It gets 20,000 miles to the isotype!
November 23, 2009 4:12 AM   Subscribe

[ScienceFilter]: I want to drive a nuclear powered car. If nuclear power is good enough for submarines, why can't the technology be scaled down? Looking for big picture such as limitations, environment, storage, infrastructure and adaptations required.
posted by Funmonkey1 to Science & Nature (25 answers total) 2 users marked this as a favorite
 
The Atomic Automobile.

Or just google "Ford Nucleon".
posted by Sova at 4:18 AM on November 23, 2009 [1 favorite]


Ford Nucleon

Main problems: size, shielding, crashes.
posted by chrisbucks at 4:18 AM on November 23, 2009


Water is another problem.

The way a heat engine works is that you let the energy flow from somewhere there's a high energy density (it's hot) to somewhere there's a low energy density (it's cool) and grab some of the energy along the way.

A submarine or ship uses the ocean water as a cool place to dump lots of energy. Nuclear power plants are located by seas, lakes or rivers for the same reason. But a car doesn't have a convenient energy sink.
posted by TheophileEscargot at 4:32 AM on November 23, 2009


Also, a nuclear submarine has lots of people working on it to make sure it doesn't break. Can you afford a similar staff for your car?
posted by gjc at 4:34 AM on November 23, 2009


1) Isotope.

2) Few infrastructure constraints are impossible if the economics support it.

3) The economics do not support it presently.

In the foreseeable future, we will have alternatives that are superior in every way to locally produced nuclear energy. Honestly, I can't imagine anything that would change that. The amount insolation on this planet and the ease of direct conversion suggests that solar (and other) power productions (partially nuclear), point to a higher payoff for energy storage innovations, not energy production innovations. Batteries, fuel cells, ultracapacitors are in the realm of the real, but miniaturizing what is an extremely poisonous and inherently inefficient power production device like a reactor is non-trivial, fraught with technological and safety constraints, and of such low demand as to assure it remains unexplored.
posted by FauxScot at 5:01 AM on November 23, 2009 [2 favorites]


You could mount an RTG onto a vehicle but considering that we use more Uranium than we can mine annually then I doubt this would be affordable for a private citizen. On top of it, cars get into wrecks pretty often. All accident scenes will have to involve hazmat and any serious breech of the RTG can permanently shutdown highways or even whole neighborhoods.
posted by damn dirty ape at 5:45 AM on November 23, 2009


"... In other news, I-95 between Boston and Providence will be closed for the next 25 years while crews work to decontaminate a stretch of road where a $20,000,000 Volkswagen Nuke hit a tree" Residents for 20 miles on either side of the road are are advised to wear respirators until further notice."
posted by paanta at 5:51 AM on November 23, 2009 [5 favorites]


I think a nuclear reactor traveling at 65mph is always going to be problematic.
posted by bshort at 6:25 AM on November 23, 2009 [1 favorite]


No, just go back in time before the causality errors.

But yeah, nthing weight and safety concerns. It's way too much to trust a consumer to maintain any type of atomic reactor that would provide the power-to-weight ratio practical for a car. If you want a nuclear powered car, an electric car hooked up to a power grid is much better, if only for the seriously reduced liabilities.
posted by mccarty.tim at 6:53 AM on November 23, 2009


Water is another problem.

The way a heat engine works is that you let the energy flow from somewhere there's a high energy density (it's hot) to somewhere there's a low energy density (it's cool) and grab some of the energy along the way.


Well, a car would be moving quickly at speed would be able to draw in a lot of fresh air. Theoretically, a car shouldn't need any more energy from a nuclear engine as it would a conventional engine, unless the nuclear engine was far less powerful.

There have actually been nuclear powered aircraft designs. None were ever built but they did build a prototype engine
On May 14, 1961, the world's first nuclear ramjet engine, "Tory-IIA," mounted on a railroad car, roared to life for just a few seconds. Three years later, "Tory-IIC" was run for five minutes at full power, producing 513 megawatts and the equivalent of over 35,000 pounds force (156 kN) thrust
Now, that particular engine wouldn't work very well in a car, but a scaled down sterling engine could. Particularly an electric car with a tiny reactor powered by, say, polonium 210 might work well. According to Wikipedia, a single gram emits 140 watts. It would only take 2kg to equal 400hp in heat energy. Even if you assumed thermal->mechanical efficiency was only 10% that's still probably enough to power a low-cost electric car.

Ultimately though, I think the safety concerns are too great. A ordinary nuclear reactor is usually burred under tons of concrete, but a car needs to be light. Nuke powered cars everywhere would allow easy access to radioactive materials to almost anyone. Accidents could cause nuclear contamination, etc.
posted by delmoi at 6:55 AM on November 23, 2009


I think the fundamental problem with nuclear (if we hand wave all the logistical concerns away) is that it really isn't suited for the task. Unless there is some nuke technology I don't know about, the nice thing about nuclear energy is that once you get it set up and going, the fuel is very energy dense and cheap. But the starting up and shutting down is really quite a process. I suspect that if you made one that would start and stop more efficiently, the overall energy to motion efficiency would be severely crippled.

