The direct observation of hydrogen molecules in irradiated solid ethanol by means of Raman spectroscopy at 77 K

Hydrogen molecules produced in ethanol glass and crystal which were irradiated at 77 K were detected directly by Raman spectroscopy at 77 K. The bands at 4133 cm^-1 for ethanol glass and 4155 cm^-1 for ethanol crystal were ascribed to the stretching vibration of hydrogen molecules. The assignment of the bands was confirmed by spectra of irradiated ethanol-d₁ and -d₅ glasses: a new band observed at 3610 cm^-1 was due to the vibration of HD molecules. The intensity of the band at 4133 cm^-1 decreased in irradiated ethanol glass containing the electron scavenger, CCl₄, at 77 K. This presents further evidence that the 4133 cm^-1 band is due to hydrogen molecules, since the solvated electron is a precursor of the hydrogen atom.     

Formation of SeO-2 radical anions at 92 K during the photobleaching of e-t in gamma-irradiated NaOH (10 M) aqueous glasses (77 K) containing selenite ions

Although the selenite ion, SeO^2-₃ is an inefficient scavenger of excess electrons (e^-_m, e^-_dry) generated in irradiated alkali metal hydroxide aqueous glasses at low temperatures, post-irradiation photostimulation of trapped electrons (e^-_t) in irradiated NaOH (10 M) glasses containing this chemical additive leads, unexpectedly, to the formation of SeO^-₂ radical anions.     

Hydrogen isotope behavior and its interaction with post irradiated energetic helium in SiC

The D₂ ⁺ was irradiated into SiC up to the saturation and thereafter He⁺ irradiation was performed to elucidate interaction mechanism between hydrogen isotope retained in SiC and irradiated energetic He⁺ by means of X-ray photoelectron spectroscopy (XPS) and thermal desorption spectroscopy (TDS). It was found that D was trapped by both of Si and C by D₂ ⁺ irradiation and only D bound to Si interacted with irradiated He⁺ in the initial He⁺ irradiation stage. Some damaged structures were introduced into SiC by both of D₂ ⁺ and He⁺ irradiation. By heating after the irradiation experiments, most of SiC structure was recovered at the temperature above 1000 K. However, some free C was migrated toward the surface and aggregated on the surface of SiC. This fact indicates that the C impurity would contaminate the plasma and/or the tritium breeding materials, which is thought to be contacted with the SiC inserts.     

Study of carbonaceous clusters in irradiated polycarbonate with UV–vis spectroscopy

The formation of carbonaceous clusters in ion‐irradiated polymer films was investigated extensively. Information about these clusters may be obtained with ultraviolet–visible (UV–vis) spectroscopy. The optical band gap (E_g), calculated from the absorption edge of the UV spectra of these polymers, can be correlated to the number of carbon atoms (N) in a cluster with the modified Tauc equation. The structure of the cluster is also related to E_g; for example, a six‐membered‐benzene‐ring‐type structure has an E_g of ≈5.3 eV, whereas a buckminsterfullerene‐type structure has an E_g of ≈4.9 eV. These clusters are responsible for the electrical conductivity in these films. In this work, polycarbonate films (20 μm thick) were irradiated with 45‐MeV Li ions at fluences of 1 × 10¹² to 1 × 10¹³ cm⁻² and were characterized with UV–vis spectroscopy and impedance measurements. The E_g values, calculated from the absorption edge in the 280–315‐nm region with the Tauc relation, varied from 4.39 to 4.35 eV for the pristine and various irradiated samples, respectively. The cluster size showed a range of 60–62 carbon atoms per cluster. The sheet conductivity (σ_dc) and loss (tan δ) values of 10⁻¹⁶ Ω⁻¹cm⁻¹ and 10⁻³ for the pristine sample changed to 10⁻¹⁵ Ω⁻¹cm⁻¹ and 10⁻², respectively, for the irradiated samples. This increase in the values of σ_dc and tan δ may be correlated to the increase in the size of the carbonaceous clusters. This study provides insight into the mechanism of electrical conductivity in irradiated polymers. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1589–1594, 2000     

Reactor neutrons irradiation effect on the photocatalytic activity of SnO<Subscript>2</Subscript> thin films

SnO₂ thin films synthesized by sol-gel are irradiated with reactor neutrons up to fast neutron fluence of 9.6 × 10¹⁷ neutrons cm^–2 at 40°C. The influence of defects generated by neutrons irradiation, through the properties modification, on the photo-catalytic activity of SnO₂ films is investigated. It is found that the photoactivity of the irradiated films is enhanced after reactor neutrons irradiation. An improvement of 41% is observed for the sample irradiated at a neutron fluence of 9.6 × 10¹⁷ neutrons cm^–2. This is attributed to several parameters modified by the reactor neutron irradiation principally the crystallite size and space charge region which are closely related to the photocatalytic performance.     

