The TMI-2 scenario

The March 1979 accident of the Three Mile Island Unit 2 (TMI-2) pressurized water reactor is discussed. It was the most severe accident to occur in a commercial operating power reactor in the United States. The progression of the TMI-2 accident was mitigated by the presence or injection of cooling water. The reactor vessel did not fail. TMI-2 represents a source of information that can be used to expand upon the present knowledge of severe accident and core melt progression and the associated behavior of fission products, and to possibly mitigate severe accidents before the reactor vessel and containment are threatened. Although the consequences of the accident were restricted-- primarily to the reactor vessel itself--the potential consequences were significant enough to warrant close study of all aspects of the accident. Although there was significant release of krypton and xenon during the accident, the extent of core damage, including fuel melting, was not confirmed until 1982, when a camera was first lowered into the core region, and a debris bed was observed at approximately 1.5 m below the top of the core region