NASA is Running Out of Plutonium

Article Updated: 24 Dec , 2015

[/caption]Decommissioning nuclear weapons is a good thing. But when our boldest space missions depend on surplus nuclear isotopes derived from weapons built at the height of the Cold War, there is an obvious problem.

If we’re not manufacturing any more nuclear bombs, and we are slowly decommissioning the ones we do have, where will NASA’s supply of plutonium-238 come from? Unfortunately, the answer isn’t easy to arrive at; to start producing this isotope, we need to restart plutonium production.

And buying plutonium-238 from Russia isn’t an option, NASA has already been doing that and they’re running out too…

This situation has the potential of being a serious limiting factor for the future of spaceflight beyond the orbit of Mars.

Exploration of the inner-Solar System should be OK, as the strength of sunlight is substantial, easily powering our robotic orbiters, probes and rovers. However, missions further afield will be struggling to collect the meagre sunlight with their solar arrays. Historic missions such as Pioneer, Voyager, Galileo, Cassini and New Horizons would not be possible without the plutonium-238 pellets.

So the options are stark: Either manufacture more plutonium or find a whole new way of powering our spacecraft without radioisotope thermal generators (RTGs). The first option is bound to cause some serious political fallout (after all, when there are long-standing policies in place to restrict the production of plutonium, NASA may not get a fair hearing for its more peaceful applications) and the second option doesn’t exist yet.

Although plutonium-238 cannot be used for nuclear weapons, launching missions with any kind of radioactive material on board always causes a public outcry (despite the most stringent safeguards against contamination should the mission fail on launch), and hopelessly flawed conspiracy theories are inevitable. RTGs are not nuclear reactors, they simply contain a number of tiny plutonium-238 pellets that slowly decay, emitting α-particles and generating heat. The heat is harnessed by thermocouples and converted into electricity for on board systems and robotic experiments.

RTGs also have astonishingly long lifespans. The Voyager probes for example were launched in 1977 and their fuel is predicted to keep them powered-up until 2020 at least. Next, the over-budget and delayed Mars Science Laboratory will be powered by plutonium-238, as will the future Europa orbiter mission. But that is about as far as NASA’s supply will stretch. After Europa, there will be no fuel left.

If plutonium-238 production is to be started again, a decision will need to be made soon. It will take eight years to start producing 5 kilograms of plutonium-238 per year, therefore any application for additional funding for plutonium-238 production for space exploration will need to be placed in next year’s budget.

Sources: New Scientist,

14 Responses

  1. vagueofgodalming says:

    …and hopelessly flawed conspiracy theories are inevitable.

    I agree with you. The only way to solve this is to have better conspiracy theories. Mahmoud Ahmadinejad, the future of space exploration needs you!

  2. Jon Hanford says:

    According to info on this story reported by Phys.Org on May 7th, “The Department of Energy announced on Thursday that it will restart its program to make plutonium-238. Spokeswoman Jen Stutsman said the agency has proposed $30 million in next year’s budget for preliminary design and engineering. ‘If you don’t have this material, we’re just not going to do’ deep space missions, said Johns Hopkins University senior scientist Ralph McNutt, who has had experiments aboard several of NASA’s deep space missions.

    So far only NASA undertakes these missions, so the shortage limits the world’s look at deep space, added Doug Allen, a satellite power expert and member of the National Academy’s study panel.

    By law, only the Department of Energy can make the plutonium. Last year then-NASA administrator Michael Griffin wrote to then-Energy Secretary Samuel Bodman saying the agency needed more plutonium.

    The National Academy report says it would cost the Energy Department at least $150 million to resume making it for the 11 pounds a year that NASA needs for its space probes. ” Link to this story here: . It also contains a link to the National Academy of Sciences report. But a least one person asked (essentially) “Is Pu-238 the only practical radioisotope for these missions? And, can a supply of Pu-238 be obtained through other nations that produce or process plutonium for their ongoing nuclear programs?” Any knowledgeable input on these two questions?

  3. Manu says:

    @ Jon Hanford:

    I googled a bit about those interesting questions.

    238Pu is an exceptionally strong alpha emitter, with a half-life of 87 years, which makes it an excellent choice for spacecraft applications.
    Wikipedia has a good list of possible alternative fuels (see Radioisotope_thermoelectric_generator#Fuels article).
    Curium-244, strontium-90 and americium-241 look like good candidates, although 238Pu is far better than any, in terms of power per mass and shielding requirements.
    I guess none of them would be much easier to get by.

