Radiation Induced Dissolution of UO2

1990 ◽  
Vol 212 ◽  
Author(s):  
Hilbert Christensen
Keyword(s):  
Corrosion Rate ◽  
Gamma Radiation ◽  
Ambient Temperature ◽  
Dose Rate ◽  
Oxidation Mechanism ◽  
Sample Surface ◽  
Oh Radicals ◽  
Water Radiolysis ◽  
Radiation Induced ◽  
Polished Specimen

ABSTRACTIn order to be able to model the effect of water radiolysis on the dissolution of fuel in the disposal vault it is essential to study the oxidation mechanism. Radiolysis of water produces radicals and molecules, amongst them the oxidizing species H2O2 and OH radicals, and, in aerated solutions, O2- as well. These species are probably responsible for the oxidation and dissolution of UO2 observed in a number of experiments. In the present investigation the effect of the oxidizing species has been studied separately using suitable scavengers. A polished specimen of UO2 was immersed in water and irradiated at ambient temperature with Co-60 gamma radiation. After irradiation the amount of uranium which had dissolved, or deposited elsewhere than the sample surface, was measured, and the oxidation of the surface was determined, using ESCA and SIMS. In 50 mM H2O2 (without irradiation) the corrosion rate was 5±3 μg.cm−2d−1 after 6 d exposure at pH 8. Corresponding rates for oxidation by O2- and OH radicals were about 3 μg.cm−2d−1, (dose rate 600±90 Gy/h.)

scholarly journals Radiation-induced oxidative damage to the DNA-binding domain of the lactose repressor

2007 ◽  
Vol 403 (3) ◽  
pp. 463-472 ◽  
Author(s):  
Nathalie Gillard ◽  
Stephane Goffinont ◽  
Corinne Buré ◽  
Marie Davidkova ◽  
Jean-Claude Maurizot ◽  
...  
Keyword(s):  
Dna Binding ◽  
Conformational Changes ◽  
Specific Binding ◽  
Classical Model ◽  
Binding Domain ◽  
Oh Radicals ◽  
Water Radiolysis ◽  
Dna Binding Domain ◽  
Fluorescence Measurements ◽  
Radiation Induced

Understanding the cellular effects of radiation-induced oxidation requires the unravelling of key molecular events, particularly damage to proteins with important cellular functions. The Escherichia coli lactose operon is a classical model of gene regulation systems. Its functional mechanism involves the specific binding of a protein, the repressor, to a specific DNA sequence, the operator. We have shown previously that upon irradiation with γ-rays in solution, the repressor loses its ability to bind the operator. Water radiolysis generates hydroxyl radicals (OH· radicals) which attack the protein. Damage of the repressor DNA-binding domain, called the headpiece, is most likely to be responsible of this loss of function. Using CD, fluorescence spectroscopy and a combination of proteolytic cleavage with MS, we have examined the state of the irradiated headpiece. CD measurements revealed a dose-dependent conformational change involving metastable intermediate states. Fluorescence measurements showed a gradual degradation of tyrosine residues. MS was used to count the number of oxidations in different regions of the headpiece and to narrow down the parts of the sequence bearing oxidized residues. By calculating the relative probabilities of reaction of each amino acid with OH· radicals, we can predict the most probable oxidation targets. By comparing the experimental results with the predictions we conclude that Tyr7, Tyr12, Tyr17, Met42 and Tyr47 are the most likely hotspots of oxidation. The loss of repressor function is thus correlated with chemical modifications and conformational changes of the headpiece.

Ionizing Radiation Effects on Interfaces in Carbon Nanotube-Polymer Composites

2001 ◽  
Vol 697 ◽  
Author(s):  
Julie P. Harmon ◽  
Patricia Anne O. Muisener ◽  
LaNetra Clayton ◽  
John D'Angelo ◽  
Arun K. Sikder ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Gamma Radiation ◽  
Total Dose ◽  
Dose Rate ◽  
Polymer Composites ◽  
Radiation Effects ◽  
Mechanical Analysis ◽  
Scanning Calorimetry ◽  
Radiation Induced ◽  
Radiation Induced Chemistry

