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An attempt was made to calculate the spur size in liquid water at room temperature from fundamental interactions. Electron trapping, elastic scattering, and positive-ion back attraction undergone in sub-excitation and sub-vibrational stages in the 100 fs time scale for thermalization were considered and included in the model. Overall diffusional broadening was estimated to be 41.2 Å, attended by the positive-ion pull back of 24.0 Å, resulting in a calculated spur size of 17.2 Å. Electron trapping is seen in competition with thermalization in the ultimate stage, which results in the trapped electron position distribution as a sum of Gaussians. [ABSTRACT FROM AUTHOR]

A quick measurement system of a continuous absorption spectrum covering a wide range from 200 to 950 nm was constructed by employing an optical multi-channel detector. Ion beam pulse radiolysis with 12.5 MeV/u He, 18.3 MeV/u C and 17.5 MeV/u Ne ions were performed with the measurement system. Transient absorption spectrum of ( S C N ) 2 • − was clearly observed in KSCN aqueous solutions within a few minutes in spite of their very small absorbance, demonstrating high sensitivity of 0.001–0.003 in absorbance in the range from 260 to 660 nm as well as short measurement time of a few minutes. Two different absorption peaks attributed to Br 2 • − and Br 3 − were observed simultaneously in NaBr aqueous solutions, showing powerfulness of the measurement system in overviewing chemical kinetics under ion beam irradiation especially in not well investigated chemical systems. [ABSTRACT FROM AUTHOR]

Abstract: In order to study radiation-induced fast phenomena, a new pulse radiolysis system with higher time resolution based on pulse-and-probe method was developed and utilized for practical work. A few picosecond electron beam generated from a linear accelerator, in which a laser photocathode RF-gun is introduced, was synchronized with a femtosecond laser pulse which is employed as the analyzing light. The synchronization precision between them was suppressed within 1.6ps (rms). Converting the fundamental laser into white light continuum or optical parametric amplification allows to measure in the wide wavelength from visible to infrared region. [Copyright &y& Elsevier]

Abstract: The yield of the hydrated electron in the picosecond time range has been re-evaluated with an ultrafast pulse radiolysis system using a laser photocathode RF-gun in combination with a conventional one, and a value of 4.1±0.2 per 100eV of absorbed energy at 20ps was derived. This is consistent with recent experimental results using a time correlation method [Bartels et al., J. Phys. Chem. A 104, 1686-1691 (2000)] and with Monte-Carlo calculations [Muroya et al., Can. J. Chem. 80 1367-1374 (2002)]. [Copyright &y& Elsevier]

The reactivity of monochlorophenols and dichlorophenols towards •OH and hydrated electrons was investigated applying pulse radiolysis coupled with time resolved spectroscopy. Rate constants, transient spectra and stability of transient species were studied for mono and dichlorophenols. Reactivity of 3,4-dichlorophenol (3,4-DCP) towards •OH and hydrated electrons, its transient spectra and respective rate constants have been explained in detail as a model for the current pulse radiolysis experiments. The trends and behaviors in the reactivity of mono and dichlorophenols towards •OH and hydrated electrons were analyzed. All the corresponding OH-adducts demonstrated λ max values range between 295 and 435 nm and their rate constants exhibited a range of (3.4–21) x 109 dm3 mol−1 s−1. Likewise, e-adducts illustrated λ max values ranged between 295 and 355 nm and their rate constants displayed a range of (0.025–6.2) x 109 dm3 mol−1 s−1. Full geometry optimizations and electron charge density calculations based on DFT (density functional theory) presented the existence of a strong correlation of electron charge density and polarizability with the reactivity of chlorophenols towards hydrated electrons and •OH radical. This research represents the first thorough exploration of its kind, aiming to comprehend the reactivity of all dichlorophenols and their corresponding transient spectra through pulse radiolysis. • Mono- & dichlorophenols reactivity with e a q − &.•OH was probed via pulse radiolysis. • Transient spectra and rate constants were investigated for all MCPs and DCPs. • 3,4-DCP served as a model to display transient spectra, k values & decay profiles. • The trends of reactivity were correlated with electron charge density using DFT. [ABSTRACT FROM AUTHOR]

