Nuclear power phase-out is when a country decides to stop using nuclear power as a source of electricity. This happens when a country decides that the risks of using nuclear power outweigh the benefits. Nuclear power produces a lot of energy, but it also produces things like radioactive waste, which is very dangerous. In a nuclear power phase-out, the country gradually shuts down all its nuclear power plants, and looks for other ways to get electricity. This could be through renewable sources like solar or wind, or through other forms of non-renewable energy like coal or natural gas.