To state the obvious, the nuclear crisis in Japan is bad and will get worse. Despite the heroic efforts of the remaining workers at the nuclear complex, it seems likely that two reactor cores will melt down and two spent fuel ponds will ignite, spewing radioactivity into the ground, air, and water. But beyond concern for the workers and those in the surrounding region, the international public has reacted to the unfolding disaster with understandable -- but nonetheless irrational -- fear for their own safety. Potassium iodide pills have been flying off the shelves in California over fears that the radiation will cross the Pacific. Hoax text messages have spread fears of contamination across Asia from the Philippines to India. In China, stores are selling out of iodized salt, as people frantically hoard it in the mistaken belief that it will counteract radiation.
It might be tempting to blame hysterical media coverage for this reaction, but in this case, most coverage I've seen has actually been fairly sober and cautious. The bigger problem has been the overly optimistic scenarios and conflicting information released by Japanese authorities. The public, not only in Japan but worldwide, simply no longer believes those in authority who tell them they are not in danger. This will make it difficult to manage the public response to the crisis going forward and may pose a grave risk for the future of the nuclear industry.
As of day eight of the crisis, here is a brief roundup of what we actually know about the situation unfolding in Fukushima.
A small group of workers, at one point as few as 50, are racing to do what 800 workers failed to do: cool the nuclear fuel inside three reactors at the Fukushima Daiichi plant. The latest available data shows that water levels inside reactors 1, 2, and 3 have fallen to cover only about half then length the fuel rods, allowing them to overheat and begin to crack. Reactor 4 does not have fuel in its core.
These three reactors contain about 200 metric tons of lightly enriched uranium; reactor 3 also contains plutonium fuel. The cores are beginning to melt. In a full meltdown, this molten fuel could drip down, burning through the steel reactor vessel and possibly breaching the concrete containment vessel -- the last line of defense before a large radioactive release. Based on radiation detection by monitors deployed by the Comprehensive-Test-Ban-Treaty Organization, it does not appear that this has yet occurred. Detection of large amounts of zirconium and barium inside the reactors would signal that a large meltdown had taken place.
Photos of the plant show that a series of hydrogen gas explosions has blown off the sides and roofs and compromised the integrity of several structures. The containment walls at reactors 2 and 3 were damaged and may have been breached. Primary and backup cooling systems are not working at reactors 1, 2, and 3. Radioactive steam appears to be leaking from these buildings. These reactor buildings also store spent fuel rods in large pools -- containing several times as much radioactive material as the reactors themselves. Two of these pools have been damaged, and the vital water that was cooling the spent fuel has drained. Without water, these fuel rods will begin to overheat, and the rods' coverings could catch fire. There are 1,760 metric tons of spent fuel in these ponds (with an additional 1,000 tons in the nearby reactor 5 and 6 complex).
The ponds contain many billions of curies of radiation that could easily exceed those associated with the reactor cores by a factor of five to 10. They have no containment structures, and radioactive smoke from these fires would spew directly into the atmosphere. Efforts by Japanese military and police to refill the ponds with water dropped from helicopters or by water cannons appear to have failed.
The biggest worry is that a spent fuel fire could contaminate the immediate area so badly that reactor workers would no longer be able to keep working to cool the overheating reactors. Then two scenarios will unfold, both far worse than authorities imagined just seven days ago.
The best worst-case scenario is that only two spent fuel ponds -- at reactors 3 and 4 -- catch fire and that the meltdowns at reactors 1, 2, and 3 are largely contained by the concrete walls surrounding the reactors. Toxic smoke would still spread massive amounts of radioactive contamination over the surrounding environment.
The worst worst-case scenario is that all three reactors with fuel in their core and all four fuel pools overheat and two or more reactors breach the concrete containment structures, burning through into the broader environment.
In either case, severe amounts of radioactive contamination will spread over tens, hundreds, or even thousands of square miles. In either case, radioactive contamination will spread over land and water, posing serious health hazards to life within 50 miles of the complex.
In an effort, perhaps, to keep the public calm, the Tokyo Electric Power Company (TEPCO) which owns the reactors, and the Japanese government which regulates them have limited the information released and constantly portrayed the situation as under control. The facts have spoken otherwise. The widening gap has now triggered a collapse of confidence on the part of the Japanese public and, it appears, the U.S. government. Brookings Institution scholar Daniel Kaufmann notes that TEPCO "infuriated Japan's prime minister, who learned of the first plant explosion at reactor 1 on Saturday from watching TV." In the early days of the crisis, TEPCO officials denied that water levels had fallen in reactors and fuel storage pools, but hours later announced extraordinary measures to pump new water in.