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New Small Fission Reactor For Deep-space Missions Demonstrated
cylonlover writes "Exploring the regions of deep space beyond Mars means sending probes where solar power isn't practical. Since the 1960s, NASA has equipped its Apollo missions and unmanned explorers with Radioisotope Thermal Generators (RTGs). These have worked very well, but they run on plutonium 238, which is currently in short supply. Therefore, the Los Alamos National Laboratory is developing a new small nuclear reactor for spacecraft that uses uranium instead of plutonium to power Stirling engines and generate electricity. At the Nevada National Security Site's Device Assembly Facility near Las Vegas, engineers from Los Alamos, the NASA Glenn Research Center and National Security Technologies LLC conducted a Demonstration Using Flattop Fissions (DUFF) experiment that produced 24 watts of electricity using a pair of free-piston Stirling engines."
I found it odd that this little blip state that Plutonium is in short supply. The reason we don't have a lot of it is because the US is actively destroying it's Plutonium reserves. There are countless patents for machines that destroy Plutonium. Here is an article about how the DOE is considering alternatives to destroying Plutonium, like using it for something constructive instead of making bombs. http://www.world-nuclear-news.org/ENF_Alternative_route_for_plutonium_destruction_1507091.html
This is the most beautiful poetry I have ever seen. Oh my God.
It's probably less the number of probes we're sending, and more the general decrease in amount of Plutonium. PU hasn't been manufactured much since the end of the cold war; everybody is busy stepping down their weapon programs instead. Now, some of that former-warhead material is great for RTGs, but the stuff degrades. It has a moderately short half-life (it has to, or it wouldn't be active enough to passively generate the heat needed for an RTG) and a lot of the stuff that was viable for spacecraft 30 years ago is pretty cold now (see the Voyager probes, for example, which are running on extremely low power).
They can't just fix the problem by sending more, either; not only is it in short supply in general, but it's too heavy to send much on a spacecraft. Instead, they send enough to run the mission at full capacity for a few years, scaling back over time. That requires a supply of pretty fresh / pure Plutonium though, and that means making and separating more of it... except doing runs into a serious political problem. We *could* keep using RTGs (although they aren't perfect by any means, they get the job done) if we could convince people to let us manufacture their fuel source...
There's no place I could be, since I've found Serenity...
You must be a Vogon.
Only critical if combined. If the rocket breaks apart or the engines explode, the core would fall apart; it lacks the explosives necessary to bring the Uranium to super-criticality. Worst likely case would be that the control rod gets jammed but the housing stays intact, but the cooling system is destroyed, leaving the core at critical and causing a meltdown. The odds of that seem extremely low, though.
It'd be a very nasty "dirty bomb" if it blew up in the atmosphere, but no more than that, and a slug of Plutonium hot enough to run a spacecraft for a few years or even decades is a nasty thing to blow up in the atmosphere too. We've been launching those for decades, though.
There's no place I could be, since I've found Serenity...
Yes, I love it that they use a device called a "DUFF which "is a sort of lab bench nuclear reactor". ;-)
It seems like you're confusing Pu-239, which is used in weapons and has a half-life of 24000 years, with Pu-238, which is not used in weapons and has a half-life of around 90 years.
It is a common misconception that weapons grade plutonium can be repurposed for RTGs. However weapons grade plutonium is Pu-239, and has a long half life, 24000 years making it unsuitable for an RTG. The plutonium used in RTGs is Pu-238, with a half life of just 88 years, and is specially made for RTG purposes.
It's wouldn't be objectively any nastier than the other toxic substances such as hydrazine that would be sprayed all over the place in an explosion. "Dirty bombs" are not something to be taken seriously. Blowing up an equal mass of mercury would be more dangerous than the uranium, and the damage uranium would pose is more that it is a heavy metal than due to it being radioactive.
"Dirty bombs" are a true terrorism weapon - they cause far more terror than is actually justified, just like the 9/11 attacks did for air travel. Radiation is all scary and mysterious and dangerous and Chernobyl and Fukushima and OMG we're all gonna die!
