Three Mile Island, 20 years later

The Three Mile Island accident is the worst in American nuclear power history

Nuclear power waning in years since accident

March 28, 1999

Web posted at: 2:55 p.m. EST (1955 GMT)

LONDONDERRY TOWNSHIP, Pennsylvania (CNN) -- Twenty years ago Sunday, an accident at Three Mile Island began with a small mechanical problem -- and ended as the worst accident in the history of American nuclear power.

The nuclear power plant's cooling towers still loom over the farms and small towns that line Pennsylvania's Susquehanna River. Back in the 1970s, they were symbols of progress.

"We actually thought the plant was too well designed to have a serious accident," said former Nuclear Regulatory Commission official Harold Denton. "It was kind of like the Titanic."

That thinking changed on March 28, 1979, when a small valve stuck open, cooling water escaped and the reactor core of TMI's Unit 2 began to melt. But at the time, nobody seemed to know what was going on.

"People were either telling us more than they knew or less than they knew," recalled Richard Thornburgh, then Pennsylvania's governor. Thornburgh recommended that pregnant women and young children leave town.

"We left with whatever we thought we needed to survive somewhere," said area resident Marsha McHenry. "It was so hard to look at everything and just try to remember it just as it was and think we would never see it again."

Workers spent years cleaning up the accident

How much radiation?

Disagreement on what had happened at Three Mile Island only added to the anxiety.

Officials admitted radiation had escaped, but probably not enough to hurt anyone. Physics professor John Leutzelschwab, who was living nearby, took his own readings and found the same thing.

"If there had been large releases, I would have seen something," he said.

But others disagreed. One anti-nuclear group held an ominous news conference, chanting slogans such as "any dose is an overdose."

While operators tried to get the situation under control, NRC scientists were in the middle of a high-stakes debate. Some thought there was a real chance a hydrogen explosion could shatter the containment building, spilling radioactive gasses into the atmosphere. Others said there was no way that was going to happen.

Former President Jimmy Carter and his wife, Rosalynn, visited the plant to demonstrate it was safe

Presidential calm

That's when the White House called, and asked whether it would be safe for the president to visit. The answer came from a man who emerged as the calming voice at the center of the crisis.

"I told him it was all right," said Denton. "That was my opinion. The NRC specializes in what-if calculations."

Five days after the accident started, Jimmy and Rosalynn Carter visited Three Mile Island.

"A lot of people felt that if the president is coming here and bringing his wife, things must be all right," said former Londonderry Township mayor Robert Reid, "and that had a calming effect."

Within days, schools reopened and families came home. On Three Mile Island, workers discovered that half the reactor core had melted. It took years to clean it up.

Nuclear energy goes downhill

And it will be years more -- if ever -- before nuclear power's reputation fully recovers from what happened at Three Mile Island.

No commercial nuclear reactor has been ordered and built since the accident -- and nearly one-fifth of the reactors in the country have shut down since 1979. In 1999, there are just over 100 reactors operating -- a far cry from the 1,000 reactors some expected by the millennium back in 1957, when the nation's first town went nuclear.

Since 1979, public support for nuclear power has dropped from 70 percent to 43 percent, and power plants are on the selling block -- including Three Mile Island. AmerGen, a partnership of Philadelphia's PECO Energy and British Energy of Edinburgh, Scotland, has offered to buy Unit 1, which is still operating, for $100 million.

It cost $400 million to build.

Correspondent Natalie Pawelski contributed to this report.