Reactor #4 was the subject of much hype yesterday. There was a fire coincident in its initiation with the explosion at Reactor #3. Immediately every conspiracy site on the Internet assumed that the cause was an uncontrollable and catastrophic fuel pool fire. There is no evidence consistent with this theory. Most-important is that radiation levels at that plant were measured at 100mSv, which is high but not immediately dangerous, 1/4 of the level around #2/#3, and emergency workers can tolerate an hour or so without acute effects. The evidence is strong that this was an industrial (not nuclear) fire and more-importantly there were later reports that the fire is out. Were the “worse-case” scenario occurring that fire could not be extinguished. To the point at hand, were you to simply walk within 50 ft of an exposed, unshielded used fuel rod of this sort you would almost-certainly take a lethal radiation dose.
Any claim that such an event is occurring that does not include a report that radiation levels are off the charts at that plant and well into the “immediate danger to life” zone should be taken with a huge grain of salt. In fact, I’ll go further – any such claimed report without the requisite backstop of the reported radiation level to substantiate it is almost certainly the product of someone attempting to run an “anti-nuke” hard-left disinformation line and you should immediately and permanently discard everything they say from that point onward as being intentionally dishonest. This particular failure mode is one of the “nightmare” scenarios that a handful of scare-mongers have run for more than 20 years. The potential is real but the facts are that as long as you can get water back into the pool via any means even if it boils off it’s not a disaster or even particularly troublesome. The phase change from liquid water to steam requires enormous amounts of energy and dissipating that energy is good, not bad, since that’s exactly what you want to happen. These are open pools and you can fill them with anything that provides water. No pressure is required unlike a reactor vessel where you must pump in fresh water against the pressure inside. So long as you can put in new water faster than it boils off there’s no emergency and these pools are huge – most are roughly the size of a basketball court in dimensions and 30-40′ deep, which means it takes a very long time for the water to boil off to the point that the fuel is exposed. A fire engine that can pull from any convenient source (including the sea, which happens to be right there) is sufficient to refill the water level.