  A self-consistent model of the chemical evolution of the globular cluster NGC
6752 is presented to test a popular theory that observed abundance anomalies
are due to ``internal pollution'' from intermediate mass asymptotic giant
branch stars. We simulated the chemical evolution of the intracluster medium
under the assumption that the products of Type II SNe are completely expelled
from the globular cluster, whereas material ejected from stars with m < 7 M_sun
is retained, due to their weak stellar winds. By tracing the chemical evolution
of the intracluster gas, we tested an internal pollution scenario in which the
Na- and Al-enhanced ejecta from intermediate mass stars is either accreted onto
the surfaces of other stars, or goes toward forming new stars. The observed
spread in Na and Al was reproduced, but not the O-Na and Mg-Al
anticorrelations. In particular, neither O nor Mg are sufficiently depleted to
account for the observations. We predict that the Mg content of Na-rich cluster
stars should be overwhelmingly dominated by the 25,26Mg isotopes, whereas the
latest data shows only a mild 26Mg enhancement and no correlation with 25Mg.
Furthermore, stars bearing the imprint of intermediate mass stellar ejecta are
predicted to be strongly enhanced in both C and N, in conflict with the
empirical data. We find that while standard AGB stellar models do show the hot
H burning that seems required to explain the observations, this is accompanied
by He burning, producing primary C, N, Mg and Na (via HBB) which do not match
the observations. (Abridged)
