IFMIF-DONES (International Fusion Materials Irradiation Facility- DEMO Oriented NEutron Source) is a neutron irradiation facility aiming at providing material irradiation data for the construction of DEMOnstration fusion power plants. This work presents nuclear analyses and associated neutronics modeling conducted on an updated design of the High Flux Test Module (HFTM) of IFMIF-DONES. Neutron fluxes, damage dose rates and gradients, gas production and nuclear heating have been calculated for the standard profile in 20 × 5 cm2 and a reduced size in 10 × 5 cm2 of the deuteron beam with 40 MeV energy and 125 mA current. The results indicate that the reduced beam can provide higher damage dose rates fulfilling the DONES requirement. On the other hand, the reduced beam size results in less irradiation uniformity, higher gas production to damage dose ratios, as well as stronger peak nuclear heating. •Comprehensive nuclear responses on the IFMIF-DONES high flux test module have been analyzed.•Comparisons have been made between the normal deuteron beam size and the reduced beam size.•The DONES irradiation capabilities have been studied for fulfilling the requirements of DEMO construction.