NASA’s Plutonium Problem Could End Deep-Space Exploration(wired.com)
wired.com
NASA’s Plutonium Problem Could End Deep-Space Exploration
http://www.wired.com/wiredscience/2013/09/plutonium-238-problem/all/
11 comments
Heck, there's Google (https://www.google.com/maps/views/streetview/oceans?gl=us&hl...), Virgin Oceanic (http://www.virginoceanic.com/), etc. exploring down there. Nothing wrong with a little deep sea action- even the military contribute.
It's much cheaper to explore the ocean than it is to explore space, and many benefits like: OTEC (http://en.wikipedia.org/wiki/Ocean_thermal_energy_conversion http://cleantechnica.com/2013/05/05/lockheed-martin-to-build...), mining ( http://en.wikipedia.org/wiki/Deep_sea_mining), etc.
Others agree:
http://www.forbes.com/sites/quora/2013/01/31/why-dont-we-spe...
http://www.cnn.com/2012/04/09/opinion/etzioni-space-oceans/i...
But, I personally think we should be exploring space and our oceans. We need to make it a top priority of all countries to fund energy and propulsion research to help make exploration cheaper. That means allocating adequate budget and raising taxes for something that the mass media and our government doesn't seem to give much of a shit about, because they don't understand the part of the world we currently are utilizing is running out of resources quickly and that we are constantly a stone's throw from mass extinction.
It's much cheaper to explore the ocean than it is to explore space, and many benefits like: OTEC (http://en.wikipedia.org/wiki/Ocean_thermal_energy_conversion http://cleantechnica.com/2013/05/05/lockheed-martin-to-build...), mining ( http://en.wikipedia.org/wiki/Deep_sea_mining), etc.
Others agree:
http://www.forbes.com/sites/quora/2013/01/31/why-dont-we-spe...
http://www.cnn.com/2012/04/09/opinion/etzioni-space-oceans/i...
But, I personally think we should be exploring space and our oceans. We need to make it a top priority of all countries to fund energy and propulsion research to help make exploration cheaper. That means allocating adequate budget and raising taxes for something that the mass media and our government doesn't seem to give much of a shit about, because they don't understand the part of the world we currently are utilizing is running out of resources quickly and that we are constantly a stone's throw from mass extinction.
You don't need Pu238 for deep sea exploration.
I wouldn't rule that out. Why wouldn't it make a great undersea battery?
Also, if we found Apollo 13 we could recover some Pu238:
http://science.slashdot.org/story/11/11/28/1637231/will-nasa...
http://unexplainedthings.tumblr.com/post/13563685365/will-na...
Also, if we found Apollo 13 we could recover some Pu238:
http://science.slashdot.org/story/11/11/28/1637231/will-nasa...
http://unexplainedthings.tumblr.com/post/13563685365/will-na...
It would, but you don't need it because you don't need years or decades of power at high depths.
Espionage is not exploration, no matter what your congressman tells you.
The plutonium is for RTGs on benthic listening buoys, which are moored deep in the water column, or anchored directly to the sea floor. They have very sensitive hydrophones, and powerful burst ELF transmitters. This allows triangulation of targets.
They're made of steel and are never intended to be recovered - so we can look forward to plutonium salts in the oceans.
The plutonium is for RTGs on benthic listening buoys, which are moored deep in the water column, or anchored directly to the sea floor. They have very sensitive hydrophones, and powerful burst ELF transmitters. This allows triangulation of targets.
They're made of steel and are never intended to be recovered - so we can look forward to plutonium salts in the oceans.
If I'm not mistaken the casing of it is very, very hard (even for space missions, where it's designed to whithstand a failed launch and reentry) and takes a very long time to degrade
Saltwater, astounding pressure and marine organisms make for a far harsher environment than the vacuum of space, or even a botched re-entry.
That said the argument I heard was that by the time they fall apart, the Pu has all but decayed.
That said the argument I heard was that by the time they fall apart, the Pu has all but decayed.
