From The Fuel Pools of Fukushima: THE GREATEST SHORT-TERM THREAT TO HUMANITY by Washington's Blog [via Global Research]
We noted days after the Japanese earthquake that the biggest threat was from the spent fuel rods in the fuel pool at Fukushima unit number 4, and not from the reactors themselves. See this and this.We noted in February:
Scientists say that there is a 70% chance of a magnitude 7.0 earthquake hitting Fukushima this year, and a 98% chance within the next 3 years.
Given that nuclear expert Arnie Gundersen says that an earthquake of 7.0 or larger could cause the entire fuel pool structure collapse, it is urgent that everything humanly possible is done to stabilize the structure housing the fuel pools at reactor number 4.
Tepco is doing some construction at the building … it is a race against time under very difficult circumstances, and hopefully Tepco will win.
As AP points out:
The structural integrity of the damaged Unit 4 reactor building has long been a major concern among experts because a collapse of its spent fuel cooling pool could cause a disaster worse than the three reactor meltdowns.
Gundersen (who used to build spent fuel pools) explains that there is no protection surrounding the radioactive fuel in the pools. He warns that – if the fuel pools at reactor 4 collapse due to an earthquake – people should get out of Japan, and residents of the West Coast of America and Canada should shut all of their windows and stay inside for a while.