The dangerous plutonium fuel in reactor number three

But Ray Guilmette of the National Council on Radiation Protection and Measurements said that what causes damage to human health is not necessarily plutonium or uranium, but the fission materials that are most likely to escape during a meltdown, such as iodine and cesium. (He explained that iodine tablets are being issued in Japan because if the thyroid is already “loaded up” with stable iodine it won’t absorb radioactive iodine, which gets excreted in urine.) Plutonium is a much smaller threat: If it were to melt, he said he expects it would become a sludge-like substance that wouldn’t be released into the environment. But if it were absorbed in the body, “it is thousands of times more radioactive than uranium,” he said…

Donald Olander, professor emeritus of nuclear engineering at the University of California, Berkeley, said that because plutonium decays quickly, it produces radiation that can kill cells in the body more quickly. But the plutonium itself would pose a severe threat only it was involved in a violent reaction that turned it into dust particles, which could be inhaled. The length of the time the fuel has been in the reactor plays a role, as the does the mix of fuel. Plutonium can be about 4 to 8 percent of a typical MOX mix, and is also found in much smaller percentages (1 to 2 percent) in more traditional uranium reactors.