The devastating 9.0 earthquake that rocked northern Japan and the ensuing tsunami have already claimed an estimated 10,000 victims. But the worst may be yet to come. Experts estimated that the next 48 hours will be crucial in determining whether Japan's nuclear disaster unfolds like the U.S. Three Mile Island accident in 1979 or like the meltdown at the Ukraine's Chernobyl plant in 1986.
Two dozen Japanese workers at the Fukushima Daiichi Nuclear Power Station along with17 U.S. crew members of the USS Ronald Reagan have already been decontaminated for radiation exposure. If offshore winds shift, as predicted by Japanese weather forecasters, then airborne radioactive clouds could be headed for the Japanese mainland in the next 24 hours.
Observers said the biggest threat is plutonium fuel. Only one Fukushima
reactor uses plutonium-enriched uranium fuel known as MOX, or "mixed oxide" fuel. A hydrogen explosion at the No. 3 reactor on Sunday (March 13) injured 11 workers. So far, Japanese officials said the
containment vessel in the No. 3 reactor appears to be holding. But
it could take weeks or even months before the MOX fuel cools to levels that no
longer threaten public safety.
"If there is a large-scale release of plutonium into the air this could become the worst nuclear disaster in history," predicted Ira Helfand, a member of the board of Physicians for Social Responsibility. "So far, the venting of radioactive steam has been blown out to sea, but tomorrow [March 15] the wind is forecast to shift to northeast which means any radiation released tomorrow will be blown straight toward Tokyo, which is less than 150 miles away."
A release of deadly plutonium would require heightened precautions to protect Japanese citizens, particularly if winds shift. Helfand said these would include staying indoors and testing water and foods supplies. "Most of the exposure to people at Chernobyl, for instance, was from
children drinking contaminated milk that had not been tested," Helfand said, resulting in high rates of thyroid cancer in children.
Making matters worse, a third explosion, this one inside Fukushima's No. 2 reactor, was
reported Tuesday morning Japan time. Tokyo Electric Power Co. confirmed that radiation from the blast likely leaked after the No. 2 reactor's containment vessel was damaged, Kyodo news service reported.
Despite safety concerns that have prompted the use of backup systems like buried diesel fuel tanks for secondary generators at U.S. nuclear plants, experts are baffled at the lack of adequate backup systems in Japan. The lack of functioning secondary generators, for example, has led directly to cooling problems linked to the three explosions at Fukushima.
Those aging boiling-water reactors were designed by General Electric. The inner reactor core--which generates heat using nuclear fission in a controlled chain reaction--boils circulating water which in turn drives a steam turbine to generate electricity. The heated water is then circulated through cooling pipes which, like a car radiator, cool the water before it re-enters the reactor.
When the earthquake struck last Friday about 80 miles off the coast of Sendai, Japan's nuclear reactors automatically shut down. Control rods were then inserted to dampen the fuel rods and stop the reactor's chain reaction. Electric pumps were supposed to continue running to circulate the hot water through cooling pipes, allowing the reactors to go into an orderly shut-down mode.
Then the power grid went down. Backup generators kicked on when the quake struck to keep cooling water circulating.