  The beta delayed deuteron emission from $^6$He is studied in a dynamical
microscopic cluster model. This model gives a reasonably good description for
all the subsystems of $^6$He and $^6$Li in a coherent way, without any free
parameter. The beta decay transition probability to the $^6$Li ground state is
underestimated by a few percents. The theoretical beta delayed deuteron
spectrum is close to experiment but it is also underestimated by about a factor
1.7. We argue that, in spite of their different magnitudes, both
underestimations might have a common origin. The model confirms that the
neutron halo part of the $^6$He wave function plays a crucial role in quenching
the beta decay toward the $\alpha$ + d channel.