The argument you heard is correct. The casings are likely made of something that is completely unaffected by saltwater, the pressures involved are neither astounding nor even interesting in this context, and... marine organisms? Which ones? Harsher than a botched re-entry?
The casings are steel, the rtg is in a ceramic capsule. You'd be amazed at what barnacles and such can pry wide open given time.
Directly related ("U.S. Starts Making Plutonium"): http://news.discovery.com/space/nasa-plutonium-production-sp...
I was going to supply that link as well. We have been working on a restart for a while. Basically the Wired article is just silly.
It's easy to read between the lines: The NASA guys think it's likely there will be problems, and that Congress will fail to act quickly when more money is needed.
$10 million vs $20 million a year? It probably cost congress more to argue about this than the cut has saved.
Thorium reactors produce PU-238 as a “free” byproduct. One more reason we should be pursuing LFTR reactor research.
Erm, sort of. It doesn't actually help that much.
As a short, but helpful, side discussion consider the breeding of Pu-239 in a reactor for use in nuclear weapons. Pu-239 works great in a nuclear bomb but other isotopes of Plutonium cause problems, specifically the high spontaneous fission rate of Pu-240 can create so many background neutrons that having a significant amount of it in a bomb can vastly increase the "pre-detonation" (fizzle) risk, which causes the bomb to have very low yield (on the same scale as the chemical explosives in the bomb). As Plutonium remains in a reactor subject to neutron flux it will naturally breed other isotopes, which is why there is a difference between weapons grade and reactor grade Plutonium. Reactor grade Plutonium can contain any variation of isotopes, essentially all of them are suitable for use in a reactor, but weapons grade Plutonium can only have a very small amount of Pu-240. And for this reason the way that weapons grade Plutonium is made is by removing fuel rods from a reactor on very short time scales and reprocessing it to remove the Plutonium then forming it back into new fuel rods and so forth. This is a very costly and complex endeavor which is why you can't just use ordinary power reactors for generating weapons grade Plutonium.
Interestingly, Pu-238 also exists in reactor grade Plutonium in substantial amounts (1% or more of the Plutonium, so nearly an entire tonne per year worldwide). However, because it's mixed up with all of the other Plutonium it would require extremely costly isotopic separation.
So, how is this relevant to Thorium reactors? Well, let's go back and look at what actually happens when Pu-238 is produced in a Thorium reactor. You start with Th-232, and under neutron flux you'll breed U-233, which is the reactor's main fission fuel. If U-233 is hit by a neutron and absorbs it instead of fissioning then you can end up with U-234, U-235, U-236, Np-237 (through a decay), and Pu-238 (through another decay). However, it's not as though things don't stop there. Pu-238 will breed into Pu-239, Pu-240, and so on, just as in a conventional Uranium power reactor.
So here you have the same problem as producing weapons grade Plutonium, you have a process that you need to stop before it goes too far, and in order to do that you need to pull the Plutonium out of the reactor at regular, short intervals. Otherwise you'll just get a buildup of ordinary reactor grade Plutonium. However, the problem is worse here because instead of being the product of just one neutron reaction (natural U-238 becoming Pu-239) the breeding of RTG grade Plutonium is the product of a long chain of reactions (taking 6 steps between the isotopes in the reactor fuel at the start and the production of Pu-238). This means the amount of production and the time scales of production are very much not helpful from the perspective of pure Pu-238 production, especially if you want to also operate a power reactor cost-effectively at the same time.
(Edit: also, there's an additional problem, because Thorium reactor fuel contains U-232, which has a short half-life and has decay products that are prodigious gamma ray sources, making reprocessing and handling even more difficult than ordinary reactor fuel. You can handle Plutonium in a glove box, but with used Thorium fuel containing U-232 you'd need to handle it via robotic manipulators in a heavily shielded area distant from humans, except that gamma radiation kills electronics like nobody's business, which is a bit of a catch-22. This is one of the key technical hurdles of Thorium reactor designs in general.)
