Fukushima reactor 4's spent fuel pool has lost structural integrity, so it's urgent to to remove the spent fuel rods before an earthquake collapses it. But removal is unimaginably hazardous too, because the rods could easily break or touch one another, leading to unconstrained fission. If the site gets too hot, water cooling will stop and the whole thing goes.
We’ve long said that the greatest short-term threat to humanity is from the fuel pools at Fukushima.
The Japanese nuclear agency recently green-lighted the removal of the spent fuel rods from Fukushima reactor 4′s spent fuel pool. The operation is scheduled to begin this month.
The head of the U.S. Department of Energy correctly notes:
The success of the cleanup also has global significance. So we all have a direct interest in seeing that the next steps are taken well, efficiently and safely.
If one of the pools collapsed or caught fire, it could have severe adverse impacts not only on Japan … but the rest of the world, including the United States.
Hiroaki Koide – a nuclear scientist working at the University of Kyoto – says:
I’m worried about whether Tepco can treat all the 1,331 [spent-fuel] assemblies without any problem and how long it will take.
... scientist David Suzuki says that Fukushima is terrifying, Tepco and the Japanese government are lying through their teeth, and Fukushima is “the most terrifying situation I can imagine”.
One slip-up in the latest step to decommission Japan’s crippled Fukushima nuclear plant could trigger a “monumental” chain reaction, experts warn.
Conditions in the unit 4 pool, 100 feet from the ground, are perilous, and if any two of the rods touch it could cause a nuclear reaction that would be uncontrollable. The radiation emitted from all these rods, if they are not continually cool and kept separate, would require the evacuation of surrounding areas including Tokyo. Because of the radiation at the site the 6,375 rods in the common storage pool could not be continuously cooled; they would fission and all of humanity will be threatened, for thousands of years.
Move south of the equator if that ever happened, I think that’s probably the lesson there.
[emphasis in red mine]