I have recently seen an interesting theory posted to explain some of the issues which would make cold fusion impossible, in particular the coulomb barrier and lack of gamma or neutron emission. The theory is that in nickel hydride, with the right conditions of temperature and energy pumped into the system via electromagnetic fields, that electrons will occasionally somehow merge with the proton in the hydrogen or deuterium by an inverse beta decay event.
That's the same as the Widom and Larsen "theory". It's complete nonsense. Inverse beta decay requires an energy input of 700,000 eV. The mean thermal energy in a block of hot metal is somewhere around 0.1 eV. It's not just
unlikely to find fluctuations that high---it's an explicit violation of the 2nd law of thermodynamics. (Extracting a neutron's worth of energy from a heat bath, as this would, would decrease its entropy. You could collect neutrons leaking out of a heat, move them to an even hotter bath to decay, and run a heat engine on the difference.)
Second, manufacturing neutrons in a block of nickel does
not lead to "heat". It leads to
thermal neutrons. Nickel is not a particularly good neutron absorber; a good fraction of neutrons must escape. A 10kW generator would be making 10^16 neutrons per second (a million curies). That's not "we were able to detect some radiation above background". That's "everyone in the room died and was buried in a lead coffin". The radiation accident that killed Louis Slotin gave him a 21 Sv dose; it's equivalent to absorbing 10^15 neutrons
total.
The strongest neutron source I've ever used was
one curie. It was not in a small pipe wrapped in tinfoil in front of a room full of journalists. It was wrapped was in a lead "pig" with foot-thick walls; everyone in the room was wearing radiation badges; only the radiation-safety officer was allowed to handle the pig itself.
Third, how big an idiot does one have to be to announce that "neutrons" are a quiet, nonradioactive way of "turning nickel into copper"? Putting neutrons into nickel turns it into radioactive nickel, primarily 59Ni, a bit of stable 61 and 62, and a bit of 63Ni. 59Ni turns into
cobalt over 100,000y, and 63 turns into copper of 100y.