Could a tank or land vehicle be nuclear powered?

[ensabah6]

Submarines are nuclear powered.

How small of a nuclear-fission powered unit be made and could it be fitted inside a tank or other land vehicles?

 

[QuantumPion]

Nuclear reactors can be made small and compact. With high-enriched Uranium you can make a reactor the size of a toaster (although its maximum power would be limited due to material constraints). I'm not sure how small steam turbines can be scaled down and still be efficient but I bet a tank-sized one would be possible. I think Ford actually conceptualized some sort of nuclear powered car in the 50's.

The problem is that shielding does not scale down as well. You still need heavy lead shielding and thick hydrocarbon materials to reflect neutrons. For a tank it might not be out of the question; but a car, in order to protect both the driver and the public, would be far too heavy.

 

[ensabah6]

Nuclear reactors can be made small and compact. With high-enriched Uranium you can make a reactor the size of a toaster (although its maximum power would be limited due to material constraints). I'm not sure how small steam turbines can be scaled down and still be efficient but I bet a tank-sized one would be possible. I think Ford actually conceptualized some sort of nuclear powered car in the 50's.

The problem is that shielding does not scale down as well. You still need heavy lead shielding and thick hydrocarbon materials to reflect neutrons. For a tank it might not be out of the question; but a car, in order to protect both the driver and the public, would be far too heavy.

Does it have to be a steam turbine and, not say, an air turbine? How many miles can you get and would the power output be enough say for reactive electromagnetic armor, electromagnetic gun, and drive train and onboard sensors and computers and electronics?

I guess the size of the nuclear reactor, along with shielding, would be the size of a M1 Abram's gas turbine engine. Use of electromagnetic armor and gun may reduce weigth of armor and size of projectiles allowing more room and weight for nuclear reactor and shielding.

 

[theCandyman]

It isn't the turbine that is the concern (unless you come up with a BWR-like concept), you would want a PWR to remove heat from the core more quickly with less power needed for the pump. Mileage is a difficult thing to measure without reactor size, fuel enrichment, mass of the transport, among other things. The reactor with shielding would probably be much bigger than an Abram could carry. I'm not completely sure, but I think most of the back half of a nuclear powered submarine is for the plant and turbine.

 

[ensabah6]

It isn't the turbine that is the concern (unless you come up with a BWR-like concept), you would want a PWR to remove heat from the core more quickly with less power needed for the pump. Mileage is a difficult thing to measure without reactor size, fuel enrichment, mass of the transport, among other things. The reactor with shielding would probably be much bigger than an Abram could carry. I'm not completely sure, but I think most of the back half of a nuclear powered submarine is for the plant and turbine.

If the tank was remote controlled and had no humans on board during military operation (obviously it needs maintance) could the shielding be considerably reduced?

 

[theCandyman]

A tank is something that is going to be shot at, you'll want shielding regardless of whether people are in it or not.

 

[ensabah6]

A tank is something that is going to be shot at, you'll want shielding regardless of whether people are in it or not.

with enough electrical power can't electromagnetic shielding be used? there's a colloidal solution with magentic-iron particles nanoparticles that cluster around electric fields forming extreme hardness.

then there's the emp gun

 

[berkeman]

You haven't addressed the heat removal aspect that Candyman brought up. What do a submarine and a fixed reactor have that a mobile vehicle doesn't have?

 

[signerror]

I'm surprised no one mentioned Pamir. The former Soviet Union built (prototype) mobile reactors on large trucks - they were not self-propelled, but they were on wheels. Of course the conclusions in this thread are entirely correct - the system ran on HEU (45%), was very big (much larger than an ordinary tank), and used small gas turbines rather than steam turbines - with a very exotic working fluid, dinitrogen tetroxide (N2O4) gas.

http://www.nti.org/e_research/profiles/Belarus/Nuclear/facilities_sosny.html

According to Belarusian nuclear scientists, the now-restructured Belarusian Institute of Nuclear Power Engineering (INPE) designed a mobile nuclear power reactor with a 700 kW capacity (according to Yermashkevich, 630 kW) and created a working model, called Pamir.[3,4] This reactor was designed for military purposes and for territories, such as the desert or tundra, where it is difficult to connect to an electricity grid. This mobile plant was designed to work in conditions from -50 degrees Celsius to +50 degrees Celsius without any water resources.[3] The Pamir reactor used uranium enriched to 45 percent U-235 for fuel, with nitrogen tetraoxide for the coolant. Tests were performed using critical assemblies and the model itself for at least 3,500 hours starting in 1985.[3,4,5] Approximately 60 emergency shutdowns took place, some of which resulted in the release of nitrogen tetraoxide and radioactive particles.[4] The project was scrapped in 1986 by a decision of the Belarusian government.

