The radiation damage model in the Particle and Heavy Ion Transport code System (PHITS) uses screened Coulomb scattering to evaluate the energy of the target primary knock-on atom (PKA) created by the projectile and the “secondary particles,” which include all particles created from the sequential nuclear reactions. We investigated the effect of nuclear reactions on displacement per atom (DPA) values for the following cases using a copper target: (1) 14 and 200MeV proton incidences, (2) 14 and 200MeV/nucleon 48Ca incidences, and (3) 14 and 200MeV and reactor neutrons incidences. For the proton incidences, the ratio of partial DPA created by protons to total decreased with incident proton energy and that by the secondary particles increased with proton energy. For 48Ca beams, DPA created by 48Ca is dominant over the 48Ca range. For the 14 and 200MeV neutron incidences, the ratio of partial DPA created by the secondary particles increases with incident neutron energy. For the reactor neutrons, copper created by neutron–copper nuclear elastic scattering contributes to the total DPA. These results indicate that inclusion of nuclear reactions and Coulomb scattering are necessary for DPA estimation over a wide energy range from eV to GeV.