ABSTRACT

“Low energy nuclear reactions” or LENR is the name now given to what was initially and poorly called “cold fusion”.  Over twenty years of scientific research on LENR have resulted in very solid experimental results, especially from electrochemical loading of deuterons into Pd.  It seems possible to trigger nuclear reactions, which yield MeV energies, with chemical energies on the order of 1 eV.  Some instances of energy gains exceeding 10 have been reported.  That gain is the same value as the goal of the International Thermonuclear Experimental Reactor, which might be achieved in about a decade. In the past two years, engineered LENR systems reportedly have energy gains exceeding 100.  The devices, which were said to exhibit such very high energy amplification values, used gas loading of protons into Ni.  Lower gain versions of such systems are now being mass manufactured for delivery to customers during 2011.  If successful, the initial products promise two significant impacts: (a) accelerated acceptance of the reality of LENR and (b) increased funding for LENR research and engineering.  Despite both scientific and engineering progress, several challenges remain. The most important is the fundamental understanding of LENR.  None of the two dozen theories on LENR is fully satisfactory.  And, a great deal of work remains on the engineering optimization of LENR energy sources.  A comparison of the history and prospects for both hot and “cold” fusion will be presented. It is concluded that small and distributed LENR sources of energy, which are safe and produce no residual radioactivity, might be in common use by the time hot fusion in large central facilities is finally ready for commercialization.