Saturday, March 19, 2011

Archived radiation data from Hino, western Tokyo

UPDATED with the excellent chart from and dosage in sieverts on a second y axis, assuming 120 CPM = 1 µSv/hour

Dr. Hiroshi Ishikawa(石川宏 博士)has a geiger counter in Hino that is posting realtime radiation readings. He is also posting raw data to an archive page (so far through 3/18). I graphed and posted those data below. I'll update this if/when Dr. Ishikawa posts more raw data.

From Dr. Ishikawa's English FAQ (translated by Alex Boyd), here is information for converting to sieverts.
Thank you for providing continuous data on radiation levels. I am much relieved by the data you publish.

I am not an expert, but I do work with radiation, so I researched the CPM / Sv/h conversion.

I expect the biggest issue now is radioactive Iodine 131, which is created by Uranium fission. Iodine 131 produces gamma radiation principally with energy of 365 keV, and according to the graph on the manufacturer's homepage this gives a relative countrate of approximately 1. Therefore 1 CPM ~ 1 mR/h = 0.01 uSv/h is appropriate.

It isn't clear what the relative countrate is relative to, but the values given for Cesium 137 (Gamma at 662 keV) and Cobalt 60 (Gamma at 1.17 MeV / 1.33MeV) are roughly the same so there should be no problem.
I've been checking this page often, and since the two spikes, I have seen no other excursions. To put this into perspective, even the spikes were not dangerous.


  1. Yet another Geiger counter graph! This one is even easier to read!

  2. Ministry of health's ongoing data:
    A live geiger counter in ota-ku, Tokyo:

  3. Added some summary statistics and 200-pt boxcar

  4. This comment is earthquake related, of interest to many of us, but off topic from this areticle, so pardon me
    ... but ...

    Area Mail (SMS-CB (Cell Broadcast)) has turned out to be very useful. The buzzing warning I hear on others' phones do often give several seconds warning of an inbound earthquake. However, smartphones can't get them. So, my question:

    Are there any "convertors" that receive the warning and then send out a regular email? If email servers are operating smoothly at the time, the messages would only be delayed a second or so, still ahead of some quakes.

    I guess such a service couldn't become very popular as it would overwhelm the cell towers in the few seconds after an area mail is sent out. It wouldn't interrupt the area mail warnings at all, however, so it might be a possible workaround till more smartphones are made compatible.

    Since SMS-CB goes directly from the cell towers in each area to the phones, a regular forwarding filter on a docomo feature phone, for example, would not even see the broadcast, from what I can figure. So, either some of our phones that do have area mail would have to have a re-transmission "app" or phone-based filter, or we'd have to make a device that can receive the docomo broadcast and re-send out a regular email. I don't think a SIM-card would be necessary, though I'm not sure. I don't actually understand why my docomo Xperia can't receive them. Are they broadcast on different frequencies? Or is the coding of the broadcast so different from a regular cell tower message that a different OS sub-routine or whatever is needed to process it? Such a backdoor would be a vulnerability, perhaps . . .

    Anyway, it seems like at least some of us could get some kind of regional re-broadcast system set up. And with the earthquakes, anyway, an area mail alert in north Tokyo being re-sent to me in south Kanagawa would still be useful.

  5. Yesterday, I installed なまず 速報 β which does work, but at the cost of the battery. To get "push" notifications of earthquakes, it appears to open a persistent connection to a server. Not really what I would call push. As a result, the phone can't sleep.

    Today, 8h 28m 44 s since being unplugged. Right now, according to spare parts, I am on 9% battery and "Time spent without sleeping: 8h 26m 57s"

    There is a chance that something else I installed is the culprit, but I am 99% sure it is namazu. I'm having trouble getting it to uninstall even.

  6. Smartphones can get CB messages, my personal HTC Desire has "Enable/disable Cell Broadcast" menu item with the "CB settings", which allow to setup different channels and/or languages. CB messages are most likely sent to "everyone" at once, not personally to every handset around the cell tower, so they don't show up as a regular SMS messages. I haven't used this feature yet since I live in a non-quake area. One thing that puzzles me, "receive channel list" is not a button but a checkbox -- probably channel lists are broadcast once in a while and cannot be retrieved at will. I've put mark in the checkbox and will report if anything happens.

  7. Whether push notifications work properly or not seems to depend on the handset. It works fine on the Galaxy S and Xperia Arc, but it polls on my IS04.
    Luckily that doesn't matter much because the IS04 supports CB.

  8. Putting the background radiation numbers in perspective:
    Normal background radiation varies from place to place but delivers a dose equivalent in the vicinity of 2.4 mSv/year (worldwide average), or about 0.3 µSv/h

    Of course that won't prevent people from being irrational. Even after I showed my wife background radiation difference compared to a year ago is negligible, she still refuses to hang the clothes outside. *sigh*

  9. Like this?
    What an idiot! What the heck does 15MsV have to do with anything? And what the heck is MsV? A MegaSecondVolt ;-)

    I know what a mSv is...

