The situation in Japan - some thoughts on Radiation

Discussion in 'Travel News' started by medhead, Mar 16, 2011.

  1. medhead

    medhead Suspended

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    #1 medhead, Mar 16, 2011
    Last edited: Mar 16, 2011
    I had a PM today that prompted me to create this thread. I was a bit uncertain about where to post it, travel inside information, general discussion or travel news. I settle in travel news because there is a bit in the news about this topic. I'll also provide some links. I should also say that I'll just be making general comments, I'm not a nuclear engineer or anything like that, that will share my thoughts as a radiation safety person. I'll try to decipher what is being reported as best I can based on my experience in this field. The other caveat is that this is a developing situation, things can change which would change my thoughts. This means that I'm going to use a lot of words like should, could, might and maybe.

    Actually one final caveat, please look at the official Australian Government Advice that can be found here: ARPANSA - Media Release March 2011

    In terms of sources of information I have been following World Nuclear News, which seems to stick to facts and also have some numbers. These guys are also on Facebook.

    Also useful/interesting:

    The Nuclear and Industrial Safety Agency of Japan

    The International Atomic Energy Agency (having a bit of trouble with them at the moment.

    TEPCO who own the reactors

    A finally website that has some pretty good background explanation is here: BraveNewClimate The full stuff on the nuclear reactors in Japan is here: Nuclear « BraveNewClimate
    Along with some thoughts on how the explosions happened: Further technical information on Fukushima reactors « BraveNewClimate

    Which gets into my ramblings. Read it or ignore as you wish. The basic question that everyone seems to want to know, is it safe? Or to quote from the PM:

    This is a really hard question to answer many because there is a fairly limited amount of information. I've seen mention of 3 "types" of radiation and radiation monitoring. The first is that we keep seeing number like 3.1 mSv per hour, 800 mSv per hour, and the radiation levels around the reactor are going up or they are going down. This seem to be spot external radiation measurements. They tell you how much radiation (gamma/neutron radiation) is being emitted, basically the strength of the radiation field at that point, per hour. This radiation is directly linked to the source (I assume the reactor), walk away and that radiation exposure decreases, get far enough away and it stops. This is also time related, you get a lot less dose from being there for 5 minutes versus 1 hour. It is this radiation that has resulted in all except 50 workers being evacuated from the reactor site. I wouldn't expect anyone to be touristing it around the reactor and if you are travelling to Tokyo those types of numbers mean nothing.

    The next type of radiation that I've seen on the TV is the contamination checks, as they increase the evacuation zone for the public. People lined up and dudes waving monitors over them. They are looking for radioactive particles that have landed on people. This is related to the third type of radiation mentioned and that is the emitted radioactive particles like iodine and caesium. These have been emitted with the steam releases. Once the steam condenses or it rains these particles drop out of the air onto the land, houses and people. The spread of these particles is going to be limited around the reactors site. Note the evacuation zone is 30 km. So there would only have been limited distribution of this stuff at this stage. The monitoring numbers reported have been in counts per minute or even counts per second. What they are trying to measure is the total amount of radioactivity in a given area on a person as there are cut offs based on counts per minute per square cm. General these will be big numbers, for example 40,000 counts per minute. Sounds big, but with some assumptions that can be boiled down to an activity number and it turns out to be pretty low - maybe the same as the total radioactivity in a banana or brazil nut in that case. This type of monitoring can be complicated to get from an esoteric counts per minute to a real activity number and then a health effect. I won't bore you with details. The thing is that these monitoring numbers are still (only) relevant for the immediate area around the reactor.

    That sort of gets me back to particles being emitted. There are reports that radiation is being detected in tokyo. These are going to be those emitted particles. At this stage the airborne concentrations should be pretty low. The effect is going to be dependant on the radioisotope involved.

    One is iodine and an effective protection against this is to take in non-radioactive iodine, potassium iodide tablets. Iodine is absorbed by the thyroid, if it is radioactive then you risk getting thyroid cancer (not nice but a very treatable cancer). Non radioactive iodine will block all the receptor sites in the thyroid and then the radioactive iodine just passes through the body with limited effect.

    There are also other radioactive particles in the air, caesium has been mentioned. The problem with these is inhalation, that is why the news talks about staying inside. This is to limit inhalation of the particles. The only real way to combat this is to follow government instructions. I assume that this is why they have said that the radiation is dangerous in the exclusion zone. In tokyo I can't imagine there would be very much of this stuff in the area. Because there is no massive big burning black could of smoke from the reactor sending crap high into the atmosphere, it mainly seems to be localised around the reactor.

    It is possible to convert an airborne concentration of a radioactive material to an effective dose, which tells us about the risk to people. I would guess that the dose in Tokyo from these particles would be very much less that the public dose limit at this stage. This is the dose (risk) below which there is no controls required on the radiation dose to the general public. don't need to control it? then it's very low risk.

