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NEOWatcher
2009-May-07, 04:57 PM
We've seen references to this before when talking about space probes (like here: http://www.bautforum.com/1195348-post17.html )

But; now its actually being publicized and being addressed.
Fuel for deep space exploration running low (http://www.msnbc.msn.com/id/30621668/)


Dept. of Energy announced will restart program to make plutonium-238
[...]
The National Academy report says it would cost the Energy Department at least $150 million to resume (http://www.msnbc.msn.com/id/30621668/#) making it for the 11 pounds a year that NASA needs for its space probes.


Now; I have one question. If this pu-238 is a byproduct of nuclear weapons, then how are they manufacturing it? Can the process be altered to be a main product?
Are nuclear weapons going to be a by-product? :think:

Siguy
2009-May-07, 08:50 PM
It is a byproduct of nuclear reactors, not weapons. It is not fissile so it can't be made into nuclear weapons, and is a poor material even for dirty bombs.

I think that the Mars Science Laboratory was a total waste of an RTG, which due to their short supply should have been reserved for Jupiter and farther.

JonClarke
2009-May-07, 10:03 PM
It is a byproduct of nuclear reactors, not weapons. It is not fissile so it can't be made into nuclear weapons, and is a poor material even for dirty bombs.

I think that the Mars Science Laboratory was a total waste of an RTG, which due to their short supply should have been reserved for Jupiter and farther.

Why?

Jon

NEOWatcher
2009-May-08, 12:08 PM
It is a byproduct of nuclear reactors, not weapons.
Well; that's what the article said.
So; are they just not processing the waste from nuclear plants?


It is not fissile so it can't be made into nuclear weapons, and is a poor material even for dirty bombs.
It may not be, but, what about any other products made by producing it?

I guess I need to learn a bit about nuclear waste processing.


I think that the Mars Science Laboratory was a total waste of an RTG, which due to their short supply should have been reserved for Jupiter and farther.
I guess everyone has thier own opinions. Solar and batteries would have put to much of a limit on MSL weightwise, so it seems like it was either RTG or nothing.

Ara Pacis
2009-May-08, 12:56 PM
Hmm, lemme see if I get this right. First they demote Pluto, and then they run short of Plutonium. Coincidence? ;)

robross
2009-May-08, 01:53 PM
I found this wiki statement interesting:

"The United States currently has limited facilities to produce plutonium-238.[1] Since 1993, the U.S. has purchased all of the plutonium-238 it has used in space probes from Russia. 16.5 kilograms in total have been purchased.[2]"

from http://en.wikipedia.org/wiki/Plutonium-238

Japan has a large nuclear industry. I wonder if they have any we could buy?

Rob

kzb
2009-May-08, 03:49 PM
Plut-238 is made specially. Weapons-grade is made specifically to be high in Pu-239, and is low in Pu-238. Plutonium from power reactors contains a bit of Pu-238 but it is swamped by the Pu-239, 240 and 241.

To make Pu-238 from "waste" Pu from power reactors would require high isotopic enrichment. I doubt this is feasible on the scale required.

tlbs101
2009-May-08, 03:54 PM
It is a byproduct of nuclear reactors, not weapons. It is not fissile so it can't be made into nuclear weapons, and is a poor material even for dirty bombs.

...


Referenced from my favorite table of isotopes:
238Pu
------
1/2 life: 87.7 yr
spin: 0+
decay modes:
Alpha = 100%
Spontaneous Fission = 1.85E-7%
MG ~= 6E-15%
SI ~= 1.4E-14%

Pu238 is fissile and under the right circumstances could be used in a nuclear weapon, but it isn't not nearly as efficient as other nuclear materials. You are right about the dirty bomb, though -- since it is primarily an alpha emitter, it would not be very useful as a dirty bomb. There would be as much danger from heavy metal poisoning as from alpha particle energy -- which in either case is... very little.

I traced the daughter products down 7 generations. Most were alpha emitters with very very long 1/2 lives and the couple of beta emitters were short lived (on the order of minutes). Pu238 is an very good source for RTGs.

.

kzb
2009-May-08, 04:02 PM
"since it is primarily an alpha emitter, it would not be very useful as a dirty bomb. There would be as much danger from heavy metal poisoning as from alpha particle energy -- which in either case is... very little."

