Water Radiolysis Products Research Articles

Calculations Simulating Spent-Fuel Leaching Experiments

Calculations of UO2-fuel corrosion and gas production from radiolysis of water have been carried out. The calculations simulated conditions of spent-fuel leaching experiments carried out within a European Union project. In some of these experiments, carried out by Forschungszentrum Karlsruhe, a fuel pellet was exposed in deionized water for 200 days, and fuel alteration and gas production rates were measured. A radiolysis model, developed previously, was used to calculate the oxidation of UO2 caused by water radiolysis products. The calculated fuel alteration rate was 2.2 × 10-8 mol UO2·(g U)-1·day-1, about three times higher than the experimental rate, 6.3 × 10-9 mol UO2·(g U)-1·day-1.The fair agreement between calculated and experimental corrosion rates shows that the model may be used for prediction of corrosion behavior of spent fuel in the repository. The calculated gas generation rates were 2 × 10-8 and 1 × 10-8 mol·(g U)-1·day-1 for hydrogen and oxygen, respectively, about six times lower than the experimental values.

亜鉛イオン共存下の高温水中におけるＳＵＳ３０４鋼の腐食およびコバルト蓄積に及ぼすγ線照射の効果

The effect of γ irradiation on the corrosion and the cobalt accumulation of type 304 stainless steel exposed to water at 561 K has been investigated. The exposure tests were carried out with and without the presence of 1.2×103 Gy/h γ irradiation and 50 ppb zinc addition. The structure and elemental depth distributions of the corrosion surface were analyzed by EPMA, XRD and GDS. In the case of no zinc addition, the amount of corrosion did not appear to change with the γ irradiation. However, the amount of crud release, the amount of corrosion film and the cobalt accumulation in the outer layer increased with the γ irradiation. In the case of zinc addition, the amount of corrosion and the corrosion film significantly increased and also the amount of cobalt accumulation increased with the γ irradiation. It is considered that these differences are related to the reaction of metal ions and radiolysis products of water. On the other hand, the zinc addition suppressed the corrosion and the cobalt accumulation even with γ irradiation. These suppression effects were reduced compared with the no γ irradiation condition.

Susceptibility of Sensitized Type 304 Stainless Steel to Intergranular Stress Corrosion Cracking in Simulated Boiling-Water Reactor Environments

Abstract Slow strain rate tests (SSRT) were conducted to evaluate the mitigating effect of hydrogen water chemistry (HWC) on intergranular stress corrosion cracking (IGSCC) of sensitized type 304 (UNS S30400) stainless steel (SS) used for in-reactor components of boiling-water reactors (BWR). The in-reactor environment was simulated by controlling water chemistry parameters such as dissolved oxygen (DO), dissolved hydrogen (DH), hydrogen peroxide (H2O2), and corrosion potential (Ecorr). Effects of the products of water radiolysis on SCC behavior were examined in the presence of a γ-radiation field. IGSCC susceptibility of sensitized type 304 SS decreased with decreasing concentrations of DO and H2O2, which suggested IGSCC of sensitized type 304 SS could be mitigated even in the in-reactor environment under HWC conditions. IGSCC susceptibility clearly was dependent upon Ecorr, as controlled by the concentrations of stable radiolytic products (e.g., O2, H2O2, and H2), regardless of short-lived radicals gene...