    I don’t think any other country produces 238Pu. 2 countries reprocess used nuclear fuel (France at La Hague and the UK at Sellafield). The French facility (although originating for mainly military purposes) only supplies those Pu isotopes that can be burnt in power plants (mixed with uranium as MOX).
    238Pu makes up only 2-3% of all Pu in spent fuel, and is not separated from other isotopes (which I guess would require very expensive separation facilities similar to those used for enriching uranium).
    It is instead made by irradiation of neptunium-237, also found in spent fuels (about 700 grams per ton).
    None of these methods would be cheap’n easy!

  4. Jon Hanford says:

    @ Manu, Many thanks for your reply to the queries in my previous post. I’ll be checking the sites and areas to reference for further info on this subject. I take it that any switch to alternative isotopes negates the cost of 238Pu startup and production. I didn’t realize that 238Pu was so hard to come by on the legitimate international market. This certainly puts the need for this isotope in a new light , as projects such as the soon-to-be-completed Mars Science Laboratory utilize RTGs that need this crucial fuel. Certainly, for outer solar system projects, I see no short-term, inexpensive alternative than to begin manufacture of this fuel for scientific purposes.

  5. cipater says:

    I think it’s a shame that misguided feelings of guilt-by-association towards Pu-238 and its production could impede things like space exploration and scientific advancement. Spend the money; make the fuel. It’s well worth it. F the outcry.

    Same goes for the American public’s feelings toward nuclear power plants. Get over it! Put it in my backyard; I’d love it. I think those big cooling towers are beautiful!

    Perhaps we should have the same attitude toward lead that we have toward Pu-238? You can make bullets from it, and it’s poisonous! Booooo lead!

  6. Nexus says:

    Is there a reason radioactive isotopes of lighter elements, with a similar half-life, are unsuitable?

  7. Maxwell says:

    People don’t have the same understanding of nuclear weapons or radioactive materials than they do of conventional explosives and highly toxic chemicals.

    The NIMBY attitude is based on fear, and instead of explaining it our Politicians exploit it for free votes.
    A world without nukes and without plutonium sounds nice… they just leave out the part where our security, science, medicine and engineering programs are all made poorer for it. Weakening the nation for a nuke free fantasy that will never come to pass.

    At present no flight that would use these materials will be hampered under the current administration. So I wouldn’t expect the restart of a nuclear facility to be a hot topic item.

  8. lomitus says:

    While I will say that I’m very much for space exploration, etc., etc., and that I am also quite happy to see a substance such as plutonium (238 or otherwise) used for constructive purposes, it must also be said that I really see nothing wrong with erring on the side of caution here. -If- there’s not other alternative and -if- this stuff can be obtained or produced SAFELY, then yes…we should go ahead and produce more for this purpose. But it must also be said that this stuff is of course very dangerous stuff…I’m no rocket scientist and even I know this! For those who say “f the public outcry”, wake up and smell the planet burning. This is still the ONLY planet we have to live on and do things rashly, even in the name of space exploration isn’t necessarily a bright idea.

    Second to that it must also be said that there is a very old adage…”necessity is the mother of invention”. Since we’re running out of this stuff and since there are obvious issues with creating/obtaining more of it, just maybe it’s time to come up with a new way of doing this….perhaps a safer and more efficient way. Maybe with things such as deep space exploration at risk, people will start putting their noodles to good use to find more practical solutions to this problem. As they also say, “you never know until you try”.

    Just my $.02 worth.

  9. Vanamonde says:

    Physics do not necessary study biology. The history of the study of the effects of radiation is one of constantly underestimating the effects and that has led to a lot of mistrust.

    I love science. I want the outer system explored and understood. I would like my grandchildren or theirs to maybe work or even live there. But I am in no hurry.

    I am ready to give all of this plutonium and shutdown all fission reactors to stop the pollution and risk of harm and wait until we learn to mine fissile material beyond this biosphere. There are asteriods that are mostly metal that may have the uranium we need to make fission reactors in space and THAT is the place for them, not in the one and only biosphere were we can breathe. The gas giants and dwarf planets beyond can wait. They are not going anywhere.

  10. outcast says:

    @ Vanamonde

    Actually fission reactors in general are the safest, cleanest, and most reliable power plants we’ve ever had. Some people believe we can get by without them, so lets analyze the situation:

    1.) Hydro is inherently limited, there’s only so many rivers and many of them have other uses.

