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Registered Member #193
Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022
BigBad wrote ...
On the contrary, one of the main causes of leukemia will be background radiation...
If that was true then leukaemia incidence would be strongly correlated with background radiation. It isn't, so it isn't (as Sulaiman has pointed out). About 80% of the risk of leukaemia (in the UK) isn't due to background radiation.
Since we know that 80% of the risk isn't due to background radiation, it's a bit silly to say that background radiation is the cause. It's even sillier to say that peaks in that background are " a likely" cause of leukaemia.
Ash Smalls "+1" comment on something which isn't objectively true says a lot about how much discussion this subject is ruled by emotion, rather than fact.
Leo Kinlen, an epidemiologist based at the University of Oxford, UK, has long argued that sites such as nuclear power stations and military bases may be more likely to host leukaemia clusters because of the relatively high population turnover in those areas.
Yes, but speculative. For strange correlations see Sulaiman wrote:
parts of Iran have natural background radiation >200 mSv/year and Leukemia occurence is not abnormally high.
One could speculate here, that a genetic predisposition for leukemia on top of the elevated radiation would tend to weed out leukemia favorable genes. In effect people living there might be radiation hardened.
Is it realistic to say that brief spikes that are only about ten times more radioactive than piss are really the cause of anything?
Dunno if your dosimetry is correct. Some quick calculation: A typical natural 2mSv/a background amounts to about 400 Bq /kg body mass. If you would put 1kg body mass inside a 1km radius cloud of 1 MBq/m³ the dose received would be about 10 MBq, i.e. 25000 times background rate. This is based on soilid angle arguments. Now I assumed, that all impinging radiation would be stopped in the body mass and also a big cloud without air attenuation effects, but for a ballpark this might hold. Much better would be a direct measurement.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Bored Chemist wrote ...
Ash Smalls "+1" comment on something which isn't objectively true says a lot about how much discussion this subject is ruled by emotion, rather than fact.
The +1 was specifically for the second statement BB made, ie:
BigBad wrote ...
The assumption that background radiation is completely harmless is obviously false.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
BigBad wrote ...
On the contrary, one of the main causes of leukemia will be background radiation. The assumption that background radiation is completely harmless is obviously false.
No, it's not obviously false. Nor is it obviously true. It's tentative, as there's not enough experimental data to test it. (where is the control group of people that were never exposed to any radiation whatsoever?)
Arguments over whether nuclear power is "safe" are mostly arguments over the validity of this hypothesis. But scientific hypotheses are proven or disproven by experiment, not debate.
Personally I would think that opening a nuclear reactor and letting all of the gaseous decay products out in one go is a little sketchy. :-/
Registered Member #193
Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022
Uspring wrote ...
Bored chemist wrote:
Leo Kinlen, an epidemiologist based at the University of Oxford, UK, has long argued that sites such as nuclear power stations and military bases may be more likely to host leukaemia clusters because of the relatively high population turnover in those areas.
Yes, but speculative. For strange correlations see Sulaiman wrote:
parts of Iran have natural background radiation >200 mSv/year and Leukemia occurence is not abnormally high.
One could speculate here, that a genetic predisposition for leukemia on top of the elevated radiation would tend to weed out leukemia favorable genes. In effect people living there might be radiation hardened.
Is it realistic to say that brief spikes that are only about ten times more radioactive than piss are really the cause of anything?
Dunno if your dosimetry is correct. Some quick calculation: A typical natural 2mSv/a background amounts to about 400 Bq /kg body mass. If you would put 1kg body mass inside a 1km radius cloud of 1 MBq/m³ the dose received would be about 10 MBq, i.e. 25000 times background rate. This is based on soilid angle arguments. Now I assumed, that all impinging radiation would be stopped in the body mass and also a big cloud without air attenuation effects, but for a ballpark this might hold. Much better would be a direct measurement.
Well, my dosimetry can't be wrong- because I didn't do any. I pointed out that the activity Bq/m^3 of these "plumes" is only roughly 10 fold higher than typical urine.
However, since you raise the issue, these plumes are gases emitting predominantly alpha and beta radiation. They are noble gases and therefore not well retained in the body. So only the small fraction of that plume that is within a few cm of the body (the range of the alphas and betas in air) can have any effect. A typical human has an area of the order of a square metre and so they are only subject to radiation from something like a twentieth of a cubic metre of air (for a range of 5 cm). So the MBq/m^3 that could "hit" someone gets scaled down to about 0.2 MBq
And even then, clothing will reduce that dose something like 10 fold. So they will actually get hit by a few tens of thousands of particles per second. Most of those are stopped by the epidermis and so can't possibly contribute to leukaemia.
