R&D for the Spallation Neutron Source mercury target

An overview of the research and development program for the Spallation Neut ron Source (SNS) is presented. The materials-related efforts in target deve lopment are emphasized in order to provide a perspective for a number of sp ecialized papers that are included in these proceedings. We give a brief in troduction and historical sketch of the SNS project. Part of the materials R&D consists of calculations of radiation damage and of transmutation rates . He and H are considered to be the most important transmutation products. Radiation effects and Hg compatibility investigations make up the major par t of the experimental effort. In the former, spallation irradiations are ca rried out in the LANSCE at Los Alamos National Laboratory and in the SINQ a t the Paul Scherrer Institute. Irradiations that simulate aspects of a spal lation environment are included to extend the parameter space of the spalla tion irradiations. The simulations are carried out at the low energy (MeV) accelerators of the TIF facility and at the HFIR reactor, both located at O ak Ridge National Laboratory. Irradiated specimens are tested for changes i n mechanical properties and are characterized with respect to microstructur al changes by transmission electron microscopy. The compatibility experimen ts cover both the effects of Hg on behavior in mechanical properties tests, and the effects of flowing Hg on mass transfer in target structural materi als. The results of this extensive program of materials work indicate that the target design and materials performance will meet their intended servic e. Published by Elsevier Science B.V.