[en] The binary alloy 85Ni-15Cr swells during neutron irradiation in a manner that is quite unrepresentative of either simple austenitic alloys or pure nickel. The nickel-chromium system is known to exhibit ordering out of reactor and this alloy was used to test the concept that alloys which develop order exhibit lower swelling rates. Chromium additions appear to depress swelling in nickel initially but also appear to suppress the tendency for swelling to saturate at high exposure. Below a transition temperature near 540⁰C the swelling is relatively sluggish and is quite insensitive to irradiation temperature. Above the transition temperature the swelling behavior is more complex but typical of austenitic alloys. The swelling transition temperature is thought to be related to the critical temperature for order-disorder transformation

[en] A refractory alloy irradiation series involving four discharged of the Materials Open Test Assembly (MOTA-1B through MOTA-1E) has been completed. This experiment contains pure Mo, Mo-41Re, TZM and Nb-1Zr. Irradiation temperatures in this experiment ranged from 404 to 730 degree C with neutron exposures yielding 8.7 to 110.8 dpa. Measurement of density changes and disk bend testing are planned to begin shortly

[en] The austenitic stainless steel designated as AISI 316 is currently being used as the major structural material for fast breeder reactors in the United States, Britain and France. Efforts are now underway in each country to optimize the swelling resistance of this alloy for further application to both fission and fusion power generating devices. The optimization effort requires knowledge of the factors which control swelling in order that appropriate compositional and fabricational modifications can be made to the alloy specification. The swelling data for this alloy are reviewed and the conclusion is reached that optimization efforts must focus on the incubation or transient regime of swelling rather than the post-transient or ''steady-state'' regime. Attempts to reduce the swelling of this steel by solute modification have focused on elements such as phosphorus and titanium. It is shown that the action of these solutes is manifested only in their ability to extend the transient regime. It is also shown that irradiation at high helium/dpa ratios does not appear to change the conclusions of this study. Another important conclusion is that small differences in reactor environmental history can have a larger influence than either helium or solutes. 31 refs., 27 figs., 1 tab

[en] This paper explores the response of three different materials to high fluence irradiation as observed in recent fusion-related experiments. While helium at fusion-relevant levels influences the details of the microstructure of Fe--Cr--Ni alloys somewhat, the resultant changes in swelling and tensile behavior are relatively small. Under conditions where substantially greater-than-fusion levels of helium are generated, however, an extensive refinement of microstructure can occur, leading to depression of swelling at lower temperatures and increased strengthening at all temperatures studied. The behavior of these alloys is dominated by their tendency to converge to saturation microstructures which encourage swelling. Irradiations of nickel are dominated by its tendency to develop a different type of saturation microstructure that discourages further void growth. Swelling approaches saturation levels that are remarkably insensitive to starting microstructure and irradiation temperature. The rate of approach to saturation is very sensitive to variables such as helium, impurities, dislocation density and displacement rate, however. Copper exhibits a rather divergent response depending on the property measured. Transmutation of copper to nickel and zinc plays a large role in determining electrical conductivity but almost no role in void swelling. Each of these three materials offers different challenges in the interpretation of fission-fusion correlation experiments

[en] The overall objective of this effort was to determine the origin of the sensitivity of void swelling and microstructural evolution in irradiated metals to environmental and material variables. A more specific objective was to assist in the interpretation of the results of the ⁵⁹Ni doping experiment designed to study the separate and synergistic effects of helium and other variables. Two of these variables are cold working and phosphorus content. 14 refs., 7 figs

[en] In three recent comparative studies in HFIR and EBR-II where the effect of helium and solid transmutants could be assessed, it was found that in each case there was no significant perturbation of the macroscopic property change under consideration. These findings reinforce the belief that fast reactors can serve as a major tool for fusion materials studies and that the effects of helium and other transmutants can be treated as second-order perturbations to be studied by other methods. A number of new fusion-relevant insights derived from fast reactor studies are presented

[en] The individual and synergistic influences of seven major and ten minor solutes on the swelling of 316 stainless steel were investigated in an irradiation experiment conducted in EBR-II. All elements exert their influence on the duration of the transient regime of swelling, through their effect on both vacancy diffusivity and precipitate evolution, often causing a complex response with increasing solute level. On a per atom basis, phosphorus is the most effective and consistent suppressor of swelling. Trace elements were found to have no significant effect. No combination of these elements appears to suppress the tendency of this steel to swell at -1%/dpa following the transient regime. 21 refs., 6 figs

[en] The steady-state swelling rate of EBR-II irradiated ternary alloys with less than or equal to 35% nickel appears to be approximately 5% per 10²² n cm^-2 (E > 0.1 MeV) or 1%/dpa, independent of chromium and/or nickel content and also independent of the irradiation temperature in the range 400 to 600⁰C. The duration of the transient regime of swelling is sensitive to these three variables, however, tending to increase with increasing nickel or temperature or decreasing chromium content. A similar relative independence of the steady-state swelling rate on temperature has been also observed in commercial stainless steels, which also appear to be approaching a swelling rate of 1%/dpa at high fluence. There is some evidence that elemental segregation plays a role in the compositional dependence of swelling

[en] When fcc metals and alloys are irradiated at elevated temperatures, they tend to evolve toward saturation microstructures that are independent of the starting state of the metal and the early details of irradiation history. This leads to property changes and rates of dimensional change that also eventually become independent of the starting state. The evolution of microstructure in complex alloys, especially during the transient regime, is usually determined by the complex interaction of many microstructural and microchemical processes. The more complex the alloy, the more difficult it is to-identify and define the separate influence of each participating mechanism. The use of irradiation studies conducted on simple metals or model alloys assists in understanding the behavior of alloys of engineering relevance. A review of such studies shows that a number of prevailing perceptions of radiation-induced microstructural evolution are not universally correct

[en] In three recent comparative studies in HFIR and EBR-II where the effect of helium and solid transmutants could be assessed, it was found that in each case there was no significant perturbation of the macroscopic property change under consideration. These findings reinforce the belief that fast reactors can serve as a major tool for fusion materials studies and that the effects of helium and other transmutants can be treated as second-order perturbations to be studied by other methods. A number of new fusion-relevant insights derived from fast reactor studies are presented