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Abstract  

A landfill leachate sample was radiolyzed with γ-rays at 12.5, 25, 50, 100, 200 and 400 kGy. The radiolyzed solutions were studied by UV–VIS–NIR spectroscopy to measure the color change, by chemical oxygen demand (COD) analysis to check the degree of mineralization of the soluble organic matter present in the leachate and by FT–IR spectroscopy of the humic substance of the leachate. The results have shown that the humic substance present in the landfill leachate is extremely refractory to radiolysis: even at 400 kGy it was detected and recovered only with minor changes. It is shown that the radiolysis followed by ozonolysis is able to cause important improvements of the leachate color and important reduction on the COD. However, the results in terms of bleaching and COD abatement after radiolysis and ozonolysis of the leachate can be achieved directly by a simple exhaustive ozonolysis of the leachate. The structural changes occurring in the humic substances and in the humic acids present in the leachate after radiolysis and ozonolysis were analyzed by FT–IR spectroscopy.

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To investigate the radio impurity in the radiolysis of 18F-FDG at high radiodose and radioconcentrated solutions and develop methods of repurification. The radiolysis of 18F-FDG was analyzed by TLC. The radio-impurity was confirmed by biodistribution and small animal PET/CT studies. 18F-FDG was unstable at high radioconcentrition over 37 GBq/mL or under basic condition. TLC, biodistribution and PET/CT all indicated that the main autoradiolysis byproduct was free fluoride ion. The radiolyzed 18F-FDG was repurified by solid-phase extraction (SPE) column. The repurified 18F-FDG had a radiochemical purity (RCP) of over 99% and significantly lower bone uptake than that was before repurification (P = 0.0003). There was a positive correlation between the recovery yield and the purity of 18F-FDG (R 2 = 0.66).

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N,N-dimethylhydroxylamine (DMHA) is a novel salt-free reducing reagent used in the separation U from Pu and Np in the reprocessing of power spent fuel. This paper reports on the radiolysis of aqueous DMHA solution and its radiolytic liquid organics. Results show that the main organics in irradiated DMHA solution are N-methyl hydroxylamine, formaldehyde and formic acid. The analysis of DMHA and N-methyl hydroxylamine were performed by gas chromatography, and that of formaldehyde was performed by ultraviolet–visible spectrophotometry. The analysis of formic acid was performed by ion chromatography. For 0.1–0.5 mol L−1 DMHA irradiated to 5–25 kGy, the residual DMHA concentration is (0.07–0.47) mol L−1, the degradation rate of DMHA at 25 kGy is 10.1–30.1%. The concentrations of N-methylhydroxylamine, formaldehyde and formic acid are (8.25–19.36) × 10−3, (4.20–36.36) × 10−3 and (1.35–10.9) × 10−4 mol L−1, respectively. The residual DMHA concentration decreases with the increasing dose. The concentrations of N-methylhydroxylamine and formaldehyde increase with the dose and initial DMHA concentration, and that of formic acid increases with the dose, but the relationship between the concentration of formic acid and initial DMHA concentration is not obvious.

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The sulphur-containing proteinaceous amino acids l-cysteine, l-cystine and l-methionine were irradiated in the solid state to a dose of 3.2 MGy. This dose corresponds to that delivered by radionuclide decay in a timescale of 1.05 × 109 years to the organic matter buried at a depth >20 m in comets and asteroids. The purity of the sulphur-containing amino acids was studied by differential scanning calorimetry (DSC) before and after the solid state radiolysis and the preservation of the chirality after the radiolysis was studied by chirooptical methods (optical rotatory dispersion, ORD) and by FT-IR spectroscopy. Although the high radiation dose of 3.2 MGy delivered, all the amino acids studied show a high radiation resistance. The best radiation resistance was offered by l-cysteine. The radiolysis of l-cysteine leads to the formation of l-cystine. The radiation resistance of l-methionine is not at the level of l-cysteine but also l-methionine is able to survive the dose of 3.2 MGy. Furthermore in all cases examined the preservation of chirality after radiolysis was clearly observed by the ORD spectroscopy although a certain level of radioracemization was measured in all cases. The radioracemization is minimal in the case of l-cysteine and is more pronounced in the case of l-methionine. In conclusion, the study shows that the sulphur-containing amino acids can survive for 1.05 × 109 years and, after extrapolation of the data, even to the age of the Solar System i.e. to 4.6 × 109 years.