    So what does that mean in effect. Well first I'll bring in some numbers; (sorry) In Australia, the average annual background radiation dose is 2.5 mSv per year. The public dose limit here and in Japan is 1 mSv. So IF one inhaled 1 mSv of these particles you would get no more that an extra 50% of what you get every year of your life. In theory the risk of 1 mSv is that 1 in 20,000 people will get a fatal cancer sometime in their life, due to that radiation. So to answer the PM in more detail, yes there is a risk of getting cancer from being exposed to radiation from the reactor, in theory. I say in theory because the major problem is that no one can prove this risk. It would require something like 12 million people in a study to prove that risk. (Note anti-nukes will happily use this theory to say 100,000s of people are going to die from very small radiation dose)

    To answer the second question from the PM, there is no way that you can ever prove that the cancer was from that particular bit of radiation at such low dose levels (if it is greater than about 100 to 500 mSv the link is more certain). You also need to remember that 1 in 3 people get cancer in their life. Of those 20,000 people getting 1 mSv, 6,665 will have cancer from other reasons and 1 from the 1 mSv of radiation

    More generally on radiation risk. There is a lot of evidence that says a dose less than 100 mSv at a slow dose rate has no risk of cancer. There are also places in the world that have much higher background radiation. Denver has 10 mSv per year and the cancer incidence rates are the same as elsewhere in the world. Other places have upto 100 mSv and no greater rate of cancer.

    Finally, I'll just say that if I was going to Tokyo I would be highly concerned about the effects of that burning oil refinery.
     
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  2. tuppaware

    tuppaware Active Member

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  3. medhead

    medhead Suspended

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  4. doctork

    doctork Member

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    Thanks medhead.

    I've trying to say much the same stuff, but far less cogently, on facebook to all who would listen. But everyone seems to say, "Don't let science and facts get in the way of hysteria!"

    I know we use screen names, but were you on ABC local radio today?
     
  5. medhead

    medhead Suspended

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    No, not me on the radio. Do you remember their name. I did get a late message to talk on abc last night, just by chance, but by the time I called back they weren't interested anymore.
     
  6. drron

    drron Enthusiast

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    Thanks for those links.It is really hard to know what is happening listening and looking at our media sources.I felt the Today show hit rock bottom today using Peter Harvey as the expert on radiatioin sickness.
     
  7. TonyHancock

    TonyHancock Senior Member

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    I'm in the UK this week, and the media here is pretty poor. It seems the we live in a world where sensationalism is top of the priority list when it comes to reporting. :(

    Thanks for the links medhead interesting stuff.

    I'm waiting for the press to start the calls for the Lucas Heights plant to be shut down.
     
  8. docjames

    docjames Senior Member

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    medhead, as you'd have the numbers far more readily available than me (although I could find exact numbers if I look hard enough), perhaps by way of comaparison you'd like to quantify the radiation exposure with some common medical scans/tests and some understandable background exposures.

    eg. radiation dose in a CT Head; CT Chest/abdo/pelvis (eg. trauma scan); Chest XRay; arm or leg XRay; vs say "FLight to London Exposure" or background exposure.

    Although maybe that'll just scare everyone off medical tests!:shock:

    imagescat-scan.jpg
     
  9. awilcockson

    awilcockson Established Member

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    Thanks medhead, a very level headed (lol) explanation.

    I just wish the sensationalist media could report it in these terms. Don't get me wrong, I wouldn't want to be going anywhere near the reactor site, but the "world is coming to an end" reporting is starting to wear thin. And I wish they'd stop referring to the possibility "China Syndrome scenario", it should be a "South pacific ocean" scenario, considering that's what's on the opposite side of the globe from Japan.
     
  10. awilcockson

    awilcockson Established Member

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    I found this one quite useful.

    Interesting that 5 return trips from Tokyo-New York gets you your maximum of 1 mSv of radiation for the year!
     
  11. oz_mark

    oz_mark Enthusiast

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    The problem we have is that on the one hand we've had some rather dubious reporting, but on the other has been less than stellar crisis communication from the Japanes government.

    Getting balance has been a bit of a task, so I too thank medhead for the explanation.

    FWIW I have been reading the material at MIT NSE Nuclear Information Hub (http://web.mit.edu/nse/) | Information about the incident at the Fukushima Nuclear Plants in Japan hosted by http://web.mit.edu/nse/ :: Maintained by the students of the Department of Nuclear Science and Engineering a.
     
