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Thomas:

 

CANDU reactors use natural uranium for fuel but any burn of the U-238 isotope mass comes after it has been transmuted to Pu-239; that is also true of nuclear weapons. However, the fact that U-238 daughters can fission is not material to the argument of if DU is a radiation hazmat or it is not.

 

The point I was trying to make with the link on coal is that I am surprised at the number of web sites and the amount of bile that is being emptied on the use of DU munitions in the Mid-East, and not over coal burning plants in the US and UK. If there were any of the terrible effects that are supposed to have been visited on the populations expose to DU why haven't they shown up in spades in America and Great Britain, since the mass of radiating material distributed is much greater there than in the combat zones in question. Yes that's right According to NCRP Reports No. 92 and No. 95, population exposure from operation of 1000-MWe nuclear and coal-fired power plants amounts to 490 person-rem/years for coal plants (vs.4.8 person-rem/years for nuclear plants, BTW). Worldwide releases of uranium and thorium from coal burning in total are about 37,300 tonnes (metric tons) annually (the annual U.S. share of those releases is about 7,300 tonnes). [Gabbard (1993)] More radioactive heavy metal is released into the environment every two years by coal burning than the total spent fuel waiting to be buried from all U.S. nuclear power production and most U.S. nuclear weapons production. [Lehman (1996]

 

I note that you did not chose to address the contents of the second link that I posted. I put that in to put the health effect of radiation into some perspective. By the way, no one is in “danger from transmutation,” ionizing radiation when it does do harm to living tissue, does so by breaking chemical bonds.

 

Please do not take this as an insult, but it is apparent that your knowledge of nuclear physics has some gaps, and it is not possible to carry on a conversation with you on this topic until you have taken steps to fill them. I would also suggest that you review some texts on neutronics for a clearer understanding of the physics of fast vs. slow neutrons, and an grasp on the concept of flux density.

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I certainly do not claim that the major hazard from DU is Nuetrons (yor speling Jdurk). I included this data because its ludicrous to plead that U238 does not emit Neutrons when it is the strongest natural n emiter (actually 35 x U235 - I misunderestimated this in my previous post). The 700 million kg of DU in temporary storage in the US may well constitute a neutron hazard as n's are nearly uncontainable and transmute enviromental atoms into short half life isotopes. (after they've finished ionising 100,000 odd molecules per n)

 

Probably the damage in Iraq is being done mostly by Alpha's

63,400,000 alphas per kg U per second (each Alpha has energy to ionise up to a million organic molecules).

=5 x 10 –5 joules per second

0.05 sv is max legal for 1 year by nuclear industry worker)

or 2.5 x 10-3 grays (joules per kg) of alphas (alpha’s are considered 20x as destructive as Gamma rays per joule).

In a 50 kg person this dose would be .125 joules per year, 4 x 10-9 J per second.

 

0.00008kg =0.08 g of uranium 238 can produce this dose in 1 year (actually its much worse for ingested U because the dose affects maybe 1% of body mass in critical areas.

(note that military DU is at least 10x this active).

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Its easy to find data illustrating that the vast majority of energy from either an A or H bomb comes from fast fission of the U238 Tamper. The purpose of the deuterium is simply to increase the neutron flux and yield.

 

The CANDU reactor does achieve most of its energy from the 0.7% of 235 in natural uranium through slow neutrons moderated by the heavy water coolant. The fission of pu 239 is not significant compared to fast fission of U238 until a fair way into the fuel cycle.

Certainly it should be easy to make a low tech pu breeder out of the DU in one airliner (u235 content 0.35%).

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With you too antiNarcism, some better background in neutronics would help you understand that your last two posts are full of conceptual errors. The physics in an neutron efficient system such as a CANDU or a fission-fusion-fission bomb cannot be used to predict the behavior of DU away from those systems.

 

I would also like to know where you got the numbers in post #52, if they are yours, I must tell you you have left several important variables out of this calculation. I suggest that you Google the term: “Nuclear cross section.” You will find that the term refers to the probability that a neutron-nuclear reaction will occur. This factor when applied to the figures you quoted will yield a much less alarming conclusion.

