There’s Still-Molten Fuel at Fukushima?

National Land Image Information (Color Aerial Photographs), Ministry of Land, Infrastructure, Transport and Tourism.

In The Telegraph today, there’s an article about the confirmation, finally forthcoming from Tokyo Electric & Power (Tepco) that in the No. 1 reactor at Fukushima Daichi, there “was” a meltdown. But in case you think this is a “post-mortem” investigation…nope! The crisis is still going on. It’s very much active.

And when I say “active,” I mean…active. Says the Telegraph:

One of the reactors at the crippled Fukushima Daiichi power plant did suffer a nuclear meltdown, Japanese officials admitted for the first time today, describing a pool of molten fuel at the bottom of the reactor’s containment vessel.

[Link.]

Molten. Molten? Molten. Not “melted and solidified.” Molten. That’s kind of bad.

Sadly, that’s not where the bullshit ends. The whole affair is still laced with double-talk. Here’s what The Telegraph said beyond that:

Engineers from the Tokyo Electric Power company (Tepco) entered the No.1 reactor at the end of last week for the first time and saw the top five feet or so of the core’s 13ft-long fuel rods had been exposed to the air and melted down…Previously, Tepco believed that the core of the reactor was submerged in enough water to keep it stable and that only 55 per cent of the core had been damaged.

[Link.]

I’m not sure whether to be more disturbed by the apparently lack of clarity on what exactly a meltdown is, or on Tepco’s math skills. Or is it the Telegraph’s math skills? Well…someone is unclear on how fractions work, that’s all I know. The generally accepted definition of a meltdown in the industry is “heat sufficient to cause core damage.” Now we get to the really technical stuff. Five-thirteenths is 38%, which is less than 55%. I’m unclear what Tepco is now announcing. “We thought only 55% of the core had experienced damage. Now we see that it’s much worse than we thought: It’s a whole 38%!” Just speaking for myself, that’s not the kind of math whiz I want working my nuclear reactor.

Meanwhile, The Atlantic Wire is both reporting that the Fukushima No 1 experienced a full meltdown. I was a liberal arts major, but I remember something about 100% being more than 55%, and considerably more than five-thirteenths. And The Atlantic Wire is also taking great pains to say that nuclear experts are not of one mind as to what the term meltdown means (true), that they may not agree on what the definition of full vs. partial meltdown may be (true), and that the difference may not be that important (kind of bullshit).

The good news is that we knew a long time ago the No. 1 reactor had not yet converted to mixed-oxide or MOX fuel, a mixed plutonium-uranium fuel that (usually) incorporates weapons-grade plutonium and which is far more toxic than the reactor-grade uranium that No. 1 was (presumably) using.

Look, I don’t mean to be a conspiracy freak or anything, but the uranium rather than MOX fuel may be why No. 1 is the reactor Tepco is confirming a meltdown in. Especially since they’re also confirming the likelihood of a containment breach from the No. 1 reactor — in which the fuel melted through the bottom of the vessel:

Now the company is worried that the molten pool of radioactive fuel may have burned a hole through the bottom of the containment vessel, causing water to leak.

“We will have to revise our plans,” said Junichi Matsumoto, a spokesman for Tepco. “We cannot deny the possibility that a hole in the pressure vessel caused water to leak”.

Tepco has not clarified what other barriers there are to stop radioactive fuel leaking if the steel containment vessel has been breached. Greenpeace said the situation could escalate rapidly if “the lava melts through the vessel”.

 

So…here we go, summarizing: the fuel is still molten, and it is hot enough to have already burned its way through steel. Liquid, molten reactor-grade uranium has breached the containment vessel, is leaking into the ocean, and they can’t hit it with a garden hose ’cause that’ll make the leak worse. That’s not great news. Seriously.

I have to say, I am skeptical of all these news reports, because it seems absolutely impossible that a full meltdown could have occurred at Fukushima, with fuel that is still molten two months after the event, and no one knew it until now. It seems pretty obvious that even when the news from Fukushima Daichi is reported truthfully — which is almost never — it is not reported in a context that means anything.

If the melted corium (melted uranium, fuel rod material, fuel rod assembly, etc) is still molten, that’s way worse than anyone has been led to believe. The Telegraph says that the fuel rods themselves, now melted down and exposed to air, can’t be cooled with more water because that will exacerbate the leak. Tepco¬† “said there was enough water at the bottom of the vessel to keep both the puddle of melted fuel and the remaining fuel rods cool,” which is crazy enough…But “melted,” not solidified, spells it out. It doesn’t make much sense to my brain, so I don’t know whether to believe the news (which seems unclear on the science) or Tepco (which seems to primarily be concerned with covering its ass).

But are we talking about decay heat or an active nuclear reaction? That’s a really important question.

One thing I couldn’t get a straight answer on was whether melted fuel rods, in which the uranium, zirconium, and steel kinda all goes glorp! together, means that an active nuclear reaction starts taking place — that is to say, have the melted rods in the No. 1 reactor re-achieved criticality, or are they just staying hot from decay heat?

A criticality means an active nuclear reaction. That means that hoppin’ neutrons from one uranium nucleus tend, at a rate higher than 1:1, to go Za-zing! into another uranium nucleus.

Decay heat just means there’s residual heat from natural radioactive decay in the uranium — which can last, significantly, for months or years following shutdown of a nuclear core.

The difference may seem minor. It’s not. The question is whether the fuel a self-sustaining reaction, or if the decay heat will dissipate naturally, and the temperature go down. Decay heat could be enough to cause core damage, as we saw in the midst of the initial crisis, in the warnings about the spent fuel pools at the No. 4 reactor. Those were said to be hot enough from decay heat — and then it was (sort of) admitted that there had been damage to the spent pool containment structure.

Why does it matter? Because the bad news is still piling up. Yesterday, ocean-bound leaking radioactive water from the No. 3 reactor (which also experienced a meltdown) was sealed. No word on how long it had been leaking. No. 2 reactor leaked radioactive water into the ocean last month.

Greenpeace has been putting out independent reports about how much radioactive iodine and cesium have been found in seaweed up to 40 miles from Fukushima — but it’s impossible to place statements like “five times the legal limit” in a meaningful context when it comes to human health. And, like I said, Greenpeace has an agenda here, and has shown in the past that it’s willing to play fast and loose with the facts when it comes to nuclear power. That’s an easy thing to do — the facts, when it comes to radiation and human health, are confusing and ambiguous.

But molten uranium is not that ambiguous. I’m not naive enough to claim “It’s either molten, or it’s not.” But if there’s molten fuel at Fukushima…why isn’t that the headline in The Telegraph, Bloomberg and the Associated Press?

Possibly related posts:

One comment on “There’s Still-Molten Fuel at Fukushima?
  1. Good post…you raise some rational questions…but I would have posted a more recent photo of the Fukushima plant…it doesn’t look like that anymore.

Comments are closed.