Almost all Generation IV systems use a closed fuel cycle design or, in the case of the VHTR and MSR, offer the possibility of a closed cycle through the use of

thorium-based fuel. Fuel recycling technology is therefore an essential element of Generation IV systems. However, current technology, which involves the separation of pure plutonium oxide, does not meet the GIF requirement for proliferation resistance (Abram and Ion, 2008). Several alternative technologies are under development, which could provide significant improvements in both the safety and economics of closed cycle plants. These are discussed below.