Reports are that Unit 2 at Fukushima has exploded this morning at 6:14 AM Japan time. The New York Times reported today that the explosion appeared to be more severe than the previous detonations at the other reactors.
This brings the total probable meltdowns of nuclear reactors at Fukushima Dai-ichi to four out of six. There is evidence of a partial meltdown in Unit 1, the Tokyo Electric Power Company (Tepco) confirmed on 13th March that a partial meltdown at Unit 3 is likely. Today they said the explosion of unit 1 had likely damaged its containment vessel. A fire has also broken out at Unit 4 at 09:40 JST and radiation levels at the plant have risen significantly. (Update 6:39 PM) Early unconfirmed reports are that this fire has been extinguished with the help of the US Military.
Spokesman Kaoru Yoshida for Tepco said today the containment chamber on its No 2 reactor may be damaged and radiation leakage is possible. There are nine nuclear reactors at three sites that are currently under states of emergency. Three at Fukushima Dai-ichi, three at Fukushima Daini and three at Onagawa. All are northeast of Tokyo and all are boiling water reactors.
Prior to this latest explosion the US aircraft carrier (the USS Ronald Reagan) had abandoned its assistance mission to Japan in the aftermath of last week's quake due to concerns over radiation leaks from damaged power plants. It is unclear how much radiation has been released or whether the remaining three larger reactors are fully intact. The carrier had already traveled through a patch of radioactivity released from the quake-stricken Dai-ichi power plant, around 250 kilometres North-East of Tokyo. US government officials said the sailors were exposed to a month's limit of radiation within an hour.
Japanese reactor operators have little choice but to periodically release radioactive steam as part of an emergency cooling process for the malfunctioning reactors, this will most likely continue for a year or more even after fission has stopped. The plant’s operator must constantly try to flood the reactors with seawater then release the resulting radioactive steam into the atmosphere, a desperate step intended to avoid a much bigger problem: a full scale meltdown of the nuclear cores.
Previously Japanese officials have said the melting of the nuclear cores in the two plants is assumed to be “partial,” and the amount of radioactivity measured outside the plants, though twice the level Japan considers safe, has been relatively modest. Tepco representatives earlier today said that there is no radiation leakage from Fukushima Dai-ichi despite the three explosions, contradicting their earlier statements and readings from independent sources. It is apparent that plant technicians are now required to work in areas that have become contaminated with radioactivity and that Tepco is following previous nuclear incidents such as Three Mile Island and Chernobyl to deny that there is any real danger.
More steam releases also mean that the plume heading across the Pacific toward Canada and the US could continue to grow. On Sunday evening, the White House sought to waylay peoples fears, saying that modelling done by the Nuclear Regulatory Commission had concluded; “Hawaii, Alaska, the U.S. Territories and the U.S. West Coast are not expected to experience any harmful levels of radioactivity.” Potassium Iodide treatments have almost sold out.
New information concerning safety at Fukushima and other reactors has recently surfaced. Apparently Japan had to shut down 17 plants in 2003 because they'd been falsifying the records about what had been happening at them and after it emerged that Tepco had hidden accidents, including the collapse of the cooling system of Japan's first commercial fast breeder reactor. In 1995 the Monju nuclear power plant sprang a leak in its liquid sodium cooling system. The reactor had to be shut down immediately and stayed that way until the beginning of last year.
New information concerning safety at Fukushima and other reactors has recently surfaced. Apparently Japan had to shut down 17 plants in 2003 because they'd been falsifying the records about what had been happening at them and after it emerged that Tepco had hidden accidents, including the collapse of the cooling system of Japan's first commercial fast breeder reactor. In 1995 the Monju nuclear power plant sprang a leak in its liquid sodium cooling system. The reactor had to be shut down immediately and stayed that way until the beginning of last year.
It is apparent that the fuel rods in unit 2 had become fully exposed from their coolant, causing a third large explosion. Several officials and industry experts said on Sunday that the top four to nine feet of the nuclear fuel in the core was not intact and the control rods appear to have been exposed to the air, a condition that can quickly lead to melting, and ultimately to full meltdown. Gauges in the reactor have been damaged making it impossible to know just how much cooling process is still functional within the core.
When the fuel was intact, the steam they were releasing had only modest amounts of radioactive material. With damaged fuel the steam is far more radioactive. The operators are now dumping seawater into the vessel and letting it cool the fuel by boiling. But as it boils, pressure rises too high to pump in more water, so they have to vent the vessel to the atmosphere, and feed in more water, a procedure known as “feed and bleed.” Forcing the seawater inside the containment vessels has been difficult because the pressure has become so great.
When the fuel was intact, the steam they were releasing had only modest amounts of radioactive material. With damaged fuel the steam is far more radioactive. The operators are now dumping seawater into the vessel and letting it cool the fuel by boiling. But as it boils, pressure rises too high to pump in more water, so they have to vent the vessel to the atmosphere, and feed in more water, a procedure known as “feed and bleed.” Forcing the seawater inside the containment vessels has been difficult because the pressure has become so great.
Another concern is that some Japanese reactors (as well as some in France and Germany) run on a mixed fuel known as mox, or mixed oxide, that includes reclaimed plutonium. It has been confirmed that unit 3 uses a mixed oxide (MOX) fuel containing plutoniun, which is a dangerous threat in tiny doses and is therefore, much more toxic than the fuel used in the other reactors. The steam etc this is releasing is far more toxic.
European Energy Commissioner Guenther Oettinger said on Monday that "safety at older German nuclear power stations must be checked rigorously" and refused to rule out closures if necessary. "The crisis at a Japanese nuclear plant had changed the world and put into question what had been previously regarded as safe and manageable."
European Energy Commissioner Guenther Oettinger said on Monday that "safety at older German nuclear power stations must be checked rigorously" and refused to rule out closures if necessary. "The crisis at a Japanese nuclear plant had changed the world and put into question what had been previously regarded as safe and manageable."
