Japan’s electric power companies run 54 nuclear reactors, with two under construction, at 17 power plants, according to figures from the International Atomic Energy, the U.N. nuclear watchdog. They produced more than 280,000 gigawatt-hours of electricity in 2010 — about 30 percent of Japan’s total electricity generation.
Most Japanese plants — including the three facing emergencies since the earthquake — use boiling-water reactors, in which water circulated through the reactor is converted to steam and used to drive a generator.
Most U.S. reactors and about 40 percent of Japan’s are pressurized-water reactors, in which reactor coolant is kept separate from the steam used to drive generators.
Both types are far different than the Soviet design involved in the 1986 Chernobyl disaster, a reactor model now considered unsafe by the international nuclear industry. In addition, the Chernobyl plant lacked the kind of reinforced steel-and-concrete containment structure that U.S. and Japanese regulators require.
Read the rest of the story: An overview of Japan’s nuclear issues .