Keichi Oshima

Effect of Gamma Radiation on the Release of Corrosion Products from Carbon Steel and Stainless Steel in High Temperature Water

The effect of gamma irradiation on the release of the soluble and insoluble corrosion products was investigated with carbon steel and austenitic Type 304 stainless steel at high temperature using a small experimental loop. It was found that gamma radiation enhances the release rates of insoluble corrosion products (crud) but does not enhance the release rates of soluble species under the experimental conditions. On the basis of the result, it was considered that the crud forms in the bulk water through the oxidation of ferrous ion by oxygen or radiolysis products.

Electrical conductivity and defect structures in non-stoichiometric uo2+x

Electrical conductivity (σ) of UO2+x was measured as a function of oxygen partial pressure (Po2) from 500 to 1400 °C in the O/U composition between 2.013 and 2.113. These data were used for the discussion of imperfection models for non-stoichiometric UO2+x with reference to the analysis obtained from the relation between excess oxygen (x) and oxygen partial pressure. The slope of log-log plots of σ against Po2 decreased with increasing temperature from 1 at 500 °C to 14 at 1400 °C in the O/U range 0.02 < x < 0.11. With increasing temperature, interstitial oxygens begin to react with lattice oxygens and a complex is produced. At high temperatures the complex decomposes to individual oxygen ion with a localized hole. The charge carrier of the conduction is a hole localized to an excess oxygen or a complex, and the electrical conduction was explained by the hopping mechanism.

ESR study on the spatial distribution of radicals trapped in the heavy ion‐irradiated n‐eicosane single crystal

Single crystals of n−eicosane were subjected to the irradiation of helium, carbon, and nitrogen ions accelerated with the cyclotron, and the results were compared with those obtained by 60Co γ‐ray irradiation. Irradiation was carried out at 77 °K. The nature and the spatial distribution of free radicals produced in the crystals were investigated by an ESR technique. The principal radical is –CH2ĊHCH2– (I) and the minor one, CH3ĊHCH2– (II); the linewidth and decay of these radicals were found to be LET‐dependent. The ESR results indicate that radicals are trapped in two regions closely and sparsely; the relative distribution in the two regions is dependent on the LET of radiations used. The mean separation between the radicals trapped in the close proximity was estimated to be approximately 16 A.

ESR study of irradiated single crystals of amino acids—I: Glutamic acid and glutamic acid hydrochloride

Abstract Single crystals of glutamic acid and l-glutamic acid HCl were λ-irradiated at liquid nitrogen temperature and the paramagnetic species formed were examined as a function of temperature by electron spin resonance techniques. The radicals observed in the temperature range 77–300 K include: HOOCCH 2 CH 2 C H ( NH + 3 ) , HOOCCH 2 CH 2 CH ( NH + 3 ) C OOH - , HOOCCH 2 CH 2 CHCOOH , HOOCCH2CH2C (NH+3) COO- and HOOCCHCH2CH (NH+3) COO-. The formation of these radicals was rationalized by a sequence of reactions which involve initially formed cation and anion radicals.

Radiation-Induced Copolymerization of Fluorine-Containing Monomers

Abstract Radiation-induced copolymerizations of various monomers, including perfluoro-olefines with CF2 O and of α-olefines with monochlorotrifluoro-ethylene, have been studied. It was found that CF2O can be copolymerized randomly via radical process, with most of monomers examined and that alternating copolymers can be obtained from the copolymerization of a-olefines with monochlorotrifluoroethylene. The structural study of these copolymers was carried out by infrared, X-ray diffraction and NMR measurements. The structure of isobutylene-monochlorotrifluoroethylene copolymer was determined precisely through proton and fluorine resonances.

Research and Development and Economic Growth in Japan

There is no question that science and technology play one of the most important roles in the economic growth of advanced countries. However, when one attempts to discover the relation between the effort devoted to research and development and the economic growth of a nation, it is not easy to find a simple correlation between them.

Design and operational features of the low temperature fissiochemical loop

A low temperature in-pile loop for the irradiation of chemical reactants, especially by fission fragments, has been designed, constructed and operated successfully. The main features of the loop are briefly described: the capsule for sample irradiation, the design and performance of the helium cooling system and safety considerations. Gaseous chemical reactants charged in an instrumented double capsule at pressures up to 20 kg/cm2, can be irradiated in a nuclear reactor at any temperature between + 20° and – 190°C, for periods up to 5hr. The thermal performance of the helium cooling system was in good agreement with the design calculations. Irradiations of ethylene and other gases could be conducted at an absorbed fission fragment dose rate of about 20 Mrad/hr, which is several times larger than the background reactor radiation. Thus, chemical reaction studies by fission fragments can be safely conducted at. ambient to low temperatures in this loop.

ESR study on yields and distribution of radicals in organic compounds irradiated with fast neutrons

Abstract Several organic compounds were subjected to the irradiation of fast neutrons, and the yields of free radicals and their spatial distributions were investigated by means of ERS in comparison with the results of γ-irradiation. The microwave saturation behavior of the radicals indicate that the local concentration of radicals are approximately 2 times larger in the neutron irradiated samples than in the γ-irradiated ones. The ratio of G -value of radical formation by neutron irradiation to that by γ-irradiation was found to be very high for aromatic compound compared with non-aromatic compound.

Radiation-Induced Polymerization of Tetrafluoroethylene in Solution

Abstract Polymerization of tetrafluoroethylene in monochlorodifluoromethane was carried out at low temperatures with -prays from a 60Co source. An activation energy of 4.3 kcal/mole was obtained for the in-source polymerization, and this is higher than that of bulk polymerization, 2.7 kcal/mole. It was found that a remarkable postpolymerization takes place even if the reaction system is in liquid state. A kinetic treatment for the postpolymerization is described.

Deposition of model crud on boiling zircaloy surfaces at high temperature

The deposition experiments were carried out under high pressure (7 MPa) at 285/sup 0/C using model compounds (..cap alpha..-hematite) to investigate the deposition process of crud on boiling surfaces. The effects of several factors, such as the diameter of the model particles (0.15 to 2.3 ..mu..m), pH (7 to 13), and heat flux of the heated surfaces (5 to 16 W/cm/sup 2/), on the deposition rate during the initial stage were investigated. It was found that the deposition rate of the hematite particle, having a narrow particle size distribution, strongly depends on the particle diameter and pH of the crud suspension. An explanation of these results was based on the assumption that the electrokinetic interaction between the particle and the surface plays an important role in the deposition process of the crud particles. Furthermore, it was found that the deposition rate of the hematite, having a narrow particle size distribution, deviates from the linear proportionality.