  10. your wife is very smart. background radiation measured by all these geiger counters across the country is mostly the gamma, which is quite harmless even in relatively large doses. the current problem, however, is more related to the radioactive isotopes, brought around by wind and rain, which emit mostly alpha and beta, undetectable by home-made geiger counters, but very harmful to the body. once you get it on your clothes (or, even worse, on your skin), it stays with you forever and the damage will be quite extensive even from the very brief exposure.

    read the yesterdays news, where the workers got their feet wet in dirty water and got nasty beta-burns while gamma sensors kept quiet.

  11. I shoulda gone into the Potassium Iodide business. I'd be rich by now!

    I have a dear friend who still implores that I get KI tablets for my kids, even though I explained that it's nearly impossible to absorb Iodine-131 the amounts dangerous to health from Yokohama. Normally intelligent people reduced to monkeys.

    How can people still believe, in the Internet age, that governments can keep secret (or fake) something like radioactivity levels? Wouldn't crowdsourcing and foreign measurements alone debunk the conspiracy theorists?

    Unfortunately I'm sure we'll be hearing about caesium-137 for a long time to come.

  12. Feel free to cite a reputable source on iodine 131 and cesium 137 (the main radioactive emissions from Fukushima) alpha & beta radiation danger levels 150 miles away via wind and rain.

    My wife does not hang clothes at ground zero.

  13. No, actually their dosimeter alarms went off but they chose to ignore them and carried on working for a further 40-50 minutes in the water.

  14. Here's a reading from tokyo/shinjuku tap water on 25th: I-131 -- 32Bq/kg, Cs-137 -- 2.1 Bq/kg, you may also get the detailed data. As far as i understand, the main source of the tap water contamination is the the wind and rain, and I think you might have had some wind as well as some rain recently in your neighbourhood too.

    I understand the current levels might seem low and not life-treating, but since contamination happens in "stripes" (low contamination areas are interchanging with higher contamination levels, see "Chernobyl") and you'll never know it until the next day, I think it's better to err on the safe side.

  15. -neither iodine 131 nor cesium 137 are alpha emittors. (See their respective Wikipedia pages for details)
    -Sievert attempts to measure the biological effects of ALL ionizing radiation (alpha, beta, gamma, etc.).
    -The becquerel (Bq) /MassUnit measures spcific activity or radioactivity in a substance. It doesn't consider the type of radiation emitted or what its effects may be.
    -There's nothing to indicate beta emissions are anything above negligable beyond the immediate vicinity of Fukushima.

    Based on examples given, you'd be more led to believe it's more dangerous to wash your clothes in the water than it is to dry it outside.
    Anyone can be an arm-chair nuclear physicist - it's where one draws conclusions without scientific basis that leads to misinformation.


  16. - I-131 and Cs-137 are BETA emitters and are responsible for thyroid and bone marrow damage respectively. if you don't like or need your thyroid and/or bone marrow, most other people do =)

    - if there's nothing beyond the vicinity of Fukushima, i wonder why they forbade drinking tap water for infants in Tokyo? does it fall within 150 miles?

  17. I give up. Fallacies win.

    Thank you. We're all misinformed, I'm now enlightened.

  18. I added a linear fit line to just the prequake values. It is nearly flat (slope on the order of 10^-15). I extrapolated this out to the far limit of the graph to serve as an easy reference. The 200-point box car average has nearly dropped to prequake levels, but appears to be leveling out at a new, slightly higher baseline.

  19. What is your take on the iodine and cesium? I am not so worried about the iodine because the half life is pretty short however I am pretty worried about the cesium that is leaking into the ocean and ground water. That crap has a half life of 30 years.

  20. This discussion seems to be the most informed that i have come across. I am looking for information about sea water radiation like MAF's which shows iodine and caesium concentrations in fish from Fukushima to Chiba. About 2 days ago the TV showed them sampling fish off Ibaragi but i don't know whether the above MAF website report is about that sampling or an earlier one. The recent dumping of large ammounts of low radiactive water by TEPCO at Fukushima No.1 reactor is worry for surfers, fishermen and consumers.

  21. > This will be nothing like Chernobyl.

    completely agree. chernobyl was basically over in a week or two, but fukushima daiichi will be here for quite a while (months or years, maybe?). there's no way anyone can plug holes in broken containment vessels, and the news about "steel wall in the sea" makes me wonder what are they really thinking about...

  22. there are air radiation level measurements in Tsukuba area:

    interesting parts are, until Mar,27th the main contaminant was I-131, but since Mar,28th there are plenty of other elements included, and it looks like it's coming from spent fuel storage, because Cs-134 and Cs-137 levels are almost the same (active fuel has much more Cs-137 compared to the Cs-134 because Cs-137 comes directly from U fission).

  23. I like all the facts. It helps people make informed decisions instead of just going on what is the current collective belief. If there is a high level in your area please take a look at the radiation safety guide and see what precautions you can take to keep you and your family safe.

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