Just What Is A Nuclear Meltdown, Anyway?

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In the wake of the 8.9 magnitude earthquake and resulting tsunami that hit Japan, the country's nuclear plants have been in a state of emergency. As of this writing, at least three nuclear reactors were experiencing partial meltdowns, with the Fukushima Daiichi Nuclear Power Station reportedly experiencing the worst radiation disaster since Chernobyl. Over the weekend, I was keeping an eye on the disaster, but after each news report, I'd been left with one burning, unanswered question: just what exactly happens during a nuclear meltdown?

Thankfully, my dad—who is a physicist—was kind enough to answer my question, even as he gave me a look that said "I told you that you shouldn't have changed your major from chemistry to literature." His response, as well as supplemental information from some of the Lopate Show's past coverage of nuclear energy, is after the jump.

A nuclear meltdown happens when there is a failure to remove heat from the fuel in the core of the reactor. When the core of the reactor gets too hot—usually because the water levels have fallen bellow the central rods which absorb neutrons—uncontrolled fission occurs. Uranium and fission by-products such as cesium are then exposed and sink to the bottom of the reactor. This, in turn, can lead to explosions—which is when the real harm comes. Once the lid is blown off of the reactor, the escaping radioactive particles are then propelled out of the reactor into the air—which can then be carried across the countryside, such as the case of Chernobyl.

Here's a really great timeline and diagram of what happened in Japan from the Washington Post.

Some of our past nuclear coverage:

  • In 2009, Dr. Ivan Oelrich joined us to talk about the shortage of nuclear technicians and operators in the United States today.
  • Also in 2009, we looked at the impact of the partial meltdown at the Three Mile Island nuclear facility three decades after the fact and its broader impact on U.S. nuclear policy with J. Samuel Walker, the historian for the Nuclear Regulator Commission and author of the book Three Mile Island
  • In 2008, we looked into how safe nuclear power really is, and how it stacks up against other energy alternatives with Dr. Richard Anderson, an expert in risk assessment and nuclear energy, and Gwyneth Cravens, a science reporter and author of Power to Save the World
  • In 2006, we looked at why no nuclear power plants had been built in this country since the Three Mile Island accident in 1979. We spoke to Adam Aston of Business Week and Scott Cullen, the Nuclear Security Project Director for the GRACE Policy Institute, about the pros and cons of investing in new nuclear power plants. 
  • Also in 2006, we looked at Chernobyl, 20 years later. The disaster produced 400 times more radiation than the bombing of Hiroshima. Journalist Adam Higginbotham explained how survivors were still dealing with the fallout.