There are all sorts of manifestations of these forces, some with high temperatures, some with low temperatures, and some with in between temperatures.
When you say something is "impossible" you really do have to say WHY.
The reason cold fusion (or if you want, call it “LENR”) is impossible has been explained many times.
Shoving two particles of the same polarity together to form an atom of a different identity—e.g. shoving nickel and hydrogen together to form copper—takes a LOT of energy.
Mathematically, the process is impossible. But math is sometimes imprecise.
When the particles are far apart, it is easy to push them together. But it becomes logarithmically more difficult the closer they get, until the energy required asymptotically approaches infinity. That energy barrier is what people refer to as the Coulomb force. In reality, at very high temperature (like that found inside a star), it is possible to overcome the Coulomb barrier on very small atoms—like a hydrogen and a helium, which have +1 and +2 charges, respectively—because the high temperature represents a huge amount of energy. But, as I saw two physicists describe it in a blog, there isn’t enough energy in the universe to overcome the Coulomb barrier of a nickel nucleus (charge of +28).
And that is why Rossi’s claims are not believable.