  The processes of defect formation and annealing in fullerene C60 at
T=(4000-6000)K are studied by the molecular dynamics technique with a
tight-binding potential. The cluster lifetime until fragmentation due to the
loss of a C2 dimer has been calculated as a function of temperature. The
activation energy and the frequency factor in the Arrhenius equation for the
fragmentation rate have been found to be Ea = (9.2 +- 0.4) eV and A = (8 +-
1)10^{19} 1/s. It is shown that fragmentation can occur after the C60 cluster
loses its spherical shape. This fact must be taken into account in theoretical
calculations of Ea.