 

If, of course, the truth is what you are after.

 

 

Oh, and your statment: "Certainly it should be easy to make a low tech pu breeder out of the DU in one airliner (u235 content 0.35%)" is balderdash.

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Character - bender
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I was thrown off an airliner once for being a pu breeder!
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Let me ask either of you this: I have lots of tubes (valves) from the /20s to /50s, which have thoriated tungsten cathodes. The Carbon was impregnated with Thorium to create efficient electron emitters. Now I know there is residual radiation from these babies, but what is your opinion of the hazards of long continuous exposure? ( I think of the parallel case of thousands of T.V. repairmen in the 60s coming down with cancer from X-rays off the back of sets.)

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With you too antiNarcism' date=' some better background in neutronics would help you understand that your last two posts are full of conceptual errors. The physics in an neutron efficient system such as a CANDU or a fission-fusion-fission bomb cannot be used to predict the behavior of DU away from those systems.

 

I would also like to know where you got the numbers in post #52, if they are yours, I must tell you you have left several important variables out of this calculation. I suggest that you Google the term: “Nuclear cross section.” You will find that the term refers to the probability that a neutron-nuclear reaction will occur. This factor when applied to the figures you quoted will yield a much less alarming conclusion.

 

If, of course, the truth is what you are after.

 

 

Oh, and your statment: "Certainly it should be easy to make a low tech pu breeder out of the DU in one airliner (u235 content 0.35%)" is balderdash.[/quote']

 

 

The numbers in post #52 have no relation to Neutrons, and I most certainly am familiar with the relevant data on neutron absorbance and fission cross sections.

Certainly you will need to enrich your 0.35% U235 uranium blocks to obtain at least a hundred kilos of 0.6%+ U235. This is easily done with a primitive electric arc in a vacuum chamber and apropriate electric and magnetic fields. Carbon fibre cloth would be an excellent substrate to deposit your U ions on, providing the moderator. enclosing your CU roll in a box of du will decrease the neccesary critical mass. "Balderdash" is not the sort of scientific explanation that convinces me this will not work.

Actually building a Pu nuke is a lot harder.

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In which case you have exposed yourself as a propagandist, not a scientist. I suspected as much. You are not interested in the truth in this matter only advancing an ideological position.

 

The noun balderdash has one meaning: trivial nonsense. And that is what the statement: "Certainly it should be easy to make a low tech Pu breeder out of the DU in one airliner (u235 content 0.35%)" is, particularly since you do know what you are talking about. You know it and I know it.

 

Now I made a statement above about radionuclides released in coal burning, yet nether you or Mr. Kerby have chosen to address this, nor have ether of you commented on the epidemiological study on radiation exposure and health I posted.

 

Perhaps you would care to now.

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Are you talking about using a farnsworth fuser to inject neutrons into some du?

 

If so, you forgot to add a little deterium/tritum gas to your vacuum chamber. The neutrons have to be liberated from somewhere.

 

Parafin wax also makes a great neutron moderator. It easier to work with than carbon fiber cloth. Beryllium can also be used to greatly increase your neutron yeild.

 

I still think it would take an long time to breed a considerable amount of U235 from a lump of DU. Does anyone have actual number we could work with here? I'm sick of all the 'should's 'could's and 'I think's (my own included).

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DV8 2XL, you make it look like you have some gaps in your knowledge too. I know that you know that only those nuclei with odd numbers of neutrons can be fissioned by thermal neutrons, but even or odd, fast neutrons can split a uranium nucleus. For those who don't know, thermal neutrons are those whose energies are low enough to be comparable with the temperature of their surroundings. Fast neutrons simply have higher energies, or can be considered to be hotter.

 

For nuclei containing an even number of neutrons, fission can only occur if the incident neutrons have energy above about one million electron volts (MeV).

