“Based on U.S. Energy Department data, assuming a total of 11,138 spent fuel assemblies are being stored at the Dai-Ichi site, nearly all, which is in pools. They contain roughly 336 million curies (~1.2 E+19 Bq) of long-lived radioactivity. About 134 million curies is Cesium-137 — roughly 85 times the amount of Cs-137 released at the Chernobyl accident as estimated by the U.S. National Council on Radiation Protection (NCRP). The total spent reactor fuel inventory at the Fukushima-Daichi site contains nearly half of the total amount of Cs-137 estimated by the NCRP to have been released by all atmospheric nuclear weapons testing, Chernobyl, and world-wide reprocessing plants (~270 million curies or ~9.9 E+18 Becquerel). It is important for the public to understand that reactors that have been operating for decades, such as those at the Fukushima-Dai-Ichi site have generated some of the largest concentrations of radioactivity on the planet.” (Robert Alvarez, former Senior Policy Adviser to the Secretary and Deputy Assistant Secretary for National Security and the Environment at the U.S. Department of Energy)

The Greatest Single Threat to Humanity: Fuel Pool Number 4

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 notedin 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.

The fuel pool number 4 is apparently not in great shape, and there have already been countless earthquakes near the Fukushima region since the 9.0 earthquake last March.

Germany’s ZDF tv quotes nuclear engineer Yukitero Naka as saying:

If another earthquake occurs then the building [number 4] could collapse and another chain reaction could very likely occur.

(Unit 4 contains plutonium as well as other radioactive wastes.)

Mainchi reported on Monday:

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.

Former Minister of Land, Infrastructure, Transport and Tourism Sumio Mabuchi, who was appointed to the post of then Prime Minister Naoto Kan’s advisor on the nuclear disaster immediately after its outbreak, proposed the injection of concrete from below the No. 4 reactor to the bottom of the storage pool, Chernobyl-style.


“Because sea water was being pumped into the reactor, the soundness of the structure (concrete corrosion and deterioration) was questionable. There also were doubts about the calculations made on earthquake resistance as well,” said one government source familiar with what took place at the time. “[F]uel rod removal will take three years. Will the structure remain standing for that long?

Asahi noted last month that – if Unit 4 pool gets a crack from an earthquake and leaks, it would be the end for Tokyo.

Kevin Kamps said last month:

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.

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