  We develop a fast and accurate machine-learned interatomic potential for the
Mo-Nb-Ta-V-W quinary system and use it to study segregation and defects in the
body-centred cubic refractory high-entropy alloy MoNbTaVW. In the bulk alloy,
we observe clear ordering of mainly Mo-Ta and V-W binaries at low temperatures.
In damaged crystals, our simulations reveal clear segregation of vanadium, the
smallest atom in the alloy, to compressed interstitial-rich regions like
radiation-induced dislocation loops. Vanadium also dominates the population of
single self-interstitial atoms. In contrast, due to its larger size and low
surface energy, niobium segregates to spacious regions like the inner surfaces
of voids. When annealing samples with supersaturated concentrations of defects,
we find that in complete contrast to W, interstitial atoms in MoNbTaVW cluster
to create only small ($\sim 1$ nm) experimentally invisible dislocation loops
enriched by vanadium. By comparison to W, we explain this by the reduced but
three-dimensional migration of interstitials, the immobility of dislocation
loops, and the increased mobility of vacancies in the high-entropy alloy, which
together promote defect recombination over clustering.