Solvatochromic shift of 4,4′-bpyH in aqueous solutions at elevated temperatures up to supercritical conditions and in various organic solvents with different dielectric constants, is investigated by pulse-radiolysis technique. 4,4′-bpyH shows a stronger solvent–solute interaction in water than in organic solvents, perhaps due to the hydrogen bond between 4,4′-bpyH and water. At 380 °C, local density augmentation, namely ρ local – ρ bulk , in supercritical water becomes 280 kg m −3 ( ρ bulk = 208 kg m −3 ), and the density enhancement factor is 8.9. Density fluctuation maximizes when ρ bulk is around 120 kg m −3 . Density inhomogeneity decreases as temperature rises, but is still remarkable at 400 °C. [ABSTRACT FROM AUTHOR]

Abstract: The results of γ analyses of soil samples obtained from 50 locations in Fukushima prefecture on April 20, 2011, revealed the presence of a spectrum of radionuclides resulted from the accident of the Fukushima Dai-ichi nuclear power plant (FDNPP). The sum γ radioactivity concentration ranged in more than 3 orders of magnitude, depending on the sampling locations. The contamination of soils in the northwest of the FDNPP was considerable. The 131I/137Cs activity ratios of the soil samples plotted as a function of the distance from the F1 NPPs exhibited three distinctive patterns. Such patterns would reflect not only the different deposition behaviors of these radionuclides, but also on the conditions of associated release events such as temperature and compositions and physicochemical forms of released radionuclides. The 136Cs/137Cs activity ratio, on the other hand, was considered to only reflect the difference in isotopic compositions of source materials. Two locations close to the NPP in the northwest direction were found to be depleted in short-lived 136Cs. This likely suggested the presence of distinct sources with different 136Cs/137Cs isotopic ratios, although their details were unknown at present. Vertical γ activity profiles of 131I and 137Cs were also investigated, using 20–30 cm soil cores in several locations. About 70% or more of the radionuclides were present in the uppermost 2-cm regions. It was found that the profiles of 131I/137Cs activity ratios showed maxima in the 2–4 cm regions, suggesting slightly larger migration of the former nuclide. [Copyright &y& Elsevier]

The large-scale synthesis and the stabilization of noble metal nanocatalysts with ultrasmall sizes are crucial to their practical application. Herein, Pd, Au, and Pt nanoparticles (NPs) are in situ embedded on boron nitride nanosheets (BNNSs) via the reduction of precursor salts induced by 60Co γ-irradiation, which is a mature technique widely used in industry. The reduction mechanism was elucidated by pulse radiolysis experiments. In comparison with other BN substrates like hexagonal BN (h -BN), BNNSs had not only large surface area of 263 m2 g−1, but also abundant hydroxyl groups produced during the sonicated exfoliation, resulting in ultrasmall sizes, large loading amounts, and uniform distribution of the anchored NPs. The particle sizes of the loaded Pd, Au, and Pt NPs were measured to be 2.9, 3.1, and 3.0 nm, respectively. As a consequence, in the model reaction of 2-nitroaniline reduction, the Pd-, Au- and Pt-BNNSs composite nanocatalysts showed much higher catalytic activities than those composites loading the corresponding NPs on other BN substrates. Particularly, most of the 2-nitroaniline could be reduced within merely 40 s when using Pd-BNNSs as catalysts, performing a rate constant of 1.1 × 10−1 s−1. The number of hydroxyl groups on BNNSs support as well as the catalytic performance of the corresponding NPs-loaded BNNSs composites could be improved by extending the sonicated exfoliation time, because more NPs were loaded and the hydroxyl groups were also proved to play an important role in enhancing the catalytic activity. Moreover, Pd-BNNSs catalysts still displayed prominent activity even after five cycles owing to the high stability of BNNSs and their strong affinity for PdNPs. This work not only demonstrates BNNSs as ideal supports to load noble metal NPs for catalysis, but also reveals the feasibility to synthesize and in situ embed ultrasmall noble metal NPs on BNNSs via γ-irradiation. γ-Radiation-induced reduction achieved facile loading of noble-metal nanoparticles on BNNSs as ideal supports for extraordinary catalytic activity and excellent reusability. [Display omitted] • BNNSs with hydroxyl groups, prepared from sonicated exfoliation, were suitable to load noble metal nanoparticles (NPs). • Noble metal NPs of Pd (Au or Pt) were in situ embedded on BNNSs by facile γ-radiation-induced reduction. • The reduction mechanism was elucidated by pulse radiolysis experiments. • NPs loaded on BNNSs possessed the smaller sizes and higher loading amounts, compared with those on other BN substrates. • NPs-loaded BNNSs showed excellent catalytic activity and reusability for 2-nitroaniline reduction. [ABSTRACT FROM AUTHOR]

