Radioactive particles inside or outside the body can kill human cells or alter their behaviour. Damaged cells can become cancerous. Large doses kill outright, small doses can take 40 years to show. One millionth of a gram of plutonium can cause lung cancer. So radiation from the nuclear industry is still to be paid for in unknown numbers of lives.
Nuclear waste is the unacceptable face of nuclear electricity.
It is also a security risk. It has to be isolated from the environment for a quarter of a million years or it will cause cancers. The several tons of waste per week from the British reprocessing plant at Sellafield is causing great radioactive contamination. More than a quarter of a tonne of plutonium has been discharged into the Irish Sea, making it one of the most radioactive in the world. The desperate search for ways to dispose of radioactive waste goes on.