It’s 1,000 lbs (not 100, as previously stated in error), and encased in a titanium sphere. This titanium sphere would likely survive re-entry if it is not damaged, and release the hydrazine once it is finally damaged enough by either the re-entry process or impact with the surface.
See How does shooting down a satellite help? over in GQ for more facty goodness.
It becomes increasingly obvious that this is not a safety measure, it is an ASAT weapons test.