Valency stabilization of polyvalent ions during gamma-irradiation of their aqueous solutions by sacrificial protection

The various aspects of valency stabilization of polyvalent ions during γ-radiolysis have been further investigated. Ce(IV) ions, which are normally reduced in their aqueous solution, were found to be stabilized for increasing periods of time when they were irradiated in the presence of increasing amounts of bromate ions. It was found that the addition of about fifteen times excess of bromate ions to a 10−3 N Ce(IV) solution stabilized the cerium ions in the tetravalent state for about 120 hours during irradiation at a dose rate of 336 Gy/h. Increasing the amount of bromate used resulted in a subsequent increase in the protection time. It has been also noted that while bromate ions protected Ce(IV) in solution, the latter ions showed a clear protective effect on the bromate used, i.e., there is a mutual protective effect. The probable mechanisms, conditions and limitations of the protection process have been discussed. Based on the data obtained in the present work, it has been suggested that the protection of Ce(IV) ions by bromate ions in aqueous solutions during γ-radiolysis is very probably due to the preferential interaction of bromate with the reducing radiolysis products of water which are capable of reducing Ce(IV) to Ce(III).

Valency stabilization of polyvalent ions during gamma irradiation of their aqueous solutions by sacrifical protection

investigated. Ce(IV) ions, which are normally reduced in their aqueous solution, were found to be stabilized for increasing periods of time when they were irradiated in the presence of increasing amounts of bromate ions. It was found that the addition of about fifteen times excess of bromate ions tO a 10 -3 N Ce(IV) solution stabilized the cerium ions in the tetravalent state for about 120 hours during irradiation at a dose rate of 336 Gy/h. Increasing the amount of bromate used resulted in a subsequent increase in the protection time. It has been also noted that while bromate ions protected Ce(IV) in solution, the latter ions showed a clear protective effect on the bromate used, i.e., there is a mutual protective effect. The probable mechanisms, conditions and limitations of the protection process have been discussed. Based on the data obtained in the present work, it has been suggested that the protection of Ce(IV) ions by bromate ions in aqueous solutions during ~/-radiolysis is very probably due to the preferential interaction of bromate with the reducing radiolysis products of water which are capable of reducing Ce(IV) to Ce(IIl). Irradiation of polyvalent ions in their aqueous systems, usually leads to changes in their valency states. It has been suggested that when subjected to ionizing radiations, all polyvalent ions with standard electrode potentials, E ~ higher than 0.8 V are reduced and those with E ~ values lower than 0.8 V are oxidised while in the range 1.15-0.7 V different investigators obtained conflicting results, i.e., both oxidation and reduction3 In the course of our studies aiming at investigating the nature of various protection processes of polyvalent ions during "t-irradiation, the protection of Fe(II), has been treated in a previous publication. 2 In that work, sodium sulphite, being a powerful reducing agent, was used as a protective agent. It has been demonstrated that the processes leading to valency stabilization of Fe(II) ions, in aqueous acidic solutions, involved the preferential interaction of the protecting agent, i.e., sulphite ions, with the

Water-rock reactions during gamma-ray irradiation

Abstract The effects of gamma-ray irradiation on water-rock reactions are investigated by comparing leaching experiments with and without irradiation. Basaltic rock fragments were leached for 887 h with distilled, deionized water, while moderately flushing with air. During the leaching a total of 10 aliquots were removed and analysed by ion chromatography and instrumental neutron activation analysis (INAA). The leached amounts of Na, K, Ca, Cs, Mg, Co, Ba, Zn and Sc were higher for the irradiated run than those for non-irradiated, but the leaching of W was depressed by irradiation. The differences in the amount of the dissolved elements between irradiated and non-irradiated runs for the same time ( radiation release ) correlate with the absorbed dose of water. Four temporal variation types of the radiation release are recognized. The radiation releases of Na, K, Ca and Cs increased linearly with irradiation time and the rate increases are on the order of 10 −9 to 10 −10 /rad(H 2 O); those of Mg, Co, Ba and Zn approached constant values. The radiation release of Sc increased linearly after a threshold value is reached, and that of W decreased linearly. These results show that water-rock interaction is promoted by gamma-ray irradiation in most cases. Of the major basalt constituents, the elements that show a linear correlation of the radiation release with the absorbed dose are contained more in the feldspars, while the elements that approach constant values with increase of absorbed dose are contained more in the mafic minerals. It is conceivable that during irradiation the behavior of an element is controlled by the reaction kinetics between water and each mineral species. Water radiolysis products generated by irradiation are likely to be the main cause of increased dissolution; they also cause changes in the valences of metal-ions in aquatic systems. The valence changes are likely a key to understanding the reaction kinetics during gamma-ray irradiation.

