Nuclear fuel spends five to six years in the reactor before it is removed and replaced with fresh fuel. In the United States, the spent fuel is removed and placed into storage until it can be disposed of. However, the fuel isn’t depleted; a great deal of energy–about 95 percent–remains in the pellets. In many other countries, the spent fuel is reprocessed and reused. The U.S., however, does not reprocess its spent fuel. Therefore, all the highly radioactive isotopes remain within it, and whole fuel assemblies are classified as high level waste. The disadvantage of this “once-through” fuel cycle is that partially used nuclear fuel is treated as waste, thereby increasing the volume and complexity of disposal.
High level waste is very radioactive; therefore, it requires special shielding during handling and transport. It also needs cooling, because it generates quite a lot of heat due to the high radioactivity level.
A typical large nuclear reactor produces 25-30 tons of spent fuel per year. Currently, spent nuclear fuel is stored in fuel pools until they are cool enough to be placed in robust “dry casks.” Dry casks consist of a steel cylinder the used fuel rods are placed in then surrounded by additional steel, concrete, or other material to provide radiation shielding. The casks are stored on-site at power plants throughout the United States.
Center for Nuclear Science and Technology Information of the American Nuclear Society
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