Uranium bullets

[DV8 2XL]

I have tried shaking the tree for a few hours now and no one I have contacted can confirm that this Fin was carrying DU trim weights in the first place. If it was it would be highly unlikely that they would burn in this sort of incident. Anyway the stab is still in a big chunk, doesn't look like it burned completely.

 

Oh, and yes I do have a bit of an agenda; because I worked with this stuff I need the truth. Wild claims and back-of-the-envelope calculations by those that think that the same arithmetic that applies to finance applies to dosimetry, anecdotes, anecdotal evidence, hysteria from people that are making a living from FUD in this matter, doesn't help me at all.

 

Let's assume for the moment that stuff is as dangerous as is claimed; boy would I have a case for Compensation, wouldn't I? Why should I work for the next fifteen years when I could retire now. The Fact is that I have no case because this stuff isn't all that dangerous. Hell, the cadmium and beryllium that I worked with gives me more pause than the uranium.

 

This stuff has been use in ordinance since 1958, but it wasn't till two tin-pot dictators tried using the issue to discredit NATO in general and the U.S. in particular that anyone noticed it. Never mind Iraq, why hasn't epidemiological studies been done to the populations near test ranges in the U.S., the U.K. and France? Why would anyone want to run a study under conditions where the confounding variables will make any conclusion scientifically suspect?

 

It's a political issue and we all know it, not a scientific one, and while one of you claims to be a policy flak for Her Majesty's Government in New Zealand, (which I still don't believe, BTW) and the other doesn't think peer review is a good way of practicing science (which I do believe) I have to ask myself if either of you is capable of a technical discussion on this topic.

[jdurg]

Are you guys also taking into account that once an atom of U-238 decays it can no longer give off any more radiation? Once it has decayed that atom no longer exists. It's not like the U-238 decays and then gives off another particle when it's daughter product decays, etc. etc, and you wind up with alpha particles produced in triplicate. So once the initial decay happens, you have to take that atom out of your 'count' for what's leftover. This is true for all the gamma rays, alpha particles and beta particles.

[antiNarcism]

Um, jdurd, are you some kind of cyborg that plans to be here billions of years to take advantage of this arguement?

[antiNarcism]

Yeah dv8 I can't see how it could get hot enuff fast enuff.

my airliner engineer mates reckon its in them all aiirbuses incl.

I have some union people ready to raise hs considering theres no mention in training for our guys here.

my reputation internationale is in high performance engineering but is of no consequence here.

I enjoyed escargot very much when my team was racing in france and switzerland, like a gene splice of Paua (nz black abalone) and grandpapas prime charolais steak fat.

Can you tell me if escagot from my regions intense volcanic and geothermal soils will have a uranium count that will damage my health?

(Its a silicious ryolite volcanisim, recycled seasludge if you will)

[Thomas Kirby]

Are you guys also taking into account that once an atom of U-238 decays it can no longer give off any more radiation? Once it has decayed that atom no longer exists. It's not like the U-238 decays and then gives off another particle when it's daughter product decays, etc. etc, and you wind up with alpha particles produced in triplicate. So once the initial decay happens, you have to take that atom out of your 'count' for what's leftover. This is true for all the gamma rays, alpha particles and beta particles.

 

For any quantity of U-238 that experiences alpha decay, there are actually about 7 half-lives of Th-234 before 99 percent of that has decayed to U-234. I am only doing the "main branch". U-238 to Th-234, one alpha and one gamma. Th-234 to Pa-234, one beta and one gamma. Pa-234 to U-234, one beta and one gamma. The U-234 is a plateau of relative stability because it has a long half-life, 245,000 years give or take. When I wrote this up yesterday, I said that the sum of the alpha and beta emissions triples after a time, and the gamma emissions triple over time. This is because there is essentially a one on one correspondence between the disintegrations of the U-238 and its daughter products. It can work this way because in a mass of U-238 that is newly refined, you have some billions of disintegrations per second. The back of the envelope calculations may give too long a time for the radioactivity to increase, too.

 

Actually, this is the contribution from the mass of atoms that are U-238 in DU. I haven't worked this out for the U-234 and U-235 that it comes with, and these are still substantial contributors.

[DV8 2XL]

Thomas, doesn't it strike you as strange that with all the web sites up against the use of DU and decrying it's effects that none of them seem to claim that the radioactivity of DU increases over time? After all these sites draw on the expertise of many leading scientists in this field (according to antiN) that I am sure this remarkable property of DU would not have escaped their notice.

 

Or then again maybe your understanding of radioactive decay needs a little fine tuning.

[DV8 2XL]

my airliner engineer mates reckon its in them all airbuses incl.

 

That's just not the case. Trim weights are made also of steel. Where, and how much trim weight is added to an aircraft depends on configuration, mods that might have been done and the airlines operating parameters.

