The purpose of this Sandia National Laboratories' sponsored study is to support existing and future activities under the National Nuclear Security Administration (NNSA) Office of Radiological Security (ORS) program to reduce the use of high-risk radiological materials in commercial applications. The study will update the 2008 National Academies consensus study on “Radiation Source: Use and Replacement” by reviewing the current state of high-risk radionuclide applications by sector (e.g., industrial, research, medical, and other commercial applications) and by reviewing the current state of existing technologies on the market that are or could be used to replace radioisotopic technologies in those applications.