Beyond that, it is just like any other electricity generation technology. Make something really hot, boil water, spin turbines, make electricity. I doubt the conversion efficiency would be nearly as beneficial in something that needs to spin up and down constantly like a car. Even if you eliminated the conversion to electricity step, and just used the boiling water to spin a turbine that direct drives the wheels, I'd expect that the time lag would be unpleasant. It takes time to melt all that sodium. I'm not sure, but I think the benefit of nuclear power is that it gets REALLY hot and that huge temp differential makes it more efficient. Anything that changes that and it loses efficiency.

(Also, if you have a plug-in electric car, you have a nuclear car. There's just more wires between you and the uranium.)
posted by gjc at 7:10 AM on November 23, 2009


The are many types of devices that generate electricity from radiation that aren't nuclear reactors and they require very little or no maintenance or supervision. Most are grouped into the category of nuclear batteries. Some of these devices could potentially power a car, especially if they are supplemented by rechargeable batteries that could be charged while the car is not in use. Some could also be shielded and contained in steel housings that would be nearly indestructible. I think the main problem is the cost of production and the cost of disposal. Refining and disposing of radionuclides is never cheap and there is always potential for serious contamination after the device has outlived its use. One good example is the many Soviet Radioisotope Thermoelectric Generators that were used to power remote outposts in Russia. They worked very well but no one collected them before they deteriorated. Now no one wants to be responsible for cleaning them up and the damaged devices are extremely dangerous. There have been deaths from people who used damaged RTGs for warmth during winter. Here's another article on the logistics of Russian RTG ownership and use.
posted by Procloeon at 7:14 AM on November 23, 2009


Seconding a Radioisotope Thermoelectric Generator. If they can fit in a pacemaker and be safe, then we should be able to use them in a car.
posted by gregr at 7:17 AM on November 23, 2009


Disclaimer: My dad built subs.

Because the operational techniques needed to keep it safe far exceed what the average person is willing or able to deal with on a daily basis. We use Systems Engineering for this stuff. Imagine just trying to start the car:

1. Conduct analysis of external state of automobile. See appendix A.
2. If score from #1 > 30 and no vetos are noted, enter automobile. Else see Veto procedures below.
3. Conduct analysis of internal state of automobile. See appendix B.
4. If score from #2 > 30 and no vetos are noted, enter security code via the keypad on the dashboard. Else see Veto procedures below.
5. When prompted raise control rods to power battery.
6. Set control rods into traveling mode so they are locked to vehicle's power needs.
7. Conduct test of emergency power off procedures. See appendix C.
8. If score from #7 > 30 and no vetos are noted, check for pedestrians or other obstructions to movement of automobile. Else see Veto procedures below.
9. Place automobile in gear and drive. Please see book "How to drive your nuclear powered Toyota Corolla" for further instructions.
Note: Manufacturer assumes no responsibility for owners use or misuse of the automobile. See appendix D-F.

Veto procedures
1. If control rods are in traveling mode set to OMG mode.
2. If raised, lower control rods into maximal position and lock in place manually.
3. Fill out Nuclear Regulatory Commission Form 55332-1A within 5 minutes.
4. If veto 6A is noted on step #3, alert local law enforcement of impending leak and take two protection capsules labeled "Cyanide".
5. We hope you have a nice day.
6. This step intentionally left blank.
posted by jwells at 7:22 AM on November 23, 2009 [4 favorites]


I'm not sure about the cooling. I don't know if it would be physically possible to put in enough heat regenerators into a car to make cooling a possibility in that size.

I mean, those giant towers you see aren't the reactors. (A fact I only recently learned...) The reactor is a much smaller. (In this photo, the reactors are the little tan buildings with white dots on top.) (This one (pdf) uses a cooling lake and doesn't even have the cooling towers.)

So the size of the cooling setup needs to be orders of magnitude bigger than the reactor. Even if the reactor was the size of a golf ball, I would expect that the rest of the car would have to be fully dedicated to cooling to even approach a sanity level. At speed, you're right, probably a regular car radiator would be enough. But what about when you jam on the brakes? Even if you shut the reactor down dead instantly, the amount if heat in the system would have to be bled off somehow, and that would require a lot of cooling capacity.
posted by gjc at 7:25 AM on November 23, 2009


Small nuclear power reactors; though all the ones listed are far too large to fit in a car.
posted by XMLicious at 7:48 AM on November 23, 2009


I am a reactor plant operator (navy submarines - mechanic, chemist, radiological controls)

I see many difficulties.

1) A shutdown reactor still requires control. There is an operator stationed at all times to maintain plant pressure and temperature in the required bands (which change, based on heatup/cooldown rate limitations and other concerns). So you'd have to write a watchbill for your family to keep an eye on it all the time.

