  Using the Bethe ansatz method, the zero frequency contribution (Drude weight)
to the spin current correlations is analyzed for the easy plane
antiferromagnetic Heisenberg model. The Drude weight is a monotonically
decreasing function of temperature for all 0<Delta< 1, it approaches the zero
temperature value with a power law and it appears to vanish for all finite
temperatures at the isotropic Delta=1 point.
