ydinpolttoaineissa

Ydinpolttoaineissa refers to the materials that serve as energy sources in nuclear reactors. Most commonly the term denotes uranium‑235 and plutonium‑239, isotopes that can sustain a controlled chain reaction. In nuclear power plants, these isotopes are contained in metal or ceramic fuel forms that are inserted into reactor cores.

The primary fuels are natural uranium, low‑enriched uranium, and mixed‑oxide (MOX) fuel. Natural uranium contains about 0.7 % of the fissile isotope U‑235, which is insufficient for most commercial reactors and must be enriched to 3–5 % for light‑water reactors. MOX fuel combines plutonium recovered from spent fuel with depleted uranium, offering a way to reuse fissile material.

The nuclear fuel cycle begins with mining and milling of uranium ore, producing yellowcake. The yellowcake is then converted to uranium hexafluoride gas for isotope enrichment. After enrichment, the uranium is fabricated into fuel rods or plates, which are loaded into reactor vessels. Following approximately 3–5 years of irradiation, the spent fuel is cooled in spent‑fuel pools or dry casks before final disposal or reprocessing.

Safety concerns center on controlling reactivity, preventing overheating, and containing radioactive releases. Strict regulatory frameworks govern each stage of the fuel cycle, from mining to final disposal, to mitigate environmental and human health risks.

Globally, the nuclear fuel cycle supports commercial electricity generation, research reactors, and naval propulsion. Advances in burnable poisons and advanced reactor designs aim to reduce waste and improve fuel utilization, while reprocessing technologies are being explored to recover more usable plutonium and reduce the volume of high‑level waste.