On Radiation

So, I think perhaps hysteria over the nuclear plant issue is getting a little out of hand in some places. Some people are leaving Tokyo - even leaving the country - over the fear of radiation. And I just recently read that the Swedish nuclear authority has been getting hundreds of calls from people worried about the effect of fallout in Sweden. Which is not ridiculous since people's fears are very real, and fear needs to be taken seriously, but the fear is misplaced and uninformed.

First, and most important, we have tens of thousands of people dead in Tohoku, and many tens of thousands still in dire need of assistance. People still miss basic shelter and water in many areas. This is the real disaster, far worse than any effect of a broken-down reactor. The nuclear thing is a noisy sideshow, nothing more.

Leaving Tokyo: Good idea - but not for the situation at Fukushima. The Tokyo area has rolling blackouts, disrupted communications and a lack of supplies, as both power and other resources are funnelled to the disaster-stricken areas. Chances are your workplace or your school is shut down anyhow, and your company may be shifting operations to branch offices out west for the time being. If you can visit relatives in Kansai or Kyushu for a few weeks that may help relieve stress in the Kanto area a little bit, not to mention relieve some stress for yourself.


Radiation: First, to be absolutely clear, I'm not an expert. I am a researcher, but not in radiomedicine, not in nuclear engineering and not in anything connected to it. Don't take my word for things - but don't take the word of other people without expertise either.

"Sievert" is a measure of a dose of radiation, like liter or cups for liquid, meter for lengths or kilogram for weights. Sievert per hour tells you the rate over time - like kilometers per hour for speed. I'll give all numbers below in the same unit, microsievert per hour (shortened uSV/h).

Peak radiation at the Fukushima I plant have been high, well into medically unsafe levels. It is truly dangerous for the workers at the plant, and people in the area have been evacuated for good reason. But the strength quickly diminishes with distance.

Highest measured radiation so far in Ibaraki prefecture, near Fukushima was 5 microsievert (uSv) per hour. Tochigi, halfway between Tokyo and Fukushima has had a peak of 1.3 uSv/h. In Tokyo the peak was 0.8 uSv/h. All these quickly dropped to near normal again. Note how the peak is lower the further away the place is. Here in Osaka there was never any detectable difference. Sweden will never see any effect from this accident at all.

Here is a live radiation counter in Tokyo. At the time of writing, you can see a slow hump of activity over last night and morning, on average around 0.1 uSv and at most 0.2 uSv/h more than usual (100 cpm is very roughly 1 uSv/h), but back to near normal again. The lower graph is the typical level.

Normal total background radiation ranges from 0.15 to 0.5 uSV/h. Exactly how much depends on where you live - Scandinavia, for instance, tends to have relatively high background radiation, with about 0.45 microsievert per hour, and there are some places in high mountain areas that naturally give you over 5 uSv/h. Tokyo, on the other hand, lies at the lower end of the range, as you can see at the link above.

Flying exposes you to more cosmic radiation, simply because you're above much of the atmosphere. While you're chewing on a rubbery chicken and watching last years hit movie on a grainy monitor you're getting about 7 uSv every hour, more than the peak value in Ibaraki.

Let's say you decide it's a good time to escape home to Sweden. The entire peak gave you around 1 uSv extra radiation, the nightly hump also totals around 1 uSv (an average of 0.1 uSv for ten hours). The constant background level in Tokyo is about 0.2 uSv/h now. You want to leave Tokyo and get home to safe, dependable Stockholm. You hop on the airplane, which gives you about 75 uSv during the trip - 75 times the peak, and 75 times the slow hump last night - and arrive in Sweden.

Sweden has a constant background radiation rate at 0.45 uSv/h - more than twice what you have in Tokyo, and higher than during that hump of activity last night. If you live in an old stone house the rate is higher still. So, leaving Tokyo for Sweden means increasing your radiation exposure, not decreasing it.

This doesn't matter, of course, as all these values are far below any unsafe levels. What is unsafe? Around 100 000 microsievert over a year - that is 11 uSv/h for a year. Occupational limits are about 2.2 uSv/h for a year, but that's work-related exposure over and above any other sources. At about 0.2 uSv/h in Tokyo you'd need five times that level to reach workplace limits and up to fifty times current levels for a whole year to get into real unsafe territory.

More on the Reactors

Good news, first: All nuclear sites except for the accident-striken Fukushima I¹ in northern Honshu are in cold shutdown and safe.

Bad news: the situation at Fukushima I seems to deteriorate. Reactors one and three - the original problem reactors - haven't worsened, and some reports seem to say they've stabilized. But now reactors two and four are having problems too. Unit four has had two fires above the containment building, near the spent-fuel storage tank. Unit two has had an explosion that seems to have damaged the containment. There was a spike of radiation around the time, that now seems to have died off again.

Good news: all effects are purely local at this time. Unless things go very, very bad the effects will stay local. Of course, no matter what happens, the already shoddy safety reputation of the Japanese nuclear industry is going to suffer badly, and rightly so.

Bad news: A number of power plants are shut down, and are not going to start up again in the close future - or ever, in the case of the reactors at Fukushima I. Tokyo is facing rolling shutdowns to ration power at least until the end of April, and northern Japanese power companies say they'll need to ration power for the next few months.

Right now a lot of companies and other facilities are shutdown and powerless in the Tohoku region, but once they restart operation, and rebuilding gets under way along the pacific coast, power consumption is going to increase again. And mid summer - June to August - is the most power intensive time of year, due to the demand for air-conditioning². And as many plants are unlikely to start up anytime soon, Tokyo may see a return to rolling blackouts at the height of summer.

If one power plant has an emergency and shuts down it doesn't matter much how much time it takes to get it operational again. But in a place where one event - a large earthquake - can shut down many plants at the same time, the time to restore power becomes a real safety issue. It is probably a mistake for a country like Japan to lean on such an unreliable source to the point where it can cripple the reconstruction after a disaster like this.

The question is what combinations of other sources could be a feasible replacement. Geothermal energy is available and underused here. The country is mountainous and there's plenty of wind - way too much wind during typhoon season, so safe, dependable power units would cost a fair bit to erect. Wave power and offshore wind is also susceptible to tsunamis of course, and a large offshore wind park crippled by a storm or tsunami is no better than the reactor it replaces. Solar is still expensive, but costs are coming down.

Any buildout of renewable source is a long-term project in any case. At least in the medium term, this would mean increasing imports and burning of gas and coal; energy sources that cause plenty more damage to health and environment than nuclear does. But they are rather more dependable, have better worst-case scenarios, faster to repair and bring up again, and it's easier to build smaller, distributed plants that are more resilient to disaster. I don't like the idea - if there's anything we need less of, it's coal-burning power plants - but that's probably what'd take to offset the unreliability of nuclear.
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#1 "daiichi", "daini" and so on means simply "number one" and "number two". I noted English-language media seems to treat it as given names, not numbers.

#2 It sounds like a frivolous luxury to northern Europeans, perhaps, but the summer heat is no joke around here. You will have weak and elderly people dying from heatstroke unless they can cool their homes.