Hirotsugu Shiraishi

An ESR study on solvated electrons in water and alcohols: Difference in the g factor and related analysis of the electronic state by MO calculation

An induction‐detecting ESR spectrometer system, capable of μs time resolution, has been set up, and measurements were made on the radiolytically produced solvated electrons in water, methanol, ethanol, and mixtures of water and these alcohols. The spectrum of the solvated electron was a singlet in all these solvents. The g factor of the hydrated electron was measured to be 2.000 47±0.000 07 at 22 °C in reasonable agreement with the reported data. While this value is significantly smaller than the free electron g factor, the corresponding g factors in methanol and in ethanol, respectively 2.002 05±0.000 07 and 2.001 97±0.000 07 at 22 °C, were found much closer to it. In both methanol–water and ethanol–water mixtures the g factor of the solvated electron varied approximately in proportion to the mole fraction. The g shift of the hydrated electron was interpreted as arising from spin density in the proximity of oxygen nuclei of water molecules. Ab initio MO calculations were performed for an anionic cluster ...

An Electron Spin Resonance Study of Free Radicals in Black Dust Deposited in Human Lungs

An Electron Spin Resonance measurement was conducted on black dust deposited in autopsied human lungs. Free radicals were detected in all specimens examined, and the spectra indicated the presence of two types of radicals, both of which are apparently singlet lines. The amount of the respective component differed from sample to sample. The component with the narrower width, 2.7 G, and the smaller g factor, 2.0025, is attributable to carbon radicals associated with the combustion of hydrocarbons, and especially its relevance to the experience of smoking was inferred. The other component, with a width of about 10 G and g factor fo 2.0037, was found to be more common among the specimens. The assignment of the latter component is not very clear, but an oxygen-related radical is a possible candidate.

Effect of radiation on chemical forms of iodine species in relation to nuclear reactor accidents

Abstract In this study the effect of radiation on chemical iodine forms was examined by the product analyses and pulse radiolysis experiments in relation to nuclear reactor accidents. It was found that a subtle balance between oxidation and reduction of iodine species is attained after relatively small doses of radiation and that hydrogen peroxide produced by radiolysis was found to play an important role in attaining this balance of the oxidation and reduction reactions. The rate constants of some relevant reactions were measured by pulse radiolysis.

Radiation chemistry of aqueous iodine systems under nuclear reactor accident conditions

Abstract Radiation-chemical behavior of cesium iodide solutions was investigated using a once-through flow system in relation to the behavior of radioactive iodine under the condition of nuclear reactor accidents. It was found that several factors such as initial concentration of CsI, pH and O 2 concentration have a large influence on the oxidation-reduction reactions in the radiolysis of the iodide solutions. A pulse radiolysis technique was applied to this system to obtain clearer understanding of the radiolysis mechanism, and the rate constants were measured with the several important reactions involved.

Hydrogen injection in BWR and related radiation chemistry

Abstract Hydrogen injection to feed water systems in boiling water reactors (BWR) has drawn wide attention as one of the possible countermeasures to the stress corrosion cracking (SCC) of 304 type stainless steel piping. To confirm the effectiveness of the hydrogen injection, a computer simulation of the complicated radiolysis reactions was carried out. The result of the simulation showed that the reactor water data monitored at the usual sampling points in actual plants reflect mainly the reactions in the downcomer portion but not in the reactor core in BWR. The calculation claimed approximately 300 ppb hydrogen in feed water to reduce the oxygen concentration in the recirculation lines to a negligible level, while one order of magnitude higher level of hydrogen is necessary to suppress oxygen in the reactor core. The computer simulation requires many radiation chemical data as in-put, among which are G values of initial products for water radiolysis at high temperature. An experimental approach was made to confirm the G values for high temperature radiolysis of water. The result does not seem to be consistent with the high temperature G values reported by Burns.

On the yield of hydrated electrons at elevated temperature

In order to estimate the yield of eaq- at 200°C a pulse-radiolysis experiment was carried out with aqueous benzonitrile (BN) solutions containing 0.5 mol dm-3 ethanol. The rate coefficient of the reaction between eaq- and BN was found to increase from 2.0 × 1010 dm3 mol-1 s-1 at 20°C to 2.1 × 1011 dm3 mol-1 s-1 at 200°C. The G-value of benzonitrile anion (BN-) was evaluated from its absorption around 310 nm using an assumption that the absorption coefficient varied proportionally to the inverse of the band width. The estimated G(BN-) in a 5.1 × 10-4 mol dm-3 BN solution was 3.1 and 3.4 mol/100 eV respectively at 20 and 200°C. The former G(BN-) is larger than Geaq at 20°C due to an effect of ethanol added to scavenge OH and H radicals, while the latter G(BN-) at 200°C is presumed to be little affected by the presence of ethanol. The result is consistent with the view that Geaq- increases significantly with temperature.

ESR study on dicarboxylic acids irradiated with low-energy electrons

Abstract ESR spectra of low-energy electron-irradiated dicarboxylic acids were compared with those of γ-irradiated ones. The lineshape and linewidth of the spectra of these samples were found to be different. The local concentration of radicals is discussed in relation to the LET effect of radiation.