Development of the JENDL special purpose data file for PKA spectra, DPA cross sections and kerma factors

Method of calculation of the neutron-induced primary knock-on atom spectra, atom displacement cross sections and kerma factors is presented based on the nuclear data from the evaluated data file of ENDF/B-5 format, supplementing the emitted charged particle spectra from nuclear cross section calculation code. Approximate and compact formulas of DPA cross section and kerma factor were derived for the reaction sum involving multi-particle emissions. The formulas are valid for medium and heavy mass nuclei. Examples of calculation on iron are given for neutron energies up to 40 MeV. Comparison was made with the kerma factor calculated by Howerton and Caswell et al. below 20 MeV and the DPA cross section with RADHEAT-V4 and TENJIN-2 code below 15 MeV. It is shown that the high energy kerma factor is governed by the charged particle emission, while the high energy DPA cross section is mainly determined from neutron optical potential. (author)