I'm not sure about this statement. I don't want to go into detail for obvious reasons but I think you're very wrong !

tlbs101
2009-May-08, 10:58 PM
"since it is primarily an alpha emitter, it would not be very useful as a dirty bomb. There would be as much danger from heavy metal poisoning as from alpha particle energy -- which in either case is... very little."

I'm not sure about this statement. I don't want to go into detail for obvious reasons but I think you're very wrong !

You can hold a chunk of pure Pu238 in your hand (pure, meaning the plutonium and most of the decay daughter products included) and you will suffer no ill effects. You can be covered with a fine dust of the material, wash it off, and suffer no ill effects.

Alpha particles don't penetrate the skin. The epidermis is usually more than sufficient to protect the inner layers of skin and certainly your internal organs. Clothed skin is even better protected.

Now... if you *inhale* or *ingest* some finely ground Pu238 dust, then you are in trouble, for the reasons mentioned. The inner cells of your lungs, esophagus, stomach, and intestines will be affected by alpha radiation and heavy metal poisoning is very likely. Heavy metal poisoning may cause more harm than the radiation.

A dirty bomb that only produces chunks and small grains of Pu metal is also less likely to cause many problems. It is hard to inhale a sand-grain sized particle all the way to your lung (possible but very difficult). A simple paper mask would be sufficient to keep those particles out of your mouth and nose. Developing a bomb to produce a fine 'mist' of Pu is very difficult.

cjameshuff
2009-May-09, 07:54 PM
You can hold a chunk of pure Pu238 in your hand (pure, meaning the plutonium and most of the decay daughter products included) and you will suffer no ill effects.

Aside from the severe burns from holding a chunk of very hot metal in your hand, you mean?

robross
2009-May-09, 08:00 PM
How much Pu238 would you need to stay below dangerous radiation levels, and yet still be hot enough to keep a cup of coffee warm? Cause that would be the ultimate geek gift - a plutonium powered coffee mug warmer.

Rob

Siguy
2009-May-09, 08:40 PM
How much Pu238 would you need to stay below dangerous radiation levels, and yet still be hot enough to keep a cup of coffee warm? Cause that would be the ultimate geek gift - a plutonium powered coffee mug warmer.

Rob
Sounds pretty expensive.

cjameshuff
2009-May-09, 09:41 PM
How much Pu238 would you need to stay below dangerous radiation levels, and yet still be hot enough to keep a cup of coffee warm? Cause that would be the ultimate geek gift - a plutonium powered coffee mug warmer.

5.5 MeV per decay, 238 g/mol, 87.75 years half life...(1 - 0.5^(1 s/87.75 years)) of the plutonium decays each second...

For a 100 W coffee-warmer:
100 W/5.5e6 eV/NA/((1 - 0.5^(1 s/87.75 years))/1 s)*(238 g/mol) = 179 g

Density of plutonium's about 19.8 g/cm^3, so that's about 9 cm^3. A disc 6 cm across and 3 mm thick. 5.5 mm if PuO2 is used instead of metallic Pu. A thin coat of iridium will stop almost all of the ionizing radiation.

JonClarke
2009-May-09, 10:14 PM
You can hold a chunk of pure Pu238 in your hand (pure, meaning the plutonium and most of the decay daughter products included) and you will suffer no ill effects. You can be covered with a fine dust of the material, wash it off, and suffer no ill effects.

Alpha particles don't penetrate the skin. The epidermis is usually more than sufficient to protect the inner layers of skin and certainly your internal organs. Clothed skin is even better protected.

Now... if you *inhale* or *ingest* some finely ground Pu238 dust, then you are in trouble, for the reasons mentioned. The inner cells of your lungs, esophagus, stomach, and intestines will be affected by alpha radiation and heavy metal poisoning is very likely. Heavy metal poisoning may cause more harm than the radiation.

A dirty bomb that only produces chunks and small grains of Pu metal is also less likely to cause many problems. It is hard to inhale a sand-grain sized particle all the way to your lung (possible but very difficult). A simple paper mask would be sufficient to keep those particles out of your mouth and nose. Developing a bomb to produce a fine 'mist' of Pu is very difficult.

