Gamma Reactor

The Gamma Reactor was an experimental energy device designed by Dr. Bruce Banner. It's intended purpose was to generate electricity using gamma radiation. It was provided by Stark Enterprises.

However, the device was sabotaged by Leader. The resulting explosion turned Banner into Hulk while the surrounding wildlife became the Outcasts. While cleaning up the mess, Leader mutated into a different kind of gamma radiated creature.

Background
The reactor was used to replace the gamma bomb from the comics. The comics used the bomb because of the ongoing Cold War and both sides designing bigger and more powerful bombs. By the time was being made, the Soviet Union had collapsed and the Cold War ended. Additionally, a year after Hulk debuted the United States signed the Partial Nuclear Test Ban Treaty refraining from above ground nuclear weapons testing. The reactor gave the series a more believable contemporary version of the classic origin.