It is shown by computer simulations that a diverging thermonuclear reaction wave in a high density plasma is an accelerating overcompressed detonation. The propagation stages of the reaction wave are classified according to different processes of energy transfer such as the α-particle diffusion, the shock heating and the electron thermal conduction. The front of the reaction wave consists of the shock compressed region proceeded by a pre-heating zone, where the effect of α-particle diffusion exceeds that of the electron thermal conduction.