Decay, Radioactive 08 : The decrease in the amount of any radioactive material with the passage of time, due to spontaneous nuclear disintegration (i.e., emission from atomic nuclei of charged particles, photons, or both)
National Environmental Policy Act (NEPA), Glossary of Terms Used in DOE NEPA Documents, US Department of Energy, Office of NEPA Policy and Compliance, USA 1998. http://energy.gov/sites/prod/files/NEPA_Glossary%2 008_2011.pdf, (EHS - Amer) {515}