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How is low-enriched uranium used in light-water nuclear reactors?

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Enrichment of uranium — uranium processing How uranium is enriched to make a nuclear weapon.

Low-enriched uranium (typically 2 to 5 percent uranium-235) is essential for light-water reactors because ordinary water, which serves as both coolant and moderator, tends to absorb more neutrons than other moderators, necessitating a higher concentration of fissile material to maintain a chain reaction.12

To prepare this fuel, enriched uranium is converted into uranium dioxide powder, which is pressed into dense ceramic pellets and sintered in a furnace at high temperatures. These pellets are then loaded into zirconium alloy cladding tubes, which are sealed and bundled into fuel assemblies.342

Inside the reactor, these assemblies are arranged in the core to facilitate controlled nuclear fission, where the uranium-235 nuclei split to release thermal energy. Periodically, a portion of these fuel assemblies is removed and replaced with fresh ones to maintain optimal power distribution and reactivity.15