bears. Image Source: NOAA via Environment News Service . At the same time, alarming comments circulated about Reactor #4 at Fukushima.  The fears about Reactor #4's threat portray a textbook Domino Effect . First, another earthquake (like the 5.9 quake on 1 April 2012 ) could cause the collapse of the floor at already-structurally-damaged Reactor #4, where spent fuel pools