Abstract In the more than 40 years of operational history of pressurized water reactors (PWRs) in Japan, sustainable development of water chemistry technologies has resulted in the world's highest secondary system component integrity; additionally, secondary system components, especially steam generator (SG) tubing, with excellent material integrity have been developed to prevent leakage of radioactive contamination from the primary to the secondary system and to maintain the heat removal function of the secondary system. Although reasonable control and diagnostic parameters for water chemistry are utilized by each PWR owner, the specific values are not shared. To ensure reliable PWR operation and to achieve the highest safety level, relevant members of the Standards Committee and the related committee organized by the Atomic Energy Society of Japan (AESJ) decided to establish water chemistry guidelines for PWRs. The Japanese PWR secondary water chemistry guidelines provide strategies for improving material integrity and the heat removal function. The guidelines also provide reasonable "action levels" for control parameters and "control values" and "diagnostic values" for multiple parameters, and they stipulate the responses when these levels are exceeded. Specifically, "conditioning parameters" are adopted in the guidelines. Good operational practice conditions are also discussed with reference to long-term experience. This paper introduces the purpose, technical background and framework of preliminary secondary water chemistry guidelines for Japanese PWRs. Addition, the differences in bases of parameter settings between the Japanese and overseas guidelines are discussed. Highlights • Framework of PWR secondary water chemistry guidelines in Japan are presented. • Guideline necessity, definitions, philosophy and technical background are mentioned. • Some guideline settings for control conditioning and diagnostic parameters and recommendations are explaines. • Chemistry strategy is also mentioned. [ABSTRACT FROM AUTHOR]

Abstract: The absorption spectra of solvated electrons in pentanol, hexanol and octanol are measured from 22 to 200, 22 to 175 and 50 to150°C, respectively, at a fixed pressure of 15MPa, using nanosecond pulse radiolysis technique. The results show that the peak positions of the absorption spectra have a red-shift (shift to longer wavelengths) as temperature increases, similar to water and other alcohols. Including the above mentioned data, a compilation of currently available experimental data on the energy of absorption maximum (E max) of solvated electrons changed with temperature in monohydric alcohols, diols and triol is presented. E max of solvated electron is larger in those alcohols that have more OH groups at all the temperatures. The molecular structure effect, including OH numbers, OH position and carbon chain length, is investigated. For the primary alcohols with same OH group number and position, the temperature coefficient increases with increase in chain length. For the alcohols with same chain length and OH numbers, temperature coefficient is larger for the symmetric alcohols than the asymmetric ones. [ABSTRACT FROM AUTHOR]

