A method of producing energy from condensed hydrogen clusters created from the desorption of hydrogen atoms from a primary material. The method of producing energy from condensed hydrogen clusters generally includes positioning at least a desorbing side of a primary material within a sealed reactor chamber. Mono-isotopic hydrogen atoms are absorbed by the primary material. Condensed hydrogen clusters are formed from the desorption of the hydrogen atoms from the primary material. Stability of the condensed hydrogen clusters is maintained by prevention of covalent bond formation and recombination into hydrogen molecules. A nuclear reaction and spallation of the stable condensed hydrogen clusters is initiated to produce reaction products. Energy may be harvested from the reaction products, such as through a coolant.