Five weeks into the Fukushima nuclear powerplant crisis, Tokyo Electric Power Co. on April 17 announced a road map leading to a cold shutdown that will minimize radioactive emissions and allow emergency evacuations around the plant to be lifted. The six- to nine-month plan calls for building new cooling systems as well as enclosures for four damaged reactors while limiting worker exposure to high radiation. “[The work is] very challenging because of the radiation levels,” says Jacopo Buongiorno, a nuclear engineer at the Massachusetts Institute of Technology, Cambridge, Mass., who is following the crisis. The nine-month schedule, he believes, “is
Arch dams, classically curved monoliths situated in narrow valleys, are not as common as other types of dams, such as embankment dams and gravity dams. ENR takes a look at some of the biggest arch dams in the world, both completed and under construction.