Why is the study of severe accidents important?
The NRC studies severe accidents because it is our mission to protect the safety of the public and the environment. One way we study accident progression is to understand historical events. In 1979, the only U.S. commercial power reactor core melt accident occurred at Three Mile Island (TMI) Unit-2, and resulted in extensive fuel damage (see the illustration to the left). As a result, radioactive gases and contaminated cooling water were released to the containment. In addition, a small amount of radioactive material was released to the atmosphere through an indirect route. However, the containment itself performed as designed, and kept the vast majority of radioactive material safely inside. The actual release had negligible effects on the physical health of individuals or the environment, according to comprehensive investigations and assessments by several well respected organizations. (For additional detail, see the Backgrounder on the Three Mile Island Accident.) A much more seriou
