In 1979, there was an incident at a nuclear power plant on Three Mile Island, in Pennsylvania, when radioactive steam leaked into the open air. Nobody was hurt, although thousands of people fled the area.

Seven years later, a much worse accident happened at the Chernobyl nuclear station in Ukraine. One of the reactors melted down, building up tremendous pressure and steam. The reactor's lid blew off, spewing radioactive materials into the atmosphere.

The Future of Safety...

These incidents stalled the nuclear industry in the United States and throughout much of Western Europe for the next few decades.

Now, though, with renewed interest in nuclear power as a non carbon emitting energy source, it's worth wondering: have nuclear plants become safer since Three Mile Island and Chernobyl?

Reliable and Safer

According to the 2009 update of an MIT study first published in 2003, nuclear power plants in the United States have become more reliable and significantly safer.

For one thing, nuclear plant operators now receive better and more rigorous training. And, according to the report, new reactor designs meet strenuous safety standards.

Close Calls

On the other hand, the MIT study also notes that since Three Mile Island and Chernobyl there have been some close calls.

For example, in 2002 the Davis Besse reactor in Ohio avoided a serious accident when a hole in the reactor vessel was discovered during an inspection. The incident is all the more troubling for the fact that the plant owners apparently ignored early warning signs.

So bottom line, the MIT report concludes that improved training and safety standards have made nuclear power relatively safer. But it's not yet clear that all nuclear plants have embraced safety as their main priority.