The extent of the catastrophe at Fukushima Dai'ichi is only now being realized in mainstream press outlets and US academic institutions. The NY Times, for example, and the American Academy for Arts and Sciences are reporting that indicates a revision from previous characterizations of the nuclear tragedy in Fukushima prefecture. Earlier news reports, with few exceptions, characterized the state of the reactors at the Tokyo Power Company's Fukushima site as "partial meltdowns." (See the 29 March 2011 entry in this weblog.) Claims of a "partial meltdown" were suspect with the reports of plutonium contamination in the soil and water outside the reactor containment vessels.
The concept of a "partial meltdown" is, at best, an imprecise state; at worst, it's a newspeak/PR term to titrate the reaction of the public to radiation and radioactive material releases into the environment. Conventionally, a "meltdown" occurs when a reactor core gets hot enough to alter the fuel rod configurations beyond design tolerance. This increases the likelihood of radiation and/or radioactive material into the environment. Putting the word "partial" in front of "meltdown," especially before the configuration of the Fukushima reactors could be confirmed visually or otherwise was a reaction based on mitigating public perception, rather than providing the public with information.
Major, mainstream media outlets, such as the NY Times, would have been doing their job properly by informing their readers of these motivations.