of CO2 ice is consistent with radiolytic production of CO2, formed by charged particle bombardment of H2O ice and carbonaceous material in Ariel’s regolith. This longitudinal distribution of CO2 on Ariel was previously characterized using 13 near-infrared reflectance spectra collected at “low” sub-observer latitudes between 30°S and 30°N. Here we investigated the distribution of CO2 ice on Ariel using 18 new spectra: 2 collected over low sub-observer latitudes, 5 collected at “mid” sub-observer latitudes (31°N–44°N), and 11 collected over “high” sub-observer latitudes (45°N–51°N). Analysis of these data indicates that CO2 ice is primarily concentrated on Ariel’s trailing hemisphere. However, CO2 ice band strengths are diminished in the spectra collected over mid and high sub-observer latitudes. This sub-observer latitudinal trend may result from radiolytic production of CO2 molecules at high latitudes and subsequent migration of this constituent to low-latitude cold traps. We detected a subtle feature near 2.13 μm in two spectra collected over high sub-observer latitudes, which might result from a “forbidden” transition mode of CO2 ice that is substantially stronger in well-mixed substrates composed of CO2 and H2O ice, consistent with regolith-mixed CO2 ice grains formed by radiolysis. Additionally, we detected a 2.35 μm feature in some low sub-observer latitude spectra, which might result from CO formed as part of a CO2 radiolytic production cycle.

RADIOLYTIC PROCESSES IN MIXTURE OF WATER WITH CARBON DIOXIDE IN THE PRESENCE OF ORGANIC MATRIX

The radiolysis of purified water, its mixture with carbon dioxide, and also with the addition of salt of potassium chloride isotope (40KCl) and plant mass to this system were carried out in order to study the mechanism of radiolytic processes taking place in the plant mass in the presence of the natural potassium isotope (40K) contained in it. It revealed that in the presence of 40KCl in the system, the formation of trace amounts of molecular hydrogen is observed (in accord with an insignificant dose of radiation from 40K). A decrease in the rate of formation of molecular hydrogen with an increase in the concentration of CO2 is observed during the radiolysis of a two-component system (H2O - CO2). An increase in the rate of formation of molecular hydrogen, carbon monoxide, methane and relatively heavy hydrocarbons (C6, C7, C8) accompanied by an increase in the absorbed dose of ionizing radiation (at stable concentrations of all components of the system) is observed when studying the kinetics of the formation of radiolysis products of the multicomponent system "H2O - CO2 - 40KCl - organic matrix". There is a tendency to reduce the rate of formation of molecular hydrogen and methane and increase the rate of formation of CO and relatively heavy (C6, C7, C8) hydrocarbons with an increase in CO2 concentration. The rates of formation of all products (H2, CO, CH4, and relatively heavy hydrocarbons) grow with an increase in the amount of organic matter in the mixture (at stable concentrations of CO2, H2O, and 40KCl). İt found that an increase in the mass of the organic matrix in the analyzed multicomponent system stimulates an increase in the formation of all radiolysis products. There is a decrease in the rate of formation of H2 and CH4, a relatively slow increase in the rate of formation of carbon monoxide, and an increase in the rate of elementary reactions of the transformation of light radiolysis products (H2, CO, CH4) into relatively heavy products (C6, C7, C8) together with an increase in CO2 concentration. The results obtained show the expediency of taking into account the contribution of ionizing radiation from radionuclides present in the environmental components, when considering multistage biochemical mechanisms of photosynthesis in order to explain the initiation of energy-intensive processes of CO2 and H2O decomposition

Effect of ionizing radiation on microbiological safety and activity of antioxidant enzymes in minced meat

A number of studies have shown the effectiveness of meat irradiation at doses of 2-6 kGy to extend its shelf life when stored in vacuum packaging. It is known that the radiation treatment of meat can lead to a decrease in the content of natural antioxidants. Furthermore, the intensity of oxidative processes is significantly higher in meat products with a high fat content (20% or more). At the same time, the optimal modes of minced meat irradiation, which make it possible to ensure safety for the population and to increase the shelf life, have not yet been established. The purpose of the research was to study the effect of various doses of ionizing radiation on the content of aerobic, facultative anaerobic microorganisms and radiolysis products, and the activity of antioxidant enzymes in chilled minced meat during storage. Material and methods. The object of the study was minced meat, consisting of beef and pork (1 : 1) with 20% mass fraction of fat. The experimental samples were irradiated on an electron accelerator UELR-10-15-S-60-1 with an electron energy of 5-10 MeV at doses of 2, 2.5 and 3 kGy. The control sample of minced meat was not subjected to radiation treatment. Determination of the total count of mesophilic aerobic and facultative anaerobic microorganisms (QMAFAnM) (CFU/kg) in control and experimental samples was determined on days 0, 7, 15 and 22. Methods for evaluating antioxidant activity included spectrophotometric determining the content of active radiolysis products that react with 2-thiobarbituric acid (TBA-AP) according to the Brajet method, total antioxidant capacity (TAOC) and activity of antioxidant enzymes in minced meat: superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx). Results. Radiation treatment of minced meat at a dose of 2.0 kGy provided a normalized level of QMAFAnM in chilled minced meat for 22 days. It has been established that the treatment of minced meat with ionizing radiation in doses of 2.0-3.0 kGy leads to a dose-dependent decrease in its TAOC and the activity of antioxidant enzymes (SOD, CAT, GPx), as well as to an increase in TBA-AP content (р<0,05). Conclusion. The dose of ionizing radiation of 2.0 kGy helps to maintain the microbiological safety of minced meat for 22 days in terms of QMAFAnM with minimal changes in TAOC values, SOD, CAT and GPx activity and TBA-AP content.