2) A startup takes a while, and is kind of a balancing act of when to do what at exactly the right time based on what you're seeing. Bringing power up through the source range up to the point of adding heat is not the time to add reactivity by drawing steam for power. It's not physically hard, but it's one of those things that seems easy to step through the several phone book sized procedure after years of theory training. It's not really safe to cookbook without the required backround knowledge.

3) Reactor plants do best at fairly constant power levels. Sure, submarine plants are designed to be capable of rapid and frequent power transients from low to full power, but you can only keep that up for so long before you have to adjust some stuff, like charging in or discharging water. You also have to have the knowledge to predict what's going to happen before it becomes an issue.

4) Nuclear maintenance is a serious pain in the ass and is ridiculously expensive. The whole reason I exist at my current job is to keep mechanics from getting excessive radiation exposure or spread radioactive contamination while working on the plants. I make bunches of money doing that. You want to pay your mechanic to have to pay me when he works on your car?

5) Nuclear maintenance makes radioactive waste. (low-level, but still). You want to have to meet all the DOT and DOE regulations for segregation, storage and disposition of all that radioactive material? Pretty much, you'd have to hire me the rest of the time to make sure you were in compliance.

6) Even during normal operation, the plant needs water charged to it and discharged from it from time to time. What are you going to do with the discharged water? [see 5.]

I bet a nuclear powered bus with a dedicated crew would work, but it really would be economically stupid.
posted by ctmf at 7:50 AM on November 23, 2009 [7 favorites]


Even aside from the practical problems:

1. Nuclear reactors don't really scale down indefinitely (as opposed to RTGs, which are an entirely different kettle of fish and probably not a good idea for a car since they aren't throttleable). Reactors rely on a nuclear chain reaction to get the fuel to give up its energy on demand, and you need a certain size to keep the reaction up. The Soviet TOPAZ-I reactors (used on spy satellites) were only a third of a ton, but I think that's without any sort of shielding.

2. Nuclear submarines are a kind of extreme case. They need to operate for a long time with no external supplies except for an infinite heatsink, they don't have a tight weight budget, and they're a Cold War military technology. None of these are true for cars.
posted by hattifattener at 9:52 AM on November 23, 2009


You can take out everything related to the particular source of heat, and you still end up with the question of why we don't have steam powered cars, and the question of why turbine-powered cars never got very far.
posted by Good Brain at 10:34 AM on November 23, 2009 [1 favorite]


For a bus or semi truck sized reactor plant, see Submarine NR-1. Obscenely expensive to maintain and operate, plus the crew has to have enough training to avoid problems like the army had with their small reactor.

That accident was largely due to poor theory training for the operators, and instigated with a crap maintenance procedure. A well-trained operator would have looked at the step that said "pull control rod by hand..." and refused to do it without some form of withdrawal rate control.

"...and now to SkyOne with the traffic: Slow around the S-curve due to a roadside loss of coolant accident. FEMA decon teams are on scene. Expect that to be cleared up around... next Tuesday. 1 mr lines are set at about 1/2 mile on either side. Roll your windows up while passing through the radioactive airborne plume if possible."
posted by ctmf at 10:37 AM on November 23, 2009


Now, that particular engine wouldn't work very well in a car, but a scaled down sterling engine could. Particularly an electric car with a tiny reactor powered by, say, polonium 210 might work well. According to Wikipedia, a single gram emits 140 watts. It would only take 2kg to equal 400hp in heat energy.

Ah, polonium 210 you say? The horribly lethal isotope that was used to poison Litvinenko? Not such a great idea.

A single gram is a huge quantity by the way, probably on the order of the total annual world production.
posted by Dr Dracator at 11:11 AM on November 23, 2009


IAANuclear Engineer.

One of my classmates did their senior design project on this subject.

All of the other problems are insignificant when compared to the problem of mass. The shielding necessary for any sort of nuclear fission reactor, no matter what the fuel used, would be too heavy to make the car's mileage all that efficient.
posted by derogatorysphinx at 12:51 PM on November 23, 2009 [1 favorite]


Also, RTGs look great theoretically, but they don't produce anywhere near enough power (on the order of 200-300 Watts) for a car.
posted by derogatorysphinx at 12:55 PM on November 23, 2009


Also, RTGs look great theoretically, but they don't produce anywhere near enough power (on the order of 200-300 Watts) for a car.

NASA has looked into switching from a traditional RTG to one that does the heat --> electricity conversion using a high-efficiency thermoacoustic stirling engine. I believe they expected 4x the efficiency of the traditional RTG (still not great, as the traditional RTGs are *terrible*), and 120W from a 16Kg device.

Still seems unlikely that the powers-that-be will ever let you drive around with a lump of plutonium in your car.
posted by madmethods at 1:53 PM on November 23, 2009


To be fair, Litvinenko died because he ate Po-210. Since it emits only alphas and has a stable daughter, its radiation is contained completely by, say, a paper envelope.

On the other hand, what Litvinenko ate was a few millionths of a gram.
posted by fantabulous timewaster at 7:32 AM on November 24, 2009


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