Dust in the lungs is a major major issue because it will stay there and a cause radiation damage to the lodgement site with a high risk of lung cancer. if the plutonium is burned it will produce a fine-grained oxide, which is easily inhaled.

Jon

Ara Pacis
2009-May-10, 12:48 PM
5.5 MeV per decay, 238 g/mol, 87.75 years half life...(1 - 0.5^(1 s/87.75 years)) of the plutonium decays each second...

For a 100 W coffee-warmer:
100 W/5.5e6 eV/NA/((1 - 0.5^(1 s/87.75 years))/1 s)*(238 g/mol) = 179 g

Density of plutonium's about 19.8 g/cm^3, so that's about 9 cm^3. A disc 6 cm across and 3 mm thick. 5.5 mm if PuO2 is used instead of metallic Pu. A thin coat of iridium will stop almost all of the ionizing radiation.

Graduations and Father's Day is just around the corner. :D

kzb
2009-May-12, 05:49 PM
Plutonium has just about the largest dose coefficient there is, by inhalation of insoluble dust particles. Plut-238 has an enormous activity per unit mass. Tiny specks of Pu-238 dust would be fearsomely alpha-active and very dangerous.

I don't want to go into much detail in case the thought police are watching, but if you work it out I think you'll see few dirty bombs could be worse than Pu-238.

sts60
2009-May-13, 02:30 PM
Such devices work by fear and denial of resources (i.e., the contaminated areas and objects) much more than they do actual lethality. In particular, Pu-238 oxide is an inhalation hazard only in a relatively narrow range of particle size; too large and it won't get into the lungs, too small and it won't be retained. A bomb simply wouldn't generate this effectively, and there's not that much Pu-238 in existence anyway. (The fuel forms and heat sources provided by DOE for NASA are, of course, designed to minimize both release and hazardous "fines".)

Regarding the thread topic - yes, we (speaking from a U.S.-centric viewpoint) certainly do need to produce more, if we intend to keep on exploring the outer solar system. The Russians (who are the only other folks with any of the stuff) are running out of Pu-238 to sell us. (Disclaimers: I am not a disinterested party as I work in the field, and all of the above is public information.)

Edited, quite a bit later, to add: This thread title is misnamed; it should be "DOE low on plutonium". DOE is responsible for providing generators to NASA and other U.S. users (per the Atomic Energy Act of 1954).

kzb
2009-May-14, 11:57 AM
Such devices work by fear and denial of resources (i.e., the contaminated areas and objects) much more than they do actual lethality.

Agreed, but I still think some people on here are in denial about the magnitude of the socioeconomic impact. You can't just tell people to go home and take a bath and everything will be OK. You are looking at basically writing-off the real estate value of a large area of a city. Remediation would cost a fortune.

Ilya
2009-May-14, 04:17 PM
Such devices work by fear and denial of resources (i.e., the contaminated areas and objects) much more than they do actual lethality.

Agreed, but I still think some people on here are in denial about the magnitude of the socioeconomic impact. You can't just tell people to go home and take a bath and everything will be OK. You are looking at basically writing-off the real estate value of a large area of a city. Remediation would cost a fortune.
But that means it almost does not matter WHICH radioactive material is used. If anything, terrorists should go not by lethality, but by what materials are most "infamous". Everyone heard about uranium and plutonium. Hardly anyone heard of cesium-137 or cobalt-60.

Ordinary unenriched uranium, which is MUCH easier to obtain than something really nasty, would have psychological impact just as bad if not worse.

kzb
2009-May-14, 05:56 PM
Ordinary unenriched uranium, which is MUCH easier to obtain than something really nasty, would have psychological impact just as bad if not worse.

I know what you are saying, but the reality is there is no comparison between the alpha activity per unit mass of Pu-238 and U-nat. Pu-238 is many orders of magnitude higher. It would be almost impossible to inhale a dangerous amount of U-nat (altho' the DU campaigners might take issue with that :) ). In contrast, a few microscopic particles of Pu-238 oxide could be lethal. And it's not heavy metal poisoning either, it's radiation.

