I would like to draw a fundamental distinction between two classes of LENR systems: Fueled and unfueled systems. In the 2011 time-frame when Rossi saw gamma, he was running an unfueled system,so was Piantelli and Celani. Russ George is now experimenting with an unfueled system.
The development of LENR fuel came latter as an innovation by Rossi. I speculate that Rossi found that when he reused ash from his reactors, they were very LENR active. Rossi perfected LENR fuel and started to use it in his tube reactors. The fuel was self contained and could be loaded in air. With this fuel, the hydrogen nickel reaction did not seem to matter anymore. Lugano is an example, Also gamma commissions went away when using LENR Fuel. I beleive that the active agent in LENR fuel is ultra dense hydrogen. Rossi, me356, the ECCO reactor and the LION reactor all use LENR fuel. Gamma will not come from these systems since ultra dense hydrogen is a superconductor. UDH has a near perfect Q factor and forms a condensate immediately and instantly. I have advised any LENR reactor builders who will lessen to produce LENR fuel directly by acquiring a Holmlid UDH generator. Just load that UDH into a tube reactor and you are good to go.