What sulfur particles in California can tell us about Fukushima

During the early weeks of the Japan 3/11 crisis, after a tsunami critically damaged the Fukushima Daiichi nuclear power plant, we talked on Boing Boing about why Americans on the West Coast didn't need to worry about exposure to radioactive fallout. Shorter version: The levels of radiation that made it across the Pacific were far too low to cause a serious health concern.

Now here's something really interesting: The levels of fallout that made it across, while too low to pose a risk to humans, were detectable by extremely sensitive scientific equipment. And those measurements are now being used to document what happened at the site of the disaster.

In the process of trying to cool down the overheating reactors, officials in Japan dumped sea water and reaction-slowing boric acid into the reactor cores. The resulting chemical reaction—chloride ions in salt water combining with fast-moving neutrons from the reactor—produced a form of radioactive sulfur. Meanwhile, scientists at the University of California, San Diego, were already measuring sulfur particles in the air as part of climate research. Days after the crisis began, their instruments picked up the radioactive sulfur that had crossed the ocean.

Now, using modeling and some basic knowledge about how particles behave, they've been able to use the information they gathered in California to estimate how high radiation levels were in Fukushima in the early days of the crisis. A couple of things they've found: Further evidence that at least one of the reactor cores suffered a meltdown, and evidence suggesting that the damaged reactors didn't re-start after the emergency began—a possibility that has been pointed out by other scientists. I'll have a more in-depth look at this study later this week. For now, check out the write ups at Nature News and USA Today.

The full research paper is at The Proceedings of the National Academy of Sciences.

(Thanks, Miles O'Brien + Jenny Marder of PBS NewsHour)



  1. Huh? That’s seriously old news:


    Also, why exactly would anybody need further evidence that the reactors suffered a meltdown? Nobody denies that, nobody is trying to hide that kind of information(*).  And microscopic traces collected on the next continent across the pacific are most certainly not the right kind of evidence to rule out a re-criticality of the reactor.

    So, exactly what is this article telling us? That we must not trust the Japanese scientists and engineers on the ground?

    (*) Yes, TEPCO was very careful in wording their press releases to only
    contain 100% verified information – which wasn’t a lot in the first few weeks after the accident. Hence they said “fuel damage” instead of “meltdown” because they could not (initially) say in all honestly whether the fuel ended up melting or was just severely damaged by the heat. The amount of radiation released into the atmosphere was not large enough to rule out a non-meltdown scenario.

    In fact, it would have been better if they still wouldn’t know – because the way they found out there must have been a meltdown was the fact that the containment leaked out the highly radioactive cooling water. After that they knew that a meltdown must have occurred to account for it … but containments are not supposed to leak …

    1. In an ideal world we could trust TEPCO to tell us all that they know. But there are some questions remaining. In particular, we’d like to know exactly how much the reactor was damaged by the earthquake alone, before the tsunami hit. 

    1. a) They said there is no danger for the US mainland and that was absolutely true.
      b) Not saying that there is a meltdown is not the same as saying there is no meltdown.

      What is this? Rhetorics 101 – How to set up a strawman?

  2. The information policy of Tepco is pretty good – unfortunately, the media do a terrible job of a) spreading the information they are given and b) explaining it. Explaining would require that they actually understand what they are talking about in the first place. But they don’t and hence the reporting is as bad as it is.

    Instead, it takes an unabashed pro-nuclear blog to write something like that (3 months ago):

    “NHK is carrying the report, from TEPCO apparently, that there is a hole in the bottom head of the pressure vessel at No. 1 plant. This appears to be in addition to the previously reported piping damage, although another report does indicate water leakage from piping connected to the primary plant occurring in the turbine building. JAIF’s now-irregular status reports do now indicate probable damage and leakage in terms of the reactor pressure vessel and also the primary containment at the No. 1 reactor plant.”


    It has also been established that there was no major damage and only one significant problem in the 45min or so it took for the tsunami to arrive after the the earthquake. That problem was that the cooling systems of reactor #1 was doing its job rather too well and automatically shut itself down after 20 minutes or so, when temperatures started to fall too quickly.

    They could have overridden the automatic shutdown, had they known how big the tsunami was (which they didn’t – just as the rest of people along the coast). Unfortunately, the damage that the tsunami caused prevented the staff from remotely turning it on again (after losing pneumatics to operate the valves), so that the core of reactor #1 overheated.

    1. Thats the official story, though I hear that it doesn’t 100% match with the computer simulations. Of course the software is GE’s etc. trade secret so nobody outside of the nuclear industry can independently verify it.

      In any case, I 100% agree that the media did a horrible job during the whole story. Absolutely clueless reporting all around.

      1. Then you should show a source and say where the mismatch is. Also, there are many observers following and reporting the Fukushima Accident who are mostly independent.

        “Mostly independent” as in “they had an education and often working experience within the nuclear industry”. But if you jack up your standards for independence so high as to exclude that, then you’d be hard pressed to find independent and competent reporting for anything.

        1. Yes having a physics PhD definitely helps to sort out the utter BS. But at one point you need to crunch the numbers and you just can’t do that as an armchair observer; A nuclear power plant is way too complicated for that, and the blueprints aren’t exactly freely available (Different implementations of the Mark I reactor design can vary considerably). The NRC or NIST could very well step in and devote some serious resources to figure things out, but it seems like government is perfectly happy to let the companies that are in the business of selling nuclear power plants do the talking.

          In all likelihood, the official story is correct. But the fact is that those with the actual information are walled off behind corporate PR departments. Which is even understandable, considering the total cluelessness of the media. But I don’t think thats a good strategy in the long run.

  3. In an ideal world TEPCO would in fact construct our atomic melting robot overlords, and their name would be cursed and spoken with a tired, practiced disgust in the furtive gatherings of purple-mohawked hackers and muscle-grafted streetrunners.

  4. …and people would have tired, cynical sex when the high wears off and smoke cheap chinese cigarettes that taste like rat poison.

  5. Men would subsist off of stolen sugar packets and half-and-half from Starbucks, poured into dixie cups hidden in their trenchcoats, and all women would have to sell themselves – one way or another. TEPCO, of course, would profit off of their misery. But only in – an ideal world.

  6. I’m just sitting here thinking how shitty it is that those reactors and containments are STILL leaking highly radioactive crap into the soil and ocean.

  7. hey, tp1024, your comments are equivalent to a dogface worrying about cancer from all those cigarettes on D-Day. And I’m not going to explain to you why.

  8. Just nit-picking: The article wrongly says that chlorine plus neutrons is a chemical reaction. The transmutation of chlorine into radioactive sulfur 35 is a nuclear reaction.

  9. I wish there was a comparison made to data (if it exists or is accessable.) from when the US bombed Japan. Was there not data collected after that tragic radio active mess moved East tward the states, then?

Comments are closed.