Water-rock reactions during gamma-ray irradiation

The effects of gamma-ray irradiation on water-rock reactions are investigated by comparing leaching experiments with and without irradiation. Basaltic rock fragments were leached for 887 h with distilled, deionized water, while moderately flushing with air. During the leaching a total of 10 aliquots were removed and analysed by ion chromatography and instrumental neutron activation analysis (INAA). The leached amounts of Na, K, Ca, Cs, Mg, Co, Ba, Zn and Sc were higher for the irradiated run than those for non-irradiated, but the leaching of W was depressed by irradiation. The differences in the amount of the dissolved elements between irradiated and non-irradiated runs for the same time ( radiation release) correlate with the absorbed dose of water. Four temporal variation types of the radiation release are recognized. The radiation releases of Na, K, Ca and Cs increased linearly with irradiation time and the rate increases are on the order of 10 −9 to 10 −10/rad(H 2O); those of Mg, Co, Ba and Zn approached constant values. The radiation release of Sc increased linearly after a threshold value is reached, and that of W decreased linearly. These results show that water-rock interaction is promoted by gamma-ray irradiation in most cases. Of the major basalt constituents, the elements that show a linear correlation of the radiation release with the absorbed dose are contained more in the feldspars, while the elements that approach constant values with increase of absorbed dose are contained more in the mafic minerals. It is conceivable that during irradiation the behavior of an element is controlled by the reaction kinetics between water and each mineral species. Water radiolysis products generated by irradiation are likely to be the main cause of increased dissolution; they also cause changes in the valences of metal-ions in aquatic systems. The valence changes are likely a key to understanding the reaction kinetics during gamma-ray irradiation.

Content of iron and copper in the nuclei and induction of pH 9-labile lesions in L5178Y sublines inversely cross-sensitive to H2O2 and x-rays.

Cells from the L5178Y murine lymphoma subline LY-R are twice as resistant to killing by ionizing radiation than the subline LY-S. In contrast, LY-R cells are more sensitive to killing by H2O2, the effect being more pronounced at 37 degrees C than 0 degree C. Initial DNA damage after H2O2 treatment (both temperatures, 5 min) has been estimated by the 'comet' assay (single-cell gel electrophoresis) and fluorescent halo technique. According to both methods, the initial damage is significantly higher in LY-R cells, particularly that inflicted at 0 degree C. Differences between DNA unwinding and rewinding abilities at pH 9 and 6.9 (estimated by the fluorescent halo technique) point to a considerable difference in pH-9-labile damage between the sublines, as observed previously for x-irradiated cells (Kapiszewska et al. 1992). In contrast to findings with x-irradiated cells, however, after H2O2 treatment this damage is more extensive in LY-R cells than in LY-S cells. Thus, the initial pH-9-labile damage corresponds to the pattern of sensitivity to H2O2 and x-rays. We suggest that this is caused by different proportions of cuprous and ferric ions found in the nuclei of LY sublines and by the different ability of these ions to react with H2O2 and water radiolysis products. The copper/iron ratio in the nucleus is 1.31 in LY-R cells and 4.84 in LY-S cells.