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Gamma irradiation studies of morin (10–5M) in ethanol and dimethyl sulphoxide (DMSO) in the dose range of 149–895 Gy and of 4.5–45 Gy were carried out, respectively, in aerated and anoxic conditions purged with nitrogen and nitrous oxide. The decoloration yield of morin was studied as a function of dose. The relative radiation sensitivity was estimated under similar conditions. The effect of the concentration (10–5–10–4M) of iodine, succinic acid and acryl amide on radiolysis of morin was investigated at constant dose in both solvents and results were interpreted in terms of scavenging reactions.

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Solvent extraction is a separation technique suitable for the treatment of used nuclear fuel. Two immiscible phases are contacted and the metals of interest are extracted from one phase into the other, most often using so called extractants. One group of extractants is the bis(triazine)-bipyridine (BTBP) type molecules. These molecules have been developed within EU research programs for the separation of actinides from lanthanides. During such an extraction process, the components of the two phases will be exposed to ionizing radiation, since the used fuel contains many highly radioactive species. Radiolytic reactions can alter the chemistry of the extracting system, and affect the metal extraction by degradation of the extractant and the formation of degradation products. In this paper the effect of irradiation with alpha particles and gamma rays, respectively, has been studied for one of the BTBP type molecules, C5-BTBP.

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Aim of this study is to investigate, by use of the pulse radiolysis technique, the mechanism of oxidation of trypthophan by OH and secondary inorganic radicals. Parallel pulse radiolysis studies were, performed on tryptophan and 1-formyltryptophan. The results seem to indicate that the most important attack on tryptophan residues is an one-electron oxidation. These results are compared with other data from the literature and a general discussion is made.

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In hypothetical accident scenarios for Light Water reactors, the extent of release of iodine upon irradiation needs to be assessed for the purpose of evaluation of the applicable source term. In this context, an understanding of the behaviour of aqueous cesium iodide solutions subjected to high gamma-ray fluxes acquires significant importance. In the present work, gamma radiolysis of a cesium iodide solution (10–2M I) with and without boron additive is investigated by irradiating with60Co source at ambient temperature. Upon irradiation of the CsI solution, iodine is liberated, and the concentration of iodide in the KOH trap present in the radiolysis vessel increases with dose. The radiolytic products I 3 , IO 3 and H2O2 formed in the irradiated solution are also estimated and G values obtained are reported. G(I 3 ) and G(IO 3 ) are of the order of 10–3 and 10–4, respectively. G(H2O2) decreases with increase in dose. Addition of boron up to 200 ppm, does not appear to alter significantly the release fraction of iodine.

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Abstract  

The -radiolysis of p-benzoquinone (Q) at different concentrations of H2SO4, Q, O2 and Cl are p-hydroquinone (H2 Q), 2-hydroxy-p-benzoquinone (2-Q-OH) and H2O2. The effect of Cl on yields is similar to its effect in deaerated solutions. The yields of H2Q and 2-Q-Oh are lower than in deaerated solutions. In the presence of simple aliphatic alcohols, a carbonyl compound is also measured in addition to those mentioned above. This system is found to be more complex than in deaerated solutions. Q and O2 were found to compete for the radical R1 R2 COH and good agreement was obtained between observed and reported rate coefficients of the reactions involved. There is some evidence that at lower pH, alcohol peroxy radicals are also able to undergo electron transfer with quinone.

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Abstract  

The products of the continuous radiolysis of p-benzoquinone (Q) at different concentrations of H2SO4, Q and Cl are p-hydroquinone (H2Q) and 2-hydroxy-p-benzoquinone (2-Q-OH). In the presence of some alcohols, a carbonyl compound is produced in addition to H2Q and 2-Q-OH. The dependence of G values of the products on these factors is described. The material balance between G(-Q) and G(H2Q)+G(2-Q-OH) is maintained. The experimental results indicate the occurrence of the following reaction:
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$H\dot Q + Cl_2 \to \to Q + H^ + + 2Cl^ -$$ \end{document}
. By competition studies, it was possible to evaluate the rate coefficients for the following reactions:
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$SO_4^{\mathop \cdot \limits^ - } + Q\xrightarrow{{H_2 O}}HSO_4^ - + \dot Q - OH(k \cong 3.5 \cdot 10^8 M^{ - 1} \cdot s^{ - 1} ), SO_2^{\mathop \cdot \limits^ - } + Cl^ - \to SO_4^{ - 2} + Cl(k \cong 3.1 \cdot 10^8 M^{ - 1} \cdot s$$ \end{document}
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