On the other hand, a person is roughly a tenth of a cubic metre and is roughly as radioactive as their urine so they are subject to the radiation from about 0.01 MBq but, since all that radiation is produced inside the body, there's no skin or clothing taking the hit. The net outcome is that about 10 times more energetic particles impact the body from within than from one of those "scary" clouds.
Your calculation, as you acknowledge, doesn't include air attenuation. The problem is that you are saying all the radiation from a 1 km range will hit (if it's in the right direction) That's absurd; most of them will be stopped by air. For the alphas and betas it's wrong by about 4 or 5 orders of magnitude. There's not really enough information to be specific about the gammas but I'd still bet on about 3 orders of magnitude.
And, if you like, I will add the activity from carbon 14.
However, since you raise the issue, these plumes are gases emitting predominantly alpha and beta radiation.
I'm very much in doubt, that there are alpha emitting fission products, but you are right about beta decays. 85Kr is the only longer living noble gas fission product I found after a quick search and indeed this particular one decays almost exclusively to the ground state of the daughter nucleus and not to an excited state, which would also imply gamma emission. Very unusual.
EDIT:I haven't found any info on what nuclides constitute the plume. Volatile candidates might be 133Xe and 131I. I also didn't find the decay scheme of 133Xe, but 131I decays with gamma emission. Both nuclides decay within days, so whether they are freed during refuelling depends on the time between the last fission event and refuelling.
Gammas can travel about 100m in air, so that the volume that contributes to the dose can be of the order of that size. That would reduce my estimate by a factor of 10. Still a big spike.
Registered Member #193
Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022
I'm betting that 222Rn is part of the story, and it's an alpha emitter. 133 Xe is a beta source 131I (beta and gamma) isn't a noble gas, so they shouldn't be counting that. However as you say, the data isn't well documented on that page. 85Kr is indeed a beta & gamma source. If the range is 100 m rather than 1 km that means that the rays from 1000 times more particles can reach you since the number scales as the volume. I will need to sit + think about how that affects the actual dose received because most of the more distant ones would "miss" you anyway. Then there's the fact that many or most people are usually inside buildings which may offer significant screening.
The biggest issue with trying to make these sorts of judgements is that we don't have the raw data- just a single sensationalist graph. It is also complicated by the fact that to a large extent, only the gammas have an effect from the outside because, even if they get through the air, the alphas and betas are stopped by the skin. On the other hand, most of the exposure to internal radiation is from the alphas and betas. I still don't think those peaks are as significant as they first look. If the effect is due to some critical time period during gestation then it should be easy to spot by looking at refuelling dates and dates of birth of children affected but remember that the mother offers significant shielding from external radiation.
I'm betting that 222Rn is part of the story, and it's an alpha emitter.
It's not a fission product. Conceivably it might be generated by neutron capture and/or alpha decays from uranium. It does play a major role in natural radiation exposure.
133 Xe is a beta source
Yes, but I couldn't find a reference about whether it also emits gammas. Most beta emitters do. Did you find a ref?
If the range is 100 m rather than 1 km that means that the rays from 1000 times more particles can reach you since the number scales as the volume. I will need to sit + think about how that affects the actual dose received because most of the more distant ones would "miss" you anyway.
Consider a sphere with the radius r around the target of radiation and a layer of thickness dr on the surface of the sphere. Its volume is 4*pi*r^2*dr. The activity in it will be proportional to this volume. The probability of hitting the target with a surface area of A will be about A/4*pi*r^2. This makes the rate of hitting the target proportional to the product of these terms i.e. A*dr. So the amount of radiation will be proportional to the radius of the cloud. To correct my first estimate of a factor of 25000 above background: One factor of ten due to attenuation effects. One factor of 2 because I was calculating with a spherical cloud instead of a hemisphere. Maybe another factor of 2 since not everywhere in the cloud there will be the peak activity value. A more realistic estimate is then 25000/40 or about 500, close to the estimate from the original article. This is a lot more than the factor of 10 you assumed. Basically this implies receiving a yearly dose within a day.
Registered Member #193
Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022
I don't think there's some big cloud of that gas anyway. If you were to measure the concentration of radioactive material anywhere other than at the chimney itself, the result would depend more on the wind direction than on the activity in the plant. So those figures are almost certainly measured in the stack. (Once again, it would be nice if the data were actually presented in the web page)
A major point of a chimney stack - whether it's on a nuclear plant or a conventional one- is to ensure that the fumes are diluted massively before they reach the ground. So, unless there's a maternity unit mounted on top of the chimney...
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Radioactive spikes from nuclear plants - a likely cause of childhood leukemia
