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'A time of acute tension'

On Saturday, March 31, 1979, NBC's late night comedy program "Saturday Night Live" announced a contest to name a new capital of Pennsylvania to replace Harrisburg.

BY SUSAN KIM | WASHINGTON, D.C. | March 26, 2004

"This was the worst kind of accident that can possibly happen."

—J. Samuel Walker

On Saturday, March 31, 1979, NBC's late night comedy program Saturday Night Live announced a contest to name a new capital of Pennsylvania to replace Harrisburg.

To many central Pennsylvania residents living near the worst commercial nuclear power accident in U.S. history, it wasn't all that funny. And for government officials in the midst of trying to calm fears of an atomic explosion, it was a nightmare.

Nearly 25 years ago, the Three Mile Island nuclear reactor facility just off the Susquehanna River had a malfunctioning pressure relief valve in the coolant system that caused the core to overheat.

The incident began early in the morning on March 28, 1979. During the course of the scare which stretched for five days some 144,000 people were evacuated from York County and nearby areas.

"It was a time of acute tension, drama and fear," remembered J. Samuel Walker, historian for the Nuclear Regulatory Commission (NRC) and author of "Three Mile Island: A Nuclear Crisis in Historical Perspective."

Walker spoke Friday at the National Museum of American History, recalling the five-day ordeal that started the morning of Wednesday, March 28, 1979, when controllers in the Three Mile Island facility noticed that something had obviously gone terribly wrong.

What did go wrong was a worst-case scenario, said Walker. "This was the worst kind of accident that can possibly happen," he said, "because the core melted."

NRC officials wouldn't know until 1985 six years later when investigators were able to insert tiny cameras through the control rods that it was more serious than people ever knew in 1979. "What they found was a void. They realized half the core had turned liquid. That's not good.

"That's what people had always worried about. It was much more than anyone realized when Governor Thornburgh [then governor of Pennsylvania] was evacuating.

"If anyone had known in 1979 that the core had melted, evacuations within a 20-mile radius would have been ordered," he said. "That included 636,000 people, 13 hospitals and one prison."

But at the time of the accident, he said, "you couldn't send somebody into the plant to find out."

What's more, he said, even the experts couldn't tell what was wrong.

The incident began with a minor mechanical breakdown a coolant valve stuck open, allowing coolant to rush out and spill over into the containment building of the plant.

Within half an hour, some 30,000 gallons of coolant about one-third of the coolant had left the core. "But the operators didn't recognize what was going on," said Walker. "Bells were ringing, lights were flashing. They knew something wasn't right. But there was no clear signal this valve was stuck open. There was no clear signal on the control panel.

"If they had closed the valve, it would not have been a meltdown. No one had paid enough attention to the human factors."

What was the danger to the public? If the containment building the large concrete structure that surrounds the reactor had collapsed, massive amounts of dangerous radiation could have escaped from the building.

"At Three-Mile Island the containment building has concrete walls that are four feet thick. They're designed to withstand forces of an accident, but there was no way to really test that."

Policymakers especially Pennsylvania Gov. Richard Thornburgh faced the difficult decision of whether to call for evacuations. "It was a gut-wrenching decision," said Walker. "Do you tell the population within 10 miles to leave? 15 miles? 20 miles? Do you conclude the plant will hold?"

No one knew. Transcripts of tapes from the NRC at the time show experts, policymakers and the press repeating the same statements over and over: "I wish we had more data. I wish we knew more."

The data that was available was interpreted differently by different groups. After the initial coolant leak, investigators found a hydrogen bubble had formed on top of a pressure valve. They became concerned that bubble could become flammable or even explosive, which would disable or destroy that pressure vessel, leaving the containment building as the only line of defense between the public and harmful radiation.

Officials at the NRC headquarters in Bethesda, Md., said that there was a chance the bubble could become flammable. But NRC experts at the site itself said there wasn't. In the end, the onsite scientists were right but for several days the public and policymakers didn't know.

People in the central Pennsylvania area depended mostly on the radio for news updates, said Walker.

The closest people came to panicking, he remembered, was on the fourth day of the accident, when the Associated Press released a story that said the NRC was concerned about a hydrogen bubble, and that the "critical point would be reached within two days," said Walker.

"The public automatically translated that into 'The NRC says an explosion will happen at Three Mile Island,' " said Walker. "Most people were thinking that if there were a hydrogen explosion, there would be an atomic bomb type of situation. That caused a near-panic."

When people were evacuated, though, Walker said, "they acted in a way that was extremely responsible. There was a great deal of anxiety as a result of the hydrogen bubble scare."

Studies conducted since the meltdown on health effects and radiation releases so far have been reassuring, said Walker "There were small releases of at least one form of dangerous radioactive gas," he said.

Studies are still going on, he said.

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