Why Fukushima is a greater disaster than Chernobyl.

• Author: Alvarez, Robert
• Position: Biodevastation

With the world's worst nuclear power disaster well over a year in the past, the news media is just beginning to grasp that the dangers to Japan and the rest of the world posed by the Fukushima-Dai-Ichi site are far from over. After repeated warnings by former senior Japanese officials, nuclear experts, and now a US Senator, it is sinking in that the irradiated nuclear fuel stored in spent fuel pools amidst the reactor ruins may have far greater potential offsite consequences than the molten cores.

After visiting the site recently, Senator Ron Wyden (D-OR) wrote to Japan's ambassador to the US stating that, "loss of containment in any of these pools could result in an even greater release than the initial accident."

This is why:

* Each pool contains irradiated fuel from several years of operation, making for an extremely large radioactive inventory without a strong containment structure that encloses the reactor cores;

* Several pools are now completely open to the atmosphere because the reactor buildings were demolished by explosions; they are about 100 feet above ground and could possibly topple or collapse from structural damage coupled with another powerful earthquake;

* The loss of water exposing the spent fuel would result in overheating and cause melting, igniting the fuel's zirconium metal cladding--resulting in a fire that could deposit large amounts of radioactive materials over hundreds of miles.

Irradiated nuclear fuel, also called "spent fuel," is extraordinarily radioactive. In a matter of seconds, an unprotected human one foot away from a single freshly removed spent fuel assembly would receive a lethal dose of radiation. As one of the most dangerous materials in the world, spent reactor fuel poses significant long-term risks and requires isolation in a geological disposal site that can protect the human environment for tens of thousands of years.

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Fukushima and Chernobyl

It's 26 years since the Chernobyl reactor exploded and caught fire, releasing enormous amounts of radioactive debris. That accident revealed the folly of not having an extra barrier of thick concrete and steel surrounding the reactor core, something required for modern plants in the US, Japan and elsewhere. The Fukushima Dai-Ichi accident revealed the folly of storing huge amounts of highly radioactive spent fuel in vulnerable pools, high above the ground.

What both accidents have in common is wide-spread environmental contamination from...