 

I think that you and Jdurg have been trying to tell me that U-238 cannot be fissioned by fast neutrons. Doing some research, I find that the term "fissile" in this usage means that the given nucleus can be fissioned by thermal neutrons. Either isotope fissions when struck by fast neutrons. The classic picture of uranium fission is of a fast neutron splitting a uranium nucleus and producing excess neutrons, which split more uranium nuclei. A nucleus that absorbs a neutron and doesn't fission interrupts the chain reaction. U-238 absorbs thermal neutrons but is split by fast neutrons. As I have finally found out, U-238 only produces one neutron for one neutron, and I would have a lot more confidence if someone had produced that fact in evidence. It's one of those basic facts that you would expect an expert to bring up in a discussion such as this. One of you should have caught me on that earlier.

 

You still get a tendency for some neutrons to split nuclei and produce neutrons which split more nuclei. I still can't see them getting away if the piece of uranium in question is more than an inch or two thick. They don't get away so well from a chunk of U-235 about four inches in diameter, you betcha. One of this thing that makes this ironic is that the newly formed nucleides would be hard to detect because the U-238 does actually act as a radiation shield. Shoot a hole in it and see what comes out. Maybe it will be what some of the "nutcases" on the net have referred to as high levels of radiation coming from American tanks that are encased in U-238.

 

And yes, you get smaller probabilities of fission as the energies increase and all that. Where did I say that the chain reactions were going to be as long, as efficient, produce as much power per pound, and so on? If you have a nice thick chunk of DU, you are going to have a region inside it where the natural emissions of the U-238 are only going to be able to travel so far without finally splitting a nucleus or being absorbed. We can pretty much discount the nuisance value of the U-235, about one in five hundred nuclei capable of producing a gain in neutrons, but chains of single neutrons might be able to last pretty well deep inside. You have to figure that if a four inch sphere of the right stuff can be exploded by chain reaction, a neutron doesn't have to travel very far to find a nucleus that it can split. For each neutron that you can see that comes out of our heavy duty shielding material, how many have been produced inside one by one? I see three things that it can do: Split a nucleus and have one child neutron. Be absorbed and produce a fissile nucleus that can produce excess neutrons. Escape. When escape is not possible, the first two will occur according to their probabilities. This mess is going to cook itself the hardest in the most shielded areas. You want to take a valid sample, it's going to have to be a core sample. You can't pay me enough to take that sample without wearing a heavy duty radiation suit.

 

A scary thing to realize is that no matter how many U-238 nuclei are split one a one by one basis, you're not going to detect any more neutrons than were emitted by natural decay. Think about it. A bucket brigade does not throw any more buckets of water from the far end of the line than are fed to it from the water source. It actually ends up with less because of spillage. That's a pretty good analogy for a chain of splitting U-238 nuclei. More is actually less.

 

And yes, I think that the behavior of U-238 in a bomb can be used to some extent to predict the behavior of DU. It is just an example of the well known fact that fast neutrons can split U-238. If they couldn't, the U.S. government couldn't detonate it using any sort of nuclear device. If it didn't produce a lot of excess energy, the U.S. government wouldn't want to try to detonate it.

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I made that statement presuming that the fusor was in operating condition and properly fueled. Would I forget to put gas in my car before a long road trip? You don't have to answer that one :embarass: Also, it would probably make a lot more sense to impact an aluminum target with helium that you can buy at a welding shop. If you can build a fusor, you can build a linear accelerator.

 

Aluminum works to increase the neutron yield and it's a lot easier to buy.

 

We're not breeding U-235, we're breeding Pu-239.

 

Are you talking about using a farnsworth fuser to inject neutrons into some du?

 

If so' date=' you forgot to add a little deterium/tritum gas to your vacuum chamber. The neutrons have to be liberated from somewhere.

 

Parafin wax also makes a great neutron moderator. It easier to work with than carbon fiber cloth. Beryllium can also be used to greatly increase your neutron yeild.

 

I still think it would take an long time to breed a considerable amount of U235 from a lump of DU. Does anyone have actual number we could work with here? I'm sick of all the 'should's 'could's and 'I think's (my own included).[/quote']

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In which case you have exposed yourself as a propagandist' date=' not a scientist. I suspected as much. You are not interested in the truth in this matter only advancing an ideological position.

