  The dynamical evolution of entanglement between two polarizable two-level
atoms in weak interaction with electromagnetic vacuum fluctuations is
investigated. We find that, for initial Bell state $\psi^{\pm}$, the decay rate
of entanglement between atoms is just the superradiant spontaneous emission
rate, which depends not only on the spontaneous emission rate of atom but also
on the modulation of the spontaneous emission rate due to the presence of
another atom. It is shown that, with the presence of a boundary, the
entanglement between transversely polarizable atoms can be protected for a very
long time. It is pointed out that when the two atoms in initial Bell state
$\psi^{-}$ are put close enough , the entanglement between them can also be
protected.
