Remembering Three Mile Island

On this solemn anniversary of the largest nuclear disaster on U.S. soil, our friends at Beyond Nuclear explore the legacy of this event – what we’ve learned, and what we still don’t know about the impact on the people and nature surrounding Three Mile Island.  

The disaster at Unit 2 of the Three Mile Island (TMI) nuclear power plant near Harrisburg, Pennsylvania, began on March 28, 1979. Today, 39 years later, the reality, of what really happened, and how many people it harmed, remains cloaked in mystery and misinformation. Unlike the popular catchphrase, TMI is a story of too  little  information.

What happened?

The two unit Three Mile Island nuclear power plant sits on an island in the middle of the Susquehanna River, just ten miles southeast of Harrisburg, Pennsylvania. TMI Unit 2 was running at full power, but had been commercially operational for just 88 days when, at 4 A.M. on Wednesday, March 28, 1979, it experienced either a mechanical or electrical failure that caused the turbine-generator and the nuclear reactor to automatically shut down.

The pressure and temperature in the reactor began to increase, but when a relief valve on top of the reactor’s primary coolant pressurizer stuck open, malfunctioning instrumentation indicated that the valve had shut. While cooling water emptied out of the reactor, operators mistakenly reduced the amount of cooling water flowing into the core, leading to the partial meltdown.

Workers deliberately and repeatedly vented radioactive gas over several days to relieve pressure and save the containment structure. Then came fears of a hydrogen explosion. But by April 1, when President Jimmy Carter arrived at the site, that crisis had been averted, and by April 27 the now destroyed reactor was put into “cold shutdown.” TMI-2 was finished. But its deadly legacy was to last decades.

Continue reading on the Beyond Nuclear blog