In the beginning of the Fukushima Nuclear Crisis, in the hours and days after the earthquake and tsunami struck, nuclear power experts assured us that no matter how bad it seemed, nuclear material would stay in the reactors. It was unlikely that the reactors would melt down, and if they did melt down a little, that would be OK because the melted down stuff would stay within the reactor vessels. No problem. What actually happened, however, is that the nuclear material in three of the reactors totally melted down, and then melted through in perhaps two or three of the reactors, but at least, probably, did not reach “China Syndrome” levels of out-of-control.<\/p>\n
What actually did happen, though, may have been worse.
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To examine that idea we need to get a handle on some terminology. There is a video down in Ana’s Feed explaining this in some detail, but I’ll give you a very brief summary here. A “meltdown” is when the fuel rods in a reactor get hot enough (from lack of proper cooling) to literally melt, and the melted stuff “melts down” to the bottom of a reactor’s vessel, the vessel in which the fuel rods and control rods (rods that dampen the nuclear chain reaction) normally reside. A “melt through” is when this mass of molten radioactive stuff breaches the vessel and gets out, where it would normally be trapped by a containment vessel or structure of some kind, depending on the design of the reactor and the plant.<\/p>\n
In the case of Fuskushima, the material in some of the reactors melted down pretty much completely, as far as we can tell, and then melted through, escaping form the reactor vessel. We were told this would not happen because each vessel was so thick, but in fact, the very thick walled vessel has lots of holes in it by design, and the objects plugging those holes were apparently no match for the masses of molten radioactive stuff. Having said that, we are not assuming that one or more vessels were not breached, cracked, or burned through in some other way as well (evidence suggesting that has been presented before and not refuted) so let’s leave that on the table as a possibility. In any event, stuff melted through.<\/p>\n
A “China Syndrome” (a term made widely known in the Jane Fonda movie) is when the molten mass of nuclear stuff that has melted through accumulates in a sufficient concentration and is sufficiently hot that it breaches the containment and goes into the substrate of the building … into the ground, the geology, the water table, whatever. What could happen is that this stuff stays hot, maybe undergoes fission if concentrated enough, and so on, but given the kind of fuel and the state of the fuel at Fukushima, what actually would happen is that the nuclear stuff would just find its way through cracks and spread through groundwater pretty much like any other stuff, but not as easily as a normal liquid (like an oil spill).<\/p>\n
But that may not have happened. According to the analysis referenced below in Ana’s feed, the base of the system … the containment designed to catch the bad stuff … more or less worked and the radioactive stuff is sitting there somewhere in the basement, somewhat spread out.<\/p>\n
Now, here’s the problem. Because there is so much radioactive stuff in the buildings and in the cracked spent fuel storage tanks, water has to be pumped in more or less all the time, although at a much lower rate than a few months ago when it was boiling off at a high rate. In theory, water that is pumped in is then pumped out, cleaned up, and reused. But what seems to be happening, in addition to this, is that water is doing the Elvis thing … it is leaving the building, via one or multiple routes to the groundwater. So, instead of getting all spread around in the underlying geology and then spreading through the groundwater, it is being held at a higher concentration in a smaller number of locations under the reactors, but still getting into the groundwater.<\/p>\n
This might be better than being loose underground, but maybe not. The fact that this material is so concentrated means that the basements of these plants cant be accessed, and thus, cleaned up. The wreckage of the damaged plants … damaged by the earthquake, the tsunami, by multiple explosions (some hydrogen gas explosions, one possible nuclear explosion) in combination with the presence of quite a bit of radioactive water, combined with piles of nuclear stuff of unknown extent, location, or configuration means only one thing, which has not really been fully admitted by TEPCO, though it has been implied: The basements of the melted-through reactors can not be approached by robots, humans, or any other agency for many, many years. The Fukushima plants will be a source of radioactive contamination of the nearby ocean for several years until some way to contain the plant from below is devised. Then, there will be several more years before engineers can begin to get at these lower, inner areas of the plants to even see what is in there. That is something that was never planned for, has never been done before, and may not be possible. But it will be expensive!<\/p>\n
There is still argument over the very interesting question of how much damage, and of what kind, was caused by the earthquake vs. the tsunami. There is a politicized and rather stupid reason why these arguments are happening. Yes, we want to know that happened, and the details will be useful in the future, but the reason people are arguing about it is to decide which “I told you so” position is right. There are those maintaining that the plant was designed to handle an earthquake and not a tsunami, and it was the tsunami that did the damage. This is reminiscent of the early days after Katrina when people who otherwise wanted to be seen as smart told us the dumbest thing I’ve ever heard in my entire life (“It was not the hurricane, it was the flood, that damaged New Orleans”). Here, we are being told that the tsunami (which was caused by the earthquake) was the real culprit. The reason why this is not important is this: Today, we can look back on the planning process for the Fukushima plants and identify the fact that people knew tsunamis of this magnitude were possible, but put that fact aside. It does not matter if the earthquake or the tsunami did the critical damage that destroyed the cooling systems. Both types of disasters were expected, eventually, and either way, there was no real backup solution. Thus the meltdowns. And the melt through. And the river. Underground. Running through it. The current evidence suggests that the earthquake knocked out the cooling systems. A government panel assessing the causes of the Fukushima disaster is explicity not addressing the earthquake, because TEPCO has already decided that it better darn well be the tsunami. What-ever.<\/p>\n
In any event, this is an interesting finding: The tsunami that hit Fukushima was a previously unobserved, or at least, very rare form of wave, which started as two separate waves, combining to form one large wave.<\/p>\n
We’ve discussed the problem of ocean contamination and accumulation. From a Woods Hole report (reference in the feed):<\/p>\n
… discharges from the Fukushima Dai-Ichi nuclear power plants peaked one month after the March 11 earthquake and tsunami that precipitated the nuclear accident, and continued through at least July.<\/p>\n
Their study finds that the levels of radioactivity, while high, are not a direct threat to humans or marine life, but cautions that the effect of accumulated radionuclides in marine sediments is poorly known.<\/p>\n
The release of radioactivity from Fukushima–both as atmospheric fallout and direct discharges to the ocean–represents the largest accidental release of radiation to the ocean in history.<\/p>\n
Concentrations of cesium-137, a radioactive isotope with a 30-year half-life, at the plants’ discharge points to the ocean peaked at more than 50 million times normal\/previous levels.<\/p>\n
Concentrations 18 miles offshore were higher than those measured in the ocean after the Chernobyl accident 25 years ago.<\/p><\/blockquote>\n
The radiation is, of course, diluting quickly as it mixes with the ocean water. The study does not cover the last several months.<\/p>\n
I’m not sure if we are quite ready to call this one yet, but there is continued discussion on the idea of an actual nuclear explosion at Reactor 3. There are several reasons to think this happened, and the current theory is that cooling water dropped low, the spent fuel pool at reactor 3 heated up, lots of the water produced hydrogen which then exploded, and this had the effect of compressing the already nearly critical fuel pellets in the pool, which caused the nuclear explosion. To refresh your memory, here is the explosion:<\/p>\n