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Why is uranium dioxide used as fuel in most nuclear reactors?

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A color-coded periodic table of the elements displays each element's symbol and atomic number, with categories such as alkali metals, noble gases, halogens, transition metals, and actinoid elements distinguished by different background colors. — actinoid element Modern version of the periodic table of the elements (printable).

Uranium dioxide ( $U O_{2}$ ) is widely used as fuel in nuclear reactors because it possesses several unique properties that make it highly reliable and effective for power generation:

Refractory Nature: It is extremely heat-resistant, with a melting point exceeding 2,800 °C (5,100 °F), allowing it to withstand the intense thermal conditions inside a reactor.1
Radiation Resistance: Its open crystal structure allows it to retain fission products and accommodate changes in its oxygen-to-metal ratio during burnup, providing excellent resistance to radiation damage.1
Stability: It is inert to many reactor coolants and can undergo long periods of use without significant swelling.1
Fabrication: It can be efficiently processed into dense ceramic pellets, which are then loaded into zirconium alloy cladding tubes to form fuel rods.21

While it has relatively low thermal conductivity compared to other potential fuels, its overall performance and relatively low fabrication cost have made it the standard fuel choice for light-water reactors.21