More Anti-Nuclear BS

[Almo]

Trees are carbon neutral. They take in CO2 during their lifetimes, then release it upon decay.

 

[Wavicle]

like radium carbonate (which is highly soluble in water)

Is that what you really meant to say? I don't think RaCO3 is soluble.

 

[drkitten]

Is that what you really meant to say? I don't think RaCO3 is soluble.

My understanding is that radium carbonate is water-soluble. If not, simply substitute your favorite soluble radium compound.

 

[Wavicle]

Unless you're talking about something with such a long half-life that it's for all intents and purposes non-radioactive (e.g. a half-life measured in hundreds of billions of years), the "long-half-life" heavy metals are among the most hazardous types of waste.

I think you are arguing in hyperbole at this point. Your example, the beta emitter Sr 90, has a half life measured in a few decades. But you have jumped from a well known example of a dangerous radioactive waste product to this strange statement about a half-life measured an order of magnitude longer than the age of the universe being all that is safe.

Can you come up with something with a half life greater than a billion years (2 orders of magnitude less than what you call safe) which presents substantial radiotoxicity in trace amounts? You consume about 1mcg of uranium per day (alpha emitter, 4.5B year half life) because it is such a ubiquitous metal (and because burning coal releases a bunch of it) yet its impact seems indiscernible. Nobody seems too worried about eating Potassium 40 either (beta emitter, 1.26B year half life, potassium ions readily dissolve in water) even though it's pretty much everywhere in small amounts.

 

[drkitten]

I think you are arguing in hyperbole at this point. Your example, the beta emitter Sr 90, has a half life measured in a few decades. But you have jumped from a well known example of a dangerous radioactive waste product to this strange statement about a half-life measured an order of magnitude longer than the age of the universe being all that is safe.

No, you're correct that I'm being somewhat hyperbolic here. I also consider U-238 to be for "for all intents and purposes non-radioactive," and I'm willing to be convinced even that U-235 (half life of 700Myears) to be more a chemical hazard than a radiological one.

On the other hand, I consider lead-202 to be quite scary. The bioactivity of released lead is well-known, and people can and do carry quite substantial lead burdens around. Pb-202 is an alpha emitter, which means that the bio-effect of the radiation it produces is quite substantial, especially in comparison with beta and gamma emitters. Since (like many heavy metals) it is concentrated in the bone matrix, this puts the highly carcinogenic alpha rays quite close to the continuously reproducing bone marrow, which is one of the more radiologically sensitive areas of the human body (leukemia, anyone?)

And Pb-202 has a half-life of about 50,000 years. Which, in turn, means that any Pb-202 that you absorb will be with you until your death, at which point it will probably continue to hang around in the human environment. (EIther you'll be cremated and someone will likely breathe your ashes eventually, or you'll be buried and the decay products will be absorbed into the enviroment.) So this becomes a radiological hazard for the next thousand generations or so.

This gets back to an earlier cpmment by Ziggurat:

But if you're talking about isotopes which last hundreds of years, then even if they stay with you until death, their long half-lives will still have prevented most of them from posing any kind of cancer risk. In other words, even for such heavy-metal elements, there's still a finite biological lifetime for the isotope, and if the radioactive half-life is longer than this biological lifetime, then the radiation risk is reduced compared to shorter-lived isotopes.

It's basically a balance of risks. The amount of Pb-202 that makes a substantial radiological hazard is less than the amount that makes a chemical hazard -- at moderate to low exposures, the cancer will kill you before the heavy-metal toxicity does. But at the same time, the radiological hazard is incredibly persistant, so it will not only kill you, but your children, your grand-children, and so on until the thousandth generation.

And that's where the real window of danger lies. The stuff with a half-life measured in days is not that big a health hazard -- if you don't drink the water that glows in the dark, you're probably safe. Even stuff with a half-life measured in months or years can be dealt with via short-term containment. The stuff that's essentially non-radioactive can be dealt with via normal chemical means. But the stuff with intermediate activity -- too long for short-term containment, but still substantially radioactive -- combines the worst of both worlds.

 

[Hindmost]

Try this site: http://web.ead.anl.gov/uranium/guide/facts/. I think of particular interest is this bit:



If I remember correctly there's a fair bit of it in ocean water as well. There is a LOT of stuff to go around. Although U235 is the favored element for reactors and comprises about 0.5% of all naturally occurring uranium, breeder reactors can convert U238 to U235 through neutron bombardment from the U235 already being used for the reactor.

Uranium is essentially everywhere--traces are found in all type of ores and rock. It tends to be in larger concentration around coal deposits. Coal fired power plants actually release more radiation than nukes due to uranium and c14 in the coal. Wearing glasses (made from glass and not plastic) will increase exposure to one's eyes due to the uranium in the silicon.

FYI: Breeders convert U238 into plutonium 239--after a couple beta decays--which is fissions very well. U235 is about 0.7% of the total uranium...a bit of a nit. It has a slightly lower concentration in parts Africa where a natural reactor operated many years ago....many years...a really long time ago.

Decay of uranium and thorium in the center of our planet keeps it warm. If it wasn't for that energy release, we wouldn't be here.

glenn

 

[Hindmost]

No, you're correct that I'm being somewhat hyperbolic here. I also consider U-238 to be for "for all intents and purposes non-radioactive," and I'm willing to be convinced even that U-235 (half life of 700Myears) to be more a chemical hazard than a radiological one.

On the other hand, I consider lead-202 to be quite scary. The bioactivity of released lead is well-known, and people can and do carry quite substantial lead burdens around. Pb-202 is an alpha emitter, which means that the bio-effect of the radiation it produces is quite substantial, especially in comparison with beta and gamma emitters. Since (like many heavy metals) it is concentrated in the bone matrix, this puts the highly carcinogenic alpha rays quite close to the continuously reproducing bone marrow, which is one of the more radiologically sensitive areas of the human body (leukemia, anyone?)

And Pb-202 has a half-life of about 50,000 years. Which, in turn, means that any Pb-202 that you absorb will be with you until your death, at which point it will probably continue to hang around in the human environment. (EIther you'll be cremated and someone will likely breathe your ashes eventually, or you'll be buried and the decay products will be absorbed into the enviroment.) So this becomes a radiological hazard for the next thousand generations or so.

This gets back to an earlier cpmment by Ziggurat:



It's basically a balance of risks. The amount of Pb-202 that makes a substantial radiological hazard is less than the amount that makes a chemical hazard -- at moderate to low exposures, the cancer will kill you before the heavy-metal toxicity does. But at the same time, the radiological hazard is incredibly persistant, so it will not only kill you, but your children, your grand-children, and so on until the thousandth generation.

And that's where the real window of danger lies. The stuff with a half-life measured in days is not that big a health hazard -- if you don't drink the water that glows in the dark, you're probably safe. Even stuff with a half-life measured in months or years can be dealt with via short-term containment. The stuff that's essentially non-radioactive can be dealt with via normal chemical means. But the stuff with intermediate activity -- too long for short-term containment, but still substantially radioactive -- combines the worst of both worlds.

I understand that lead 202 would be a bad health hazard--both chemically and radioactively. However, there is not much of it around. It does not occur in nature and it is not easy to manufacture. (I don't see any reason to make it as well since it would not serve any commercial purpose) It certainly isn't produced in nuke plants. I really don't think it is something to be concerned about.

glenn