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 pro-jectile and the ''secondary particles,'' which include all particles created from the sequential nuclear reac-tions. We investigated the effect of nuclear reactions on displacement per atom (DPA) values for the following cases using a copper target: (1) 14 and 200 MeV proton incidences, (2) 14 and 200 MeV/ nucleon 48 Ca incidences, and (3) 14 and 200 MeV and reactor neutrons incidences. For the proton inci-dences, 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 48 Ca beams, DPA created by 48 Ca is dominant over the 48 Ca range. For the 14 and 200 MeV neutron incidences, the ratio of partial DPA cre-ated 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. Ó 2012 Elsevier B.V. All rights reserved.