This report presents the results of progress made during the first year of a three year program on the investigation of swelling mechanisms in refractory metals irradiated at elevated temperatures, i.e. 0.3 T sub m - 0.6 T sub m (where T sub m = melting point in K). The objective of this work is to achieve an understanding of the elevated temperature swelling in these body centered cubic (bcc) metals by a close coupling of theoretical development and experimental verification. Originator supplied keywords include: Swelling, Radiation effects, Ion bombardment, Refractory metals, Theory of swelling, Ion-simulation irradiation.

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Studies on the effects of heat-treating and testing environments for the refractory metals have been limited primarily to the unalloyed metals and a few alloys of columbium and molybdenum. Most of this work has relied on compositional changes as a means of assesing the effects of various environments on these materials. It has been shown that all of these materials are subject to contamination or purification in various test environments. The residual gases H2, CO(or N2), and H20, constitute the major sources of contamination when testing columbium and tantalum materials in vacua. Under the same conditions, molybdenum and molybdenum alloys containing carbon and reactive-metal additions are subject to serious decarburization. Nonreactive gaseous atmospheres also cause serious changes in material chemistry, since small quantities of noxious gases are contained in the atmosphere. Several promising methods of circumventing material chemistry changes during various longtime, high-temperature exposures are being used and/or evaluated. (Author).