As an integral part of the International Project on Innovative Nuclear Reactors and Fuel Cycles (INPRO), several collaborative projects were established by its members. The collaborative project Global Architecture of Innovative Nuclear Energy Systems Based on Thermal and Fast Reactors Including a Closed Fuel Cycle (GAINS) was one of them. This publication presents the study, its results and the conclusions drawn. A major achievement of the project is the development of a unique heterogeneous world model considering specific nuclear energy strategies of various States. This model simulates important realities of the global nuclear energy system thus enabling the assessment of resource, financial, and proliferation risks and identification of areas for beneficial multilateral cooperation. It shows that innovative nuclear technologies serve as a driving force for enhancing the sustainability features of nuclear energy supply, while a multilateral approach amplifies the positive effects of the technological innovations.