ORNL Achieves Milestone with Plutonium-238 Sample
By producing 50 grams of plutonium-238, Oak Ridge National Laboratory researchers have demonstrated the nation’s ability to provide a valuable energy source for deep space missions. (Credit: ORNL)
OAK RIDGE, Tenn., Dec. 22, 2015 (ORNL PR) – With the production of 50 grams of plutonium-238, researchers at the Department of Energy’s Oak Ridge National Laboratory have restored a U.S. capability dormant for nearly 30 years and set the course to provide power for NASA and other missions.
Plutonium-238 produces heat as it decays and can be used in systems that power spacecraft instruments. The new sample, which is in the same oxide powder form used to manufacture heat sources for power systems, represents the first end-to-end demonstration of a plutonium-238 production capability in the United States since the Savannah River Plant in South Carolina ceased production of the material in the late 1980s.
Researchers will analyze the sample for chemical purity and plutonium-238 content, then verify production efficiency models and determine whether adjustments need to be made before scaling up the process.
“Once we automate and scale up the process, the nation will have a long-range capability to produce radioisotope power systems such as those used by NASA for deep space exploration,” said Bob Wham, who leads the project for the lab’s Nuclear Security and Isotope Technology Division.
The success of Wham and a team of engineers and technicians at ORNL comes two years after NASA began funding the DOE Office of Nuclear Energy through a roughly $15 million per year effort to revive the department’s capability to make plutonium-238.
Production begins at Idaho National Laboratory, which stores the existing inventory of neptunium-237 feedstock and ships it as needed to ORNL. Engineers mix the neptunium oxide with aluminum and press the mixture into high-density pellets. They use the High Flux Isotope Reactor, a DOE Office of Science User Facility at ORNL, to irradiate the pellets, creating neptunium-238, which quickly decays and becomes plutonium-238.
The irradiated pellets are then dissolved and ORNL staff use a chemical process to separate the plutonium from remaining neptunium. The plutonium product is converted to an oxide and shipped to Los Alamos National Laboratory, where the material will be stored until needed for a mission. Remaining neptunium is recycled into new targets to produce more plutonium-238.
There are currently only 35 kilograms, or about 77 pounds, of plutonium-238 set aside for NASA missions, and only about half of this supply meets power specifications. This is only sufficient to power two to three proposed NASA missions through the middle of the 2020s. Fortunately, the additional material that will be produced at ORNL can be blended with the existing portion that doesn’t meet specifications to extend the usable inventory.
With continued NASA funding, DOE’s Oak Ridge and Idaho national laboratories can ensure that NASA’s needs are met, initially by producing 300 to 400 grams of the material per year and then, through automation and scale-up processes, by producing an average of 1.5 kilograms per year.
“With this initial production of plutonium-238 oxide, we have demonstrated that our process works and we are ready to move on to the next phase of the mission,” Wham said.
The next NASA mission planning to use a radioisotope thermoelectric generator is the Mars 2020 rover, due to be launched in July 2020. The mission seeks signs of life on Mars and will test technology for human exploration and gather samples of rocks and soil that could be returned to Earth.
UT-Battelle manages ORNL for the DOE’s Office of Science. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit https://science.energy.gov/.
18 responses to “ORNL Achieves Milestone with Plutonium-238 Sample”
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50 grams! Great Britain is sitting on a huge stockpile of Plutonium! We’ve recycled nuclear materials from Russia since the Soviet U. failed. We buy Russian made rocket engines. Why don’t we buy and reprocess British PU? Here is a recent BBC article on the 1000 year stockpile of energy (http://www.bbc.com/news/sci…. My tweet on it: https://twitter.com/telluri…
“Plutonium from spent civilian power reactor fuel typically has under 70% Pu-239 and around 26% Pu-240, the rest being made up of other plutonium isotopes”
https://en.wikipedia.org/wi…
So it’s probably mostly Pu-239 and Pu-2240, which is not the type of Plutonium needed for RTGs, which is Pu-238.
There’s very likely to be -some- Pu-238, but it would take a lot of processing to get it.
So 4% of 140 Tonnes is still a lot of “other”. Generally, something at 4% ‘purity’ before refinement is an excellent starting point. But of the 140 Tonnes of material, as described in the BBC article, it is not completely clear how much of that is Plutonium (all isotopes). It states, “Plutonium is extracted from reprocessed nuclear waste and was originally stockpiled as a source of fuel for a new breed of experimental nuclear reactors.” It seems mostly to be PU. Extracting just one Tonne of 238 would far exceed 50 grams, ya think, and outlast NASA’s dreams by decades.
You’re right, that “other” also includes some other fission byproducts (miscellaneous other radioactive elements) as well as other Plutonium isotopes, such as Pu-241 and Pu-242. I would presume that the amount of Pu-238 is a fraction of a percent of the total, it’s a fairly rare isotope even in reactor waste.
Even so, it may not be worth it to process that much Plutonium, even if the yield is a tonne of Pu-238, though I’m not sure of what the cost would be to do so. Isotopic separation is time and energy intensive and is quite costly.
Another consideration is that processing it would also separate out the other isotopes, and
Pu-240Pu-239 is the isotope used in nuclear bombs. Whoever processes this Plutonium for the Pu-238 will end up with a lot of weapons-grade Plutonium as well.All good points. Remaining questions are: what is ORNL using as a starting point and what would be the cost and red tape to transfer a higher grade material (if so) to USA from Britain despite Brits being allies?