Irradiated bivalve mollusks: Use of EPR spectroscopy for identification and dosimetry

High energy radiation treatment of foodstuff for microbial control and shelf-life extension is being used in many countries. However, for consumer protection and information, the European Union has adopted the Directives 1999/2/EC and 1999/3/EC to harmonize the rules concerning the treatment and trade of irradiated foods in EU countries. Among the validated methods to detect irradiated foods the EU directives also include Electron Paramagnetic Resonance (EPR/ESR) spectroscopy.We describe herein the use of EPR for identification of four species of bivalve mollusks, i.e. brown Venus shells (Callista chione), clams (Tapes semidecussatus), mussels (Mytilus galloprovincialis) and oysters (Ostrea edulis) irradiated with ⁶⁰Co γ-rays. EPR could definitely identify irradiated seashells due to the presence of long-lived free radicals, primarily CO₂⁻, CO₃³⁻, SO₂⁻ and SO₃⁻ radical anions. The presence of other organic free radicals, believed to originate from conchiolin, a scleroprotein present in the shells, was also ascertained. The use of one of these radicals as a marker for irradiation of brown Venus shells and clams can be envisaged. We also propose a dosimetric protocol for the reconstruction of the administered dose in irradiated oysters.     

On the spin relaxation of57Fe(III) species produced through EC-decay in diamagnetic57Co-labelled Co(III) compounds

Absorption Mössbauer spectra of high-spin⁵⁷Fe(acac)₃ incorporated in diamagnetic Co(acac)₃ and in paramagnetic Mn(acac)₃ and of the γ-ray irradiated (⁵⁷Fe, Co) (acac)₃ and (⁵⁷Fe, Mn) (acac)₃ were compared with emission spectra of⁵⁷Co-labelled Co(acac)₃. Magnetic hfs is found in the spectra of (⁵⁷Fe, Co) (acac)₃ at 78 to 195 K, whereas such hfs is observed neither for the spectrum of⁵⁷Co-labelled Co(acac)₃ nor for that of γ-ray irradiated (⁵⁷Fe, Co) (acac)₃). The absence of magnetic hfs in the spectrum of diamagnetic⁵⁷Co-labelled cobalt(III) compounds was ascribed to the spin-spin interaction due to the radicals produced in the vicinity of the decayed atom.     

ESR study of lithium nitrate irradiated with gamma-rays with total doses from 10 to 100 Mrad

Natural non-pretreated polycrystalline lithium nitrate was irradiated by gamma-rays of⁶⁰Co with total radiation doses from 10 to 100 Mrad, at room temperature. No color centers were observed in samples irradiated in this range. X-ray and infrared studies evidenced the distortion of the lattice planes. In general, the following species were detected NO₂, NO₃ radicals, and NO₂ ²⁻, NO₃ ²⁻, O₂ ⁻ ionic radicals.     

Stability of polyvinylpolypyrrolidone against gamma-ray irradiation in HNO3 media

Polyvinylpolypyrrolidone (PVPP) is a resin with adsorption selectivity for U(VI) in HNO₃ media. The stability of this resin has been examined against gamma-ray irradiation using HNO₃ solutions of various concentrations. Samples of PVPP immersed in HNO₃ solutions up to 6 mol·dm^?3 (=M) were irradiated by a ⁶⁰Co source at 3.6 kGy·h^?1 to reach 0.90 MGy at room temperature under ambient atmosphere. As a result, no clear decrease in the capacity for U(VI) when added in 3 M HNO₃ was observed for any samples, or rather the capacity was found to increase by approximately 50 % for PVPP irradiated in 6 M HNO₃. It was indicated from some spectroscopic analyses of the irradiated samples that the irradiation causes the cleavage of the pyrrolidone ring of PVPP. This occurs by the addition of an oxygen atom originating from HNO₃, followed by the formation of straight-chain groups with multiple coordinative atoms by the successive addition of oxygen, finally leading to the generation of a primary-amine-type weakly-basic anion exchange resin. The increase in the U(VI) capacity would be due to the formation of the straight-chain groups. However, such structural changes were not observed by heating at 323 K in up to 6 M HNO₃ for 20 days. Thus, it was shown that PVPP is a heat-resistant resin.     

