The study of nuclear reactions in condensed matter – typically within the lattice of a highly hydrided metal like palladium. The history of CMNS is long, stretching back over 90 years to the very first fusion experiments conducted using linear accelerators (source)

Low Energy Nuclear Reactions (source)

Lepton Hadron Conversion Loop (source)

The third process of nuclear energy production, next to fusion and fission.
It is nucleosynthesis, resulting from radiative n-capture, e-capture, beta decay, and quasiparticle assisted weak nuclear transformations or QAWNT (isotopic shifts and transmutations) (source)

Quasiparticle-assisted weak nuclear transformation (source)