The boson tendency to clump deuterons in palladium, which is caused by an attractive force, supplies kinetic energy to deuterons moving toward the center of the cluster. On the other hand, repulsive forces between deuterons in the cluster reduce the tendency to clump. The deuteron with kinetic energy determined from these two forces may penetrate the barrier by a tunneling effect at the center of the cluster. In this research, the transmission coefficient and power density generated from cold nuclear fusion are calculated as functions of the number of deuterons included in the cluster. When a nonlinear screened deuteron-deuteron pair potential is used as a repulsion, power densities for clusters that include 24 deuterons are 10.8 W/cm3, which gives good fit to the experimental results of 10 W/cm3 by Fleischmann et al.