Storms knock out TVA nuclear units, power lines

The backup electricity generators at many of Japan's nuclear power stations lack the capacity to keep reactor cores cool if another earthquake and/or tsunami strikes. So say sources at Japan's electricity utilities who have been comparing the power capacity of the backup generators available against that needed to keep reactors safe from thermal runaway and meltdown...

So Japan's nuclear regulator NISA has urged the nation's 11 nuclear plant operators to deploy extra truck-mounted generators on higher ground, where a tsunami won't swamp them, allowing power to be fed to the reactor cooling systems via heavy-duty waterproof cables.

But today Japan's Kyodo news agency quotes unnamed sources within various nuclear utilities saying that the power these, and existing, backups can provide is just not enough. At Hamaoka, a plant critically straddling a quake-vulnerable subduction zone, Chubu Electric Power's nine newly deployed diesel generators lack the power to cool the five reactors. That means there will be a delay in getting enough backup power until three extra gas turbine-powered generators can be acquired and safely positioned...

http://www.newscientist.com/blogs/shortsharpscience/2011/04/the-back-upelectricitygenerato.html