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* The plant is safe now and will stay safe.
* Japan is looking at an INES Level 4 Accident: Nuclear accident with local consequences. That is bad for the company that owns the plant, but not for anyone else.
* Some radiation was released when the pressure vessel was vented. All radioactive isotopes from the activated steam have gone (decayed). A very small amount of Cesium was released, as well as Iodine. If you were sitting on top of the plants’ chimney when they were venting, you should probably give up smoking to return to your former life expectancy. The Cesium and Iodine isotopes were carried out to the sea and will never be seen again.
* There was some limited damage to the first containment. That means that some amounts of radioactive Cesium and Iodine will also be released into the cooling water, but no Uranium or other nasty stuff (the Uranium oxide does not “dissolve” in the water). 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.
* The seawater used as cooling water will be activated to some degree. Because the control rods are fully inserted, the Uranium chain reaction is not happening. That means the “main” nuclear reaction is not happening, thus not contributing to the activation. The intermediate radioactive materials (Cesium and Iodine) are also almost gone at this stage, because the Uranium decay was stopped a long time ago. This further reduces the activation. The bottom line is that there will be some low level of activation of the seawater, which will also be removed by the treatment facilities.
* The seawater will then be replaced over time with the “normal” cooling water
* The reactor core will then be dismantled and transported to a processing facility, just like during a regular fuel change.
* Fuel rods and the entire plant will be checked for potential damage. This will take about 4-5 years.
* The safety systems on all Japanese plants will be upgraded to withstand a 9.0 earthquake and tsunami (or worse)
* I believe the most significant problem will 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.

As of 7 pm EDT Sunday 3/13/11

We reported earlier about the situation at Fukushima Dai-Ichi reactor Unit 1. The nuclear crisis in Japan took a turn for the worse as serious problems developed in reactor Unit 3.

Officials from Tokyo Electric reported that after multiple cooling system failures, the water level in the Unit 3 reactor vessel dropped 3 meters (nearly 10 feet), uncovering approximately 90 percent of the fuel in the reactor core. Authorities were able to inject cooling water with a fire pump after reducing the containment pressure by a controlled venting of radioactive gas. As they did with Unit 1, they began pumping sea water into Unit 3, which is highly corrosive and may preclude any future use of the reactor even if a crisis is averted.

However, Tokyo Electric has reported that the water level in the Unit 3 reactor still remains more than 2 meters (6 feet) below the top of the fuel, exposing about half the fuel to air, and they believe that water may be leaking from the reactor vessel. When the fuel is exposed to air it eventually overheats and suffers damage. It is likely that the fuel has experienced significant damage at this point, and the authorities have said they are proceeding on this assumption.

One particular concern with Unit 3 is the presence of mixed-oxide (MOX) fuel in the core. MOX is a mixture of plutonium and uranium oxides. In September 2010, 32 fuel assemblies containing MOX fuel were loaded into this reactor. This is about 6% of the core.

I have done considerable analysis on the safety risks associated with using MOX fuel in light-water reactors. The use of MOX generally increases the consequences of severe accidents in which large amounts of radioactive gas and aerosol are released compared to the same accident in a reactor using non-MOX fuel, because MOX fuel contains greater amounts of plutonium and other actinides, such as americium and curium, which have high radio-toxicities.

Because of this, the number of latent cancer fatalities resulting from an accident could increase by as much as a factor of five for a full core of MOX fuel compared to the same accident with no MOX. Fortunately, as noted above, the fraction of the fuel in this reactor that is MOX is small. Even so, I would estimate this could cause a roughly 10% increase in latent cancer fatalities if there were a severe accident with core melt and containment breach, which has not happened at this point and hopefully will not.

While the authorities continue playing down the possibility of a breach of the primary containment at these reactors, I remain concerned. Fukushima Dai-Ichi reactor Units 1, 2, and 3 are boiling water reactors with Mark I containments. The Mark I is unusually vulnerable to containment failure in the event of a core-melt accident. A recent study by Sandia National Laboratories shows that the likelihood of containment failure in this case is nearly 42% (see Table 4-7 on page 97). The most likely failure scenario involves the molten fuel burning through the reactor vessel, spilling onto the containment floor, and spreading until it contacts and breeches the steel containment-vessel wall.

The Sandia report characterizes these probabilities as “quite high.” It’s not straightforward to interpret these results in the context of the very complicated and uncertain situation at Fukushima. But they are a clear indication of a worrisome vulnerability of the Mark I containment should the core completely melt and escape the reactor vessel.

Smoke seen rising from Fukushima Daiichi plant No.3 reactor -TV

Mon Mar 14, 2011 2:18am GMT

March 14 (Reuters) - Smoke was seen rising from the No. 3 reactor at Japan's Fukushima Daiichi nuclear plant, domestic media images showed.

Operators had earlier halted injection of sea water into the reactor, resulting in a rise in radiation levels and pressure. The government had warned that an explosion was possible because of the buildup of hydrogen in the building housing the reactor.

Japan's nuclear crisis: the causes and the risks
The Guardian - ‎12 hours ago‎
The Japanese authorities have classified the situation as a level 4 "accident with local consequences" on the International Nuclear and Radiological Event Scale.The scale runs from zero for a deviation in normal operations to seven for a major accident ...

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  0254: To recap, in the past hour we have had reports of a new tsunami which appears to have been a false alarm, and a blast has wrecked a wall at a nuclear reactor but its containment vessel withstood the impact. We also had reports of 2,000 bodies found on the tsunami-ravaged north-eastern coast.
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  0250: For more details of the explosions at Reactor 3, link text hereread our breaking news story.
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  0247: Mr Edano said major radiation leaks were unlikely from Reactor 3.
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  0243: Japanese government spokesman Yukio Edano has just spoken on TV. Says that water injection at Reactor 3 seems to be continuing, and the containment vessel is still safe.
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  0242: Reactor 3 withstood the explosion(s), its operator says - Japanese news agency Jiji.

justdrew wrote:well, if the aliens are ever going to do anything, now would be a good time

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0351: Full quotes from Yukio Edano on the explosion: "We believe that there is a low possibility that a massive amount of radiation has been leaked. But it is similar to the time when the hydrogen explosion took place in number 1 reactor (which exploded on Saturday). In the case of number 3 reactor, we can see higher level of radiation. We are now collecting information for the concentration of the radiation and the dose."

0409: The Japanese government has just said there was no marked change in the radiation level after the blast at Reactor 3. According to an article in the New York Times, the US aircraft carrier Ronald Reagan, which is sailing in the Pacific, passed through a radioactive cloud from Japan's stricken reactors on Sunday. Crew members received a month's worth of radiation in about an hour, government officials were quoted as saying.