Abstract: Two histidine-containing natural dipeptides, carnosine and anserine (β-alanyl-1-methyl-l-histidine), have been examined for their antioxidant and radioprotective abilities. Pulse radiolysis studies indicated the antioxidative properties of carnosine and anserine aqueous solutions at different pH. The rate constants for the reaction OH radical with carnosine at neutral pH were determined to be 5.3×109 M−1 s−1 at 300nm, and 4.1×109 M−1 s−1 at 400nm, respectively. Carnosine and anserine also protected plasmid pUC18 DNA from X-ray radiation-induced strand breaks as evidenced from the studies by agarose gel electrophoresis. Carnosine showed higher protective efficiency under the experimental conditions. Our data demonstrated that carnosine and anserine may play an important role in the maintenance of the antioxidant system. [Copyright &y& Elsevier]

Abstract: In the present work, laser photolysis techniques have been used to study the transient species of silybin (abbreviated as SLB) in ethanol solutions. It has been demonstrated that the exposure of silybin to 248nm excimer laser gives rise to monophotonic ionization with a high quantum yield. The transient species have been identified, and a series of related kinetics parameters have also been obtained. For the sake of comparison, we approached the problem using another way to reduce silybin, i.e. attack of solvated electrons, esol −, produced in pulse radiolysis. The rate constant for reaction of esol − was determined to be 3.8×109 dm3 mol−1 s−1 at 720nm, which is consistent with 4.6×109 dm3 mol−1 s−1, obtained by laser photolysis. [Copyright &y& Elsevier]

Abstract: Measurements of primary g-values (at ∼10−7 s after the initial ionizing event) of , OH and H2O2 were extended to the very high linear energy transfer (LET) region (∼700eV/nm) near the Bragg peak. Heavy ions (4He2+, 12C6+, 20Ne10+, 28Si14+, 40Ar18+ and 56Fe26+) of energies up to 28GeV were provided by the Heavy Ion Medical Accelerator in Chiba (HIMAC) of the National Institute of Radiological Sciences (NIRS) in Chiba, Japan. Energies of the ions were decreased down to about 10MeV/u for 4He2+ using an energy absorber made of polymethylmethacrylate (PMMA) plates in order to vary the LET values. Beam was visualized after passing through the energy absorber using agarose gel of aqueous solution containing methyl viologen and sodium formate in order to determine how long ions can penetrate into water. Based on the information of the penetration depth of ions in samples, much attention was paid to dose correction and LET evaluation. The obtained data were plotted as a function of (Z eff/β)2 also instead of LET in order to discuss effects of physical track structures on product yields, resulted in better universality. [Copyright &y& Elsevier]

Abstract: The absorption spectra of the hydrated electron in concentrated LiCl, LiClO4, Li2SO4, MgCl2 and Mg(ClO4)2 deuterated water solutions were measured by pulse radiolysis techniques from room temperature to 300°C at a constant pressure of 25MPa. With increasing temperature, the absorption band of the solvated electron for all solutions shifts to larger wavelengths. Whatever the temperature, shifts to shorter wavelengths of the absorption spectrum were observed as salt effects. The results on the shape and broadening of the absorption spectrum are discussed. [Copyright &y& Elsevier]

Abstract: Water radiolysis has been investigated with heavy ions having energies up to 28GeV provided from the Heavy Ion Medical Accelerator in Chiba (HIMAC) at the National Institute of Radiological Sciences (NIRS). Beams of 4He2+, 12C6+, 20Ne10+, 28Si14+, 40Ar18+ and 56Fe26+ with respective energies of 150, 400, 400, 490, 500 and 500MeV/u corresponding LET values of 2.2, 13, 30, 54, 92 and 183eV/nm, respectively, were taken for the irradiation. The LET changes in sample solutions can be neglected due to their high energies for the irradiation of 1-cm cells. Primary g values have been determined for three important products, hydrated electron (e− aq), hydroxyl radical (·OH), and hydrogen peroxide (H2O2) as track segment yields (differential yields) under the conditions of neutral pH. With increasing LET, the g values of e− aq and ·OH decrease from 2.4 and 2.6 in 4He2+ radiolysis to 0.9 and 1.1 (100eV)−1 in 56Fe26+ radiolysis, respectively. It was also found that the primary g value of e− aq is smaller than that of ·OH for any type of ion beam. For the 12C6+ beam, other energies such as 290, 220, 135MeV/u were taken for the irradiation to investigate the effects of type or atomic number of ions on the measured yields. Furthermore, effects of dissolved oxygen on enhancement of H2O2 production have also been investigated with aerated NaNO3 solutions. The presence of dissolved oxygen caused 15–35% enhancement in H2O2 yields for all beams. In addition, the results of the present work were compared with reported track segment yields. [Copyright &y& Elsevier]

