The world needs a new source of energy, an unspillable source.

fusion in fission reactor?

why doesn’t fusion reaction occur in reactors using heavy water as coolant?
I do not mean chain reaction. Even a few instances.
As for as I know, energy of the liberated neutrons is about 1 MeV, while fusion of deuteron requires about 5GeV. But if it is so, than how they create fusion in bombs. And if some other metal is used in fusion bombs, than why cant they add it to reactors ?