What scares you most about nuclear waste?
Nuclear or Radioactive Waste - Types
Radioactivity (often but inaccurately called radiation) occurs when atoms spontaneously disintegrate, emitting high-energy particles called alpha and beta particles and gamma rays (similar to x-rays). There is a certain amount of natural background radioactivity, for example due to radon. If there is too much radioactivity, however, living tissues can be damage and cancer caused. Radioactivity is measured in Becquerel (Bq), but the absorbed dose is measured in grays (Gy) and the effective dose is measured in sieverts (Sv). The absorbed dose depends on the size of a body and its distance from the source of radioactivity. The effective does also takes into account the relative proportions of the different kinds of particles and how much damage each kind to do. Whether or not the does was inhaled or ingested also makes a difference.
Radioactive waste may contain a mixture of isotopes of different elements. Each isotope has a different half-life - the amount of time taken for it's radioactivity to be reduced by a half. For example, the main isotopes spread after the Chernobyl disaster were iodine-131 with a half-life of 8 days, and caesium-137 with a half life of 30 years. In contrast, plutonium 239 has a half-life of 24,200 years, plutonium 238 has a half-life of 87 years and iodine 129 has one over 15.7 million years.
Another factor affecting risk is the pathway that an isotope can take. For example, iodine becomes concentrated in the human thyroid and radioactive iodine can be removed from the body relatively quickly by taking ordinary iodine tablets. Other isotopes are not so easily removed and therefore may cause damage over a much longer period. The solubility of an isotope can also make a big difference to humans and the environment, and those which don't dissolve may concentrate in estuaries to be taken up and concentrated by marine creatures which become our sea food. This can lead to a delay between the initial fallout or contamination and the start of significant harm. It is important to keep radioactive waste out of the water, soil or the air.
One of the major problems with nuclear power is the safe disposal of radioactive waste. In the 1950s, this problem was dismissed. By the 1980s, however, it was seen as a major problem, and people were active in protesting about plans to store it near them.
Nuclear wastes come in varying degrees of radioactivity. High level radioactive wastes may be reprocessed. Reprocessing, or recycling, is chemical processing. Uranium and plutonium are recovered from spent fuel and can be used for weapons production, Reprocessing itself produces radioactive wastes, however. It increases the complexity and volume of waste without reducing the amount of radioactivity. Uranium ore tends to be cheaper than reprocessed fuel, and there is concern if weapons grade fuel is produced, so the repreocessed materials need to be guarded and reprocessing is not popular in all quarters. Magnox fuel (fuel rods encased in a magnesium alloy, an obsolete design) has to be reprocessed as it corrodes in ponds. It becomes unstable and unsafe. There are reprocessing plants in the UK (Sellafield - formerly Windscale), France and Russia.
High level radioactive wastes (HLW) are the spent nuclear rods after any reprocessing. They are cooled in ponds then vitrified and stored. They form a very small percentage of all radioactive waste. Any surplus plutonium is also considered HLW. One tonne of used nuclear fuel produces 0.1 cubic metres of HLW containing 99% of the radioactivity.
Intermediate level radioactive wastes (ILW) are encapsulated and stored. They comprise fuel cell cladding, and contaminated materials. They are far less radioactive than HLW. They may be encapsulated in cement in steel drums then stored. One tonne of used nuclear fuel produces 1 cubic metre of ILW containing 1% of the radioactivity.
Low level radioactive wastes (LLW), which tend to be bulky, are compacted and stored. They are items such as laboratory equipment, clothing and paper towels from nuclear plants, hospitals and other industries. A large volume also comes from the building materials of decommissioned power plants. The reactor buildings themselves are clad in concrete and left for decades on decommissioning. One tonne of used nuclear fuel produces 4 cubic metres of LLW containing 0.00% of the radioactivity.
Nuclear waste can cause disagreements between countries - for example, Ireland objects to the level of wastes discharged from Sellafield into the Irish Sea. The radioactive fallout from the Chernobyl accident fell over many European countries.
Some places that have radioactive wastes have large communities and workforces as a result of a variety of activities having been undertaken on site, for example Sellafield in the UK, Cap de la Hague near Cherbourg in France and Hanford Nuclear Reservation in Washington, USA. More recently a deep disposal facility has been established near Carlsbad, New Mexico, USA and at Gorleben, Germany.
Radioactive waste comes with various degrees of risk, both actual and perceived. People tend to be scared at the thought of radioactivity.
Radioactive waste disposal has to bear in mind the needs of future generations; sometimes many of them - the waste will remain radioactive long after the benefits of the nuclear power production have been enjoyed. Even the decommissioning of old nuclear power plants can take generations. Nuclear accidents such as Windscale (1956), Three Mile Island (1979), and Chernobyl (1986) have made people more mistrustful of safety claims. However, if we do not fins alternative fuels to replace fossil fuels as they run out, we may be left with no choice but to build more nuclear power plants, and therefore generate more radioactive waste.
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