A world model to estimate the energy fraction supplied by nuclear power was developed. The world was divided into ten local regions, within each of which the interactions between economy, society, and technology were considered. Inter-regional interactions taking place through the markets of food and energies and through economic aids were also considered along with the interaction with global environment. Both the relational forms between global variables and the values of various coefficients were determined by the use of available data bases. The time-dependent factors for the policies to be taken and for the technological development in the future were introduced. Some example calculations are given.