Nuclear and radiation accidents happen when there is a malfunction that causes too much radiation to be released. Radiation is a type of energy that can be very dangerous, and too much of it can cause sickness and even death. Nuclear accidents usually happen in big factories that make lots of energy from nuclear energy, and radiation accidents happen when radiation sources like medical x-rays are not used or handled carefully. In both cases, people can get very sick from the radiation, so it's very important that people are very careful with nuclear and radiation sources.