AbstractThe purpose of this research was to probe nanotube-polymer composites for evidences of radiation induced chemistry at the interface of the host polymer and the nanotube structures. Single wall carbon nanotube (SWNT) / poly (methyl methacrylate) (PMMA) composites were fabricated and exposed to gamma radiation with a Co60 source at a dose rate of 1.28 X 106 rad/hour in an air environment for a total dose of 5.9 Mrads. Neat nanotube paper and neat PMMA were also exposed. Spun coat films of SWNT/PMMA were exposed to gamma radiation with a Ce157at a dose rate of 4.46 x 103 rad/hr for a total dose of 3.86 Mrads. Both irradiated and non-irradiated samples were compared. Glass transition temperatures were characterized by differential scanning calorimetry. Dynamic mechanical analysis and dielectric analysis evidenced changes in relaxations induced by irradiation. Irradiated composites exhibited radiation induced chemistry distinct from degradation effects noted in the pure polymer. Scanning electron microscopy provided images of the SWNTs and SWNT/PMMA interface before and after irradiation. This investigation imparts insight into the nature of radiation induced events in nanotubes and nanocomposites.

Electron Paramagnetic Resonance Spectrometry-based Assessment of Free Radicals Scavenging Potential of N-acetyl Tryptophan Glucoside

2017 ◽  
Vol 2 (3) ◽  
pp. 317 ◽  
Author(s):  
Poonam Malhotra ◽  
Yana Karamalakova ◽  
Galina Nikolova ◽  
Darshana Singh ◽  
Raj Kumar
Keyword(s):  
Free Radicals ◽  
Free Radical ◽  
Gamma Radiation ◽  
Radical Scavenging ◽  
Control Group ◽  
Water Radiolysis ◽  
In Vivo Models ◽  
Radiation Induced ◽  
Free Radicals Scavenging

<p>Gamma radiation generates free radicals in biological system by inducing cellular water radiolysis. If not neutralised, free radicals oxidise vital bio-macromolecules causing structural and functional impairment and contribute to cell death. In present study, free radical scavenging activities of a novel bacterial secondary metabolite, N-acetyl tryptophan glucoside (NATG) was assessed against gamma-radiation induced damage in vitro and in vivo models. Effect of irradiated NATG (UV and gamma radiation 8 Gy and 20 Gy) on its free radical (DPPH radicals) and SOD-like activity was evaluated using EPR spectrometry. To assess the effect of NATG irradiation on its antioxidant potential, EPR based ascorbate, PBN and NO radicals scavenging activities were evaluated in blood and spleen tissue of strain A male mice. Results of the study indicated significant (p &lt; 0.05) increase in DPPH radicals scavenging ability of irradiated NATG as compared to un-irradiated NATG. Similarly, irradiated NATG exhibited significant (p &lt; 0.05) elevation in SOD-like activity as compared to control. Subsequently, NATG treatment displayed enhanced antioxidant activity as evident by significant (p &lt; 0.05) decline in ascorbate, PBN and NO radicals at 1 h and 2h in blood and spleen tissues homogenate of treated mice as compared to control group. In conclusion, NATG possesses significant free radicals scavenging and radio protective capabilities against gamma radiation induced oxidative stress.</p>

Effect of External Gamma Irradiation on Dissolution of the UO2 Matrix

2004 ◽  
Vol 824 ◽  
Author(s):  
C. Jégou ◽  
B. Muzeau ◽  
V. Broudic ◽  
S. Peuget ◽  
A. Poulesquen ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Gamma Radiation ◽  
Gamma Irradiation ◽  
Dose Rate ◽  
Homogeneous Solution ◽  
Water Radiolysis ◽  
Γ Radiation ◽  
Alpha Emitters ◽  
Leaching Experiments ◽  
Alpha Radiolysis

AbstractLeaching experiments were done on UO2 pellets doped with alpha-emitters (238/239Pu, 1500 - year batch), in the presence of an external gamma irradiation source (A60Co = 260 Ci, γ dose rate = 650 Gy h−1). The effects of α and γ radiation and the nature of the cover gas (air or Ar + 4% H2) on water radiolysis, and on oxidizing dissolution of the UO2 matrix, are quantified and discussed. The cover gas clearly has a major role in the effect of γ radiolysis. The dissolution rate in an aerated medium is 83 mg m−2 d−1 compared with only 6 mg m−2 d−1 in Ar + 4% H2. The rate drop is accompanied by a reduction of about four orders of magnitude in the hydrogen peroxide concentrations in the homogeneous solution. The UO2 alteration rate under gamma radiation in Ar + 4% H2 is comparable to the rate obtained in the presence of alpha radiolysis alone for the doped UO2 pellets with the highest alpha activities (4.75 × 108 Bq/g UO2, 15 - year batch).