Effect of copper ions on the radiostability of protein-polyelectrolyte mixtures

Aqueous solution of polyacrylic acid (PAA), poly-N-isopropylacrylamide (PNIPAAm), bovine serum albumin (BSA), superoxide dismutase (SOD) and their mixtures (PAA-BSA, PAA-Cu-BSA, PNIPAAm-BSA, PAA-SOD) were irradiated in the presence of oxygen in neutral media (pH 7.0) with ⁶⁰Co γ-rays. In addition, aliquots of aqueous solutions of PAA, PAA-Cu²⁺, BSA and PAA-Cu²⁺-BSA saturated with N₂ and N₂O were also irradiated. The decomposition rate of irradiated solutions were measured by UV-visible spectrophotometry, fluorescence spectroscopy, and high performance liquid chromatography (HPLC). Protective effect of copper ions on radiolysis of aqueous solution of PAA-Cu-BSA and conversion of Cu(II) to Cu(I) was observed. The possible mechanism of this phenomenon is discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Investigations into the characteristics of irradiated zircaloy cladding material in connection with reactor operation and spent fuel reprocessing

To monitor and improve the performance of nuclear fuel assemblies, the uptake of gases (oxygen, nitrogen and hydrogen) is determined in zircaloy cladding materials. Gas chromatography and/or mass spectrometry combined with hot vacuum fusion were applied. Deviations from the initial concentrations (ca. 5 μg g^?1 H₂, 30 μg g^?1 N₂ and 1200 μg g^?1 O₂) in the “as fabricated” condition, are important in estimating cladding corrosion. The material characteristics of zircaloy are altered substantially by the neutron irradiation and the chemical environment in the reactor coolant, thus the irradiated material must also be studied. For reprocessing safety consideration, the ignition and explosion parameters of unirradiated and irradiated zircaloy dusts were examined. Standard methods, tailored to hot-cell operation, were used to evaluate the minimum ignition temperature of a dust layer on a heated surface at constant temperature, the ignition temperature of a dust cloud, the auto-ignition temperature of a cylindrical dust formation as a function of sample volume, and the explosion pressure and pressure rise in a 20-l spherical chamber. Samples of fines (<100 μm diameter) were characterized by measuring their density and particle-size distribution, and by scanning electron microscopy. For samples of irradiated zircaloy, the ignition temperatures were lower and the explosion pressures and pressure rises higher than for unirradiated zircaloy. These findings can be explained by the different particle-size distribution of irradiated material samples. The increased brittleness of the irradiated material produces more small particles (<20 μm) which favour ignition and explosion.     

Application de l’Analuyse par Radioactivation Neutronique et du Calcul Electronique au Dosage non Destructif de Traces de Chlore dans les Silices-alumines

A method applicable for serial determination of traces of chlorine in SiO₂−Al₂O₃ catalysts by neutron activation is described. The results are evaluated by means of a computer. The³⁸Cl activity is subtracted from the activity of the interfering components (⁵⁶Mn,²⁴Na) and this enables a direct γ-spectrometric determination. In praxis ten samples should be irradiated simultaneously and for this reason 3 standards are irradiated together with the samples to correct for the fluxus gradient. The reproducibility of the method is better than 2 per cent for 10–300 mg samples with a Cl content of 10 ppm.      

Observation of radioactive hetero-fullerenes using radiochemical techniques

Fullerenes, C₆₀ and C₇₀, were irradiated by 8 and 10 MeV deuterons. The irradiated samples were dissolved in CS₂ and filtered to remove insoluble by-products. Finally, radioactive fullerenes and products, such as fullerene dimers, trimers labeled with¹³N, were isolated and detected in the liquid phase by radiochromatography. This suggests that the energy rich¹³N atoms successfully incorporated into the fullerene cages and that the disrupted cages reacted with neighboring cages.     

DTA and X-ray diffraction investigations of laser-irradiated CeO2 powders

The TG and DTA curves and diffractograms of powdered CeO₂ samples irradiated with a CO₂ laser beam with powers of 0.41–1.39 kW/cm² are presented. The laser treatment induced structural changes and probably generation of a metastable phase. X-ray diffraction coupled with thermal analysis was used to establish the structural modifications in the irradiated samples after heating.     

Effect of proton irradiation on structure and optical property of PTFE film

Effects of protons on chemical structure and optical properties of polytetrafluoroethylene (PTFE) film were investigated in the energy range of 60 to 170 keV to simulate the effects of space proton irradiation environment. The results show that for PTFE film irradiated with protons, the change in C_1s spectrum, along with those in F_1s and the FT‐IR spectrum after irradiation, demonstrates that two processes take place simultaneously. One is substitution in which carbon to fluorine bonds can be broken by the protons and some positions of fluorine are occupied by active protons; the other is the carbonification, which results in the change of surface color and an increase of carbon percentage on the irradiated surface. For the PTFE film irradiated with 150 keV protons, the spectral absorbance ΔA_λ in the wavelengths longer than 300 nm increase unmonotonously with proton fluence, and an abnormally recovery decrease of the ΔA_λ with the increase of fluence in the range of 5×10¹³ cm^?2 to 10¹⁵ cm^?2 is observed. The change of the ΔA_λ could be related to the competition of the carbonification and the substituting effect. The carbonification increases the ΔA_λ, while the substituting increases the amorphousness amount, leading to an increase in the transparency of the film. In addition, the creation of radicals can also contribute to the increase in absorbance. Copyright © 2003 John Wiley & Sons, Ltd.     