That's their purpose, more than actually causing fatalities.
Just because you're paranoid doesn't mean there isn't an invisible demon about to eat your face
You might want to read a bit about fission reactors. A controlled reaction producing heat to be used. That is what it is. It isn't a pile of hot isotopes. Those have been used in the past. As often the case, reading the article might have helped. Or maybe reading about fission reactors on Wikipedia. Good luck.
My father was is the first lot of troops into Nagasaki and he stayed there for as part of the Japanese Occupation Force. They were given no warnings about radiation, no protective equipment, and allowed to pick and pry wherever they wanted among the ruins. HIs photos were taken from pretty much every part of the city.
He had no health problems that could be attributed to radiation. Those of his friends and shipmates who were there also were the same. In every case when they suffered serious ill health it was due to smoking or drinking.
What I have noticed though is curious congenital conditions occasionally popping up in their children, about 1 child in 4 or 5, when there was no history of it previously. This may or may not be coincidence but while these conditions may be awkward for those that have them, no-one has died from one yet.
I myself have worked with radioactive materiels and while they creep the bejesus out of anyone who has anything to do with them the radiation is not overly dangerous at low levels except over long periods, say taking x-rays every day. Even spending six months in Nagasaki starting two weeks after they dropped a plutonium bomb on it didn't cause any problems among the people I know who did it.
I said - don't look Ethel!..., but it was too late..., she'd already looked.
No, the boron in the control rod stops the reaction when inserted. If the control rod comes out then you would have a critical mass. I assume that thermal expansion of the core gives this a negative coefficient reactivity which probably makes it safe. This still seems somehow more problematic than launching an RTG with a sub critical mass of Pu.
Removing the control rod starts the reaction, but it is a sub-critical mass so there is no explosion.
Just because it is enriched Uranium doesn't mean that it is enriched to weapons grade.
Nah, the younger engineers are just infatuated with steam-punk... Wait till you see the generation of satellites with the brass fittings... woohoo!,/p>
No, that's the bean burritos.
I said - don't look Ethel!..., but it was too late..., she'd already looked.
It is a fission reactor.
The reactor speed is controllable with a boron carbide control rod. If it was just nuclear decay then it would not be controllable. The "old" RTG's were just powergenerators running off decay energy.
By the way: how did you think a normal fission reactor works? It's just enhanced and controlled nuclear decay that heats up a bunch of water to form steam. This steam dives a turbine that drives a generator: He presto, power! (for a more detailed explanation: just ask. I don't know the details of the reactions but others here do.)
The main difference here is that they used Stirling engines and scaled it down big time. Sterling engines are probably used because they are incredibly reliable, despite being expensive and not very efficient. There is no way to fix a broken power supply in space, especially if you need to replace parts.
Well, I might have a way, but it only works on a semi spherical planet in a vacuum.
It's a HaiKKKu
Table-ized A.I.
I was going to ask why they would use moving parts instead of something like cool chips (quantum electron tunneling). But then I realized that there probably isn't anything that is tested and ready yet. Then I realized that posting on Slashdot about things I know nothing about, will probably inflame the pedants and incite comments regarding my lack of knowledge and poor grammar/spelling. But then I posted anyway.
We are indeed inflamed, and our comments are duly incited.
Sheesh, evil *and* a jerk. -- Jade
Nuclear reactors have been used in space since the 1960s, by both the US and USSR. They've generally powered thermocouple-type electrical generators, which are inefficient but very reliable. The one US reactor launched massed 290Kg and produced 500 watts. Soviet reactors were bigger and produced more power.
The innovation here is a small unit around 65Kg that produces only 24 watts. Electronics has become so low-power that a 24 watt power plant is useful.
Note that all these reactors are unshielded.
Why contaminate the rest of the Universe? We have ruined our own planet and now we're going to ruin someone else's.
They should only allow green energy in space - solar, or hydro, or wind turbines. Wind turbines would work fine on Mars...
