What happens to radioactive waste?
Nuclear power is an amazing technology, but cleaning up after it isn’t simple
Disposing of the by-products of nuclear power is no simple task
How do you store waste when its dangers could outlast the human species? It’s a question we need to address after harnessing the awesome power of nuclear energy.
Nuclear fuel is usually a radioactive-enriched uranium pellet. About three atoms in every hundred are in a form called uranium-235. A uranium pellet is a small cylinder of uranium-235 about a centimetre long and wide. This nuclear pellet releases as much energy as burning a tonne of coal. Most often power plants use pellets sealed in fuel rods made of an alloy of the metal zirconium. Bundling rods together speeds up their radioactive decay in a chain reaction that releases heat. In power plants, these are covered in water. The steam that comes off drives turbines and generates electricity without releasing the greenhouse gas carbon dioxide, which is causing climate change.
The clues to the origins of the power and danger of nuclear energy are in its name. The laws of physics say when the nucleus at the heart of an atom is stable, and when it isn’t. It’s all down to the number of protons and neutrons in the nucleus. For example, in one form of uranium, the number of protons and neutrons means that the nucleus falls apart, or decays, easily. Part of the nucleus flies away as radiation, releasing energy as it does. When uranium fuel rods are bundled tightly together, the radiation from one rod triggers a uranium atom in a rod nearby to decay. That can then trigger another atom to decay, and another. Nuclear power plants are designed to keep this chain reaction going safely.
Eventually, the fuel rods release less energy, and then they must be replaced. But they’re still very hot, and could be deadly if not handled carefully. A bundle of unshielded fuel rods could still release enough radioactive energy to kill you
“Uranium-235 in waste fuel rods makes them dangerous – and useful”