Three Mile Island engineers William Behrle (from left0, Michael Benson, Sam Griffith and Martin Cooper enter the containment building from the personal airlock in Middletown, Pa., on Aug. 15, 1980.
About 300 workers at the stricken Fukushima Dai-ichi nuclear plant in Japan are trying to prevent the crisis there from becoming something worse. So far, at least 15 of these workers have been injured by explosions. An additional 17 have suffered what the Japanese government called "deposition of radioactive material" to their faces. Two are missing.
Experts say those numbers offer a reminder of the risks faced by nuclear workers when something goes wrong.
"There are certainly people who are putting themselves in harm's way to minimize the adverse consequences to the population as a whole," says Jim Tucker, a biologist at Wayne State University. "I think this is a tremendous heroic effort on the part of these people."
Tucker has studied workers exposed to radiation at the Chernobyl Nuclear Power Plant in the former Soviet Union. An explosion and fire there in 1986 released large amounts of radiation. Dozens of workers died soon after the incident, and many more were exposed to radiation as they moved in to try to figure out what had happened.
"The core material had flowed like lava downhill wherever it could inside this reactor building," he says. "They didn't know where it had gone because it was much too hot to approach at first."
Tucker says workers who went in soon after the incident became known as the liquidators, and many of them encountered high levels of radioactivity.
"They knew the risks," he says. "They took them on for the public good."
The workers in Fukushima are facing different challenges. One of those challenges is trying to figure out whether nuclear fuel is actually melting. That's the same question workers had at the Three Mile Island nuclear plant in Pennsylvania, says Sam Walker, an author and historian.
Walker wrote a book about what happened at Three Mile Island in 1979 after the reactor's core began to overheat. He says that incident began with tremendous confusion.
"There were 100 alarms going off at the same time," he says. "But there wasn't any clear indication of exactly what was going on in the reactor."
And like Fukushima, Walker says, there were problems with the massive pumps that usually keep water flowing through the reactor.
"As the accident got worse, they were vibrating so much that they would have self-destructed," Walker says.
By the time workers at Three Mile Island finally got things under control, about half of the reactor's core had melted. But the workers there weren't exposed to much radiation.
Some workers at the Fukushima plant probably have been exposed to high levels, perhaps similar to the levels encountered by the Chernobyl liquidators.
If the levels are similar, most of the Fukushima workers may be OK, says Vladimir Gudkov, a physicist at the University of South Carolina who was working in Leningrad when the Chernobyl incident occurred.
Gudkov says he has friends who worked as liquidators and, like most of the other people who went in after the explosion and fire, they have not developed health problems from the radiation.
Deaths were mostly among people who were at the plant when it blew up, he says. The Soviet Union declared these workers national heroes and built monuments in their honor.
The Chernobyl liquidators who survived received metal badges — these badges depict radioactive particles passing through a drop of blood.