Adlep, somewhere in this thread, there's a detailed explanation about isotopes, and how Rossi's claims cannot possibly be true. I've been in labs with millions of dollars worth of equipment, all designed to study isotopes - the level of precision in measurements is astounding. E.g., the mass of nucleus with such precision that it would be like noticing while finding the weight of a Boeing 747 that the pilot in it had a quarter in his pocket that hadn't been accounted for.
Rossi isn't making claims on the frontier of science - he's making claims about things that are quite well understood. If there's something that mainstream science missed along the way, it would be just absolutely amazing. New discoveries in this field aren't made by individuals working in their garage with leftover plumbing parts. New discoveries in this field are made by teams of highly educated people, working with very expensive equipment. It's akin to NASA sending out astronauts to find a new asteroid between Mars and Jupiter, and someone else making the claim that they built a car in their garage and drove to the asteroid belt and found an asteroid shaped like one of the heads on Easter Island. When asked to examine the car, "no, you can't see it." When asked to examine the statue, "you can look at it, but you can't touch it."