Radiation Physics and Chemistry (1977)最新文献

A method of simultaneously removing sulfur dioxide and nitrogen oxides from high sulfur, coal-fired utility boiler combustion gases is discussed. Process development history is briefly presented and salient details of a commercial demonstration unit currently under construction at an electric utility power plant in Indiana are given. Detailed discussion on the design details and performance requirements of a cable connected set of 80 kW electron beam sources precedes a discussion of the projected economics of the process. Requirements for future electron beam machine configurations and capacities as well as impact on the radiation machine manufacturing industry, assuming acceptance of the process by the electric utilities, are presented.

A generalized kinetic mechanism for radiation induced oxidation of nitrogen oxides from exhaust gases in the absence of sulfur dioxide is formulated. The responses obtained by the mathematical simulation are in good agreement with reported experimental results.

Although the industrial exploitation of radiation processing in the medical and allied fields has been successfully marketed and applied for the past two decades in South Africa, the introduction of food radurisation on an industrial level adds a completely new dimension to the marketing of this processing technique. Extensive research into the use of radiation for the treatment of various foodstuffs has been carried out by the Nuclear Development Corporation of South Africa for more than a decade, resulting in South Africa being one of the first countries where a commercial irradiator dedicated to this branch of radiation processing, was established. The marketing of this process is especially difficult due to the emotive aspects associated with radiation and man's sensitive reaction to anything pertaining to his food. This situation was made even more difficult by the general public's apprehension towards nuclear activities throughout the world. In an attempt to transform the unfavourable public image associated with this process, an important first step was to form a National Steering Committee for the Marketing of Radurised Food, the members of which were drawn from various agricultural controlling bodies, the Department of Health, and other controlling bodies held in high esteem by the public, such as the Consumer Council and representatives from commerce and industry. This approach proved to be very successful and greatly assisted in creating a climate whereby the public in South Africa today generally has a favourable attitude towards the radurisation of foodstuffs. The development of this marketing strategy for food radurisation in South Africa is discussed in detail.

The magnetic media industry is studying means to improve the recording density, durability, product uniformity and production efficiency and to reduce wetting agent migration in the magnetic film. The use of electron beam curable resin binders for magnetic coatings is one of the approaches being studied for this.

This paper compares the wetting efficiencies of several electron beam curable systems with a conventional resin and a conventional wetting agent. In this study it has been demonstrated that EB resins can be designed to effect proper magnetic pigment dispersion.

The radiation effect of various pH values on polyvinyl alcohol aqueous solutions and on organic solutions, as well as those of scavengers in the aqueous solutions were examined. The gelation dose R_g changes with various pH values; a small amount of free radical scavengers in the system inhibits the crosslinking of polymer molecules and raises R_g. Degradation of polyvinyl in alcohol dimethyl sulfone solution occurs after irradiation, providing a mechanism of radiation-induced crosslinking of polyvinyl alcohol aqueous solutions is initiated by the transient species H and OH of water, but not the species e^-_aq.

The problem of delocalization of the energy initially absorbed by the medium is considered. We present a rigorous derivation of the formula for the delocalization due to the uncertainty principle for particles of arbitrary velocity. Using the value of the effective range of the electromagnetic field of a moving particle, we estimate the dimensions of the collective excitation area. We also discuss the possible radiation-chemical consequences of the initial delocalization of the energy absorbed by the medium.

Carbon dioxide based gas mixtures, similar to those used as coolants in the Advanced Gas-cooled Nuclear Reactors, have been radiolyzed at the comparatively low dose rate of 3 Gy s^-1 using γ-radiation from a ⁶⁰Co source. The concentrations of certain C₄ and C₅ alkanes, ethanal and propanone, produced by radiolysis, have been determined under different conditions of temperature, pressure, gas composition, and surface area. Observations showed that these compounds were produced in concentrations of the order of 1/1000 of the methane concentration and that the production of these “trace organics” varied in a complex way with the experimental parameters. Mechanisms for the production of these organics have been proposed. Some unidentified products of radiolysis were observed and suggestions are made as to their nature.

An accurate and inexpensive spectrophotometric readout method is given for free radical dosimetry. The stable free radicals in irradiated alanine/glutamine powder, when dissolved in a solution containing ferrous ammonium sulphate and xylenol orange in 0.05 N H₂SO₄(FX), oxidize ferrous ions and the xylenol orange forms a complex with ferric ions produced in the solution. The absorbance of the complex is measured at 525 nm for alanine and at 540 nm for glutamine. The influence of various parameters, such as size of the container, weight of the powder dissolved, xylenol orange concentration, purity of distilled water, postirradiation stability and dose-rate dependence on the response of the dosimetric technique, has been investigated. It was found that the dosimetric response is independent of dose-rate. Alanine does not show any significant postirradiation fading. Irradiated glutamine powder is stable for about a month, the fading is less than 2% up to three months later, and it increases to only about 5% over a period of six months. The reproducibility of the method is better than ±2%, and it offers an alternative to ESR and lyoluminescence techniques for free radical dosimetry. A dose of 0.01 to 4 kGy can be measured with an alanine dosimeter and 0.1 to 100 kGy with a glutamine dosimeter. Empirical relationships between absorbance and dose are given.