Radiation-induced isomerization of thiourea into ammonium thiocyanate

The products of γ-radiolysis of solutions of thiourea are reported to be ammonia, sulfur, cyanamide, dicyanamide, and possibly guanidine sulfate. Ammonium thiocyanate, the product of isomerization, has not been observed although it is found to be one of the products in the themal decomposition of aqueous solutions of thiourea over the temperature range of 100–180°C. Hence, the observation of a close to 1% yield of the isomerization product in a 6.25% (0.82M) solution of thiourea, at neutral pH on exposure to γ-radiation from a60Co suurce at room temperature, would appear to be a result of interest in radiation chemistry. This paper present results on the variation of the yield of the isomerization product with the γ-dose. The experiments consisted in irradiating 2 ml of 0.82M aqueous solution of thiourea at neutral pH and under normal atmospheric conditions, i.e., at room temperature and with dissolved air present. The source of radiation was a 2.5 kCi (nominal)60Co source. The method used to detect and measure the isomerization product, ammonium thiocyanate was based on the well-known color reaction between CNS− and Fe+3 monitored spectrophotometrically at 450 nm, after obtaining the calibration curve of absorbance and concentration of NH4CNS. The yield of NH4CNS, expressed as\(G_{NH_4 CNS} \) was 0.083 molecules of NH4CNS for 100 eV absorbed. A suitable mechanism for the process of isomerization is suggested involving the hydrated electroneaq, the major primary product of water radiolysis. The mechanism is consistent with the observed effect of the addition of acetone, a well-known electron scavenger. This suppressed the yield NH4CNS by about 25%.

The interaction of alcohol radicals with human hemoglobin. I. Spectral properties of hemoglobin in the visible range.

Aqueous deoxyhemoglobin solutions (2 mg/ml) were gamma-irradiated by a 60Co source in the presence of methanol, ethanol, 1-butanol and t-butanol under N2O or argon. The effects of the interaction of the particular alcohol radical species with hemoglobin were determined according to the detected spectral alterations in the visible range. The amounts of stable final products in the form of methemoglobin (MetHb) and the sum of hemichromes and cholehemichromes (Hemichr) were estimated in irradiated preparations. For preparations irradiated under N2O, the radiation yield for MetHb formation was three-fold lower in the presence of ethanol and 1-butanol [G(MetHb) = 0.33] compared with preparations irradiated in the presence of t-butanol or without alcohol [G(MetHb) = 1.00]. The yield of hemichromes and cholehemichromes in preparations irradiated under N2O increased in the order: ethanol (G = 0.38), 1-butanol (G = 0.52), t-butanol (G = 0.59), and in the absence of alcohol (G = 0.72). The high effectivity of t-butanol radicals for iron oxidation and Hb destruction is apparently due to their oxidative properties, compared with the other radicals. It was also shown that ethanol radicals reduce MetHb 10 times more effectively [G(Fe(II) = 2.5] compared with t-butanol radicals [G(Fe(II)) = 0.24]. For samples irradiated under argon all the observed changes were similar, regardless of the presence of alcohols. This effect can be attributed to reconstruction reactions of Hb molecules in the presence of both oxidizing (OH or t-but.) and reducing agents (e-aq). The following sequence of effectivities of water radiolysis products and secondary alcohol radicals for hemoglobin destruction has been identified: meth; eth.-->1-but.-->e-aq-->t-but.-->.OH.

Oxidation of nuclear fuel (UO 2) by the products of water radiolysis: development of a kinetic model

Radiolysis of groundwater will produce oxidants and reductants which can affect the oxidation and dissolution of used fuel (UO 2) placed in a geological disposal vault. A kinetic model to describe the oxidation of UO 2 by the products of radiolysis of water is described. This model assumes that a monomolecular surface layer of UO 2 reacts as if it were dissolved in a thin layer of water of a thickness corresponding to the diffusion range of the radicals formed during radiolysis. In this manner we can use the rate constants for the reactions of radiolytic species with dissolved uranium as an analog of the heterogeneous system for which rate constants are unknown. The refinement of this model, based on a series of electrochemical and open-circuit corrosion experiments, is described. Model predictions are compared with dissolution rates measured in these experiments.

