In the last few decades, several scientific papers have reported experimental evidence of anomalous nuclear reactions occurring in condensed matter during electrolytic phenomena or mechanical instabilities such as fracture (in solids) and cavitation (in liquids). Despite the numerous research activities carried out in the field of the so-called “Cold Nuclear Fusion”, it remains today not fully understood. As already treated in Chaps. 10 and 11 , the formation of cracks on the external surfaces of the electrodes used during electrolysis tests, together with chemical composition changes and anomalous subatomic particle emissions, are detected. A macromechanical interpretation of the experimental evidence can be based on low-energy phono-fission nuclear reactions, which are a consequence of hydrogen embrittlement, microcracking, and THz phonons. In the present chapter, the results of four identical experimental test repetitions with Pd and Ni electrodes are discussed. In particular, the excellent repeatability of nuclear and stoichiometric balances between the chemical compositions of both electrodes, before and after the test, is consistently emphasized.