"Backup power initially worked, but failed when the sea wall protecting the site was found to be no where near high enough to stop the tsunami from flooding the generators," said Mary Olson, a nuclear waste specialist at the Nuclear Information and Resource Service. "Of course, the generators should not have been placed in low-lying areas behind the sea wall--that was clearly a human error."
Once the emergency generators were knocked out, eight sets of backup batteries were brought online to keep the pumps going. Initially that worked too, but after about eight hours and hundreds of damaging aftershocks, their power was exhausted and plant operators began loosing control of the rising temperature inside the containment vessels.
"For every single nuclear reactor in the world, 50 percent of the risk comes from loss of power to the site. Reactors do not power themselves, but depend on external sources of electricity for their control rooms, pumps and other auxiliary equipment," said Olson. "A nuclear reactor does not have a switch. You can stop it generating electricity, but you can't turn off the heat."
The only option left to plant operators was pumping seawater into the containment buildings in a last-ditch attempt to cool off the inner containment vessel, which is made from concrete and steel. Nevertheless, steam pressure building up in three reactors have now caused explosions and deepening concern about the integrity of the reactor containment vessels.
"Unfortunately, it is extremely difficult to pump seawater into the containment vessel because there is too much pressure inside. There are pipes that can allows water to be pumped in, but right now the pumps are not working, and its not clear that the pipes are even connected," said Olson.
According to the International Atomic Energy Agency, the No. 2 reactor lost is normal cooling capability late Monday (March 14), prompting emergency workers to start pumping sea water into the damaged reactor. On Tuesday morning, a hydrogen explosion rocked the No. 2 reactor’s containment building, causing a release of radioactive steam clouds that coincided with a pressure drop inside the inner containment vessel, indicating that its outside shell had possibly cracked.
Also on Tuesday, a fire broke out in the No. 4 reactor containment building, which had been shut down before the tsunami hit last Friday. Spent fuel rods in its storage pool were apparently exposed while workers concentrated on the three other damaged reactors. Large amounts of radiation were reportedly released into the air before the fire was extinguished.
According to Japanese officials, radiation levels in and around the Fukushima plant spiked to 400 millisieverts per hour after the No. 2 reactor explosion and the No. 4 fire, prompting Japanese Prime Minister Naoto Kan to expand the evacuation order from 12 to 18 miles from the plant.
Wind shifted inland on Tuesday, causing radiation levels to temporarily jump 10 times higher than normal as far away as Tokyo, according to Japanese officials, who claimed the rise was not major health hazard. By nightfall local time, according to the U.N. weather agency, winds had shifted back out to sea, lowering radiation levels in Tokyo and around the Fukushima plant. That could indicate that the inner containment vessel at the No. 2 reactor remained intact and that the spent fuel rods stored in No. 4’s pool were again covered with water.
After fueling reactors for up to six years, spent fuel rods are stored underwater for 10 to 20 years in pools at the bottom on containment buildings. All six Fukushima reactors have spent fuel rod pools at the base of their containment buildings. The water both cools the fuel rods and provides shielding from radiation. These storage pools are now exposed to the air at the Nos. 1 and 3 reactors, but officials said they will not release radioactive materials as long as they are covered with water. Workers were said to be using fire trucks to pump in sea water.
It remains uncertain whether or not molten uranium and plutonium inside the reactors will burn through the containment vessels since rising temperatures can no longer be controlled. If the containment vessels are breeched, the Chernobyl scenario becomes a possibility, some experts think.
If the containment vessels hold--either through luck or the process of venting steam to relieve the mounting pressures inside--then the remaining hazards will be the venting of radioactive air from inside the containment vessels and from the fuel pools exposed by the hydrogen explosions.
Most of the Fukushima reactors have operated well beyond their expected 25-year life expectancy. The plant began operating in 1971. The No. 1 reactor was to have been decommissioned in 2011, but Japanese regulators recently gave operator Tokyo Electric Power a ten-year extension of its operating license for the reactor.
Early Wednesday morning local time, yet another fire broke out inside the containment building at the No. 4 reactor, according to Reuters. Tokyo Electric Power did not immediately release information on the level of radiation being released, but warned that the cooling systems were also failing in the Nos. 5 and 6 reactors, which also were off-line when the tsunami hit.
I noticed that the German pebble bed reactor has lots of graphite like Chernobyl, which was one of the mistakes to come out of that incident. I'm not sure of the implications for a pebble bed reactor compared to the Chernobyl design, perhaps one of our more knowledgeable members can elaborate?
I agree with you to some extent, but putting your backup systems (diesel generators) in the firing line is a little worrying, but not as much as storing spent fuel where continuous power is required. This is really pushing it. I think spent fuel storage is still the nuclear industry's biggest failing.
No service industry accounts for all possible scenarios. Firstly, all designs are done to meet some specifications. If your specficiation is to withstand an earthquake of 8.0 and Tsunami of 5m, its too bad you got hit by 9 and 6m Tsunami. Secondly, no human being can think of all possible scenarios.
It is not yet clear if the situation could have been controlled better with timely action. I would not blame bad engineering just as yet.
After all the raving on about how pebble bed reactors are so safe and Thorium is so great this really seems to swing the argument away from nuclear doesn't it. It seems like all these "new" technologies just have new risks.
I keep hearing how thorium reactors are the answer to everything.
Check this link out:
Germany built a thorium reactor, then shut it down four years later. It was too expensive to run. The German taxpayers ended up paying about 100 million dollars to shut it down.
A fair enough concern, but if you visit the site you'll see that its coverage of Fukashima (including a real-time discussion forum) is very much focused on the technical facts of the situation.
You can choose to agree or not with the site author's opinion on nuclear energy, which is no secret (in contrast to that of many of the so-called "experts" trotted out by the mainstream media, who are often current or former members of activist organizations like "Friends of the Earth," Greenpeace and "Union of Concerned Scientists").
"Get government out of the nuclear power indemnification business and let the industry settle at a true cost equilibrium."
Yea now there's a good idea! lets have NO government oversight (evil regulation). don't worry, business can regulate itself! the market will take care of EVERYTHING! great idea,.... oh! and the "market" will have a buying opportunity in Japanese real estate just for you VincePG.
the free market economic theory has now been proven false and dangerous on multiple fronts and is merely a useful tool to be implemented for short stretches, not a permanent scenario. freedman style free markets are as much a science as Scientology.
This catastrophe is a perfect storm of stupid ill conceived ideologies such as deregulation (yea i know its Japan and not the US but similar corporate forces are at play), as well as deceitful business interests in the name of profitability.
people die when company's lie.
These conflicting amounts prompted me to look it up, it seems about 10g for one person. I'm assuming quickly as I also found that 1g could cause lung cancer if inhaled. I also found that 1g could cause could kill a few people due to lung cancer. All that said, if you had 100g and let everyone on earth hold it for a time they would probably all be dead or dying. It's important to have the how explained. Regarding your sperm, I'm assuming you mean in one "sitting", I'm afraid you flatter yourself :-) as apparently there are between 2 and 500 million sperm in one shot, you will at best only manage 1/4 to 1/3 of the women of child baring age.
David Patterson, known for his pioneering research that led to RAID, clusters and more, is part of a team at UC Berkeley that recently made its RISC-V processor architecture an open source hardware offering. We talk with Patterson and one of his colleagues behind the effort about the opportunities they see, what new kinds of designs they hope to enable and what it means for today’s commercial processor giants such as Intel, ARM and Imagination Technologies.