Answer:
a process that involves rearrangement of the molecular or ionic structure of a substance, as distinct from a change in physical form or a nuclear reaction
25 gigaseconds is equal to 2,500,000,000,000 centiseconds
The first step is splitting the atoms. Then there are control rods that absorb free floating nerons that are a result of fission. Next they heat they water pipe. Finally when they heat the pipe and water it turns to steam and they use it to harness energy!