The Collaborative International Dictionary of English v.0.48:

brisance \bri"sance\ n.
   the shattering or crushing effect of a sudden release of
   energy as in an explosion; -- used especially as a measure of
   such a shattering power, applied to high explosives.
   [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

brisance
    n 1: the shattering or crushing effect of a sudden release of
         energy as in an explosion