  It is well known that no time-independent galactic cosmic ray (GCR) flux
model can account for the observed linear relationship of Be and B abundances
with metallicity. In this contribution we solve the time-dependent CR
propagation equation using simple analytic time dependences for the CR spectrum
at the source, the galactic CR escape-length and gas density evolution. The CR
fluxes so obtained are used to study the early evolution of the LiBeB
abundances in the Galaxy.