[Thomas Kirby]

I've seen a few that claim that the radioactivity of DU increases over time. I've seen it enough times, and yes, antiNarcism does concur, within this discussion thread. In fact, I think that almost every anti-DU site claims that DU increases in radioactivity over time.

 

I haven't even started on the chain down from the U-234 that DU already contains. U-234 decays 18,400 times as fast as U-238.

 

If we actually could start with pure U-238, every atom that decays has better than a 99 percent chance of decaying again, twice, in less than six months. To say it another way, better than 99 percent of the U-238 that does decay will decay twice more in less than six months. I'm beginning to repeat myself here, but it takes 7 half-lives to reduce the quantity of a radioactive element to 1/128 of its original volume, leaving less than 1 percent or you could say getting rid of better than 99 percent. The half-life of Th-234 is 24.1 days. 7 times 24.1 days is 168.7 days, almost twelve days less than six 30 day months. It decays to Pa-234, with a half-life of 6.75 hours. 20 half-lives of Pa-234 equals 135 hours, less than a week. More than 99 percent of any quantity of Th-234 that is six months old or older will have gone through those two conversions.

 

In this case, when we say that the probability is 99 percent that Th-234 converts to U-234 within six months, we also say that 99 percent of that Th-234 has emitted two beta rays and two gamma rays within six months after it was created by the decay of U-238. Equilibrium with Th-234 will be reached when enough of the Th-234 has aged so that it decays as fast as it is produced. By definition this means that it disintegrates as often as the U-238 it is produced from disintegrates. Equilibrium between Th-234 and Pa-234 will be achieved within a much shorter time, so there will not be much delay from the time that Th-234 is disintegrating as fast as it is produced to the time that Pa-234 is disintegrating as fast as it is produced, and as fast as the Th-234 is produced. It will take me a little time to compute just how long it takes to reach this equilibrium, but it will take less than six months.

[DV8 2XL]

Simply asserting something doesn't make it so. Please reference your sources. And if it isn't clear by now. I do not think antiN a credible source of information.

 

What you are asserting is just not so, and your calculations claiming to prove it demonstrate a total lack of understanding of the physics involved.

 

Here's the decay chain for 238U:

 

238U -> 234Th -> 234Pa -> 234U -> 230Th -> 226Ra -> 222Rn -> 218Po -> 214Pb -> 214Bi -> 214Po -> 210Pb -> 210Bi -> 206Tl -> 206Pb (stable)

 

The 214Po is far, far more radioactive than the 238U with a half-life of a couple milliseconds; however, since an atom of 238U has to decay in order to produce an atom of 214Po, it's radioactivity is limited. 238U has a half-life of 4.5 Billion years. Since T1/2 of 238U is much, much greater than T1/2 of any of it's decay products, the amount of any daughter nuclide should be in equillibrium. In short, DU does *not* get more radioactive over time. I just wanted to make that point a little bit clearer.

[antiNarcism]

Oh dear. Look DV8 this is very simple decay physics and Tom has got it right.

 

You can build a simple model to clarify the picture in your head.

 

1.)take half a dozen buckets, each is going to represent an element in the decay series, label them as such.

2.) put a hole in each bucket, hole size relative to the inverse of the half life. The flow rate will represent our decay events at each stage.

3.) Stack the buckets on top of each other and fill only the top one (U238) with water.

4.) observe how the total of the flows thru all of the holes increases over time.

[antiNarcism]

DV8 can you take one of your radiation sensors and give me a reading at, say, 20mm from a block of DU a couple mths old plus.

It would be even more helpful if you could break this into gamma and beta components.

Large block radiation should be relatively constant per surface area. Can't figure why its so hard to find.

[DV8 2XL]

No, antiN that analogy is just plain wrong. Nether one of you seems to understand the fundamental nature of decay is that mass is lost. Try using this calculator:

 

http://www.shodor.org/UNChem/advanced/nuc/nuccalc.html

 

In your bucket analogy mass is conserved. The whole point of nuclear energy is that mass is converted to energy. You can't have your cake and eat it too.

[DV8 2XL]

...from a block of DU a couple mths old plus.

 

From the time it was refined..from the time it was cast?

[antiNarcism]

Mature U238 that has reached its final equilibrium will have 6 beta decays and 7 alpha decays in the period of time it takes for one 238 alpha decay.

[antiNarcism]

No' date=' antiN that analogy is just plain wrong. Nether one of you seems to understand the fundamental nature of decay is that mass is lost. Try using this calculator:

 

http://www.shodor.org/UNChem/advanced/nuc/nuccalc.html

 

In your bucket analogy mass is conserved. The whole point of nuclear energy is that mass is [i']converted[/i] to energy. You can't have your cake and eat it too.

 

E=mc^2 sir

5 MeV = 8 x 10 –13J (energy of 1 u238 alpha emission)

do your math

 

From refined.

 

[antiNarcism]

1.5 x 10^-10J is the energy you'd get if you converted just one nuclear particle (p,n) entirely to energy.