In short, the fact that Thorium reactors produce Pu-238 isn't helpful, because existing reactors do too, but in either case it's hard to get at.
As a short, but helpful, side discussion consider the breeding of Pu-239 in a reactor for use in nuclear weapons. Pu-239 works great in a nuclear bomb but other isotopes of Plutonium cause problems, specifically the high spontaneous fission rate of Pu-240 can create so many background neutrons that having a significant amount of it in a bomb can vastly increase the "pre-detonation" (fizzle) risk, which causes the bomb to have very low yield (on the same scale as the chemical explosives in the bomb). As Plutonium remains in a reactor subject to neutron flux it will naturally breed other isotopes, which is why there is a difference between weapons grade and reactor grade Plutonium. Reactor grade Plutonium can contain any variation of isotopes, essentially all of them are suitable for use in a reactor, but weapons grade Plutonium can only have a very small amount of Pu-240. And for this reason the way that weapons grade Plutonium is made is by removing fuel rods from a reactor on very short time scales and reprocessing it to remove the Plutonium then forming it back into new fuel rods and so forth. This is a very costly and complex endeavor which is why you can't just use ordinary power reactors for generating weapons grade Plutonium.
Interestingly, Pu-238 also exists in reactor grade Plutonium in substantial amounts (1% or more of the Plutonium, so nearly an entire tonne per year worldwide). However, because it's mixed up with all of the other Plutonium it would require extremely costly isotopic separation.
So, how is this relevant to Thorium reactors? Well, let's go back and look at what actually happens when Pu-238 is produced in a Thorium reactor. You start with Th-232, and under neutron flux you'll breed U-233, which is the reactor's main fission fuel. If U-233 is hit by a neutron and absorbs it instead of fissioning then you can end up with U-234, U-235, U-236, Np-237 (through a decay), and Pu-238 (through another decay). However, it's not as though things don't stop there. Pu-238 will breed into Pu-239, Pu-240, and so on, just as in a conventional Uranium power reactor.
So here you have the same problem as producing weapons grade Plutonium, you have a process that you need to stop before it goes too far, and in order to do that you need to pull the Plutonium out of the reactor at regular, short intervals. Otherwise you'll just get a buildup of ordinary reactor grade Plutonium. However, the problem is worse here because instead of being the product of just one neutron reaction (natural U-238 becoming Pu-239) the breeding of RTG grade Plutonium is the product of a long chain of reactions (taking 6 steps between the isotopes in the reactor fuel at the start and the production of Pu-238). This means the amount of production and the time scales of production are very much not helpful from the perspective of pure Pu-238 production, especially if you want to also operate a power reactor cost-effectively at the same time.
(Edit: also, there's an additional problem, because Thorium reactor fuel contains U-232, which has a short half-life and has decay products that are prodigious gamma ray sources, making reprocessing and handling even more difficult than ordinary reactor fuel. You can handle Plutonium in a glove box, but with used Thorium fuel containing U-232 you'd need to handle it via robotic manipulators in a heavily shielded area distant from humans, except that gamma radiation kills electronics like nobody's business, which is a bit of a catch-22. This is one of the key technical hurdles of Thorium reactor designs in general.)
In short, the fact that Thorium reactors produce Pu-238 isn't helpful, because existing reactors do too, but in either case it's hard to get at.
Contamination with plutonium-240 was a big problem during the Manhattan Project. They'd done the preliminary calculations based on cyclotron-produced plutonium-239, which was pure enough that a gun design with a long tube was feasible. ("Thin Man")
The plutonium-239 that came out of the Hanford reactor had a much higher contamination rate. This required a much faster assembly of the critical mass in order to avoid a fizzle. The gun design would have to be so long that it couldn't fit on a plane. Whereas implosion could provide the required rapid assembly in a limited space. Thus, "Thin Man" was out, and "Fat Man" was in. Implosion was no longer a secondary option -- it was the only option.
