Three Mile Island

The Three Mile Island Accident

On 28 March 1979, there was an accident at the Three Mile Island nuclear power station near Harrisburg, Pennsylvania. A relatively minor malfunction in the secondary cooling circuit caused the temperature in the primary coolant to rise. This in turn caused the reactor to shut down automatically. At this point a relief valve failed to close, but instrumentation did not reveal this, and so much of the primary coolant drained away that the residual decay heat in the reactor core was not removed. The core suffered severe damage as a result.

Aftermath

There were no injuries or adverse health effects to the public from this accident. Although some radioactive gas was released a couple of days after the accident, it was not enough to cause any dose above regular background levels to local residents.

Lessons Learned

This accident highlighted the need for a consistent and coherent public information and communication strategy. The accident at Three Mile Island was accompanied by communications problems that led to conflicting information available to the public. This contributed to the public's fears about the accident.

The accident also highlighted the need for both national and international plans to handle a peacetime nuclear emergency.

Positive Outcomes

As a direct result of this nuclear incident and the crash of COSMOS 954 in the Northwest Territories, the Canadian government established the Federal Nuclear Emergency Plan (FNEP) in 1984. This plan was developed to coordinate the federal government's response to a peacetime nuclear emergency, like the one at Three Mile Island.

In addition to the FNEP, Canada and the United States created the Canada-United States Joint Radiological Emergency Response Plan (JRERP), an agreement ensuring mutual assistance in the event of a peacetime radiological event that could affect either, or both, countries.