THERMONUCLEAR An adjective referring to the process in which very high temperatures are used to bring about the fusion of hydrogen nuclei with the accompanying liberation of energy. A thermonuclear device is one in which part of the explosive energy results from thermonuclear fusion reactions. The high temperatures required are obtained by means of a fission explosion. X-RAYS Penetrating electromagnetic radiation similar to gamma rays but of non-nuclear origin and of lower energy. YIELD The total effective energy released in a nuclear detonation. It is usually expressed in terms of the TNT equivalent required to produce the same energy release in an explosion. Nuclear detonation yields are commonly expressed in kilotons or megatons (thousands or millions of tons) of TNT equivalent. Many of the definitions cited above have been adapted from Glasstone and Dolan; Atomic Energy Commission, Nuclear Terms; and Bureau of Radiological Health Publication Number 2016. 209