The last of four regular power lines supplying the Russian-held nuclear power plant at Zaporizhzhia in Ukraine was briefly cut on Thursday, meaning the plant had to resort to backup power for the first time, thinning its defenses against a meltdown. In all nuclear power plants, fission of nuclear fuel gives off heat to then produce steam that turns turbines to generate electricity. That process must be controlled to prevent a runaway chain reaction that would overheat and in the worst case cause a meltdown like those at Chornobyl or Fukushima. Zaporizhzhia, in Russian-occupied southern Ukraine near front lines along the major Dnipro River, is Europe’s biggest nuclear power station and its area has been repeatedly hit by shelling in the past few weeks. Reactors like the six at Zaporizhzhia, two of which are in operation, have a primary cooling circuit in which electrical […]