Spent reactor fuel, containing roughly 85 times more long-lived radioactivity than released at Chernobyl, still sits in pools vulnerable to earthquakes.
More than a year after the Fukushima nuclear power disaster began, the news media is just beginning to grasp that the dangers to Japan and the rest of the world are far from over. After repeated warnings by former senior Japanese officials, nuclear experts, and now a U.S. senator, it's sinking in that the irradiated nuclear fuel stored in spent fuel pools amidst the reactor ruins pose far greater dangers than the molten cores. This is why:
- Nearly all of the 10,893 spent fuel assemblies sit in pools vulnerable to future earthquakes, with roughly 85 times more long-lived radioactivity than released at Chernobyl
- Several pools are 100 feet above the ground and are completely open to the atmosphere because the reactor buildings were demolished by explosions. The pools could possibly topple or collapse from structural damage coupled with another powerful earthquake.
- The loss of water exposing the spent fuel will result in overheating and can cause melting and ignite its zirconium metal cladding resulting in a fire that could deposit large amounts of radioactive materials over hundreds, if not thousands of miles.
The urgency of the situation is underscored by the ongoing seismic activity where 13 earthquakes of magnitude 4.0-5.7 have occurred off the northeast coast of Japan between April 14 and 17. This has been the norm since the first quake and tsunami hit the Dai-Ichi site on March 11 of last year. Larger quakes are expected closer to the power plant.
Spent nuclear fuel is extraordinarily radioactive and must be handled with great care. In a matter of seconds, an unprotected person one foot away from a single freshly removed spent fuel assembly would receive a lethal dose of radiation within seconds. As one of the most dangerous materials on the planet, spent reactor fuel requires permanent geological isolation to protect humans for thousands of years.
It's been 26 years, since the Chernobyl reactor exploded and caught fire releasing enormous amounts of radioactive debris -- seriously contaminating areas over a thousand miles away. Chernobyl revealed the folly of not having an extra barrier of thick concrete and steel surrounding the reactor core that is required for modern plants, in the U.S., Japan and elsewhere. The Fukushima Dai-Ichi accident revealed the folly of operating several nuclear power plants in a high consequence earthquake zone while storing huge amounts of highly radioactive spent fuel in vulnerable pools, high above the ground.
What both accidents have in common is widespread environmental contamination from cesium-137. With a half-life of 30, years, Cs-137 gives off penetrating radiation, as it decays and can remain dangerous for hundreds of years. Once in the environment, it mimics potassium as it accumulates in the food chain. When it enters the human body, about 75 percent lodges in muscle tissue, with, perhaps, the most important muscle being the heart.
Last week, Tokyo Electric Power Company (TEPCO) revealed plans to remove 2,274 spent fuel assemblies from the damaged reactors that will probably take at least a decade to accomplish. The first priority will be removal of the contents in Pool No. 4. This pool is structurally damaged and contains about 10 times more cesium-137 than released at Chernobyl. Removal of SNF from the No. 4 reactor is optimistically expected to begin at the end of 2013. A significant amount of construction to remove debris and reinforce the structurally-damaged reactor buildings, especially the fuel- handling areas, will be required.
Also, it is not safe to keep 1,882 spent fuel assemblies containing ~57 million curies of long-lived radioactivity, including nearly 15 times more cs-137 than released at Chernobyl in the elevated pools at reactors 5, 6, and 7, which did not experience meltdowns and explosions.
The main reason why there is so much spent fuel at the Da-Ichi site is that the plan to send it off for nuclear recycling has collapsed. It was supposed to go to the incomplete Rokkasho reprocessing plant, just south of the Fukushima nuclear site, where plutonium would be extracted as a fuel for "fast" reactors. This scheme is based on long discredited assumptions that world uranium supplies would be rapidly exhausted and that a new generation of "fast" reactors, which held the promise of making more fuel than they use, would be needed. Over the past 20 years the Rokkasho's costs have tripled along with 18 major delays. World uranium supplies are far from depleted. Moreover, in November of last year, Japan's "fast" reactor project at Monju was cancelled for cost and safety reasons -- dealing a major blow to this whole scheme.
Despite the enormous destruction from the earthquake and tsunami, little attention was paid to the fact that the nine dry spent fuel casks at the Fukushima Da-Ichi site were unscathed. This is an important lesson we cannot afford to ignore.