ืีNuclear energy was developed as an alternative to fossil fuels such as coal and oil for producing electricity. However, radioactive waste from nuclear generating plants now poses a serious health hazard. Leaks at nuclear plants also have threatened the lives of people who live near them. In order to prevent this, the nuclear reactor must have some protection like a thick steel shell and thick concrete structure around the radioactive core. For radioactive waste, technologists must cover it with lead, and then bury it in salt formations far underground.