What the Media Doesn't Get About Meltdowns

The nuclear power emergency in northeast Japan grows more treacherous and uncertain, as plant operators struggle to contain escalating dangers at several nuclear reactors in hopes of preventing a disastrous release of radioactivity into the environment.

The unfolding crisis in Japan continues to draw comparisons with the world's previous nuclear power accidents. The big question is the degree to which Japan's current nuclear power emergency resembles the more contained 1979 U.S. Three Mile Island accident, or the worst in history, the 1986 Chernobyl catastrophe in the Ukraine.

"I covered Chernobyl and I covered Three Mile Island," NBC's chief science and health correspondent Robert Bazell said today. "So far it's not anything like Chernobyl. Let's keep our fingers crossed that it will continue to stay that way." A jet-lagged Bazell, who had just arrived in Tokyo, stressed, "the situation here is still not under control." He emphasized that "it is a race against time" to prevent a serious breach of the containment structures housing the nuclear fuel cores in at least two reactors at Japan's Fukushima Daiichi nuclear power station, as well as potential dangers at several other plants in the region.

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.

Presented by

Cristine Russell is a senior fellow at Harvard Kennedy School of Government and the president of the Council for the Advancement of Science Writing.

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