The plutonium-239 that came out of the Hanford reactor had a much higher contamination rate. This required a much faster assembly of the critical mass in order to avoid a fizzle. The gun design would have to be so long that it couldn't fit on a plane. Whereas implosion could provide the required rapid assembly in a limited space. Thus, "Thin Man" was out, and "Fat Man" was in. Implosion was no longer a secondary option -- it was the only option.
This isn't specific to thorium, but could liquid fueled reactors allow for chemical separation of Pu-238, as it's the first Pu isotope in the chain?
Obviously the ability to do something like that is still far off; I'm not actually sure how we previously made usable Pu-238. Is it isotopic separation from breeder reactors?
Obviously the ability to do something like that is still far off; I'm not actually sure how we previously made usable Pu-238. Is it isotopic separation from breeder reactors?
According to Wikipedia [0] it isn't all sorrows. There are other fuels available in large quantities at a low price, like Strontium-90 used in many Russian radioisotope thermoelectric generators. Other fuels like Americium-241 are also showing big promise, and are available commercially in large quantities. Americium-241 also has a much longer half-life, and can hypothetically power a device for centuries.
0: https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_ge...
0: https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_ge...
It's actually really interesting what a relatively tiny amount of Pu-238 is needed to power deep space missions for decades, 36lb (16.3kg) of Pu-238 amounts to a sphere with a radius of 5.82cm according to wolfram alpha.
> Every so often an atom of neptunium-237 absorbs a neutron emitted by the core’s decaying uranium, later shedding an electron to become plutonium-238.
Doesn't it shed a proton to become plutonium 238 and, as a consequence, loses an electron?
Doesn't it shed a proton to become plutonium 238 and, as a consequence, loses an electron?
Proper description of what's going on:
http://en.wikipedia.org/wiki/Beta_decay
http://en.wikipedia.org/wiki/Beta_decay
Thank you very much, I was under the impression that the electron was lost from the orbital cloud, not the nucleus!
Edit: Looking back at my math it was an off-by-one error in the wrong direction. :)
Edit: Looking back at my math it was an off-by-one error in the wrong direction. :)
http://upload.wikimedia.org/math/5/5/7/557cb46ae9126680a7d57...
Basically one of the neutrons kicks out a beta particle and becomes a proton. The atomic number goes up but the mass number stays the same.
Basically one of the neutrons kicks out a beta particle and becomes a proton. The atomic number goes up but the mass number stays the same.
France has the resources to make Pu-238, though I am not sure if they currently have the facilities/equipment. If the situation really is politically impossible in the US and Russia keeps on flaking out, we could always try buying more from the French again and let them deal with the politics.
If we are shitcanning missions because we don't have Pu-238, then why doesn't NASA just take the money they would have spent on those programs and spend it on more Pu-238 instead? Surely that should buy us enough Pu-238 for at least remaining uncancelled missions.
If we are shitcanning missions because we don't have Pu-238, then why doesn't NASA just take the money they would have spent on those programs and spend it on more Pu-238 instead? Surely that should buy us enough Pu-238 for at least remaining uncancelled missions.
> If we are shitcanning missions because we don't have Pu-238, then why doesn't NASA just take the money they would have spent on those programs and spend it on more Pu-238 instead? Surely that should buy us enough Pu-238 for at least remaining uncancelled missions.
Requires an act of congress. Need I say more?
Requires an act of congress. Need I say more?
To elaborate on maaku's answer, as the article points out, "the Atomic Energy Act forbids NASA to manufacture plutonium-238."
The idea is for NASA to buy Pu-238, not make it. I am not sure how much Congress micromanages their budget though, it may very well be the case that money meant for probes cannot be redirected to buy Pu-238.
Buy it from ... whom? As the article points out, Russia "reneged on a deal to sell 22 pounds to the U.S." and might not have any left for sale.
There are no other producers of 238Pu. (And for that matter, Russia stopped producing it years ago.)
Edit: Here's a link for you. http://www.nasa.gov/pdf/636900main_Howe_Presentation.pdf .
