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TEPCO officials confirmed today the months-long of suspicion that the Reactor No. 1 at Fukushima suffered a full meltdown. According to the disclosure today, workers discovered earlier this week that No. 1's containment vessel has been leaking water and today discovered a sizeable hole they believe was created by fallen fuel pellets. The water leakage not only indicates that the clean up efforts will take longer than originally expected but also that the worst case scenario was already underway when TEPCO said it had been avoided.

Before anybody panics over the very scary phrase "full meltdown," it's worth pointing out that nuclear scientists don't necessarily agree on what that means. The difference between a "partial meltdown," which is what we were lead to believe had happened, and a "full meltdown," which is the term dominating today's headlines, is unclear and perhaps not even that important. According to Columbia's David Brenner, a "full meltdown" occurs when the exposed fuel melts through the bottom of the containment vessel. That's not the dangerous part, though. When asked in an interview about the danger of meltdowns, Brenner said:

They’re certainly not good. You can contrast the two major nuclear incidents of the past: Both Chernobyl and Three Mile Island were meltdowns, but the difference in scale is enormous. Chernobyl was the equivalent of 1 million Three Mile Islands. A “meltdown” certainly is not a good thing, but the ultimate consequence is how much radioactivity is released into the environment. You can have a situation like Three Mile Island, where it’s extremely small amount, or a situation like Chernobyl.

The Fukushima disaster is already as bad as Chernobyl according to the International Atomic Energy Association's scale, but the radiation levels released are yet to be determined. Semantics and classifications aside, the people of Japan's situation is scarier than before for one reason: that big hole that's leaking radioactive water puts a serious damper TEPCO's plan to cool the reactor by dousing it with water. Even if they plug the leak, it's unclear how much more radioactive water has seeped into the ground or ocean around the plant. This is the third leak discovered by officials, and it may very well not be the last.

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