The rapid growth of human economy in the late 20th century gave rise to great concern over sustainability of the world. A pessimistic “Full World Model” forecasts that human economy could not develop further. The nuclear fission (and fusion later), however, could release huge amount of energy to create sufficient useful material resources and turn the said pessimistic modelinto a new optimistic “Sustainable World Model”.The dilemma of nuclear energy (Military Giant vs. Civil Dwarf) jeopardizes its performance as a “Technologic Fixer”. According to Mother Nature’s teachings, the elimination of the root-causes of the design-based risk factors could solve this problem. Recent technology break-through from inherent safety to natural safety has been made in China. The proposed full-power natural circulation “Nuclear Hot Spring (NHS)” reactor could operate solely on natural forces without complex man-made coolant circulation equipment and human-operated control systems. The cheap, unlimited supply of energy from nuclear energy could change the geopolitics forever, and finally eliminate the root-causes of most international and regional conflicts.