Abstract: The absorption spectra of solvated electrons in 1-propanol and 2-propanol have been investigated from 22 to 270°C at a fixed pressure of 7MPa, by using both nanosecond pulse radiolysis and laser photolysis techniques. The results show that, even up to supercritical conditions, it is still possible to measure unambiguously the absorption spectra of solvated electron in these two propanols. The peak positions of the absorption spectra show a red-shift (shifts to longer wavelengths) as temperature increases, similar to water and other alcohols, but the temperature efficiency, dE max/dT, of 1-propanol is larger than that of 2-propanol. In addition, in clear contrast to that of pulse radiolysis, in laser photolysis experiments, an increase in the maximum absorbance of the absorption spectra of solvated electron with temperature up to ∼200°C is attributed to the increase of absorbance (CTTS absorption band) of I− anion at 248nm with increasing temperature. [Copyright &y& Elsevier]

Abstract: γ-Radiolysis and pulse radiolysis of phenol in aqueous solution up to supercritical condition have been carried out. G-values of phenol consumption and product formation have been determined. While dihydroxybenzenes were major products at room temperature, multi-ring compounds and benzene were formed above 300°C. This indicates reaction mechanism was changed above 300°C, where phenoxyl radical plays a predominant role. This is supported by the observation of phenoxyl radical in pulse radiolysis. In supercritical water, the G-values increased with decrease of density. [Copyright &y& Elsevier]

Abstract: A product analysis study of γ-irradiated benzophenone aqueous solutions from room temperature to 400°C has been carried out by the combination of a flow irradiation system and a liquid chromatographic method. At room temperature, the main decomposition products are phenol and hydroxybenzophenone isomers. In high temperature and supercritical water solutions, 9-fluorenone appears as an important product and the G-value of benzophenone consumption depends significantly on the water density under supercritical conditions. [Copyright &y& Elsevier]

The method of pulse radiolysis was used to study radiation-induced transformations of carboxymethylcellulose (CMC) of various degree of substitution (DS) in aqueous solution. The kinetics of the reactions of intermediate products of water radiolysis with this polymer indicated that hydroxyl radicals react very rapidly with the CMC, i.e. the rate constant is about 1×109dm3mol-1s-1 and independent of the DS of the CMC. On the other hand, the hydrated electron can be practically neglected as a precursor for macroradicals formation since its reaction rate constant with CMC is low, i.e. 4.0–5.0×106dm3mol-1s-1. As the result of OH radicals attack on the CMC, radicals on the main-chain, as well as on side groups (carboxymethyl) are formed. Environmental conditions determine the life-time of macroradicals, typically tens of minutes were detected. Most importantly, the pH level of the solution was observed to determine the preferential reaction pathway. Lowering the pH led to increased macroradicals recombination and gel formation. [Copyright &y& Elsevier]

Abstract: Carboxymethyl chitosan (CMCTS) at a highly concentrated aqueous solution forms hydrogel by ionizing irradiation. To study on radiation-induced reaction mechanism of CMCTS in an aqueous solution, CMCTS radicals formed by reactions with OH radical were observed by ESR method. As a result of ESR spectral analysis, CMCTS radicals were identified as radicals on carboxymethyl groups. [Copyright &y& Elsevier]