Research on UO2 modification of a direct ethanol fuel cell Pt/C catalyst.

Radioactive UO2 powder was prepared by hydrothermal method and a set of Pt–xUO2/C catalysts were synthesized by impregnation method for solving the problem of low activity and easy poisoning of anode Pt/C catalysts for a direct ethanol fuel cell. XRD, TEM, EDS, XPS and ICP-MS characterization showed the successful loading of Pt and UO2 onto the carbon carrier. Electrochemical workstation and single cell test results confirm that the catalytic performance of Pt–10% UO2/C is significantly better than Pt/C-eg. It is speculated that the synergistic effect of Pt and U enhances the catalytic activity and UO2 improves the resistance to CO poisoning by releasing O2 stored in the lattice space, while the α-particles released by 235U can also generate radiolysis product OH and promote the oxidative desorption of CO from the Pt surface.

Development of fluorescein-based dosimeter for radiation processing applications

Dosimetry forms an inseparable part of radiation processing. Many dosimeters are available to cover wide range of doses used in radiation processing. These include the Fricke, ceric-cerous, alanine ESR Alanine (Electron Spin Resonance Technique), dichromate, and radiochromic films. Low-dose radiation processing applications (&lt;2 kGy) such as insect disinfestation, shelf-life extension, and sprout inhibition use imported dosimeters. At present, radiochromic films/waveguides are used for low-dose applications; however, the dosimeters are costly and subject to sanctions and supply restrictions from country of origin. The present work discusses the development of system that can be used as a routine dosimeter for radiation processing facilities in the dose range of 200–2500 Gy. Iodine is generated by the action of radiolysis products of water on iodide and iodate present. Generated iodine halogenates fluorescein to erythrosine with the help of bicarbonate. Increase in absorbance due to the formation of erythrosine can be related to the absorbed dose and used in routine dosimetric applications. As the change is radiochromic, it advantageously provides a visual indication of dose received.

Migration testing of metallized polypropylene films treated with ionizing radiation

An UHPLC-QTOF/MS method was employed to identify chemicals migrating from metallized polypropylene (met PP) films. The migration test was conducted by converting met PP films into pouches filled with 95% ethanol as a fatty food simulant and treating the pouch samples with gamma and electron beam irradiation at a dose of 10 kGy. A temperature of 22 °C and a duration time of 21 days were used for the migration test. Over 10 chemicals were identified, 3 of them were intentionally added substances (IAS), while the rest were considered as non-intentionally added substances (NIAS) including radiolysis products (RPs) derived from antioxidants. Based on the identification results, 5 chemicals (3 hindered phenolic compounds, 1 phosphate compound and 1 phosphonate compound) were selected and their migration behaviors were evaluated under the effect of irradiation. It was found that irradiation treatment significantly reduced the migration level of all substances. The extent of decrease was dependent on their stability under irradiation. The phosphate/phosphonate compounds recorded higher stability resulting in less decrease (3–25%) in migration level. The hindered phenolic compounds were susceptible to irradiation and a large drop (45–88%) of migration level was observed. Potential risks of met PP films were evaluated by comparing the migration levels of selected chemicals with their migration limits either listed in Regulation (EU) No. 10/2011 or established with Cramer classification. The results showed that the migration level of the phosphonate compound was above the recommended migration limit, which may present a safety concern.