Ara Pacis
2009-May-14, 07:18 PM
Such devices work by fear and denial of resources (i.e., the contaminated areas and objects) much more than they do actual lethality.
I don't want to hijack this further, but I think the dismissing of "dirty bombs" as psychological bombs is only relevant if referring to improvised "dirty bombs". Certainly, it is possible to create an advanced radiological device that can distribute radionuclides that are immediately hazardous to human health due to radiation effects. However, the short half-lives of such isotopes would mean that whoever constructs such a device would have a limited timeframe in which to produce, process and deploy such materials.

Siguy
2009-May-15, 01:05 AM
I always hear Plutonium described as "the most toxic substance known to man" which is so, so wrong and it irritates me to no end.

Ara Pacis
2009-May-15, 01:12 AM
I always hear Plutonium described as "the most toxic substance known to man" which is so, so wrong and it irritates me to no end.

I hear that too. I think they say that because it's got a long halflife. So I tell them "well, thank goodness for that!" Isn't bismuth the element with the longest halflife?

Ilya
2009-May-15, 02:35 AM
I hear that too. I think they say that because it's got a long halflife. So I tell them "well, thank goodness for that!" Isn't bismuth the element with the longest halflife?
No, "they" do not actually reason even that much. They say it because Ralph Nader once claimed it. (Maybe still claims.)

kzb
2009-May-15, 11:21 AM
It's not because it's got a long half-life. It's radiotoxicity, measured in dose per unit activity inhaled, is one of the highest there is. It's radiotoxity in terms of mass depends on the plutonium isotope or mixture of isotopes under consideration.

Plut-238 has a shorter half-life than the "usual" isotope, Pu-239. It's alpha activity per unit mass is much higher and hence its toxicity per unit mass is also much higher. It's toxicity per unit mass inhaled will be many orders of magnitude greater than bismuth I can assure you.

Having said that, there are probably chemical compounds that are more toxic by ingestion, and if you were to search through the Table of Isotopes you could undoubtedly find radionuclides with greater toxicity per unit mass. But Pu-238 is definitely towards the top of the league in isotopes that can be obtained in quantity.

sts60
2009-May-15, 07:42 PM
You can't get it very easily, and there's no more being made. That's part of the problem that is the topic of this thread, but is fortunately also an obstacle to bad guys. And yes, it is radiotoxic, but the chief hazard is inhalation, and as I've mentioned that's dependent on a narrow range of particle sizes. Despite the hysterics of the "no-nukes-in-space" crowd, 238Pu is not the champion of substances you need to lose sleep worrying about.

That said, I agree that bad guys would very likely select something with "name recognition" for the emotional effect, even if remediation could be done in ordinary bunny suits and respirators with minimal worries about hard radiation. And I also agree that whatever was used, it would be a really disruptive and expensive event. Let us fervently hope such a scenario remains nothing more than an ugly thought exercise... And with that, I'll stop my contribution to derailing the thread.

To go back on-topic, the shortage of 238Pu is a very real problem, one that could bring [new] deep-space science to a screeching halt in the next decade, and have significant impact on human lunar exploration. In case anyone's wondering, there are other isotopes, but for various reasons 238Pu is the fuel of choice. It's got us to Jupiter, Saturn, Uranus, and Neptune; it's got us to the poles of the Sun; it's getting us to Pluto and interstellar space; it brought us years of science from the lunar surface, and it will not only power the new Mars rover; it's helped warm the three solar-powered rovers deployed to Mars so far. Isotope power is not glamorous like reactors, but it has left Earth orbit and, at least in the case of U.S. launches, has never failed its mission. (Again, yes, I'm biased, but it's also a fact.)

aquitaine
2009-May-17, 02:13 PM
It just seems to me that this whole issue is another result of the anti-nuclear hysteria. I still remember the big uproar about using it when Cassini and Galileo were launched.

mugaliens
2009-May-18, 08:38 AM
Hmm, lemme see if I get this right. First they demote Pluto, and then they run short of Plutonium. Coincidence? ;)

I think you have a good Mickey on the issue, Ara - it's plain Goofy!

kzb
2009-May-19, 05:48 PM
The dose coefficient of Pu-238 is approx 1E-05 to 1E-04 Sv/Bq depending on solubility of the inhaled form.

I've done some calcs and sub-nanogram amounts are of definite radiological concern.

This does not stop me supporting the use of radioisotope generators however. As people have said, the things are designed to survive an accidental re-entry.