A dynamic model for nuclear emission by implosion of cavitation bubble is proposed, and the criteria (realizing conditions) for nuclear reaction are discussed by the methods of molecular kinetics. The hot core, in which the D+-D+ fusion may take place, has to have the minimum limit for its size, and the core radius with less than a few 10(-6) M cannot give rise to nuclear emission for C3D6O. There exist two critical radii, that is, the initial and upper critical radius for the bubble as well as the lower critical radius for the core (the final bubble). The upper critical radius must be several times larger than 10(-3) m. The relationships between the critical radii and the critical temperature are discussed. The confining time of the plasma energy in the core is calculated by the energy loss rate, and it is concluded that the nuclear reaction may be possible if both the radii are adequately large. Possibility of self-reproduction of the nuclear reaction is also discussed. (C) 2003 International Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.