  We consider deuteron formation in heavy ion collisions at intermediate
energies. The elementary reaction rates (Nd -> NNN) in this context are
calculated using rigorous Faddeev methods. To this end an in-medium Faddeev
equation that consistently includes the energy shift and Pauli blocking effects
has been derived and solved numerically. As a first application we have
calculated the life-time of deuteron fluctuations for nuclear densities and
temperatures typical for the final stage of heavy ion collisions. We find
substantial differences between using the isolated and the in-medium rates.
