A group of 10 countries (Argentia, Brazil, Canada, France, Japan, Republic of Korea, South Africa, Switzerland, UK and US) are working together specifically to develop a roadmap to pursue R & D on future Generation IV systems (Generation IV Nuclear Energy Systems, 2003). These innovative reactor systems are described in subsequent chapters. The GIF initiative is relatively recent, starting in January 2000 and initiated by the United States Department of Energy (USDOE). The objectives are to develop future reactor systems that are competitively priced, while addressing safety, waste, proliferation and public perception concerns. The reactors cover water, gas-cooled thermal and fast spectra, liquid metal (sodium, lead and lead-bismuth) cooled and molten salt designs.