What Happened at Fukushima Daiichi ?

There's a very long, but good article explaining what has happened at Fukushima Daiichi.  You can find it on several sites, but here's one.

Its most important conclusions are that

• "The plant is safe now and will stay safe.
• "A very small amount of Cesium was released, as well as Iodine.
• "There was some limited damage to the first containment. There are facilities for treating the cooling water inside the third containment. The radioactive Cesium and Iodine will be removed there and eventually stored as radioactive waste in terminal storage.
• "There will be some low level of activation of the seawater, which will also be removed by the treatment facilities.
• "The safety systems on all Japanese plants will be upgraded to withstand a 9.0 earthquake and tsunami (or worse).
• "The most significant problem will probably be a prolonged power shortage. About half of Japan’s nuclear reactors will probably have to be inspected, reducing the nation’s power generating capacity by 15%. This will probably be covered by running gas power plants that are usually only used for peak loads to cover some of the base load as well. That will increase your electricity bill, as well as lead to potential power shortages during peak demand, in Japan."

Comments

[Doug Andersen]

This is a not-so-complicated engineering failure. I am a former Boeing electrical engineer, not a nuclear engineer, so I am not in a position to know if the cores will melt down to the water table and poison the atmosphere, etc., but I can describe the mindset that let this disaster happening.

It’s all about probability. When the reactor was designed, the probability that this disaster would happen was calculated to a probability of less than 10 to the power of -9 (one in a billion; considered “extremely improbable” in regulatory terms). Since it actually happened, that probability was obviously wrong; it turned out to have a probability of “1”. The engineers were way off, but the regulatory agencies drank their cool-aid at certification time and signed off on the plant.

My 7-year-old could tell you that a big earthquake could cause a big tidal wave. Their engineers knew that too, but what was the probability of it? Picking numbers out of the blue, they most likely calculated 1 in a million for an earthquake, and 1 in a thousand for a huge tidal surge. Multiply those numbers together and the event will never happen; it would be “extremely improbable” by probability mathematics.

This probability mindset gives license for engineers to dumb down designs. I saw this happen all the time. One would say at Boeing, “if that switch failed, the pilots would have no indication that they have a problem with an engine” which would be answered by “our probability calculation is that a switch failing would be one in a million.” Boeing lost more than a few airframes with this attitude.

What are needed are bullet-proof designs. We need systems that are inherently safe at the cost of efficiently. I have always been pro-nuclear; but no more until probability is erased from the equation.

[Anton Ferré]

Considering that the huge earthquake combined with the tsunami flattened every industrial plant in the region, including a refinery, the fact that the nuclear plants were 50 years old and still only suffered minor damage due to the tsunami shows that the plants are safe.

The main problem is the power shortage that is going to hinder the recovery of Japan but considering the magnitude of the chatastrophe we can say it didn't went so bad.

[Geoff]

There are three things that really stuck our for me about this disaster
1) The incredibly small amount of damage to structures resulting from the magnitude 9 earthquake. Amazing contrast to the Kobe earthquake or to the 1989 magnitude 6.1 earthquake in San Francisco.
2) Reminded again of how devastating tsunamis are. When Krakatoa exploded at the the end of the 19th C, 35,000 people lost their lives, almost entirely due to tsunamis (not called that then.)
3) The length of time it has taken to restore off-site power to Fukushima Daiichi. I suspect that Fukushima Daini would also be in dire straits right now, if off-site power hadn't been restored so rapidly.