The mixed oxide fuel rods used in the compromised number three reactor at the Fukushima Daiichi complex contain enough plutonium to threaten public health with the possibility of inhalation of airborne plutonium particles. The compromised fuel rods supplied to the Tokyo Electric Company by the French firm AREVA.
Plutonium is at its most dangerous when it is inhaled and gets into the lungs. The effect on the human body is to vastly increase the chance of developing fatal cancers.
One of the unique characteristics of mixed oxide fuel is that relatively little of the plutonium in the fuel rods is used up in the fuel cycle in a reactor. “When the plutonium in the fuel rods goes into a reactor for commercial power, a very little of it is going to be consumed. I don’t know what percentage, maybe half percentage or something like that, but it’s going to generate an extraordinary amount of contamination throughout the fuel rods…,” says William Lawler, an expert on radioactive waste.
The damaged number three reactor was undergoing its first fuel cycle using MOX at Daiichi. MOX fuel was first used in a thermal reactor in 1963, but it did not come into commercial use until the 1980s. One reason proponents of MOX reactor fuel support its use is because, once the fuel is burned in a reactor, it is so hot that terrorists would not be able to steal a fuel assembly.