This kind-of follows on from the “what to do with nuclear waste” thread.
The anti-nuclear people like to quote big half-lives to indicate how long nuclear waste remains dangerous.
I was always under the impression that the longer the half-life of an isotope, the less radioactive it actually is and vice-versa. Take the following example:
You have 2 million atoms of isotope A, which has a half life of 1 million years and beta-decays to a stable isotope. After 1 million years, about a million atoms have decayed giving an average of one decay a year. One beta-emission per year isn’t going to harm anyone.
Now take isotope B, which is similar but has a half-life of an hour. So you get your million beta emissions in the space of an hour, which is a little more worrying.
Firstly, is there anything wrong with this reasoning?
Secondly, how long does it take a spent fuel rod to decay to the point where it’s no more radioactive than natural uranium? I’ve heard figures from 600 years to millions, depending on who’s talking.
The concern is that, if it’s highly toxic, a long half life makes it difficult to handle/dispose. Your reasoning seems right about shorter halflives meaning more frequent emissions (hopefully, a physicist here can help out…Chronos?). But I think the key is whether the material is an alpha-, beta-, or gamma-emittor. Alpha and beta particles are fairly safe, unless you inhale them like from radon. But gamma rays are a bigger concern. Anyone know what characteristics nuke waste has?
Another major problem is that nuclear waste is often made of stuff that is toxic even ignoring the radioactivity, which is what is the major concern. If it were radiocativity alone, then all other things being equal a short half-life, and thus highly active sample, would be worse. But crap like plutonium will kill you by poinsoning you faster than by radiation.
Plus, beyond a certain threshold, it’s kind of moot how much radiation it gives off. If something gives off radiation is 1,000,000 times greater than what is considered safe, and has a half life of 100,000 years, does it really matter if you compare it to something that has a half life of a few days, but is 100,000,000,000 times greater than what is considered safe? Their both overkill, and so I’d rather have something disappear quickly than fester for a long time.
"Anyone know what characteristics nuke waste has?"
I am in the middle of a document review for the Idaho High-Level Waste & Facilities Disposition Draft Environmental Impact Statement (DOE/EIS-0287D). An electronic copy can be found here. Obviously different sites have different types of waste, but as this is on my desk at the moment, this is what I will from. You can find other documents here.
As for the type of particles emitted from the waste, both are problematic. The concern with alpha- and beta- particles is that in time, they could end up in the atmosphere or in the ground water supply, which could lead to inhalation and / or ingestion.
Inhaling or ingesting alpha and beta particles isn’t going to do you any harm. In fact you are doing it right now. Alpha particles are just helium nuclei and beta particles are electrons. (You know, those things shooting out of your CRT at you!) For that matter, gamma rays are just photons (also flying out of your CRT at the speed of light!). The problem is the amount of energy they contain when they leave the nucleus. Alpha and beta particles are pretty easily knocked down to room temperature, at which point they are harmless.
Fundamentally, there are two dangers from radioactive materials. The first is that the high energy particles emitted can damage surrounding materials. To a small extent this is a problem for inanimate objects – steel becomes brittle after long, intense exposure – but the greater concern is for living tissue. Large doses of radiation can disrupt cellular function immediately, small doses my be carcinogenic. The second danger from radioctive materials is that they can alter the nuclei of surrounding elements and make them radioactive in turn. And there is no guarantee the newly-created radioisotopes will be either more or less benign than the original ones.
The first danger is avoided by shielding or isolating the radioactive materials and is pretty well understood. The second danger is more problematic. What do you do when your radioactive shielding becomes radioactive?
Escaping alpha and beta particles aren’t so dangerous in themselves. It’s the resulting environmental radioisotopes that they’re concerned about. They can and do migrate and become subject to ingestion and inhalation.
Obviously, A and B radiation is only a problem if you’re very near the source. It is important to keep in mind that “knocking them down to room temperature” involves absorbing that energy. Water does a pretty good job, but storage containers generally don’t: the heat generated due to A/B absorption causes rapid decay, especially in a corrosive environment such as salt water.
Yeah, and that piano falling on your head from out the 10th-floor window is just a musical instrument.
Also, most A or B emitters are also gamma sources, since the daughter isotope is generally formed at a very high energy state and has to emit a photon to cool.
I think you are over simplifying. Note the following;
Low Energy beta-emitters
Low energy beta radiation is blocked readily by the skin or by plastic film or paper. Thus it poses no radiation hazard unless it is ingested and enters body cells where it can exert its effects at very short distances. Dosimeter badges are not needed or required. It is important to take precautions to prevent ingestion or inhalation. Good work habits and frequent wipe checks for surface contamination are essential.
High Energy Beta-emitters (eg Phosphorous-32, Chlorine-36)
High energy beta radiation (high velocity electrons) penetrates skin readily. Whole body dosimeter badges must be worn. As well, the high velocity electrons displace orbital electrons from molecules and cause the emission of low-energy X-rays called bremsstrahlung. This displacement effect is more efficient in dense materials. Thus it is necessary to shield high energy beta radiation with low density shielding. About 1 cm of plastic or wood is effective shielding for either Phosphorus-32 or Chlorine-36. Substantial irradiation of the hands can occur when these radioisotopes are handled. It is mandatory to wear finger badges if more than 1.35 mCi of Phosphorus-32 is handled and finger badges are recommended if amounts of more than 135 µCi are handled. Good work habits are essential to prevent accidental ingestion. Contamination checks are most conveniently done with a standard survey meter with a common Geiger-Muller detector.