Radiation chemistry of the hippocampal brain slice

The in vitro hippocampal brain slice is a 0.4 mm thick neural network that can be used to study brain responses to radiation and related injuries. This preparation is unique in that it responds to ionizing radiation within minutes after exposure without complications from changes in vascularity, blood flow, blood pressure, etc. Electrophysiological studies have shown that x- and γ-rays alter synaptic transmission and spike generation, elements of normal brain activity. To evaluate the role of hydroxyl free radicals ( ·OH) in these changes, slices were exposed to dilute H 2O 2 solutions. EPR spin trapping experiments verified that ·OH is produced. Neural responses, while similar, were not identical to those due to radiation, possibly because of a different distribution of ·OH. Although H 2O 2 is freely diffusible, it produces ·OH at specific sites where, e.g. iron reduces it. In contrast, x- and γ-rays produce ·OH more uniformly throughout the tissue. H 2O 2 may provide a better model for high-LET radiation where yields of radical products of water radiolysis are decreased and peroxide reactions predominate.

NMR relaxation enhancement in gels polymerized and cross-linked by ionizing radiation: A new approach to 3D dosimetry by MRI

A new type of tissue-equivalent medium for magnetic resonance imaging of the dose distributions produced by ionizing radiation has been developed. Agarose gel is infused with acrylamide and N, N′-methylene-bis-acrylamide (Bis) comonomers, which are readily polymerized by free radical initiators in de-aerated aqueous solutions. Polymerization and cross-linking induced locally by free radical products of water radiolysis increase the rate of water proton spin relaxation gradually up to doses of about 15 Gy. The slopes of the dose-response curves at 64 MHz are 0.015 and 0.28 s −1 Gy −1 for R 1 and R 2, respectively. The agarose matrix as well as the high (50% by weight) relative concentration of the cross-linker (Bis) per total comonomer limit the spread of polymerization so that the spatial distribution of the radiation dose is faithfully represented in the resultant spatial distribution of relaxation rates. The gel can be imaged with conventional magnetic resonance imaging devices with high spatial resolution and accuracy. In addition, due to the well established effect of the precipitation of insoluble agglomerates of highly cross-linked acrylamide, the optical turbidity of the gel increases gradually with the absorbed dose. This may provide an additional means of visualizing the dose distribution in three dimensions. The major advantage of the acrylamide-Bis-agarose gels over those that depend on ionic chemical dosimeters, for example, Fricke-infused gels, lies in the lack of diffusion of radiation-induced chemical changes subsequent to or concurrent with irradiation.

Calculation of the yields of water radiolysis products from fast-neutrons in a vver core

Calculation of the yields of water radiolysis products from fast-neutrons in a vver core

Determination of Criteria for Selecting A UO2Fuel Dissolution Model for Nuclear Fuel Waste Management Concept Assessment

ABSTRACTAssessing the concept of direct disposal of used nuclear fuel in a geological vault requires a model to predict the dissolution rate of UO2in groundwater. A solubility-limited model can be used to calculate the dissolution rate of UO2fuel under non-oxidizing conditions. When the oxidative dissolution of UO2is an irreversible process, a kinetic model is more suitable to describe the dissolution of UO2under oxidizing conditions. Experimental studies were carried out using electrochemical techniques and X-ray photoelectron spectroscopy, XPS, to determine criteria for selecting the appropriate model for estimating used-fuel dissolution rates as a function of the redox conditions in the vault at the time of container failure. UO2electrodes were subjected to prolonged (>1000 min) potentiostatic oxidation, and the rate of oxidation and dissolution of UO2fuel was investigated as a function of the applied potential. UO2oxidation was also carried out by the products of water radiolysis and studied as a function of dose rate, total dose and solution chemistry.These studies show that significant oxidative dissolution of UO2appears possible for potentials more positive than -100 mV vs SCE in solutions with a pH close to that of the deep groundwaters, i.e., from 6 to 10. A kinetic model, which takes into account the mechanism of UO2oxidation, is more appropriate to estimate dissolution rates of UO2fuel for redox conditions more oxidizing than -100 mV vs SCE.

