Three Mile Island

Days after the 1979 accident, Three Mile Island plant technicians enter the containment building housing the disabled Unit 2 reactor.

This Thursday marks the 40th anniversary of the accident at Three Mile Island’s Unit 2, then a newly minted nuclear reactor that had been running for a mere 90 days.

It took years to determine, but we now know that the accident caused a partial meltdown of the reactor core and instantly cooled the movement for nuclear power in the United States.

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The accident, which began at 4 a.m.  March 28, 1979, was caused by a combination of human error, design deficiencies and equipment failures.

When word got out, thousands of Lancaster County residents fled the area, and the fears of those first few days are still burned into the collective consciousness of a generation.

The impact of what happened on an island in the Susquehanna River profoundly affected both the nuclear industry and the public’s attitude toward power from the atom.

Waves of “lessons learned” required U.S. nuclear plants to be retrofitted with added safety features. Among them, fire protection, piping, containment building isolation and a plant’s ability to shut down automatically, independent of human operators.

The role of human error in the accident let to increased operator training and added staffing. Though there was no evidence of substance abuse by TMI operators, control room staffers are now subjected to testing for alcohol or drug use.

Emergency preparedness both by the plant and for those living close to a nuclear facility were revamped. And the U.S. Nuclear Regulatory Commission now has at least two in-house inspectors daily at each plant.

Before the accident, owners of nuclear plants did not have to have money saved and set aside for the eventual closure and dismantlement of plants. Now they do.

Did the accident harm anyone?

Multiple studies by the NRC, three federal agencies, the state and two universities all concluded that the small amount of radiation released during the accident had negligible effects on residents, plants or animals living near the plant.

But because measuring health effects is an inexact science and the factor of latency periods and scant cancer inventories at the time, to this day there is still debate over cancers.

Some who have developed cancers continue to blame TMI. Suspicions are fueled by the fact that Pennsylvania has one of the highest rates in the country for thyroid cancer, the cancer most associated with radiation exposure.

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