 

The noun balderdash has one meaning: trivial nonsense. And that is what the statement: "Certainly it should be easy to make a low tech Pu breeder out of the DU in one airliner (u235 content 0.35%)" is, particularly since you do know what you are talking about. You know it and I know it.

 

Now I made a statement above about radionuclides released in coal burning, yet nether you or Mr. Kerby have chosen to address this, nor have ether of you commented on the epidemiological study on radiation exposure and health I posted.

 

Perhaps you would care to now.[/quote']

 

please provide me with these links about U in coal. Perhaps this is the reason for the vast increase in cancer stats in last 200 years.

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Thomas, I have been debating this issue on the net for several years now in various places, and I have found that it is best to probe my opponents a little before engaging them fully. Some like you it would seem, truly seek an understanding of the issues and the physics, others are only interested in using half-truths and outright dissemination to discredit nuclear energy and have been using the issue of DU munitions to further that agenda. To this end I admit to using a bit of dissemination myself.

 

I commend you for delving into this outside this discussion and making yourself more familiar with this topic; and you are right that the term “fissile” is burdened with a bit of a usage issue.

 

However, I sill think that you have a bit of a way to go. You said: “ I see three things that it can do: Split a nucleus and have one child neutron. Be absorbed and produce a fissile nucleus that can produce excess neutrons. Escape. When escape is not possible, the first two will occur according to their probabilities.” Yes. Please look in the probabilities, when you do you will find that escape is the most likely one, and by a wide margin. Quite simply this isotope does not manifest a significant amount of chain-reaction activity. And the situation will not be any better for a “a nice thick chunk”, do the math and you will see why.

 

Your reasoning is good, you just need to factor in some more data.

 

“The behavior of U-238 in a bomb can be used to some extent to predict the behavior of DU” Only inside a bomb. The density of the neutron fluxes in that environment, plus the other factors that come into play are very different than natural spontaneous decay.

 

Consider this. While I suppose that one could keep solders in the dark about the radiation hazards from their equipment, (tho I don't know why you would) it is not that easy to hide that sort of thing during the manufacturing cycle. Trade Unions, Workman's Compensation Agencies, and Group Insurance Underwriters, not just in the US but in other jurisdictions have a vested interest in this issue, yet I haven't seen any of them up in arms over DU. In fact the only groups that I have seen making a fuss are those with an ideological objection to the war in the Mid-East, or those who are begging money to carry on their work. Even without any knowledge of the science involved, that alone would give me pause.

 

 

antiNarcism: it is the first link in post #47 in this thread.

 

Perhaps this is the reason for the vast increase in cancer stats in last 200 years

 

I wouldn't be too quick to draw the conclusion that the radioactive components are solely to blame.

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Are you talking about using a farnsworth fuser to inject neutrons into some du?

 

If so' date=' you forgot to add a little deterium/tritum gas to your vacuum chamber. The neutrons have to be liberated from somewhere.

 

Parafin wax also makes a great neutron moderator. It easier to work with than carbon fiber cloth. Beryllium can also be used to greatly increase your neutron yeild.

 

I still think it would take an long time to breed a considerable amount of U235 from a lump of DU. Does anyone have actual number we could work with here? I'm sick of all the 'should's 'could's and 'I think's (my own included).[/quote']

Nope, simple electromagnetic separation, like a mass spectrometer. Not so cost effective for large scale stuff , but the way to enrich until the 60's.

Not so sure about parafin. Not conductive so you can't give it the -ve charge to attract U ions, and the H absorbs Neutrons too.

Actually you don't need a moderator if you have enough U. Fast neutrons travel 7 cm average in solid Umetal b4 hiting anything, bounce around 130 times off u238 b4 being absorbed ( U235 or othe oddmass fission isotopes absorb them first chance, hence chain reaction potential at 0.6% U235 etc)

actually only 1 in 500,000 fast n impacts with u238 causes fast fission unless you have the Unbelievable energy flux and huge uranium density produced by a bomb.

