Fabrication of a simple material system for study of Hg in a stainless steel

The Spallation Neutron Source (SNS), currently under construction at Oak Ridge National Laboratory, is expected to employ a Hg target encased in a stainless steel. Little is known about the metallurgical behavior of this materials engineering system, which will occur in a service environment involving elevated temperatures and intense radiation. Under normal equilibrium conditions, however, Hg is known to be insoluble in and non-reactive with solid Fe and Cr but to form one or more intermetallics with Ni. Hg has been implanted into alloy 304L. After implantations at 400 and 500 C to a fluence of 3 x 1016 cm-2 sub-micron sized precipitates of Hg are formed, as judged, for example, from their solidification behavior on cooling during TEM observation. The formation of such a system of micro-targets and possible studies employing them as in situ TEM specimens are discussed, which can provide useful empirical information in conjunction with SNS target development