A Review of the Effect of Irradiation on the Corrosion of Copper-Coated Used Fuel Containers

Radiation induced corrosion is one of the possible modes of materials degradation in the concept of long-term management of used nuclear fuel. Depending on the environmental conditions surrounding the used fuel container, a range of radiolysis products are expected to form that could impact the corrosion of the copper coating. For instance, γ-radiolysis of pure water produces molecular oxidants such as H2O2 and the radiolysis of humid air produces compounds such as NOx and HNO3. This review is confined to a discussion of the effect of γ-radiation on the corrosion of copper-coated containers. A simplified mixed-potential model is also presented to calculate the extent of copper corrosion by using the steady-state concentration of H2O2 generated during the first 300 years of emplacement, when the radiation field is significant.

Reactivity of Ru oxides with air radiolysis products investigated by theoretical calculations

Quantitative predictions of the release of volatile radiocontaminants of ruthenium (Ru) in the environment from either nuclear power plants (NPP) or fuel recycling accidents present significant uncertainties while estimated by severe accidents nuclear analysis codes. Observations of Ru from either experimental or modeling works suggest that the main limitations relate to the poor evaluation of the kinetics of gaseous Ru in the form of RuO3 and RuO4. This work presents relativistic correlated quantum chemical calculations performed to determine the possible reactions pathways leading to the formation of gaseous Ru oxides under NPP severe accident conditions, as a result of reactions of RuO2 gaseous with air radiolysis products, namely nitrous and nitrogen oxides. The geometries of the relevant species were optimized with the TPSSh-5%HF functional of the density, while the total electronic energies were computed at the CCSD(T) level with extrapolations to the complete basis set CBS limit. The reaction pathways were fully characterized by localizing the transition states and all intermediate structures using the internal coordinate reaction algorithm (IRC). The rate constants were determined over the temperature range 250-2500K. It is revealed that the less kinetically limiting pathway to form Ru gaseous fraction is the oxidation of Ru by nitrogen oxide, corroborating experimental observations.

Investigation of mechanisms of radiolytic H2 production in C-S-H: Influence of water content and radiation induced defects

Water radiolysis is a major concern for the conditioning of radioactive waste in cement materials. Synthetic calcium silicate hydrates (C-S-H), the main hydrates of concrete, were synthesized with different calcium to silicate ratios and relative humidity. The samples were irradiated under γ- and electron beam irradiation. The radiolytic hydrogen production was quantified and the radiation induced defect produced at low temperature was characterized by electron paramagnetic resonance. The results show that the radiolytic H2 production and defect production are 20% sensitive to the relative humidity.

Characterisation of radiogenic monoalkenes in Australian oils and condensate

Thirteen Australian oils and one condensate, covering oil reservoir ages from Mesoproterozoic to Early Cretaceous, show monoalkene contents varying from 0.01 to 22.3 wt% of the whole liquid. Radiolysis of saturated hydrocarbons is the most likely process leading to oils with high alkene contents. The major radiolytic component is an unresolved complex mixture (UCM). The bulk of the resolved alkene compounds are positional isomers of n-alkenes. Methyl branched and cyclohexyl alkenes are minor components. Internal n-alkene isomers have a trans configuration dominant over the cis isomer. The oil with the longest reservoir residence time shows the highest content of internal n-alkenes relative to terminal 1-alkenes as well as the highest trans/cis ratio, suggesting the extended time has resulted in rearrangement to near thermodynamic equilibrium of the congruent monoalkenes. The radiolytic monoalkenes in the Ordovician-reservoired oil with the highest alkene content is likely influenced by a higher probability of intermolecular interactions and different product pathways in a complex mixture. Here, the relative proportion of alkene mimics the relative abundance of n-alkanes, suggesting that radiolytic C–C bond cleavage is suppressed when the alkene/alkane ratio is elevated and that the preferred pathway of n-alkane radiolysis favours the production of terminal monoalkenes. Radiolysis of the alkane UCM together with crosslinking and branching of n-alkane-derived radiolysis products contribute to the higher relative proportion of the alkene UCM. The similar carbon and hydrogen isotopic ratios of the n-alkanes and n-alkenes supports a parent–daughter relationship.

Detection of gamma-irradiated red peppers using a combination of 5,6-dihydrothymidine and thymidine as irradiation indicator

A method for determining the irradiation histories of plant-based food items was developed. The developed method was based on that used for determining the irradiation history of animal-based food items. The liquid chromatography–tandem mass spectrometry (LC-MS/MS) technique was used to analyze the total amount of (5S)- and (5R)-5,6-dihydrothymidine (sum of (5S)- and (5R)-DHdThd; total DHdThd), which are radiolytic products of thymidine (dThd). Red peppers were used as a model for plant-based food items. Powdered or homogenized red peppers were processed using lysis buffer-containing proteinase K, RNase A, and cellulase to obtain crude DNA. The crude DNA was further purified using a solid-phase extraction column. The DNA was enzymatically digested to produce nucleosides. Following this, the concentration of total DHdThd to dThd ratio (total DHdThd/dThd) was analyzed as an irradiation indicator using the LC-MS/MS technique. The total DHdThd/dThd in red peppers was increased in a dose-dependent manner. The presence of trace amounts of total DHdThd/dThd (<1/16th–1/4th of that formed from approximately 1 kGy-irradiated red peppers) was detected in samples produced from non-irradiated dried red peppers. It was assumed that the product was formed during the drying process. The presence of trace amounts of total DHdThd does not hinder the process of determination of irradiation history (in the presence of total DHdThd/dThd). Finally, the total DHdThd/dThd, as an irradiation indicator, can be applied to a wide range of animal- and plant-based food items.