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when the reactor radius is more than 25cm, Neutrons produced at the centre cannot escape.

 

I spoke to the head of nuclear physics at Auckland University today. He was adamant that he wouldn't get within 100 paces of the uncoated oxidising blocks of U in airliners, though would not be concerned if one was in a plastic bag. (inhalation risk)

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Um, my data on neutron production by Al hit by alphas shows 1 n per 500 000 ish alphas. Might increase the yield in a bomb but can't see the value in taking a chain reaction past parity. Photonuclear alpha production is simularly low yield and only really kicks at higher energies.

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"...simple electromagnetic separation..." Putting the word "simple" in front of a process name doesn't make it so antiN. Squeezing weapons-grade material out of scrap DU is a fool's errand if I ever heard one. Do the math and see how much mass and how much time and how much energy you would have to pump into this process. Terrorists aren't building a bomb outa spent shells they dig up from the desert anytime soon.

 

Oh right, I forgot all of the DU was aerosolized after it was fired ;)

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when the reactor radius is more than 25cm, Neutrons produced at the centre cannot escape.

 

Try again. The center in that cross section is rather small. Just how many neutrons are going to be captured?

 

I spoke to the head of nuclear physics at Auckland University today. He was adamant that he wouldn't get within 100 paces of the uncoated oxidising blocks of U in airliners, though would not be concerned if one was in a plastic bag. (inhalation risk)

 

Appeal to Authority is a rhetorical vice, I'm sure you can do better than that. What that worthy person will or will not do is not germane to this issue. For all I know he might be the type that washes his hands fifty time a day or puts on rubber gloves before using the john. I not saying this is the case you understand, just that his option carries little weight in this matter just because of his post.

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Pardon my total ignorance about airliner manufacture, but what possible use can depleted uranium have in construction: Aren't planes supposed to be light so they can fly? I just bought some interesting aluminium honeycomb material which is incredibly strong but light. I was told it was used for airplane wing structures.

 

So are the new locking cockpit doors made of depleted uranium armor or what?

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DU would make lousey armor, it suspect it would more than likely be Titanium, it`s both very light and incredibly strong, it used also in fighter jets, the pilot sits in a "bath tub" made of it.

 

I`m Guessing if DU were to be used in a plane, it would probably be as some sort of ballast, as it`s heavier than lead of the same size.

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Depleted uranium is also used in a number of civilian applications, generally where a high density weight is needed.

 

Such applications include sailboat keels, as counterweights and sinker bars in oil drills, gyroscope rotors, and in other places where there is a need to place a weight that occupies as little space as possible. Tungsten could be used instead, but it is much more expensive.

 

Aircraft may also contain depleted uranium counterweights (a Boeing 747 may contain 400–1,500kg).

 

An unexpected application is in Formula 1 racing cars. The rules state a minimum weight of 600kg but builders strive to get the weight as low as possible and then bring it up to the 600kg mark by placing depleted uranium where needed to achieve a better balance.

 

Because of its high density, depleted uranium can also be used in tank armour, sandwiched between sheets of steel armor plate. For instance, some late-production M1A1HA and M1A2 Abrams tanks built after 1998 have DU reinforcement as part of its armour plating in the front of the hull and the front of the turret and there is a program to upgrade the rest.

 

From the Wikipedia entry: Depleted uranium

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Depleted uranium is also used for radiation shielding, such as the caste used to store highly radioactive waste and medical sources.

 

DU is also used in some x-ray equipment. (http://www.varian.com/osup/sup257.html)

 

I even heard at some point during the late 50s and early 60s, DU was used for the little weights placed inside spraypaint cans to mix up the paint, of course this is no longer done.

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Now I could see solar cells and things like LEDs being made from DU Oxide semiconductors, I don't think you'll see many logic circuits come from this stuff.

 

Stray radiation has the nasty habit of forcing electrons into the conducton band, or in other words, your gates would randomly go into conduct when excited by radiation.

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