Q&A: How dangerous is the plutonium found at Fukushima power plant?
TOKYO, March 29, Kyodo
Plutonium has been detected in soil at five locations in the crippled Fukushima Daiichi atomic power plant of Tokyo Electric Power Co. The following are questions and answers regarding the potential health hazard of the highly toxic material.
Q: What are the salient characteristics of plutonium?
A: Plutonium emits alpha rays which get lodged in people's bones and lungs after being inhaled and could become highly carcinogenic. One half-life of plutonium-239, a variant of the radioactive element, is estimated at 24,000 years. It could keep emitting radiation inside a human body and is difficult to eliminate.
Q: How will the plutonium discovered this time at the plant affect human health?
A: The plutonium-238 isotope reading at one of the five contaminated spots was 0.54 becquerel per kilogram of soil. Tokyo Electric Power (TEPCO) said that it is the same level as found in most soil so it is not a health hazard. Experts of the Nuclear and Industrial Safety Agency also say that it does not pose any immediate threat to human health.
Q: How far has the plutonium traveled from the reactors?
A: Since plutonium is a heavy element, it is generally considered unlikely to travel very far. But given other highly concentrated radioactive materials were found outside the buildings that house the nuclear reactors, experts say it is necessary to stay vigilant over unfolding developments.
Q: How does plutonium differ from other radioactive materials traced to the nuclear power plant such as radioactive iodine and cesium?
A: Unlike iodine and cesium, which have been released in gaseous form, the plutonium appears to have leaked before having evaporated. Its boiling point is around 3,232 C. This could mean that the condition at the power plant has become even more serious because a mixture of damaged nuclear fuel and water might have found its way outside.
Q: Where does the plutonium come from?
A: At the moment, it is difficult to identify the exact location. But the plutonium might have come from the No. 3 reactor that conducts so-called ''pluthermal'' power generation, using plutonium-uranium mixed oxide fuel. But it is possible that it leaked from any of the No. 1 through No. 4 reactors because plutonium is a byproduct of uranium-based power generation.
Q: What should be done to prevent the further spread of the plutonium?
A: It is essential to increase efforts to cool the reactors and pools storing the spent nuclear fuel.
==Kyodo