Nuclear power plants took on increased restrictions on radioactive waste material after the Three Mile Island accident in 1979. The DPRI (Electric Power Research Institute) underwent an in depth research program to investigate fission behavior in severe accident scenarios. The EPRI program included experiments to obtain fundamental data and the development of computer-based models. After the accident, many international organizations got involved in similar research programs. In the study it will show what happened on Three Mile Island and the new safety precautions that have revolutionized the new standards for nuclear power plants.