On Friday, March 11, Japan's Fukushima Daiichi power plant was affected by a massive earth -quake, and is facing a possible meltdown. Uncertainty and fear have been feeding on each other over the struggle to cool nuclear reactors after a tsunami caused by Friday's 8.9-magnitude earth -quake swept away primary and backup cooling systems. The words "meltdown" and "Chernobyl" have conjured images of radioactive vapors rising from the coastal Fukushima nuclear facilities, and sweeping the Pacific Rim, raining down on crops and people. After all, the containment zone has expanded several times, and a blast at one reactor indicated a partial core meltdown. Yet a number of American and European scientists, as well as diplomats familiar with the thinking inside the Vienna-based International Atomic Energy Agency (IAEA), are cautiously taking the edge off the worst fears: Robert Engel, former IAEA inspector and Swiss nuclear engineer told Reuters Sunday that a partial meltdown "is not a disaster", and that he doubted a complete meltdown is possible. The details of the current Japanese reactor crisis bear little similarity to the Soviet-era meltdown at Chernobyl, which came about through design flaws and human error before it spread a radioactive cloud across much of Europe and Asia 25 years ago.