    2.) Wind & solar both have huge problems with intermittantcy, I’m not saying there isn’t a place for them, but large scale they are inherintly limited by the simple facts that the weather is not always the same all the time. The sun doesn’t always shine and the wind doesn’t always blow. Some may say storage, but batteries on that scale would massively drive up the cost of the power facilities plus you would have to build drastically over baseline capacity to provide enough excess power to charge them. They also have huge problems with efficiency, or rather lack of it. In smaller and/or densly populated countries like Japan this is a huge issue. It would mean taking up far more of our land then we would if we went with nuclear, the energy density is simply far too low. Let’s also not forget that in the US according to an article I found on the internet, there have been many NIMBY’s who dont want wind or solar farms…..anywhere because of the space they use or their effect on property values.

    3.) So that only leaves fossil fuels, while they are more efficient than wind or solar they are far LESS efficient than nuclear. 1KG of fissioning Uranium has the energy equivelance of 1000-2000 tons of coal, and uranium (as well as thorium) is very abundant.

    The nuclear reactors we have today are all old generation 2 designs, if one were to be built today it would be a generation 3 design with such features as passive cooling which make them virtually meltdown proof.

    France runs entirely on nukes and they wont have the looming power shortages other western nations already have had or will have. We can learn from this.

  11. Vanamonde says:

    “Actually fission reactors in general are the safest, cleanest, and most reliable power plants we’ve ever had.”

    Except that

    a) after 40 years of operation, you are left with tons of radioactive waste, “hot” for thousands of years longer than any human institution has even lasted with no plans for anyone to pay to take care of this stuff and no permanent resting place. Nuclear advocates never figure this in the economy and our great-grandchildren will hate us for these crimes.

    b) commerical nuclear power is so “safe”, we have a special law that limits the liability of the companies that run them in case of an accident, so they can survive an accident that a community does not. Why must you need such a law if it is so safe? Look at your insurance on your home. Nuclear accidents are not covered there either, not at all.

    c) The industry itself is full of corruption. They spec’d the facility at Glen Rose, TX (one of the last ones built in the US) at about $770 million to build. It ended up costing over $8 billion. People there are paying TWICE per kilowatt/hour that people in other parts of Texas are paying. And again, that includes not a penny for taking care of the tons of waste it will produce over about 40 years of operation. Who is going to pay to watch and protect the high level stuff for 100,000 years?

    Nuclear fission on this scale in the one and only known biosphere is a crime against all known lifekind.

    I am very angry about this. And I apologize for being so off-topic, I will post no more on this.

  12. outcast says:

    a) True there is radioactive waste, but it is actually dangerous for a century, plus you can reprocess it to greatly reduce the amount of waste available. Compare this with coal pollution that is spewed into the air for us to breathe. According to the American Medical Association 50,000-100,000 deaths in america are due to the long term inhalation of particulate air pollution, most of which comes from coal plants. At least we can puit radioactive waste in a figurative box and put somewhere away from us.

    If that wasn’t enough, gen 3 reactors are far more efficient than the ones we use now, so the majority of the waste we will make in the future has already been produced.

    b) The reason why is the same as why most industrial accidents have limited liability. You can’t take out insurance on your home for nuclear accidents because the vast majority of people don’t live anywhere near a reactor. So why would it be necessary?

    c) You’re comparing how the industry was 30 years ago and expecting that nothing has changed. True at the time it did have issues, but many of these have been resolved. The cost of electricity in the UK is 4 times that of France. If the french can have cheap electricity, why can’t we?

    This isn’t really off topic, the debate over nuclear power is part of why we don’t have enough plutonium for our space probes.

  13. Astrofiend says:

    I reckon we should be making Plutonium by the bucket load – it is just so damn useful, particularly for exploring space.

    People can lah-di-dah about the dangers of nuclear material all they like, but the fact is that living is inherently dangerous. To use the classic example – cars kill hundreds of people everyday, but they are deemed so damn useful that nobody who is of a reasonable mind would ever suggest that this inconvenient fact means they should all be wiped out.

    The chemicals we use on a daily basis are probably responsible in most part for the ungodly rise in the incidence of almost all forms of cancer this day in age, but nobody suggests we ditch all our modern conveniences because of this.

    P.S – am I the only one here that finds nuclear weapons to be completely awesome and fascinating? Feel free not to reply if you believe what I just said verges on blasphemy, or if you’re going to accuse me of supporting their use on people – that is a completely different matter. But personally, I find them to be a triumph of science and engineering – man’s incredible ability to be able to comprehend and influence matter and energy on incomprehensible scales.

    Nuclear Weapons are awesome. There – I said it.

  14. SeaFire says:

    “Nuclear Weapons are awesome. There – I said it.”

    Astrofiend, give me one good use for nuclear weapons!

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