The Greatest Single Threat to Humanity:
Fuel Pool Number 4
Washington's Blog: 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.]
Akio Matsumura talks about nuclear power plants, spent fuel pools, and the trouble with Reactor 4 at Fukushima.
a few snippets from article -
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...
...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...
The storage pool in the No. 4 reactor building has a total of 1,535 fuel rods, or 460 tons of nuclear fuel, in it. The 7-story building itself has suffered great damage, with the storage pool barely intact on the building’s third and fourth floors. The roof has been blown away. If the storage pool breaks and runs dry, the nuclear fuel inside will overheat and explode, causing a massive amount of radioactive substances to spread over a wide area. Both the U.S. Nuclear Regulatory Commission (NRC) and French nuclear energy company Areva have warned about this risk.
A report released in February by the Independent Investigation Commission on the Fukushima Daiichi Nuclear Accident stated that the storage pool of the plant’s No. 4 reactor has clearly been shown to be “the weakest link” in the parallel, chain-reaction crises of the nuclear disaster. The worse-case scenario drawn up by the government includes not only the collapse of the No. 4 reactor pool, but the disintegration of spent fuel rods from all the plant’s other reactors. If this were to happen, residents in the Tokyo metropolitan area would be forced to evacuate...
Unit 4 storage pool… The entire building is listing including the pool. What they have is steel jacks underneath the pool to try to keep the floor from falling out or the pool from flipping over.
If that cooling water supply is lost, it will be just a few hours at most before that waste is on fire. 135 tons outside of any radioactive containment. They would be direct releases into the environment. 100% of cesium-137 could be released to the environment.