David Lochbaum, director of the Nuclear Safety Program at Union of Concerned Scientists, has written a blog post entitled "Dark and Dangerous: Station Blackout."
It is part of the "Disaster by Design/Safety by Intent" series of blogs, posted at "All Things Nuclear" on the UCS website.
The blog post complements another Lochbaum wrote on March 17, 2011 -- six days (three meltdowns, and four explosions) into the the Fukushima Daiichi nuclear catastrophe, about which he co-authored a book, Fukushima: The Story of a Nuclear Disaster (New Press, 2014). That one was entitled "Nuclear 'Station Blackout,'" and explained the significantly increased risks of a core meltdown, in the event of atomic reactors experiencing not only loss of off-site power (LOOP), but also emergency diesel generator (EDG) failure, as happened at Fukushima Daiichi due to the earthquake and tsunami. Fukushima Daiichi's operating reactors had eight hours of DC battery backup, which nonetheless proved incapable of preventing three meltdowns over the course of the next several days.
By way of comparison, prior to the Fukushima catastrophe, only a small fraction of U.S. reactors had eight hours of backup batteries; most only had four hours worth.
Lochbaum's insights on the significantly increased risk of core meltdown and catastrophic radioactivity release, due to station blackout, sheds important light on U.S. reactors -- such as Davis-Besse in OH, where EDGs likely would not function properly in an emergency.
In fact, in another blog post by Lochbaum dated Oct. 20, 2015, also about loss of power at atomic reactors vitally needed to run safety and cooling systems, he documents a 2001 incident at Davis-Besse negatively impacting DC batteries connected to safety significant systems.