Here's the worst-case scenario: sometime soon, workers at the crippled Fukushima Daiichi nuclear plant will realize they can't pump seawater into the cores of the wrecked reactors fast enough to keep up with the steady heating. The temperature in the core will exceed 5,000°F (2,760°C), causing hundreds of uranium fuel rods to slump to the bottom of the containment vessel like melted wax. The fuel will burn through the foundation of the plant, sinking into the ground and contaminating the water table. Pressure in the cores will climb high enough that the vaultlike vessels will no longer be able to withstand it. Before long they will erupt in a radioactive cataclysm, spreading a deadly, carcinogenic cloud across Japan and depending on the whims of the wind around the world.
Here's the much-better-case scenario: those same workers will soon get ahead of the heating curve, adding cool seawater to the reactors at the same time as the fuel rods' natural decay causes them to lose heat by themselves. Some people exposed to radiation will get sick; some workers may die. The radioactive plumes will dissipate; the plant will be shut down; the evacuees will go home. You don't need to stock up on iodine pills or canned goods or batteries.
It's still too early to say whether the bright yin or the dark yang will be closer to how the Fukushima drama unfolds, and true clarity may not come for a long time yet. What is certain is that whatever happens, we all need to start thinking very hard about how we got into this mess and how we can prevent it from ever happening again.
Death by radiation has always been humanity's great self-inflicted wound. Nature may have cooked up the unstable elements that contain and emit radioactive energy, but it also took care to hide the stuff away burying it in mountains, sealing it in planetary cores. Humans had to work very hard to pick that natural lock. It wasn't until the past seven decades that we understood the elemental energy of radioactive rocks well enough to distill it into pellets, rods and lumps and, in our first demonstration of our newfound power, use it to incinerate two Japanese cities at the end of World War II.
Japan is suffering once more, and we are again left to examine the wisdom of having ever let the radioactive genie out of the bottle and at just the time that nuclear power had been experiencing a bit of public redemption. As the world struggles with the realities of climate change and the political and fiscal costs of our dependency on fossil fuels, many have accepted that nuclear power must be part of any sensible energy mix.
But that was before Fukushima; before the rolling explosions of nuclear-reactor containment buildings; before the ever-expanding danger zone, which started at 3 km (1.9 miles) and by March 15 stood at 30 km (18.6 miles); before tens of thousands of people were displaced and 140,000 more were urged to stay sealed inside their homes. When a government official like Chief Cabinet Secretary Yukio Edano starts speaking gobbledygook like "At this point we can say we are moving in the direction of stabilizing the situation in a certain managed manner," you can be pretty sure he's not stabilizing anything. And when what's not being stabilized is radioactivity, even the wisest heads start to get spooked. "This is extremely scary," says physicist Kenneth Bergeron, a former research scientist for Sandia National Laboratories in Albuquerque, N.M., who specialized in reactor accidents. "It was not at all inevitable that it had to play out like this."
Rewriting the Book
The known unknowns keep piling up at Fukushima the number of people who will die of radiation poisoning, where the wind will carry the radioactive plumes. At the most personal level, we don't know how to count up our exposure to stray radiation or how the residue from Fukushima that may invade our bodies uninvited compares with the amount we admit willingly from an X-ray or even a day at the beach.