Japanese reactor operators now have little choice but to periodically release radioactive steam until the radioactive elements in the fuel of the stricken reactors stop generating intense heat, a process that can continue for a year or more even after fission has stopped.
In the best case, operators will pump enough seawater and other coolants to squelch overheating. Such a success would prevent further releases of radiation beyond the unknown amount spewed into the air by controlled venting and the explosion of a reactor containment building.
In such a scenario, the only casualties would probably be the handful of plant workers reported Sunday to be suffering from acute radiation sickness.
If the last-ditch efforts to cool the reactors fail, the heavy cylindrical cores — each containing tons of radioactive fuel — could flare to hotter than 4,000 degrees and melt through the layers of steel and cement engineered to contain them.
Such a meltdown may be under way, said Arnie Gundersen, chief engineer at the consulting firm Fairewinds Associates. Gundersen helps oversee the Vermont Yankee nuclear plant, whose reactors are the same vintage and design as those of the stricken Japanese reactor.
If a full meltdown occurs, a huge molten lump of radioactive material would burn through all containment, destroy the building and fall to the ground, exposed. A toxic stew of exotic radioactive particles would then spread on the wind and rain.
