His name was initially Nathaniel Tryon, who was a security guard at a nuclear power plant. He and two other thugs formed the TNT Trio and broke into the power plant. They were caught in a nuclear meltdown were Nathaniel would have to wear a containment suit for the rest of his life. He had managed to obtain superstrength and the ability to fire radioactive blasts. He used these powers to try and kill those he thought were responsible, but was stopped by Superman. Abraxas Industries would later have him released as part of a work release program, though it was actually a plot by Vandal Savage to kill Superman. Savage's scheme would be revealed however and Neutron would be returned to prison. He was later held at S.T.A.R. labs with the villainess Jinx. He and Jinx were freed by the Fearsome Five and joined the team, though Neutron quickly left the team. He eventually came to work for the villain Conduit, and was sent with Warp and Plasmus to kill Jonathan and Martha Kent. Superman managed to defeat the team however. Neutron later joined the Secret Society of Supervillains. He was apparantly killed when Lex Luthor used him as a power source for a teleporter and the device self destructed.
Neutron appeared in Justice League Unlimited as a member of Grodd's Legion of Doom. He was killed during the mutiny along with the other villains that sided with Grodd. He also appeared in Smallville along with Parasite, Livewire, and Plastique. This team was searching for Doomsday and Neutron would be killed after letting him get away the first time.