Attention has centred on units #1, 2 and 3 of the Fukushima Daiichi plant (all Boiling Water Reactors built in the 1970s). Current concern is focused on unit #2 (more below). Units 4, 5 and 6 at the site were not in service at the time of the earthquake and their situation is stable.
At a nearby plant, Fukushima Daiini, the situation is now under control, and units are in, or approaching, cold shutdown
What is of most current concern?
Units 1 and 3: the situation now seems fairly stable. There is some concern that holding pools for spent nuclear fuel (SNF) may have been damaged by the hydrogen explosions, but nothing is confirmed. Provided the pool walls remain unbreached and the SNF is covered with water, the situation should not escalate. Note: Although still ‘hot’, the SNF decay heat is many orders of magnitude lower than the fuel assemblies within reactors 1 to 3.
Unit 4: A fire has started at the building of Unit #4. Note that the reactor of this unit is stable and was not operating at the time of the earthquake.
Unit 2: This is now of most concern, and the situation continues to change quickly
Fukushima Daiichi Unit 1 reactor
o As of 12:00AM on March 15, the injection of seawater continues into the primary containment vessel.
• Fukushima Daiichi Unit 2 reactor
o At 12:00PM on March 14, in response to lower water levels, TEPCO began preparations for injecting seawater into the reactor core.
o At 5:16PM on March 14, the water level in the reactor core covered the top of the fuel rods.
o At 6:20PM on March 14, TEPCO began to inject seawater into the reactor core.
o For a short time around 6:22PM on March 14, the water level inside the reactor core fell below the lower measuring range of the gauge. As a result, TEPCO believes that the fuel rods in the reactor core might have been fully exposed.
o At 7:54PM on March 14, engineers confirmed that the gauge recorded the injection of seawater into the reactor core.
o At 8:37PM on March 14, in order to alleviate the buildup of pressure, slightly radioactive vapor, that posed no health threat, was passed through a filtration system and emitted outside via a ventilation stack from Fukushima Daiichi Unit 2 reactor vessel.
• Fukushima Daiichi Unit 3 reactor
o At 11:01AM on March 14, an explosion occurred at Fukushima Daiichi Unit 3 reactor damaging the roof of the secondary containment building. Caused by the interaction of hydrogen and oxygen vapor, in a fashion to Unit 1 reactor, the explosion did not damage the primary containment vessel or the reactor core.
o As of 12:38AM (JST) on March 15, the injection of seawater has been suspended.
The lesson so far
Japan suffered an earthquake and tsunami of unprecedented proportion that has caused unbelievable damage to every part of their infrastructure, and death of very large numbers of people. The media have chosen to report the damage to a nuclear plant which was, and still is, unlikely to harm anyone. We won’t know for sure, of course, until the last measure to assure cooling is put in place, but that’s the likely outcome. You’d never know it from the parade of interested anti-nuclear activists identified as “nuclear experts” on TV.
From the early morning Saturday nuclear activists were on TV labeling this ‘the third worst nuclear accident ever’. This was no accident, this was damage caused by truly one of the worst of earthquakes and tsunamis ever. (The reported sweeping away of four entire trains, including a bullet train which apparently disappeared without a trace, was not labeled “the third worst train accident ever.”) An example of the reporting: A fellow from one of the universities, and I didn’t note which one, obviously an engineer and a knowledgable one, was asked a question and began to explain quite sensibly what was likely. He was cut off after about a minute, maybe less, and an anti-nuke, very glib, and very poorly informed, was brought on. With ponderous solemnity, he then made one outrageous and incorrect statement after another. He was so good at it they held him over for another segment
The second lesson is to the engineers: We all know that the water reactor has one principal characteristic when it shuts down that has to be looked after. It must have water to flow around the fuel rods and be able to inject it into the reactor if some is lost by a sticking relief valve or from any other cause – for this, it must have backup power to power the pumps and injection systems.
The designers apparently could not imagine a tsunami of these proportions and the backup power — remember, the plants themselves produce power, power is brought in by multiple outside power lines, there are banks of diesels to produce backup power, and finally, banks of batteries to back that up, all were disabled. There’s still a lot the operators can do, did and are doing. But reactors were damaged and may not have needed to be even by this unthinkable earthquake if they had designed the backup power systems to be impregnable, not an impossible thing for an engineer to do. So we have damage that probably could have been avoided, and reporting of almost stunning inaccuracy and ignorance. Still, the odds are that no one will be hurt from radioactivity — a few workers from falling or in the hydrogen explosions, but tiny on the scale of the damage and killing around it.
It seems pathetic that Russia should be the only reported adult in this – they’re quoted as saying “Of course our nuclear program is not going to be affected by an earthquake in Japan.” Japan has earthquakes. But perhaps it will be, if the noise is loud enough.