Gamma Radiation Induced Effects on Cefuroxime and Cefotaxime. Investigation on Degradation and Syn-Anti Isomerization

1994 ◽  
Vol 20 (16) ◽  
pp. 2493-2508 ◽  
Author(s):  
E. Ciranni Signoretti ◽  
L. Valvo ◽  
P. Fattibene ◽  
S. Onori ◽  
M. Pantaloni
Keyword(s):  
Gamma Radiation ◽  
Radiation Induced

scholarly journals Molecular Hydrogen as a Potential Clinically Applicable Radioprotective Agent

2021 ◽  
Vol 22 (9) ◽  
pp. 4566
Author(s):  
Shin-ichi Hirano ◽  
Yusuke Ichikawa ◽  
Bunpei Sato ◽  
Haru Yamamoto ◽  
Yoshiyasu Takefuji ◽  
...  
Keyword(s):  
Radiation Damage ◽  
Molecular Hydrogen ◽  
Regulation Of Gene Expression ◽  
Animal Experiments ◽  
Radiation Energy ◽  
Water Radiolysis ◽  
Low Dose Radiation ◽  
Oxidizing Power ◽  
Radiation Induced ◽  
Radioprotective Agent

Although ionizing radiation (radiation) is commonly used for medical diagnosis and cancer treatment, radiation-induced damages cannot be avoided. Such damages can be classified into direct and indirect damages, caused by the direct absorption of radiation energy into DNA and by free radicals, such as hydroxyl radicals (•OH), generated in the process of water radiolysis. More specifically, radiation damage concerns not only direct damages to DNA, but also secondary damages to non-DNA targets, because low-dose radiation damage is mainly caused by these indirect effects. Molecular hydrogen (H2) has the potential to be a radioprotective agent because it can selectively scavenge •OH, a reactive oxygen species with strong oxidizing power. Animal experiments and clinical trials have reported that H2 exhibits a highly safe radioprotective effect. This paper reviews previously reported radioprotective effects of H2 and discusses the mechanisms of H2, not only as an antioxidant, but also in intracellular responses including anti-inflammation, anti-apoptosis, and the regulation of gene expression. In doing so, we demonstrate the prospects of H2 as a novel and clinically applicable radioprotective agent.

scholarly journals A DNA-Damage-Induced Cell Cycle Checkpoint in Arabidopsis

Genetics ◽  
2003 ◽  
Vol 164 (1) ◽  
pp. 323-334
Author(s):  
S B Preuss ◽  
A B Britt
Keyword(s):  
Cell Cycle ◽  
Gamma Radiation ◽  
Cell Cycle Progression ◽  
Cell Cycle Checkpoint ◽  
Phase Cell ◽  
Cycle Arrest ◽  
Cycle Checkpoint ◽  
Radiation Induced ◽  
High Doses ◽  
Regulation Of Cell Cycle

Abstract Although it is well established that plant seeds treated with high doses of gamma radiation arrest development as seedlings, the cause of this arrest is unknown. The uvh1 mutant of Arabidopsis is defective in a homolog of the human repair endonuclease XPF, and uvh1 mutants are sensitive to both the toxic effects of UV and the cytostatic effects of gamma radiation. Here we find that gamma irradiation of uvh1 plants specifically triggers a G2-phase cell cycle arrest. Mutants, termed suppressor of gamma (sog), that suppress this radiation-induced arrest and proceed through the cell cycle unimpeded were recovered in the uvh1 background; the resulting irradiated plants are genetically unstable. The sog mutations fall into two complementation groups. They are second-site suppressors of the uvh1 mutant's sensitivity to gamma radiation but do not affect the susceptibility of the plant to UV radiation. In addition to rendering the plants resistant to the growth inhibitory effects of gamma radiation, the sog1 mutation affects the proper development of the pollen tetrad, suggesting that SOG1 might also play a role in the regulation of cell cycle progression during meiosis.

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