Strange because the majority of Japanese casualties, let along people who just got sick, were from radiation in the fallout rather than the blast itself.
const int one = 65536; (Silvermoon, Texture.cs)
SJW, n: "Someone I don't like, and by the way I'm a fuckwit" - AC
There is no heat that could cause a meltdown in the first place. The reactor will not have run for any significant amount of time at any significant enough power level to release enough heat to melt anything that isn't made of butter ... and even that might be a close call that depends on outside temperatures.
The fuel rods will consist mostly of U-235, which is much less radioactive than the Pu-238 that is commonly used and doesn't release any heat by itself. The radioactivity only comes into play once the reactor has been started up. But hopefully that will only happen after the probe is on its way away from earth.
IANARS, but it seems to me that while this is a great idea, there's a weak point in the mechanical linkages and the stirling engine.
RTGs use thermocouples which, while never very efficient, have the advantage of being solid state - a huge reliability benefit.
If you have this sort of system powering deep-space probes (or hell, near-space systems) I'd think that aside from all the normal wear-and-tear issues of any linkage (lubrication, debris, even erosion over time) would be exacerbated by the thermal extremes in space. Further, the vibration created through the rest of the craft couldn't be helpful for the lifespan of the other components. Finally, for the sorts of precision needed for space operations (pointing a space telescope comes to mind) the constant oscillation of mass within the craft probably would make other things significantly more difficult.
Again, not a rocket scientist, but from my point of view as 'cool' as this is, and as useful as it may be, it doesn't seem like something very applicable to space operations.
Tinfoil hat bit:
Now...if one needed a long-term power source for something much less precise like earthly drone operations... (I don't know the mass/power here at all)...
-Styopa
The halflife of Pu-238 is 88 years. The Voyagers' Pu is only about a half-of-a-halflife old. The falloff in power for a Pu RTG is due largely to material degradation in the thermocouples that generate electricity, not due to a drastic falloff in heat.
Yes, lots of people protested NASA's risky space launch of a nuclear reactor but failed to stop the launch. The cops treated them just like they treated OWS. Sigh.
From the link:
The Cassini rocket will be powered by 72 pounds of plutonium -- the most ever rocketed into space. Protesters say that if the rocket explodes it could sprinkle deadly poison for hundreds of miles.
Winds can blow (plutonium) into Disney World, Universal City, into the citrus industry and destroy the economy of central Florida," said Michio Kaku, a protesting physics professor from New York. He claimed that casualties could run as high as a million people if there were an accident.
What? If you split it up into 1 million 30 milligram doses and had people directly inhale it or inject it into your blood, yeah that would do it. You could injest that much and survive (cancer risk goes up, but it is well under the LD50 of 500mg for ingestion, cyanide is more lethal) But exploding it over the ocean where people are very unlikely to encounter any at all? Maybe that is the kind of science you get form a TV physicist. Make up a scary story to get yourself headlines.
As far as the OWS quip goes, some of these people did break into a secure facility by jumping the fence. Though they deserve to be arrested it is no reason for police brutality. However the article only says that there were only arrests.
I'm a good cook. I'm a fantastic eater. - Steven Brust
I'm sure that in 1985, plutonium is available in every corner drugstore, but in 2011, it's a little hard to come by.
crazy dynamite monkey
Bzzt.
Your 52kg figure is for a naked sphere of U235. This article mentions a reflector. This article also makes no mention of a second mass, or that the reactor ever reaches criticality. Sub-critical assemblies can still multiply the flux from a static neutron source, so plenty of power with no potential of runaway reactions. Also, the article is about deep-space missions and mentions probes. So I'm guessing no crew, no halves, and no fizzouts.
No, "critical mass" is defined as the amount that can create sufficient runaway escalation of the fission rate by capturing the energetic byproducts of fission to stimulate more fission in a positive feedback loop.
I'll tell you what: I'll give you 1 gram of the radioactive isotope of your choice, if you can stop its fission. You can't. You can only moderate its rate somewhat. Clearly it's self-sustaining on every level down to the individual atom