  12. doctork

    doctork Member

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    Ask and ye shall receive!

    raddosetable.jpg

    From the latest BMJ (British Medical Journal for the non-medics among you)
     
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  13. medhead

    medhead Suspended

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    #13 medhead, Mar 16, 2011
    Last edited: Mar 16, 2011
    I can do some comparisons pretty easily right now. That reminds me of a couple of things I forgot to mention. The highest reported dose I've seen for one of the plant workers was 100 mSv. That is at the top of the range where the dose effects are not readily provable, however it is also well within the dose limit for emergency response. I saw that dose a day or 2 ago and I only mention it as it gives an upper range on real doses. I still think that most people (especially the public) would be less than 5 mSv

    By comparison to other exposures, I was actually looking at some medical exposures today.
    A whole body CT, neck to pelvis would average 10 mSv, maximum of about 20-25 mSv. This is highly dependent on the machine and various parameter.
    Head CT about 8 mSv - looking at Facial bones and skull for fractures (early Saturday morning ;))
    Cardiac CT 15 to 30 mSV
    Plain chest x-ray [-]~0.3[/-] 0.02 mSv. Got that wrong.
    Inventional radiology, this is real time xray use when they are putting things (shunts, balloon things etc.) in your heart or veins. (sorry for the technical terms :rolleyes:) these are the big ones typically 10 to 60 mSv. But the sky is the limit in some respects and there have been a few cases of radiation burns on patients. It's a bit hard to translate that to effective dose but something like 150+ mSv. But I really must stress that the burn happens because there is much higher radiation exposure localized to an area of the skin. The complex bit is translating that skin dose to a whole body effective dose, such as the number I quoted. A whole body uniform exposure of 150 mSv wouldn't cause a burn.

    For flight dose, I'm not up of these as much but from memory my ADL-SYD flights are about 0.003 mSv each. I have an average dose per hour number at work that I'll put in here. Of course flight related radiation exposure is highly variation being different if your flying parallel to the equator or across the equator and also depending on solar flares.

    Edit: for flying dose NZ to London the average dose is 0.003 mSv per hour. Say for a 20 flight time 0.06 mSv.

    In terms of the risk I mentioned a risk of fatal cancer of 1 in 20,000 per 1 mSv. That is the same as the risk of having a car crash if driving 60 km in NSW or the risk of death in a car accident if driving 5000km in NSW or the risk of death from smoking 75 cigarettes (iirc).
     
  14. medhead

    medhead Suspended

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    The Japanese have a website where you can enter 2 airport codes and a date and it'll estimate dose based on solar flare activity and all that stuff. I haven't been able to get it to work :( my Japanese is poor.
     
  15. drmikki

    drmikki Member

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    Medhead, if you want to PM me the website, and some dates and airports I will get you some answers :p

    I find the cumulative skin dose effect for radiation very interesting, particularly as I get irradiated on a regular basis at work. The lead gowns used for radiation-related procedure cover the torso but the hands and arms are uncovered and the most vulnerable to radiation particularly given the need to position the patient for the Xray. Additionally, I believe there is also significant risk of long term damage to the eyes, causing cataracts etc. I think that you can get lead-lined glasses but they are heavy and VERY expensive.

    At this stage in the Japan crisis, I would not have any qualms about heading to Japan for relief work. I think the radiation risk to me from the flight and from doing surgical procedures is higher than the risk from the reactor accident, at least at this stage.
     
  16. dajop

    dajop Senior Member

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    medhead thanks also for this analysis, hard to find in the general media. I've just spent the last week in Beijing, and yesterday my staff member therewas giving me updates from his wife throughout the day, the latest one being those in Beijing and NE china should stay indoors and have showers immediately after any exposure to rain. I indicated this sounded a bit over the top and suggested that he rely on official advice from the government, or more reliable sources than rumours spread over the internet.
     
  17. medhead

    medhead Suspended

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    ARPANSA have now updated their advice @3am. South easterly winds, so Beijing should be ok ;). Of course, showering is an effective precaution.

    Maybe I should ask where you work. But you should have 2 radiation monitors one that you would wear outside the lead at your collar or breast pocket. This gives an idea of eye exposure. There are separate dose limits for eyes and skin. I have heard that some doctors have developed cataracts.
     
  18. futaris

    futaris Established Member

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    http://www.nytimes.com/2011/03/17/world/asia/17nuclear.html?_r=1&hp

     
  19. doctork

    doctork Member

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    Cataracts are at least a deterministic phenomenon (did I just write two words with total 9 syllables?). ie., high risk cuts in at cumulative 7Gy (fractionated multi-dose). Unfortunately for the residents of Fukushima, and to a lesser extent, us frequent flyers, carcinogenesis is a stochastic phenomenon - no safe threshold dose, just increasing risk with exposure.
     
  20. medhead

    medhead Suspended

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    You made me dig out the tissue weighting factors. The last set of international recommendations talks about a threshold of 1.5 Gy for 1% incidence of morbidity (and mortality) to develop vision impairment (cataracts) with a time period of several years. The current occupational limit for the eye is 1/10th of that threshold. The monitoring I've seen would be no more than 1/3rd of the limit.
     

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