Industrial production and purification of <Superscript>32</Superscript>P by sulfur irradiation with partially moderated neutron fluxes and target melting

Target purification of S_α is carried out by distillation at 444±2 °C under N atmosphere and diluting the vapors in CS₂. The solution is filtered through fiberglass, Teflon and cellulose to obtain S_α by CS₂ evaporation. Once 30 g of this target are irradiated with fast neutron fluxes from 4.5 to 7.4·10¹² n·cm⁻²s⁻¹ from 6 to 12 hours, the nuclear reaction ³²S(n,p)³²P takes place. So, the irradiated S_α sample is placed in a Pyrex container situated inside a furnace as the most important piece of equipment in one aluminum and Lucite glove box. The distillation of irradiated sulfur takes place at 444±2 °C under N atmosphere during 1–2 hours. The vapors are connected to a sulfur diluter containing 20% CS₂ aqueous solution, followed by an activated carbon filter and the two similar additional sulfur diluters. Once cooled, the distillation chamber keeps the radioactive, carrier-free ³²P stuck to the wall. Then 25–50 ml of 0.1N HCl acid was injected by suction and heated again at 110±2 °C during 1 hour. The corresponding chemical reaction takes place and the labeled H₃ ³²PO₄ solution is produced. In such a way, industrial production of ³²P labeled molecules has started in Mexico, with an initial production of 3700–5550 MBq per week.     

Mössbauer spectroscopic study of γ-ray irradiated potassium borate glasses

Potassium borate glasses denoted by the formula xK₂O · (100 ? x)B₂O₃ · 7Fe₂O₃ were irradiated with ⁶⁰Co-γ-rays at room temperature. Mössbauer parameters for the irradiated glasses containing alkali equal to or higher than 20 mole% showed that the s-electron density at the iron nucleus increased without any change of the steric configuration of oxygen atoms around the iron nucleus. The increase of s-electron density was ascribed to electron transfer from the nonbridging oxygen to the iron nucleus. The presence of the nonbridging oxygen was also confirmed by the irradiation effect of the borate glass (x = 30) prepared using the enriched isotope of ⁵⁷Fe₂O₃. Mössbauer parameters for the irradiated glass suggest that the newly observed Fe²⁺ ions are in tetrahedral symmetry.     

Chemical effects induced by γ-irradiated alkali halides in aqueous binary mixtures of nitrates and iodides

Dissolution of -irradiated chlorides of sodium and potassium in a solution of NaNO₃ and KI results in the formation of NO ₂ ^– and iodine as stable products. The variation in the yields of the products with the amount of irradiated salts is studied. The effect of photoannealing of the irradiated salts on the yields of nitrate and iodine in the mixture is discussed on the basis of photoannealing reactions of the colour centres.     

Feasibility study for the production of 32 P-labeled diphosphonic acids by neutron irradiation and radiochemical separation

Two simple diphosphonates, CH₆P₂ O₆(MDP) and C₂ H₈ P₂ O₇ (HEDP),have been irradiated with neutrons to produce the corresponding ³²P-labeled compounds. After irradiation for 0.5–5 hours in a thermalneutron flux of 4.2 . 10¹⁶ n . m ^—2 s^—1 the irradiated compounds were dissolved and fractionated using a SephadexG10 column. The separated fractions were identified using planar paper chromatographyand autoradiography. The labeling yield was ca 35% for each of the compounds,and the specific activity attainable ranged up to 4.8 GBq . mol ^—1 . For practical applications, the labeled diphosphonates have to bepurified further.     

Radioanalytical method for determination of the chemical forms of35S hot atoms in reactor-irradiated AlCl3−FeCl3

A radioanalytical procedure for the determination of the chemical forms of³⁵S in reactor irradiated crystals AlCl₃, FeCl₃ and AlCl₃?FeCl₃ is described. The method includes:³⁵S extraction with trichloroethylene, precipitation of³⁵S^2? as iron sulfide and of (³⁵SO ₄ ^2? +³⁵SO ₃ ^2? ) as Ba-salts. All fractions are converted to, and measured as, BaSO₄.