Radiation Effects In Materials Research Articles

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The Use of Accelerators to Study Irradiation Effects in Materials

There is currently high interest in the use of accelerators to study irradiation effects in materials to be used in reactors. The effects produced by heavy ion irradiation (e.g., nickel ions irradiating stainless steel) and fast neutron irradiation are qualitatively similar. Time to achieve the damage state characteristic of end-of-life service is hours as compared to several years in available reactors. Some of the successes in this area are described herein as well as some of the many problems to be solved in order to establish quantitative relationships.

Defects in Crystals

One of the most important applications of the electron microscope in recent years has been to the observation of defects in crystals. Replica techniques have been widely utilized for many years for the observation of surface defects, but more recently the most striking use of the electron microscope has been for the direct observation of internal defects in crystals, utilizing the transmission of electrons through thin samples.Defects in crystals may be classified basically as point defects, line defects, and planar defects, all of which play an important role in determining the physical or chemical properties of a material. Point defects are of two types, either vacancies where individual atoms are missing from lattice sites, or interstitials where an atom is situated in between normal lattice sites. The so-called point defects most commonly observed are actually aggregates of either vacancies or interstitials. Details of crystal defects of this type are considered in the special session on “Irradiation Effects in Materials” and will not be considered in detail in this session.

Neutron-Spectra Calculations for Radiation-Damage Studies

Fast-neutron spectra were computed using three different codes: GNU-II, HFN, GE -HAPO-S-X. Significant diffurences in spectra were seen as codes with varying degrees of refinement were used. GE -RAPO-S-X was chosen for calculating cross section values and testing damage models because of its greater accuracy and wider applicability. The calculations illustrate spectral differences existing at different points in a reactor lattice. The spectra are used to compute relative activation for such fast-neutron flux monitor materials as Ni/ sup 58/, Fe/sup 54/, and Am/sup 243/ and to calculate gross vacancy production using widely varying damage models. From the results it was concluded that calculation of spectra in irradiation facilities is necessary for the proper reduction of monitor activities to neutron exposures and for correlation of observed radiation effects in materials irradiated in dissimilar facilities. (auth)

Radiation Chemistry of Organic Compounds

Radiation Chemistry of Organic Compounds By Dr. A. J. Swallow. (International Series of Monographs on Radiation Effects in Materials, Vol. 2). Pp. xiii + 380. (London and New York: Pergamon Press, 1960.) 84s. net.

Radiation Effects in Materials

A review is given of the mechanisms of radiation damage, and of some of the resulting effects. The discussion is divided into three categories: (1) mechanisms of damage production, (2) nature and mobility of the imperfections produced, (3) effect of the imperfections on the measurement of the properties of the solid. Principal attention is given to metals, with related observations in semiconductors cited.