  We show that the available constraints relating to $^{6}$LiBeB Galactic
evolution can be accounted for by the so-called superbubble model, according to
which particles are efficiently accelerated inside superbubbles out of a
mixture of supernova ejecta and ambient interstellar medium. The corresponding
energy spectrum is required to be flat at low energy (in E^-1 below 500 MeV/n,
say), as expected from Bykov's acceleration mechanism. The only free parameter
is also found to have the value expected from standard SB dynamical evolution
models. Our model predicts a slope 1 (primary) and a slope 2 (secondary)
behaviour at respectively low and high metallicity, with all intermediate
slopes achieved in the transition region, between 10^-2 and 10^-1 Z_sol.
