The anomalous nuclear phenomena observed in intermittent neutron emission and the extremely large branching ratio (105–108) of tritium to neutron production are associated with coherent phonon excitation and de‐excitation due to phase transitions in the low temperature PdDx deuteride. The non‐linearity, which comes from the many‐body effect of the surrounding atoms of deuteron and palladium in the phase transition, plays an important role in the intermittent neutron burst and in generating a larger fusion reaction rate than the fusion rate calculated by screened Coulomb potential, based on the mean field theory.