Neither Magnox nor Advanced Gas Reactors have effective secondary containment. Indeed the containment structures of European reactors which are meant to withstand the effects of an internal explosion are inadequate. The Chernobyl reactor was the most successful Soviet model - much of its technology was similar to that in the West and it had a number of extra safety features. Political leaders do not seem to understand this. 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.