The reactor core is a nuclear battery that powered a Providence research ship.
During one night, the research ship was attacked by Serge to prevent it from entering his territory. The ship sunk with the reactor core, but the radioactive rods inside the core became a threat to the mainlands and the seas. Doctor Holiday helped organize a mission for Agent Six and Rex to retrieve the rods that could've already been leaking radioactivity. In the ocean, they entered Aquania and met Serge. He told them about the cores and felt that they would be a major liability to the sea's pollution. Later, he even considered leaving the cores when the research ship began to fall beneath a sea trench. Eventually, Serge helped Rex retrieve the rods before they were crushed by the water's pressure and disposed of them.
- 202. "Waste Land"