Nuclear waste is caused by industrial, scientific and medical processes that use radioactive materials. The most significant source of nuclear waste is a nuclear reactor. Fuel used in nuclear reactors to generate heat for electricity becomes nuclear waste after it has been used for years.
Industrial causes of nuclear waste include operations carried out by nuclear power stations, producing radioactive waste. Nuclear waste can generate low to medium radiation over a long period of time. The radioactivity resulting from nuclear waste can then propagate through soil, water and air, causing extensive pollution. Nuclear waste cannot be treated or degraded biologically or even chemically; therefore, it poses long-term hazards to all living organisms.
Mining and refining activities of thorium and uranium are also major causes of nuclear waste. The mining of radioactive ores, such as phosphate and uranium ores, involves crushing processes that generate radioactive by-products.
The nuclear fuel cycle, mostly used in medical, industrial and scientific processes, also releases nuclear waste. Spent fuel is dangerously radioactive, and it remains toxic for many years. This type of fuel can never be used unshielded. It is normally kept under water for a few years until the radiation reduces to levels that can be accommodated by the concrete in large storage casks.
To curb nuclear pollution, vitrification can be used for both long-term storage and disposal of nuclear waste.