Dr. William Lettis is an invited participant to the International Atomic Energy Agency (IAEA) working committee to update Specific Safety Guide (SSG) -35 “Site Survey and Site Selection for Nuclear Installations”. In addition to a general update of the entire Safety Guide, Dr. Lettis is responsible for developing the seismic ground motion and permanent ground deformation (e.g., surface fault rupture) criteria for site screening and site selection. In addition to providing recommendations and guidance on the siting of a nuclear installation at a new site, the Safety Guide also provides recommendations and criteria for locating a new installation at an existing site. In particular, the new safety guide addresses the siting of next generation Small Modular Reactors (SMRs), microreactors and floating reactors, as well as conventional large, water-cooled reactors. The two-year working committee will complete its recommended update to SSG-35 at the end of 2026.