Today In History

On March 29, 1978 at the Three Mile Island nuclear power plant located near Harrisburg, Pennsylvania, there was an accident and part of the core in the # 2 reactor melted. Some radioactive gas was released but no deaths or injuries were reported to local residents. When the accident occurred, the # 2 reactor was operating at 97% power. There was a minor malfunction in the secondary cooling circuit which caused the temperature in the primary coolant to rise, which caused the reactor to shut down automatically in one second. A relief valve failed to close, and most of the primary coolant drained away, resulting in the core damage. The operators were unable to diagnose the problems or respond timely or properly to the unplanned automatic shutdown of the reactor. Deficient control room instrumentation and inadequate emergency response training proved to be primary causes of the accident. The cleanup of the damaged nuclear reactor system took nearly 12 years and cost approximately one billion dollars. The cleanup was uniquely challenging. Plant surfaces had to be decontaminated, water used and stored during the cleanup had to be processed, and 100 tons of damaged uranium fuel had to be removed. For 18 years, The Pennsylvania Department of Health maintained a registry of more than 30,000 people who lived within five miles of Three Mile Island at the time of the accident. The state's registry was discontinued in mid-1997, with no evidence of unusual health trends in the area