The Japan Syndrome

The Japan Syndrome

Update: Explosion; What's with the Containment?

This happened sometime during the night, or at least, I couldn't find news reports at about 12:30 a.m. Central. The BBC report, last updated this morning at 8:14 Central, says the Japanese authorities are claiming that the "container housing the reaction was not damaged and radiation levels have now fallen. . . . [T]he concrete building housing the plant's number one reactor had collapsed but the metal reactor container inside was not damaged." Four workers were injured. It's clear that steam escaped, but it's not yet clear how contaminated the steam was. Radioactive cesium and iodine had been detected hear the number one reactor before the explosion. If the metal reactor container inside the concrete building was not breached, that's certainly good news. Although it's too early to rely on the frantic bits of official releases being reported worldwide, it's still possible that the steam, which is being blown out to sea, was not wildly dangerous. The damage to the nuclear plant, however, is considerable, and the damage to the nuclear power industry worldwide is incalculable.

Original post: Japan has 33 nuclear reactors, of which half a dozen or more were shut down by the earthquake. One in particular is turning some hair gray: the 480MW Fukushima nuclear plant about 160 miles north of Tokyo.

The plant had emergency systems, of course. The violent shaking of an earthquake triggers a shutdown in which the control rods are plunged into the nuclear core material to damp off the chain reaction. But the control rods don't work properly if they are allowed to melt -- and it's hot in there. So there's an emergency cooling system, which is basically a lot of liquid (water? I don't know) circulated by pumps through a cooling tower and cooling pond. The pumps are electric. The primary system is to run the pumps on the normal power grid, but the power grid was knocked out by the tsunami. Not to worry; there's a back-up: diesel generators. Unfortunately, those were knocked out by the tsunami, too. But hold on: there's a back-up back-up, which is batteries. They last for 8 hours.

The U.S. military has a crash-priority task to get more generators and/or batteries in there, along with everyone in Japan who can help with the same. If they lose the back-up back-up power to the cooling pumps, all the coolant can boil off in as little as an hour. When the coolant boils off, the reactor core can melt. At Three Mile Island in 1979, loss of coolant for 30 minutes led to a 50% meltdown. Not that meltdowns punch through the crust of the Earth or any of that nonsense, but radiation levels do start rising, and you worry about radioactive steam building up pressure and breaching the containment structure. Indeed, the Japanese government announced earlier today that the pressure was 50% above normal and that they planned to vent some gas to prevent too high a build-up. The gas is "slightly radioactive," they report. They also state that the level is so minimal that the release would cause no danger.

I'm as big a supporter of nuclear energy as you'll find, but that doesn't inspire my confidence. It's one thing to know that the U.S.S.R. couldn't build adequate safety systems, but Japan? It was a big earthquake, but not unprecedented, particularly in an especially earthquake-prone region. The tsunami was a well-known consequence of earthquakes at low altitudes near the coast. It's not hard to predict that an earthquake and tsunami might knock out the power grid. So how come the back-up diesel generators weren't someplace safer? How come the batteries are adequate only for 8 hours? I'd like to think that nuclear reactors were a little more conservative than this.

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