Quick search by citation:

42 U.S. Code § 9302 - Definitions

For the purposes of this chapter—
(1)
fusion” means a process whereby two light nuclei, such as deuterium and tritium, collide at high velocity, forming a compound nucleus, which subsequently separates into constituents which are different from the original colliding nuclei, and which carry away the accompanying energy release;
(2)
magnetic fusion” means the use of magnetic fields to confine a very hot, fully ionized gas of light nuclei, so that the fusion process can occur;
(3)
energy system” means a facility designed to utilize energy released in the magnetic fusion process for the generation of electricity and the production of hydrogen or other fuels;
(4)
fusion engineering device” means a magnetic fusion facility which achieves at least a burning plasma and serves to test components for engineering purposes;
(5)
demonstration plant” means a prototype energy system which is of sufficient size to provide safety, environmental reliability, availability, and ready engineering extrapolation of all components to commercial size but which system need not be economically competitive with then alternative energy sources; and
(6)
Secretary” means Secretary of Energy.