All our wishes go out to friends and strangers alike in Japan, in light of the terrible events of the last two days. I am preparing this article to provide information on the status of the nuclear power facilities in the Sendai region. I am doing so to counter inflammatory and irresponsible misinformation I have encountered in various forums and social networks of which I am a part (e.g. statements that a "nuclear explosion" has occurred).
For the record I am resolutely anti-nuclear for three main reasons: a) it incontrovertibly leads to the proliferation of materials for nuclear weapons, b) it produces extremely hazardous waste that we will never be able to clean up, c) is not economically viable if one considers the true costs of the reactors, infrastructure, storage, clean-up and other costs. But in this article I am not here to preach but rather accumulate basic facts. I mention this only in case some more rabid elements assume I am pro-nuke.
There are two power stations directly affected by this natural disaster, both located in Futaba District, Fukushima Prefecture, Japan. Fukushima Dai-ichi Nuclear Power Station (aka Fukushima I) has six reactors (784 MW except Unit 1 at 460 MW), of which units 1-4 were running on 11 March 2011. (Units 5-6 were shut down for regular maintenance.) Fukushima Daini Nuclear Power Station (aka Fukushima II) has four reactors of 1100 MW each. Each are old-style reactor systems using a simple steam conduction principle. The nuclear reaction produces intense heat with converts water liquid to vapour (steam), which then drives turbines for electricity. Fukushima I Unit 1, the oldest, had been operational since 1971.
The earthquake ID usc0001xgp, magnitude 8.9, occurred at 14:46:23 local time, on 11 March 2011 centred about 130 km east of Sendai, Honshu. Nine minutes later a tsunami warning was sent out from the Pacific Tsunami Warning Center. Since the wave front was reported (where?) as travelling at a speed of 10 km per minute or greater, this would have meant the warning would have been received onshore at most four minutes before the wave impacted.
Despite this, it now appears that those on the coast of Sendai had advance warning by way of sirens and announcements through public address speakers. The Japanese are well trained for earthquakes and knew to move to higher ground, even without such announcements. However, no-one expected a wave of up to ten metres in height and reports now indicate that many simply could not evacuate fast enough. The largely low-lying ground meant that water travelled up to 10km inland, depending on the lie of the land.
This earthquake broke the mains electricity connection and triggered automatic shut-down procedures at Fukishima I at 14:48. This involves full insertion of control rods into the material in the core. This prevents further nuclear reactions at which time the reactor is said to be "subcritical". The main steam isolation valves are closed, so that there is no longer a direct connection from the reactor core to the outside world. (In any case, I believe there is no direct connection in this design, since there is an intermediary circuit of water.)
It then takes some time for the reactor to cool down (on the order of days) during which time cool water must be pumped into the core. Due to flooding caused by the tsunami, the generators supplying power to these pumps failed (either for a period or entirely -- information is unclear). As a third system, batteries would be brought online, but these last only for a short period. What is required in the longer term is either: a continuing supply of charged batteries, working diesel generators, or restoration of the power grid. In this regard, news reports of the US Army flying in "coolant" was misinformation, unless there was some reason for them to fly in water when there was plenty at hand. It might instead be presumed they were arriving with more fuel for the generators or more batteries.
Issues with getting enough coolant into the cores meant that temperatures in the suppression chambers exceeded 100 degrees in the various units. It was thus deemed necessary to release pressurised air, in order to cool the buildings. This air would contain radiation in terms of Nitrogen 14. Before the venting occurred, residents were evacuated from an area 3km in radius. This would be to avoid them breathing in radiation that, though low in itself, might cause long-term health issues.
Following this, on-site radiation stations (at the perimeter of each plant) read high enough to trigger the report of an "incident" under Article 15, Clause 1 of the Act on Special Measures Concerning Nuclear Emergency Preparedness.
At Dai-ichi a further earthquake (140 such with magnitudes up to 6.2 occurred in the period after the main quake according to the U.S. Geological Survey) caused an explosion at Unit 1 at 15:36, as widely reported in the media. Four workers were injured. Furthermore, following an earlier accident (likely the initial earthquake) a tower crane operator working in the exhaust stack was confirmed dead at 17:17. The radiation "incident" was reported at 16:17. The evacuation zone was increased from 10km to 20km at 19:11.
At Daini the radiation "incident" was reported at 15:29. The government set the evacuation zone at 3km by 17:00 and 10km at 19:00. Unit 1 was first cooled by isolation condenser, followed by sea water at 20:20pm, and then boric acid subsequently. Units 2 and 3 are being cooled by water. This indicates a more serious problem with cooling in Unit 1. Three workers were injured on-site. An employee working in Unit 1 was irradiated at 106.3mSv, enough to require decontamination procedures.
What concerns everyone is how much radiation has been let loose into the general environment as a result of the drastic measures taken to cool the multiple reactors. The Kyodo news service reports that radiation is 8x normal outside the plant, 100x normal in the control room and 1000x normal in the containment area. Evacuees are now being scanned for radiation.
The System for Prediction of Environment Emergency Dose Information (SPEEDI) is not showing figures for those power plants nor two others in the north of Japan. Rather than read any conspiracy theory into this, I suggest it is simply due to lines being down.
The International Atomic Energy Agency has established the International Nuclear and Radiological Event Scale (INES) in order to rate the severity of any nuclear mishap. Reuters has reported the current accident is rated a 4, Accident With Local Consequences. For reference, Three Mile Island was a 5, and Chernobyl was a 7. But these are only general categories and do not tell us much.
Besides those sources already linked, I have used the Tokyo Electric Power Company (TEPCO) bulletins, which seem to me remarkably frank and timely. My general information comes from the BBC, Reuters, Sky News, etc. though I remain entirely sceptical of mainstream media.
I will update this article with missing information and developments only for a short while.
Update: The TEPCO site is off-line, likely swamped with requests.
Update: Nitrogen 14 is indeed a component of the vented steam, but as this is not radioactive I am not sure why the steam has been labelled as such.
Update: Coastal areas had some (not much) time to evacuate so I have added further info to my description.
Update: As of 13 March the automated cooling system at Dai-ichi Reactor 3 has failed. Pressure has been reduced by manually opening the safety valve, injecting sea water and boric acid as in Reactor 1 previously. It can be assumed that there is now a risk of the building exploding as did Reactor 1, due to accumulated Hydrogen.
Update: I mention in the body of the article that an earthquake caused the explosion of the Reactor 1 building shell, since this is what TEPCO reported. I wish to clarify this matter. What exploded was Hydrogen gas, created when the shells of the cooling rods melt. The presence of such is indicative of a serious problem with cooling. It could well be that an earthquake triggered the explosion, since the Hydrogen has to mix with something (Oxygen, say) to become flammable.
Update: The use of sea water indicates a serious problem since the corrosive effects of this liquid means the reactor can never be used again. TEPCO is writing off these expensive installations in an attempt to forestall further problems.
Update: According to the Nuclear Information and Resource Service website, TEPCO has reported that six to ten feet of the core of Reactor 3 has been exposed for some time. The bulletin was dated 18:30 13 March but the time of the announcement is not stated.