Fukushima update – Nuclear reactor nearly under control?

Four months in to Japan’s Fukushima nuclear disaster, we’re finally starting to get some good news. Sources inside the Japanese government and Tokyo Electric (TEPCO) say they have just about completed the first phase of their plan to defuse the reactors.

Of course, this remains the worst nuclear accident in history, millions of tons of radioactive material still threaten lives from Tokyo to Seattle and beyond, and it will be years before the situation comes close to being “safe”. But as Japanese restaurants wrestle with the idea of serving their customers radioactive beef, it’s nice to have some good news for a change.

Cooling

The first thing that had to happen was a consistent cooling system to keep the reactors from melting down further – at least two had gone beyond meltdown and into “melt-through”, partially melting away their containment. Since the reactor cores are cooled by water, and water flows out of leaks, that has made things tricky.

According to the Daily Yomiuri, “TEPCO has set up a coolant circulation system that uses water leaking from the reactors and flowing into the reactor buildings. Although frequent troubles have kept the operating capacity of the network to decontaminate radioactive water at around 75 percent, the system itself is working well to keep the temperature inside the nuclear reactors at about 100 C.”

Keep in mind that 100 C is the boiling temperature of water, so “cooling” is a relative term. And they don’t have the leaks stopped… but they have them under control.

And speaking of leaks…

Radiation releases

You might well expect that part of “having the reactor under control” would mean “not belching radioactive gasses out into the atmosphere.”

But you’d be wrong. Again, in the inimitable words of the Daily Yomiuri, “According to the sources, the government and TEPCO concluded that the amount of radioactive substances released from the nuclear reactors is steadily decreasing. The results were obtained by measuring the amount of radioactive substances on the ground surrounding the nuclear power plant and the air above the facility’s buildings.”

So still leaking. But not as much. So that’s good.

Not exploding

This is also an important one, and somewhat misunderstood. Because we are all familiar with “nuclear bombs”, there’s a misconception that the nuclear fuel in the reactor can explode. That’s not so much of a problem, really – it tends more to get very very hot and melt down, melting everything around it. That’s the origin of the “China syndrome” concept – if nothing was to stop it, it would just keep melting its way into the earth’s crust (but not all the way down to China… and certainly not if you were starting in Japan in the first place).

The real problem is hydrogen gas, which IS highly explosive. That’s what blew the reactors in the first few hours of the situation, after the Tsunami knocked out the plant’s backup power.

But hydrogen needs oxygen to explode, so the best way to minimize the danger of hydrogen explosions is to minimize the oxygen. They’ve already filled two of the reactor buildings with nitrogen, which is inert and won’t allow any hydrogen that builds up to blow up. The No 3 reactor may be too leaky for that to work, but they started trying today.

The one downside: injecting nitrogen means more radioactives will get pushed out through those leaks…

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