For Want of a Nail

For Want of a Nail

Brave New Climate has one of the most comprehensible descriptions of the Fukushima reactor accident that I've seen so far, though there's a lively debate in the comments section about how accurate it is. While quite a few of the comments sound like ignorant hysteria, others make me wonder, since I don't know nearly enough to be able the answer the questions they raise. By far the most amazing part of the story to me is why it proved impossible to get backup generators in there fast enough to circulate the coolant to bleed off the post-shutdown residual heat:

Things were going well for an hour. One set of multiple sets of emergency Diesel power generators kicked in and provided the electricity that was needed. Then the Tsunami came, [at least five times as big as the plant had been designed for]. The tsunami took out all multiple sets of backup Diesel generators.

. . . When the diesel generators were gone, the reactor operators switched to emergency battery power. The batteries were designed as one of the backups to the backups, to provide power for cooling the core for 8 hours. And they did.

Within the 8 hours, another power source had to be found and connected to the power plant. The power grid was down due to the earthquake. The diesel generators were destroyed by the tsunami. So mobile diesel generators were trucked in.

This is where things started to go seriously wrong. The external power generators could not be connected to the power plant (the plugs did not fit). So after the batteries ran out, the residual heat could not be carried away any more. [Emphasis supplied]

There are hundreds of comments, but it took a while for someone to say, "Really? The plugs didn't fit? They couldn't just wire around somehow?" (But more colorfully.) Another commenter tried to explain why that might be harder than you'd think:

I think that we’re talking 100s of KVA needed to run the coolant pumps. You can’t exactly splice those wires without dedicated tools. You need a hydraulic ram with correct die to do attach lugs to the wire. You can’t do temporary insulation using electrical tape either. It just takes ONE missing piece for the job to be stopped. You don’t have the right die for the size of the wire available, or you don’t have the lugs, or, or, or. It’s very easy NOT to be able to do such a job when it’s unplanned for.

The following commenter is beating an anti-nuke drum, but I do take seriously his caution about the inevitability of human error:

[Y]ou can be certain humans will screw up. Constantly. And do things like build nuclear power plants on a subduction zone – with small containment vessels – and then put the power hookups for the cooling system in the basement. The cooling system which is the only thing that stands between them and a meltdown. It’s cheaper. Or extend the operating licenses of dozens of plants here and in Europe even though they are past there design lifetimes (and some like Vermont Yankee are leaking radioactivity into the the ground water). It’s cheaper. Or the contractors that cut this and that corner.

Along those lines, there are reports that all coolant is now being supplied by fire trucks, but the trucks keep running out of gas, or sustaining damage from the explosions.

In spite of all this, the author's conclusion is that the "core catcher" is there in case back-ups one, two, three, and four fail. The core catcher is designed to catch anything that slags down and is built to hold up easily to the total residual heat of the powered-down core. It will be a tedious and expensive business to clean up, but that's a headache for TEPCO, not the civilized world or even the immediate neighborhood. He believes there's practically no risk of a containment rupture, no matter what happens to the outside buildings, whose primary function is to keep rain off of the reactor and perform some air/steam filtration. In particular, he minimizes the level of radiation that can be detected in either the vented steam or the debris from the hydrogen explosion

I'm not finding very good information yet about that last part. It all seems to have been translated through a couple of layers of bureaucrats and/or journalists who don't have the slightest idea what they're talking about.

By the way, if you want to see how differently the story reads when an operator isn't as scrupulous as TEPCO, try this account of Chernobyl, especially the role of the grid operator, who insists that the plant power back up halfway through its safety test, because someone out there needs the electricity. Then reflect on the fact that Chernobyl had no containment dome of any kind. Then consider whether warm-hearted socialists make better engineers than the cold fish-eyed capitalists.