“Production begins at Idaho National Laboratory, which stores the existing inventory of neptunium-237 feedstock and ships it as needed to ORNL. Engineers mix the neptunium oxide with aluminum and press the mixture into high-density pellets. They use the High Flux Isotope Reactor, a DOE Office of Science User Facility at ORNL, to irradiate the pellets, creating neptunium-238, which quickly decays and becomes plutonium-238.”
Transfer costs probably wouldn’t be very high, at least not compared to the cost of isotope separation. But there would need to be a very high level consultation with the atomic management agencies of the respective countries for that to be worked out. As allies it probably wouldn’t be a big deal, I imagine the UK would want to retain control of the rest of the Plutonium once it is processed. Could take years to negotiate the details.
Importing British material could still be cheaper but as we both imagine, the political and social hurdles could be too much. American made may cost more but at least the timeline might be practical for NASA missions.
what do you base your premise on, that you claim that it is cheaper to separate this than to simply breed it? Breeding this is cheap and fast. In addition, they should have a simple to separate set of elements (different elements are easy/cheap to separate vs. isotopes of the same element).
“Isotopic separation is time and energy intensive and is quite costly.”
Oh yes!.
“Pu-240 is the isotope used in nuclear bombs”
239, surely?.
Yes, that’s right. Had lots of numbers in front of me, sorry xD
Nope. it comes down to costs and where they want to head with the breeding.
It makes good sense to breed this.
And as to UK’s PU, that is just BEGGING for us to build out the gen IV reactors.
There has been plenty of analyses of future power needs for the World and many assert that a combination of sources will be necessary including nuclear. I think that technology is advancing so more quickly that renewable sources (solar & wind) plus the reduced power demands from conservation and efficiency gains is making fission reactors marginal.
Use of the spent fuel design (TWR) of Terrapower might fill a niche for developing countries and balancing supply with solar. Nuclear development should focus on fusion. Fission should have limited and short term use in the 21st and be phased out along with hydrocarbon fuels sooner than later.
Certainly, we need PU-238 for deep space or long duration missions such as Curiosity. Security around nuclear fuel and designs makes knowing the cost and red-tape of various approaches not so clear. I do not see links to fact sheets here (yet). I’ve tried to stick to ‘why not’ the British supply. It could be you and Houg are just waving the stars n’ stripes banner in leaning towards in-house production. Your assertion that the ORNL process is simple and cheap(er) might be correct.
Tim,
First off, AE can NOT provide 100% of the power 100% of the time. In addition, NO NATION should every depend on solar/Wind 100%. In fact, no nation should depend on it more than 33%.
The reason is that if a super volcano blows, like Yellowstone, it removes BOTH wind and solar. The last thing that you want is to lose energy when you most need it. BTW, China is working very hard on weather modification, esp. the ability to generate clouds. When you do that, you lose the sun and wind.
Secondly, TWR is a joke. Total joke. It will be another 20 years before something comes of it. And to put it in 3rd world nations is just about insane. Instead, we should develop Gen IV reactors from Flibe and Trans Atomic. In their cases, the reactors are produced in factories, shipped in and actually use ‘nuclear waste’. If we replace all of the current nuke site with these, we no longer need to bring in any more uranium. Just use the old waste. And this burns up 95% of the waste, leaving us with 5,000 tonnes, rather than 100,000 tonnes that we currently have.
Finally, if we had up to 1/3-1/2 of our power from such a thing, it would enable us to stop all coal, and most of the nat gas. Interestingly, it would tide us over until real fusion power happens.
Nothing will ever come of TWR – the technology is decidely dubious and the plutonium mine left over afterwards is more so. Fast reactors in general are a tricky business. Breeding uranium 238 to plutonium only makes sense in a world of scarce and/or expensive uranium, which it is neither. Fast breeders are also motivated by the low efficiency of light/heavy water reactors and the expense of fuel reprocessing.
As you say, gen 4 molten salt reactors are the way to go, with the race to be first being between Terrestrial Energy of Canada, with their IMSR and China. China are very very keen to displace coal asap. Using IMSR tech we could replace all coal, gas and present nuclear with no increase in present uranium mining. This sort of tech could easily power the world for thousands of years at less cost than coal does now.
I wish you had not made the statement regarding super volcanoes. The rest of your statements are reasonable but that one is not. Such events occur on a long time scale – (10s, 100s of) 1000s years. All solar energy has to do is fill a gap of about 50 to 100 years. Fusion will eventually be mastered in this century and the likelihood of a supervolcano blocking out the Sun’s rays is very low.
Also, I gave you reasons why breeding PU-238 is so much cheaper. In essence, you have a sample that is composed almost of all pu-238, and other elements. These are CHEAP to separate. Simple chromatography can be used on this.
OTOH, separating isotopes is hard. VERY hard. That is why Iran took forever to make it happen for their centrifuges. It took them a long time to either steal the info, or discover it for themselves. And then they have to build EXPENSIVE centrifuges that run day and night for over a year working to get 100% separation. The energy costs on this is high.
Yet, you have not come up with any reason why you want to take good nuke material that is great for a fuel and work hard to separate out less than .01% of it. Yes, the amount of Pu-238 should be less than 1%.
I would argue that for a Mars mission, you don’t need something like PU-238, you could easily make do with a shorter lived material…
These rovers are proving they can last decades so PU-238 is a good fit and they know how to apply it in an RTG. I haven’t read of any other materials that would offer clear advantages. You’d think NASA would jump on designing an alternative RTG based on another radioactive material.