[DV8 2XL]

That's the whole point the mass is gone, changed into energy and radiated away from the source. That's why any given block doesn't increase it's overall radioactivity. Your assumptions are predicated on the mass staying constant.

 

As for the readings, I'm afraid I can't help you there, I don't have that sort of data on raw stock.

[antiNarcism]

No particles of any mass are lost. Energy of any human nuclear technology (except isolated particle/antiparticle Annihilation in advanced accelerators) exploits the higher nuclear binding energy at either end of the periodic table.

 

You are doing science a disservice by polluting this forum with your ignorance.

The hypothisis that you are a nuclear industry spindoctor whether you are aware of it or not, is far from disproved

[DV8 2XL]

No particles of any mass are lost

 

Your nailed aren't you? You know exactly what I'm talking about, and now your just uttering rubbish to cover your humiliation.

 

To clarify: the mass leaves the sample, converted into kinetic energy. You have blindsided yourself on this one, because at some point in time you did know this but you couldn't put it together or see how it was relevant to the discussion at hand.

 

My big mistake was thinking you knew anything about this subject.

[Thomas Kirby]

Uranium atoms don't disappear when they decay. They convert to other atoms. A small portion of the mass of the nucleus leaves as an alpha particle, another small portion as a gamma ray. Then you have Thorium-234. One beta particle and gamma ray later, you have Pa-234. Another beta particle and gamma ray later, you have U-234. This is using only the main branches for the estimate, which is going to throw the numbers off some.

 

I get 5.88 * 10^6 decays per second from a mole of U-238. Starting with pure U-238 and nothing else, obviously U-238 is the only source of radiation. Each decay produces a nucleus of Th-234. Obviously new nuclei of Th-234 come from other U-238 that didn't decay. The decay constant of U-238 that I estimate from formula is 9.77 * 10^-18. There's a lot more where the Th-234 came from. We're not going to see a significant decrease in production of Th-234 in the next few years.

 

Again, starting with pure U-238, Th-234 will build up until there is enough of it that its own decay will equal production. When the number of atoms times the decay constant of Th-234 equals 5.88 times 10^6, then the decay of the Th-234 is in equilibrium with the decay of a mole of uranium. It cannot decay any faster than the uranium does because it cannot decay any faster than it is produced. I get about 9.53 *10^12 nuclei. Computing the time it takes involves using a power series, and I'm not up for it today. In one second, 5.88 * 10^6 Th-234 are formed, and the odds of even one decaying are less than even because the decay constant is less than the number of nuclei. After ten seconds you can start talking about one to two Th-234 nuclei decaying, and after a hundred seconds, it's pretty close to 36 decays of Th-234 per second. That's the decay constant times the current supply of Th-234. That decay constant, by the way, is 6.17 * 10^-7.

 

In the beginning, the production of Th-234 outnumbers the number of decays (or you could call it conversions) about a million to one. In a thousand seconds, you have about 362 conversions for the 5.88 E6 produced, and the ratio is already down to 16200 to 1. After 10 thousand seconds, it's down to 1620 to 1.

 

When you reach that magic number of Th-234 nuclei, production equals loss. That's equilibrium. The magic number of Pa-234 is a lot less because of its shorter half-life. Again, it's the number of atoms times the decay constant. Since we're looking for the number of atoms, divide the number of decays we want by the decay constant. I get a decay constant of 5.92 * 10^-5 and 9.93 * 10^10 nuclei of Pa-234. After that it is U-234 which has a half-life of 245,000 years, so it will take it a long time to reach equilibrium. It's a lot easier to calculate how many nuclei per mole of U-238 it takes to reach equilibrium than it is to get the exact time. It takes about 1.62 million seconds to produce the right number of Th-234, but a lot have decayed in that time also.

 

Each element that reaches equilibrium decays just about as often as the U-238 that produces it. If you don't believe me, maybe you will believe these sources:

 

Florida State University

 

The Open University

 

The reasons that this phenomenon can continue to increase radioactivity for some time include the fact that each year, about one over 9 billion of the U-238 is actually converted. A half-life of 247,000 years for U-234 means that its activity is about 18000 times that of U-238 and it takes the conversion of 1/18000 of the U-238 to reach the equilibrium state. This is close to what is found in nature, according to the EPA about .0055 percent. That's the one that takes the most U-238 and the most patience. What you will wind up with is a one on one correspondence with the decay of U-238 and these daughter isotopes. The U-238 sets the basic rate and the daughters multiply that rate.

 

It's called "secular equilibrium." You're going to see the first plateau of equilibrium by the time six months have passed. The next plateau is reached after several million years. We don't have to worry about that too much.

[Psion]

I'm amazed by how many replies this thread has gathered.

[Phi for All]

There is much good info in this thread and now it is veering off-course. If you wish to discuss aspects further, start a very specific thread.

 

Closed.