The Mainichi Daily News
13 April 2011
http://mdn.mainichi.jp/mdnnews/national/news/20110413p2a00m0na012000c.html
Nuke plant workers fear water poured on reactors could overflow and leak radiation
Emergency workers are fighting an uphill battle to contain one of the troubled nuclear reactors in northeastern Japan, as they cannot pour large amounts of water on it to cool it down for fear that it will be contaminated with radiation and overflow.
It was discovered on April 13 that the temperature of water in the spent fuel pool of the No. 4 reactor at the Fukushima No. 1 Nuclear Power Plant had risen to 90 degrees Celsius. The level of radiation around the reactor is very high at 84 millisieverts per hour. Under normal conditions, the level of radiation is 0.0001 millisievert per hour, a level where people can walk by the pool with ordinary clothes on.
The workers are unable to cool it down sufficiently because they are only pouring on an amount of water that evaporates from the fuel pool, to prevent it from overflowing. Therefore, they are in difficult dilemma.
Of the 1,331 fuel assemblies stored in the pool of the No. 4 reactor, 548 are new and therefore they could generate more heat than ordinary spent nuclear fuel. Heated waste from the fuel is believed to have caused the fuel pool to boil, and exposed fuel rods in turn overheated. It is then believed that hydrogen was generated after the rods’ cladding tubes reacted with water and exploded four days after the March 11 disaster. The fuel rods were said to have stopped being exposed after receiving water supplied from concrete pumping trucks.
The Tokyo Electric Power Co. (TEPCO) used a remote control system to collect samples of water from the pool on April 12. At that time, the temperature of water in the pool was found to be 90 degrees Celsius against 84 degrees Celsius recorded on the eve of the hydrogen explosion. A high level of radiation — 100,000 times the normal level — was detected in the atmosphere about 6 meters above the fuel pool.
The power company says the fuel was covered with water and not exposed. On the question of why the level of radiation was so high, the power firm said, “We think either the fuel in the pool was damaged or materials seeped out from the pressure vessel.” Based on that assumption, the power company is analyzing the ingredients of the radioactive materials.
Concrete pumping trucks are currently being used to supply water to cool down the fuel pool, but if the amount of water is increased further, radioactive water will overflow, making it even more difficult to deal with the spread of contaminated water. In the meantime, as long as workers keep supplying only the amount of water that evaporates with the heated waste, they are not able to prevent the pool from boiling. “We want to restore the recirculating cooling system (using seawater), but we cannot do that because radiation in the reactor building is high,” said TEPCO executive Junichi Matsumoto.
end quote.
This is a technical issue complained bitterly about by opposing scientists over many decades, only to have the technical facts disputed by nuclear authorities. The so-called “nuclear age” is reduced to the sophiscation of concrete pumps and evaporation rates.
