The results of tensile testing involving Waspaloy indicate that the failure strain was gradually reduced at temperatures ranging between ambient and 300°C. Further, serrations were observed in the engineering stress versus strain diagrams in the temperature range of 300-600°C. The reduced failure strain and the formation of serrations in these temperature regimes could be the result of dynamic strain aging of this alloy. The extent of work hardening due to plastic deformation was reduced at temperatures above 300°C. A combination of ductile and intergranular brittle failures was seen at temperatures above 600°C. c¢ was detected at all tested temperatures.

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Transmutation of nuclear waste is currently being considered to transform long-lived isotopes to species with relatively short half-lives and reduced radioactivity through capture and decay of minor actinides and fission products. This process is intended for geologic disposal of spent nuclear fuels for shorter durations in the proposed Yucca Mountain repository. The molten lead-bismuth-eutectic will be used as a target and coolant during transmutation, which will be contained in a subsystem vessel made from materials such as austenitic (304L) and martensitic (EP-823 and HT-9) stainless steels. The structural materials used in this vessel will be subjected to welding operations and plastic deformation during fabrication. The resultant residual stresses cannot be totally eliminated even by stress-relief operations. Destructive and nondestructive techniques have been used to evaluate residual stresses in the welded and cold-worked specimens. Results indicate that tensile residual stresses were generated at the fusion line of the welded specimens made from either austenitic or martensitic stainless steel, with reduced stresses away from this region. The magnitude of residual stress in the cold-worked specimens was enhanced at intermediate cold-reduction levels, showing tensile residual stresses in the austenitic material while exhibiting compressive stresses in the martensitic alloys. Comparative analyses of the resultant data obtained by different techniques revealed consistent stress patterns.

Austenitic Alloy 617 has been identified as a candidate structural material in hydrogen generation using nuclear heat. A temperature of 950°C has been recommended to achieve the maximum efficiency in hydrogen generation involving numerous chemical reactions. The tensile properties of this alloy have been determined at temperatures ranging from ambient to 1000°C. Simultaneously, the fracture toughness of this alloy is being evaluated using fracture-mechanics-based compact tension specimen. This paper presents the results of tensile testing of this alloy as a function of temperature. The results of fractographic evaluations using scanning electron microscopy are also included.

Transmutation of spent nuclear fuels (SNF) is currently being considered to transform long-lived isotopes to species with relatively short half-lives and reduced radioactivity through capture and decay of minor actinides and fission products. This process is intended for geologic disposal of SNF for shorter durations in the proposed repository at the Yucca Mountain site. The structural material (Type 304L stainless steel/Alloy EP-823) surrounding the transmutation target will be subjected to welding operation and plastic deformation during fabrication, which could induce residual stresses in it. Destructive ring-core, and nondestructive x-ray diffraction, neutron diffraction, and positron annihilation spectroscopic techniques were used to evaluate residual stresses in welded and cold-worked specimens of both materials. The results indicate that, in general, for a welded specimen consisting of Alloy EP-823 and Type 304L stainless steel on opposite sides, compressive and tensile residual stresses were observed in the former and latter materials, respectively. However, a welded specimen consisting of only Alloy EP-823 on both sides showed tensile residual stresses. The extent of residual stresses in cold-worked specimens was enhanced with increased level of cold-reduction. In case of a bent specimen, compressive and tensile residual stresses were noticed in the convex and concave sides, respectively.