of these decisions has been demonstrated over many years of operation of EBR-II. Advantages Breeder reactors (such as the IFR) could in principle extract almost all of the energy contained in uranium or thorium, decreasing fuel requirements by nearly two orders of magnitude compared to traditional once-through reactors, which extract less than 0.65% of the energy in mined uranium, and less than 5% of the enriched uranium with which they are fueled. This could greatly dampen concern about fuel supply or energy used in mining. What is more important today is why fast reactors are fuel-efficient: because fast neutrons can fission or "burn out" all the transuranic waste (TRU) waste components (actinides: reactor-grade plutonium and minor actinides) many of which last tens of thousands of years or longer and make conventional nuclear waste disposal so problematic. Most of the radioactive fission products (FPs) the reactor produces have much shorter half-lives: they are intensely radioactive in the short term but decay quickly. The IFR extracts and recycles 99.9% of the uranium and Transuranium elements on each cycle and uses them to produce power; so its waste is just the fission products; in 300 years their radioactivity will fall below that of the original uranium ore. The fact that 4th generation reactors are being designed to use the waste from 3rd generation plants could change the nuclear story fundamentally—potentially making the combination of 3rd and 4th generation plants a more attractive energy option than 3rd generation by itself would have been, both from the perspective of waste management and energy security. "Integral" refers to on-site reprocessing by electrochemical pyroprocessing. This separates spent fuel into 3 fractions: 1. Uranium, 2. Plutonium isotopes and other Transuranium elements, and 3. Nuclear fission products. The uranium and transuranium elements are recycled into new fuel rods, and the fission products are eventually converted to glass and metal blocks for safer disposal. Because fractions 2 and 3 (the combined transuranium elements and the fission products) are highly radioactive, fuel-rod transfer and reprocessing operations use robotic or remote-controlled equipment. This is also claimed to be a feature; not a bug; since fissile material that never leaves the facility (and would be fatal to handle if it did) greatly reduces the proliferation potential of possible diversion of fissile material. Safety In traditional light water reactors (LWRs) the core must be maintained at a high pressure to keep the water liquid