  Globular clusters host multiple stellar populations that display star-to-star
variation of light elements that are affected by hot hydrogen burning (e.g.,
He, C, N, O). Several scenarios have been suggested to explain these
variations. Most involve multiple star formation episodes, where later
generations are born from material contaminated by the nucleosynthetic products
of the previous stellar generation(s). One difficulty in the modelling of such
scenarios is knowing the extent to which processed and pristine material are
mixed. In this context, beryllium abundances measured in turn-off stars of
different generations can provide new information. Beryllium originates from
cosmic-ray spallation and can only be destroyed inside stars. Beryllium
abundances can thus directly measure the degree of pollution of the material
that formed stars in globular clusters. Turn-off stars in globular clusters are
however faint and such studies are beyond the capabilities of current
instrumentation. In this work, we show the progress that the CUBES spectrograph
will bring to this area. Our simulations indicate that CUBES will enable the
detection of variations of about 0.6 dex in the Be abundances between stars
from different generations, in several nearby globular clusters with turn-off
magnitude down to $V$ = 18 mag.