> In the past, the United States had an adequate supply of 238Pu, which was produced in facilities that existed to support the U.S. nuclear weapons program. The problem is that no 238Pu has been produced in the United States since the Department of Energy (DOE) shut down those facilities in the late 1980s. Since then, the U.S. space program has had to rely on the inventory of 238Pu that existed at that time, supplemented by the purchase of 238Pu from Russia. However, Russian facilities to produce 238Pu were also shut down many years ago, and the DOE will soon take delivery of its last shipment of 238Pu from Russia. The committee does not believe that there is any additional 238Pu (or any operational 238Pu production facilities) available anywhere in the world.
Full details are in "Radioisotope Power Systems: An Imperative for Maintaining U.S. Leadership in Space Exploration", National Research Council committee report. ISBN: 0-309-13858-2, 74 pages, (2009)
There are no other producers of 238Pu. (And for that matter, Russia stopped producing it years ago.)
Edit: Here's a link for you. http://www.nasa.gov/pdf/636900main_Howe_Presentation.pdf .
> In the past, the United States had an adequate supply of 238Pu, which was produced in facilities that existed to support the U.S. nuclear weapons program. The problem is that no 238Pu has been produced in the United States since the Department of Energy (DOE) shut down those facilities in the late 1980s. Since then, the U.S. space program has had to rely on the inventory of 238Pu that existed at that time, supplemented by the purchase of 238Pu from Russia. However, Russian facilities to produce 238Pu were also shut down many years ago, and the DOE will soon take delivery of its last shipment of 238Pu from Russia. The committee does not believe that there is any additional 238Pu (or any operational 238Pu production facilities) available anywhere in the world.
Full details are in "Radioisotope Power Systems: An Imperative for Maintaining U.S. Leadership in Space Exploration", National Research Council committee report. ISBN: 0-309-13858-2, 74 pages, (2009)
> Buy it from ... whom? As the article points out, Russia "reneged on a deal to sell 22 pounds to the U.S." and might not have any left for sale.
Now, that's interesting.
The Chinese are planning to land an RTG-powered spacecraft on the moon in December 2013. That's just 3 months away. Evidently they managed to get hold of some Pu-238 to power their spacecraft with.
Either they manufactured the isotope themselves, or they outbid us for the 22 pounds that Russia was planning to sell.
Now, that's interesting.
The Chinese are planning to land an RTG-powered spacecraft on the moon in December 2013. That's just 3 months away. Evidently they managed to get hold of some Pu-238 to power their spacecraft with.
Either they manufactured the isotope themselves, or they outbid us for the 22 pounds that Russia was planning to sell.
Interesting indeed!
There's talk about it at http://forum.nasaspaceflight.com/index.php?PHPSESSID=a4sdshu... . The best they found is this quote:
> "The nuclear power system will make China the third country apart from the United States and Russia to be able to apply nuclear technology to space exploration," Ouyang said.
Various newspaper article use that quote to say it was domestic production.
Parsed carefully, that doesn't say that they created the RTG, only that they applied it.
There's talk about it at http://forum.nasaspaceflight.com/index.php?PHPSESSID=a4sdshu... . The best they found is this quote:
> "The nuclear power system will make China the third country apart from the United States and Russia to be able to apply nuclear technology to space exploration," Ouyang said.
Various newspaper article use that quote to say it was domestic production.
Parsed carefully, that doesn't say that they created the RTG, only that they applied it.
France could produce it, given time.
This is is a situation that has been discused for some time: http://energy.gov/sites/prod/files/nepapub/nepa_documents/Re...
See the end of that document for discussion of Pu-238 from the UK and France. Notably it was thought in 1993 that France could have Pu-238 production going in a period of a few years ("late 90s" from 1993). To my knowledge the Pu-238 situation in France has not changed one way or the other since then. If the situation is either no more Pu-238, or Pu-238 in several years from France, then I would say that going to the French isn't a terrible idea. We didn't pursue getting Pu-238 from the French at the time because we thought that Russia was going to have us covered.
