Indeed it is also a race to find reliable, real-time public information about the rapidly changing Japan nuclear power emergency, amidst a sea of confusing, conflicting and often limited information emanating from sources across the world. Dealing with the aftermath of the monstrous earthquake and tsunami, as well as the nuclear crisis, has clearly stretched Japanese government and company officials to the breaking point, and their communication has frequently failed to keep up with the story. At the same time, the media covering the Japan's nuclear power situation, on the ground and around the globe, face a challenging array of often-unconfirmed information and speculation.

Of immediate concern is the prospect of a so-called "meltdown" at one or more of the Japanese reactors. But part of the problem in understanding the potential dangers is continued indiscriminate use, by experts and the media, of this inherently frightening term without explanation or perspective. There are varying degrees of melting or meltdown of the nuclear fuel rods in a given reactor; but there are also multiple safety systems, or containment barriers, in a given plant's design that are intended to keep radioactive materials from escaping into the general environment in the event of a partial or complete meltdown of the reactor core. Finally, there are the steps taken by a plant's operators to try to bring the nuclear emergency under control before these containment barriers are breached.

In the Three Mile Island accident, a partial core meltdown occurred in one reactor unit but remained largely within the plant's containment barriers and little radiation was released to the environment. The Chernobyl catastrophe, however, resulted in a massive environmental release of radiation following a core meltdown. An important distinction is that the Chernobyl plant lacked crucial containment structures found at the Three Mile Island and Japanese plants.

According to the International Nuclear and Radiological Event Scale, which rates the severity of nuclear power plant incidents on a scale from zero to 7, Chernobyl was rated a 7, the highest level of severity and the only such accident. Three Mile Island was ranked a 5, "an accident with wider consequences." Thus far, the Japanese nuclear emergency at Fukushima Daiichi has been rated a 4, an "accident with local consequences," but this is of course a preliminary estimate.

On CNN's Reliable Sources show Sunday, host Howard Kurtz raised questions about the difficult balance between legitimate concern and fear mongering in the around-the-clock coverage of an evolving emergency. Radio host Callie Crossley criticized the repeated media warnings of possible nuclear meltdown: "Nobody told me what it meant....I thought that was extremely irresponsible." Guest Mike Chinoy, a former CNN Asia correspondent, countered that the media "don't have the luxury of putting something together....This is a scary story."