Notice the warning against accidental ingestion/inhalation. Allowing a beta emitter to plant itself internally near target organs to do it’s damage is not ever a good idea.
How about you demonstrate how inhaling beta particles will do no harm.
Inhaling beta particles isn’t a problem. Inhaling beta sources is. The sources Rocket quotes say this. They say nothing about ingesting the particles themselves.
Once again, the problem with radiation isn’t the particles they throw. The problem is the energy those particles carry and how good they are at passing that energy on to your vital molecules.
Alphas are very ionizing, so they can do a lot of damage. But they are also charged, so they’re easily absorbed in a short distance. I’ve heard it said that a sheet of paper will shield you from any alpha particles coming out of radioactive metals.
Betas are lighter, so they’re more penetrating. But they are also easily absorbed. Like Rocket says, a centimeter of wood will shield them.
Gamma is made up of photons, which have no charge. This makes them much harder to absorb. That means they are a lot harder to shield from, but also that they don’t ionize easily.
So I’d rather have a few gammas than a few alphas strike my cells from within (in other words, without any shielding, not even my skin). But there’s no such thing as only a few gamma rays in these situations, so they are usually considered the worst form of radiation, because they’re hard to shield against.
By the way, I also think one of the considerations we need to make when talking about storing radioisotopes is what they’ll do to the surrounding materials. If they emit loads of alphas, they may not irradiate you directly. But they will make the container radioactive over time, and what sort of decay products will it have?
>>>>>>Inhaling or ingesting alpha and beta particles isn’t going to do you any harm. In fact you are doing it right now. <<<<<<<
Alpha and Beta emitters do their WORST damage when ingested!Alpha emitters Strontium 90…and cobalt 60 ((if I remember my Navy training correctly)) are the biggest concern after a nuclear accident.Those nucleides are absorbed by calcium and actually become part of your bones structure.Many children were seriously affected by drinking milk from cows that ingested fallout from the Chernobyl accident.Strontium was absorbed into the calcium rich milk.
Due to their relativly low energy Alphas can be shielded by clothing or even paper.The damage done to the body is ,I believe,on a multiple of 20 times greater than the damage caused by a thermal (slowed down) neutron.
Apparently Saltire is the only one reading this carefully enough to note the difference between alpha and beta particles and alpha and beta emitters. I wouldn’t (and didn’t) suggest ingesting the emitters, but as I stated before, we, all of us, you and me, all god’s chillun, the whole wide world, are surrounded by trillions and trillions of alpha and beta particles. A few million more “end[ing] up in the atmosphere or in the ground water supply” pose absolutely no health risk whatsoever.
I once deliberately inhaled billions of alpha particles in conjuction with twice as many beta particles and do you know what the health effect was? They made me talk like Mickey Mouse.
For those who still don’t get it – I was not suggesting that nuclear waste poses no health hazards. I was responding sarcastically to an incorrect statement.
This would be true if you were comparing an equal number of atoms of radioactive isotopes. However, the amount of radoactive material is usually measured in Curies - that is, number of disintegrations per second. (Actually, 1 Curie = 3.7 * 10^10 disintegrations per second). So if you have one Curie of Am-241 (half-life 458 years) and one Curie of Cm-244 (half-life 17.6 years), they both emit roughly the same amount of radiation and are equally dangerous in the short term. The difference is that the lump of Am-241 will remain dangerous for a much longer period of time.
If you look closely back through the thread, Phobos originally brings this up, but I think mistakely changes horses and back again in midstream;
Quote:
But I think the key is whether the material is an alpha-, beta-, or gamma-emittor. Alpha and beta particles are fairly safe, unless you inhale them like from radon.
Then Rythymdvl, again I think mistakenly, makes the statment you quoted referencing “particles”.
In my opinion the underlying thought (and concern) is about the emitters, and your statement only served to confuse the uninformed and the situation.
Whoops… my apologies. The main point of my post was to answer the question Anyone know what characteristics nuke waste has?. I am working with an EIS at the moment, so the answer was right in front of me. I believe “But I think the key is whether the material is an alpha-, beta-, or gamma-emitter. Alpha and beta particles are fairly safe unless you inhale them like from radon” is what spurred the question in the first place. My last bit addressed that - the concerns with A/B emitting waste is that it will get into the groundwater, etc., possibly leading to the ingestion of the emitter. The confusion was created by sloppy writing, i.e. using particle instead of emitter. Again, my apologies. I am off to drink a choco-covered neutrino bar.
A while back I read about a study of the mortality (of survivors of the Hiroshima/Nagasaki Atom bombs of WWII). The scientists noticed something strange-it seems that after a certain age, people who were exposed to the radiation had LOWER mortality rates that the non-exposed population!
Can radiation actually be benficial? or is this just a statistical fluke?
I also recall reading that radiation therapy is helpful to people who have auto0immune diseases (like arthritis)-it seems the radiation suppresses the immune system enough to allow relief of the symptoms.
I can explain those statistics, egkelly, without assuming a fluke or that radiation is beneficial. If you’re not killed instantly from the blast or quickly from radiation poisoning, the biggest danger from radiation is cancer. Now, folks have varying levels of vulnerability to cancer: some will develop it more easily than others. When your sample consists only of those who’ve already lived to a certain age, what that basically means is that anyone with the slightest disposition to develop cancer, has already died of it, so your sample group now consists soley of cancer-resistant folks. Since cancer from other sources than A-bombs is a very common cause of death, these resistant folks are going to have lower mortality. In other words, only the strong survive. This may be good for the species, in the long term, but it’s not good for any individual.