  Consider a PEL-Shimura variety associated to a unitary group that splits over
an unramified extension of Q_p. Rapoport and Zink have defined a model of the
Shimura variety over the ring of integers of the completion of the reflex field
at a place lying over p, with parahoric level structures at p. We show that
this model is flat, as conjectured by Rapoport and Zink, and that its special
fibre is reduced.
