NASA’s Plutonium Problem Could End Deep-Space Exploration
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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?
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.
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.
That said the argument I heard was that by the time they fall apart, the Pu has all but decayed.
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...
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.
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?
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.
0: https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_ge...
Doesn't it shed a proton to become plutonium 238 and, as a consequence, loses an electron?
Edit: Looking back at my math it was an off-by-one error in the wrong direction. :)
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.
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?
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)
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.
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?
Different political climate. Things that may be politically impossible in the US may not be in France, and vice versa.
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.
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.
Biased much?
That would be Pu-239, not Pu-238. Remember, the Libyans wanted him to build a bomb -- not a spaceship.
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.