Limits on the contribution of early endogenous radiolysis to oxidation in carbonaceous chondrites’ parent bodies

Context.Carbonaceous chondrites have undergone alteration in their parent bodies and display oxidized secondary phases, including sulfates in CI and CM chondrites. The cause of the formation of these sulfates is yet to be determined.Aims.This study investigates the potential of endogenous radiolysis of water (i.e., radiolysis caused by radionuclides present in the rock) on the parent bodies of carbonaceous chondrites. Radiolysis may have contributed to the enhanced degree of oxidation of CI and CM chondrites, and we also examined CV chondrites as a case with no measured sulfates.Methods.We quantified the oxidants produced by radiolysis and how much of the sulfur content could be oxidized to form sulfates by this method. The amount of oxidants was calculated using a radiolytic production model developed and used for Earth and planetary applications that takes into account relevant physical parameters (water-to-rock ratio, grain density) and composition (amount of radionuclides, sulfur content).Results.For CM and CI parent bodies, even using a very favorable set of assumptions, only slightly more than 1% of the available sulfur can be oxidized into sulfates by this process, significantly below the amount of sulfates observed in these chondrites.Conclusions.Endogenous radiolysis is unlikely to have significantly contributed to the abundance of sulfate in CI and CM meteorites. The hypothesis of oxidation of sulfur by large quantities of O2accreted with primitive ice, on the other hand, is quantitatively supported by measurements of O2in comet 67P/Churyumov-Gerasimenko.

Thermal evolution of water and hydrogen from Apollo lunar regolith grains

The evolution of water and molecular hydrogen from Apollo lunar sample 15221, a mature mare soil, was examined by temperature program desorption (TPD) experiments conducted under ultra-high vacuum conditions. Desorption at the grain/vacuum interface with re-adsorption as water transports though the void space of the grains and activated sub-surface diffusion were found to reproduce the experimental TPD signal. Signal from the grain/vacuum interface yielded the second order desorption activation energies and site probability distributions. Water from sample 15221 exhibited a broad distribution of activation energies peaking at 130 kJmol−1 extending up to 350 kJmol−1 at zero coverage limit with an onset of 110 kJmol−1 at full coverage. Our results suggest that water and hydrogen originating from lunar regolith contributes a minor amount to the observed mass in the LCROSS impact event. The abnormal amount of molecular hydrogen observed in the ejecta plume of the LCROSS impact may indicate that the radiolytic production of H2 from electron and galatic cosmic rays of physisorbed water is a contributor to the vast quantity of molecular hydrogen detected.

Gamma and pulsed electron radiolysis studies of CyMe4BTBP and CyMe4BTPhen: Identification of radiolysis products and effects on the hydrometallurgical separation of trivalent actinides and lanthanides

The radiolytic stability of the highly selective ligands CyMe4BTBP and CyMe4BTPhen against ionizing gamma radiation was studied in 1-octanol solution. CyMe4BTBP and CyMe4BTPhen are important extractants for a potential treatment of used nuclear fuel. They were studied under identical experimental conditions to directly compare the effects of gamma and pulsed electron radiolysis on the ligands and systematically study the influence of structural changes in the ligand backbone. Distribution ratios of Am3+, Cm3+ and Eu3+, the residual concentration of CyMe4BTBP and CyMe4BTPhen in solution, and the formation of radiolysis products were studied as a function of absorbed gamma dose and presence of an acidic aqueous phase during irradiation. Quantitative and semi-quantitative analyses were used to elucidate the radiolysis mechanism for both ligands. Addition products of alpha-hydroxyoctyl radicals formed through radiolysis of the 1-octanol diluent to the ligand molecules were identified as the predominant radiolysis products. These addition products also extract trivalent metal ions, as distribution ratios remained high although the parent molecule concentrations decreased. Therefore, the utilization time of a solvent using these extractants under the harsh conditions of used nuclear fuel treatment could be considerably longer than expected. Understanding the radiolysis mechanism is crucial for designing more radiation resistant extractants.