It’s been over four months since the earthquake and tsunami devastated Japan and crippled the Fukushima Daiichi Nuclear Power Station, which led to partial nuclear meltdowns in three of its reactors. Japan’s government now says that those reactors are stable, and are headed toward a cold shutdown. David Biello, associate editor at Scientific American, says that while this announcement is good news, there are still many problems that plant operators must assess. The most crucial is what to do with the hundreds of tons of reactive water that were contaminated in the process of keeping the reactors cool during the crisis.