Pretty much immediately.
When I first learned how a nuclear power plant works, I thought that couldn’t possibly be right. It seemed so absurdly simple.
In the broadest sense, a nuclear plant is no different from a coal plant, or a natural gas plant. All of them are, essentially, steam engines. They use heat to boil water to make steam, and that steam drives a turbine that makes electricity. The only difference between them is
- The emissions they create
- The fuel they need
- How efficiently they use that fuel
When a nuclear plant splits atoms the only thing they use that energy for is to boil water.
Even at nearly 40 years old that STILL blows my mind. When I was a kid I was sure there had to be some science fiction process that goes on in a nuke plant, like something out of Half Life. But no. The inside of a nuclear plant is just this.
Only it burns uranium instead of coal.
So to answer the question, scientists realized that nuclear energy could make electricity the moment they discovered how much heat is generated by fission. Because that’s how humans had been generating power for over a century.