Last Nuclear Reactor Stopped at Ukraine's Zaporizhzhia Plant

"Europe's largest nuclear plant has been reconnected to Ukraine's electricity grid," the Associated Press just reported. But that only means that engineers can now "shut down its last operational reactor in an attempt to avoid a radiation disaster as fighting rages in the area."The six-reactor Zaporizhzhia plant lost its outside source of power a week ago after all its power lines were disconnected as a result of shelling. It was operating in "island mode" for several days, generating electricity for crucial cooling systems from its only remaining operational reactor. Nuclear operator Energoatom said one of those power lines was restored "to its operational capacity" late Saturday, making it possible to run the plant's safety and other systems on electricity from the power system of Ukraine. "Therefore, a decision was made to shut down power unit No. 6 and transfer it to the safest state - cold shutdown," the company said in a statement. Energoatom said the risk remains high that outside power is cut again, in which case the plant would have to fire up emergency diesel generators to keep the reactors cool and prevent a nuclear meltdown. The company's chief told The Associated Press on Thursday that the plant only has diesel fuel for 10 days. Today NPR reminded readers that nuclear reactors "are more like charcoal grills than gas stoves. Even after they're shut off, they remain hot for a long period of time. Water must still circulate in the cores to prevent a meltdown." Here's a chart showing exactly how "released thermal power" drops quickly - but does not stop. And it also notes that "Cooling failures after an emergency shutdown of a reactor were the first cause of serious accidents... evidenced by the accidents at Three Mile Island in 1986 and at Fukushima in 2011." "The first led to the loss of one reactor, the second to the loss of 3 reactors and releases of radioactivity into the environment."

Read more of this story at Slashdot.