This is is a situation that has been discused for some time: http://energy.gov/sites/prod/files/nepapub/nepa_documents/Re...
See the end of that document for discussion of Pu-238 from the UK and France. Notably it was thought in 1993 that France could have Pu-238 production going in a period of a few years ("late 90s" from 1993). To my knowledge the Pu-238 situation in France has not changed one way or the other since then. If the situation is either no more Pu-238, or Pu-238 in several years from France, then I would say that going to the French isn't a terrible idea. We didn't pursue getting Pu-238 from the French at the time because we thought that Russia was going to have us covered.
What's the point of referring to a 1993 document when the 2009 document I pointed to says "The committee does not believe that there is any additional 238Pu (or any operational 238Pu production facilities) available anywhere in the world."
Yes, anyone with nuclear reactors is functionally able to make 238Pu. The document outlined a possible alternative method to use a 5 MW, licensed TRIGA reactor, available at various universities and in many countries.
> "If the situation is either no more Pu-238, or Pu-238 in several years from France, then I would say that going to the French isn't a terrible idea."
Why do you think that situation exists when the authors of the National Research Council report on the topic thinks it's not possible?
The document says that extensive French facility modifications would be needed, and further discussion would be needed even to establish that that option could be considered. Unlike the UK discussion, there isn't even a mention of how much France might be able to produce. That's your optimism? Is such a facility even still available some 20 years later?
So your suggestion is that the US should convince a foreign country to make extensive changes, plus do years of production? Interesting. Why is that better than making it in the US?
Yes, anyone with nuclear reactors is functionally able to make 238Pu. The document outlined a possible alternative method to use a 5 MW, licensed TRIGA reactor, available at various universities and in many countries.
> "If the situation is either no more Pu-238, or Pu-238 in several years from France, then I would say that going to the French isn't a terrible idea."
Why do you think that situation exists when the authors of the National Research Council report on the topic thinks it's not possible?
The document says that extensive French facility modifications would be needed, and further discussion would be needed even to establish that that option could be considered. Unlike the UK discussion, there isn't even a mention of how much France might be able to produce. That's your optimism? Is such a facility even still available some 20 years later?
So your suggestion is that the US should convince a foreign country to make extensive changes, plus do years of production? Interesting. Why is that better than making it in the US?
> Why is that better than making it in the US?
Different political climate. Things that may be politically impossible in the US may not be in France, and vice versa.
Different political climate. Things that may be politically impossible in the US may not be in France, and vice versa.
Certainly. And pigs may fly. But why do you think your conjecture has any basis in reality, much less is more believable than the report from the aforementioned council?
> Political ignorance and shortsighted squabbling, along with false promises from Russia, and penny-wise management of NASA’s ever-thinning budget still stand in the way of a robust plutonium-238 production system.
Biased much?
Biased much?
Probably a non-issue, because more Plutonium-238 can be easily created using existing infrastructure. As demand of this stuff goes up and supplies dwindle, someone is gonna make more of it sooner or later.
There are legal constraints on Pu-238. Market forces do not apply, unfortunately...
Maybe they can use a box full of old pinball parts.
Its production is verboten.
Actually DOE has started a production program using $10mil appropriated through NASA, http://spaceflightnow.com/news/n1303/20pu238/#.UjuOO6x3O4B
The original plan was to fund $10mil through NASA and $10mil through DOE for a total of $20mil per year, but DOE lost their half of the funding due to Solyndra-related politics.
The original plan was to fund $10mil through NASA and $10mil through DOE for a total of $20mil per year, but DOE lost their half of the funding due to Solyndra-related politics.
You sound like you didn't read the linked-to article, which details all of that except for the Solyndra politics.
There's no ambiguity here. He didn't.
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> By 2005, according a Department of Energy report (.pdf), the U.S. government owned 87 pounds, of which roughly two-thirds was designated for national security projects, likely to power deep-sea espionage hardware...
how about the U.S. government does less deep-sea espionage-- in the name of deep-space science?