Ethan Siegel does a thorough job of discussing why it is unlikely that the E-Cat is fusing nickel into copper, as Rossi claims. To summarize: We know that nickel does not fuse into copper even inside stars. If the extreme heat and pressure of stars is not enough to result in this fusion, it's unlikely adding a few catalysts under moderate pressure will do so.
Fusion should produce a lot of radiation, including high energy gamma rays. None were detected, and if they were present much greater shielding would be needed to protect anyone near the device. This is pretty much a deal-killer – no radiation = no fusion.
In prior tests the copper found in the device after alleged fusion took place had the same isotopic ratio as normal copper, which would not be the case if the copper were freshly made by adding a proton to nickel. Also, by Siegel's calculations there was more copper found in the device than would have resulted from even a completely efficient fusion process.
From a scientific point of view, the claims made for cold fusion in the E-Cat device are extremely improbable, and the evidence we have does not support such claims. We don't have a clear scientific explanation for how the device can work, with evidence (in terms of output products and radiation detection) that match predictions from a specific model.
What we do have are very curious anomalies.
http://theness.com/neurologicablog/index.php/e-cat-cold-fusion-claims-are-back/