Calculations of the yields of water radiolysis products in a nuclear reactor

Calculations of the yields of water radiolysis products in a nuclear reactor

Gamma‐irradiation of 7‐ketocholesterol in aqueous dispersions and liposomes

7‐Ketocholesterol in aqueous sodium stearate dispersions or incorporated into liposomes was exposed to gamma radiation at 0–4°C to a dose of 50 kGy. Substrate degradation was noted in all systems, but occurred to a much greater extent in dispersions (≈90%) than in liposomes (0–25%). The difference in degree of degradation is attributed to dissimilarities in the micro‐environment of 7‐ketocholesterol in the two systems. The principal decomposition product was identified as 7‐ketocholestanol, a compound that can arise from hydrogenation of the double bond of the starting material. Also detected, but in lower concentration, were the epimeric 7‐hydroxycholesterols resulting from the reduction of the original carbonyl function. Both 7‐ketocholestanol and the epimeric 7‐hydroxycholesterols are believed to be secondary species generated by the interaction of the starting material with the primary radiolysis products of water. In addition, many minor degradation products were noted but not identified.

Reactivity of Ions of Actinides Towards Inorganic Free Radicals in Irradiated Aqueous Solutions

The paper is a short review of experimental data obtained during the study of reactivity of ions of actinides towards inorganic free radicals in irradiated aqueous solutions by pulse radiolysis method. The values of rate constants of reactions of these ions with primary products of water radiolysis (eaq −, H, OH, O−) and secondary radicals formed via reactions of these products with solutes and/or as a result of direct action of ionizing radiation on solutes (SO4 −, NO3, Cl2 −, CO3 −, O2 − etc.) are listed. The peculiarities of the reactivity are discussed. The examples of application of the obtained data for the simulation of radiolytical transformations of ions of actinides are presented.

Studies on the radiolysis of U(VI)-thoron complex

This work is an investigation of the radiation stability of thoron-uranium complex. It deals mainly with the effect of absorbed dose on the absorption spectra of the complex at different complex concentrations. The radiolysis of the complex, was also investigated in presence of varying concentrations of ethanol and methanol. The decrease in absorbance at the characteristic peak as a function of absorbed dose, complex concentration, and alcohol concentration was used to calculate the G-value and the specific rate of bimolecular interaction of the complex molecule with water radiolysis products. The radiolysis mechanism was discussed in the light of the results.

Purification and partial characterization of goose ceruloplasmin

The preparation and properties of ceruloplasmin from goose blood plasma are described. Ammonium sulfate was used to precipitate the crude protein followed by adsorption and elution from DEAE-Sephadex A-50. Further treatment with an ethanol-chloroform mixture and Sephadex G-200 yielded an intensely blue protein possessing a high degree of chemical purity and biological activity. Goose ceruloplasmin, existing in two forms, appears to be a single polypeptide, apparent M r 121,300, with an A 610 A 280 ratio of 0.07. Copper represented 0.32%, which corresponded to six atoms of copper per protein molecule. Although the amount of EPR-detectable copper was the same as in mammalian ceruloplasmins there were some differences in EPR parameters, mainly in A ∥. Goose ceruloplasmin's amino acid composition, although similar in many residues to human ceruloplasmin, was lower in tyrosine, cystine/cysteine, and acidic amino acids. Valine was found as the N-terminal amino acid. Hexose, hexosamine, sialic acid, and fucose accounted for 6.65% of the weight. Goose protein contained only half the sialic acid of human ceruloplasmin. Two values for K m using either p-phenylenediamine (0.64 and 0.053 m m) or o-dianisidine (0.76 and 0.15 m m) were evaluated from Line-weaver-Burk plots. EPR studies on reactions with water radiolysis products at cryogenic temperatures allowed us to discover that goose ceruloplasmin, like human and bovine ceruloplasmins, possesses Superoxide dismutase activity.