International Journal of Radiation Applications and Instrumentation. Part C. Radiation Physics and Chemistry最新文献

The results of theoretical and experimental investigations of SO₂ oxidation in an air flow by a high current pulse electron beam and impulse corona discharge are presented in this work. It was shown that in non-equilibrium plasma and in a certain range of current density and humidity the energy cost of oxidation is significantly reduced to a value corresponding to the chain character of the process. These results were explained by realization of the ion-molecule chain SO₂ oxidation mechanism and confirm the effect of non-equilibrium plasma catalytic activity in chemical reactions. It was shown that ion-molecular chain processes in droplet phase can also cause additional reduction of oxidation energy costs.

The influence of high energies on a gas stream under certain conditions, may produce sulphuric acid. In this case a degree of gas purification of sulphur dioxide of up to 99% is obtained, and energy expenditure is 0.2–1.0 kW per 1 kg of final product. Describing these processes may be recommended as part of their future development and industrial and commercial realization.

The purpose of this paper is to outline the electron beam window efficiency and its ability to operate at electron beam power levels approaching MW in geometries suitable for process stream. A windowless high power electron accelerator designed as a point source can offer: compact construction, high energy and high beam power operation, no window is required (primary or secondary), no losses in the output system and better performance in efficiency and cost when beam power level is above 500 kW. The following disadvantages are considered for windowless accelerators: the necessity of using a multistage vacuum pump system, non-homogeneity of dose distribution, additional processes caused by higher temperature levels and no experience in flue gas application.

Laboratory experiments on irradiation induced aerosol formation from gaseous sulphur dioxide in humid air are presented. This work is connected to the aerosol particle formation process in the electron beam technique for cleaning flue gas. As a partial process of this method primary products of the radiolysis of water vapour convert sulphur dioxide into gaseous sulphuric acid which then nucleates with water vapour forming small acid droplets. This experimental work has been performed on relatively low absorbed doses. Aerosol particle formation is strongly dependent on dose. In the experiments, the first aerosol particles were detected already on absorbed doses of 0.1–10 mGy. The particle size in these cases in the so-called ultrafine size range (1–20 nm). In this article three experimental set-ups with some characteristic results are presented.

The technological scheme and main parameters of the test facilities for removal SO₂ and NO_x from exhaust gases of the “Southern” Moscow power plant by using electron beam treatment have been represented. The possibility of improvement of the efficiency of the electron beam clean-up process of the gases by aerosol water spraying has been considered.

An experimental facility for electron beam treatment of simulating flue gas has been constructed at SINR Academia Sinica. The process for removal of SO₂ and NO_x in flue gas was investigated. In particular, several important parameters, such as the irradiating dose absorbed, temperature of reaction and stoichiometry of ammonia, were studied. A by-product, a compound of ammonium sulphate and ammonium sulphate-nitrate, that can be used as agricultural fertilizer was checked and measured. The removals of SO₂ and NO_x were 92 and 77.5%, respectively, with an absorbed irradiating dose of 17 kGy.

It was shown in Part I of this series (Crouzet and Marchal, 1992) that the overall effect of nitroxyl radical > NO derivatives of hindered aliphatic amines (HA) on the kinetics of the γ-radiation-induced autoxidation of 2,4-dimethylpentane (DMP) samples in open glass test tubes at 25°C with I = 72 rad min^-1 is similar to the effects, at the same concentration (ca 3 × 10^-2 M) of BHT (Ionol) which is a typical chain-breaking phenolic antioxidant even though the mechanisms of action of the two kinds of inhibitors are quite different. This result must originate from the competition of the trapping of alkyl radicals and H atoms by O₂ and > NO.

To get a quantitative answer to this problem, the modelling of the kinetics of the decrease of the oxygen concentration [O₂] in liquid samples undergoing γ-radiation-induced autoxidation is established and applied to our DMP samples. The conclusion of this modelling is that [O₂] reached a constant value very close to the initial equilibrium value [O₂]₀. Thus the study of the competition itself is possible.

The modelling is also done for liquid samples undergoing chemically-induced autoxidation by AIBN thermolysis at 60°C and applied to DMP. It appears that analysis of chemically-induced autoxidation as is usually done is not appropriate for such a study though interesting because H atoms are not produced.

A digital system was designed to control a 4 MeV Van de Graaff electron accelerator by a desktop computer for automatic performance of routine procedures like the daily conditioning of the accelerator or the formation of a new injector cathode. The modifications of the accelerator controls, the interface and a new voltage stabilizer circuit are described and the voltage conditioning and the cathode formation procedures are discussed.

The nature and distribution of radioactive species resulting from (nγ) neutron-capture reactions in the metal atoms of zirconocene dichloride and molybdocene dichloride were investigated. Retention values of 20.22, 12.63 and 20.23% were obtained for Zr-95, Zr-97 and Mo-99 respectively. β-Transformation in ⁹⁵Zr-zirconocene dichloride and ⁹⁹Mo-molybdocene dichloride led to approximately 80% of the respective daughters Nb-95 and Tc-99m being retained at the same molecular form as the parent.

For the simple liquid-core optical waveguide dosimeter (consisting of: LED-OWG dosimeter-neutral OWG-photodiode), changes of the light spectrum transmitted through the OWG dosimeter were studied as a function of absorbed dose (from 1 to 10 Gy). From these spectral data (differential approach) the values of absorbance vs dose, as if they were measured with a photodiode, were derived, and intercompared with the directly measured ones by a PIN photodiode (integral approach). The agreement was better than ±5%. The influences of errors in optical misalignment, “dark” current, light intensity reading were quantitatively estimated and discussed.