There's a longer description in a Russian-language news article:

http://translate.google.com/translate?hl=en&sl=auto&tl=en&u=http://news.tut.by/society/98447.html

It's quite far from being nuclear-propelled, if you consider the specs. The system takes up four large trucks, the reactor one weighing 60 tons - but the electric output is only 630 kW = 845 hp. (Experts - is it cooling that is the limiting factor here?)

I also found a related paper on the N2O4 Brayton cycle from 1979 - it makes extensive reference to Russian research:

"Potential performance improvement using a reacting gas (nitrogin tetroxide) as the working fluid in a closed Brayton cycle"

http://ntrs.nasa.gov/search.jsp?R=7...=false&qs=Ns=ArchiveName%7c0&N=4294946812+295

("reacting gas" means it dissociates during the thermodynamic cycle: N2O4 <--> 2 NO2.)

Perhaps you may be interested in nuclear propelled airplanes? The US designed such a system, and found it viable.

http://www.ornl.gov/info/ornlreview/rev25-34/net425.html

There are photos of the test engines on wikipedia (they are located at Idaho National Lab):

http://en.wikipedia.org/wiki/Aircraft_Reactor_Experiment

 

[ensabah6]

You haven't addressed the heat removal aspect that Candyman brought up. What do a submarine and a fixed reactor have that a mobile vehicle doesn't have?

How much heat does a toaster sized fission box need to have removed?

 

[QuantumPion]

How much heat does a toaster sized fission box need to have removed?

According to wiki, an M1 Abrams tank's engine is 1500 HP. So at 30% thermodynamic efficiency, ~3700 kW. That's quite a bit of heat flux for a toaster! :)

 

[ensabah6]

According to wiki, an M1 Abrams tank's engine is 1500 HP. So at 30% thermodynamic efficiency, ~3700 kW. That's quite a bit of heat flux for a toaster! :)

good point

 

[mheslep]

According to wiki, an M1 Abrams tank's engine is 1500 HP. So at 30% thermodynamic efficiency, ~3700 kW. That's quite a bit of heat flux for a toaster! :)

It might a bit more efficient than that, the Abrams uses a turbine engine - at least when running at full power it should exceed 30% efficiency.

 

[mheslep]

While miniature nuclear reactors are interesting, miniaturization is not the main problem to my mind. The question is how does one make the reactor safe in the case of a catastrophic accident (or attack for a military vehicle) AND relatively useless from a weapons proliferation stand point. I don't know how to answer these two questions. What type of reactor would be most benign if the vehicle carrying it hit an IED or was hit by a train at a crossing? CANDU? Anyone?

 

[QuantumPion]

While miniature nuclear reactors are interesting, miniaturization is not the main problem to my mind. The question is how does one make the reactor safe in the case of a catastrophic accident (or attack for a military vehicle) AND relatively useless from a weapons proliferation stand point.


I don't know how to answer these two questions. What type of reactor would be most benign if the vehicle carrying it hit an IED or was hit by a train at a crossing? CANDU? Anyone?

If you don't want the enemy to be able to steal your reactor and make it into a weapon, you can use reactor-grade plutonium (pu+239 + pu-240).

As for making a reactor sturdy enough to survive conditions related to warfare, I'd imagine some sort of self-contained metal cooled reactor would be best. But no matter what the design is, even if heavily shielded and protected, a direct hit from a big bomb or armor penetrating shell or what have you will ruin your day. :p

 

[mheslep]

If you don't want the enemy to be able to steal your reactor and make it into a weapon, you can use reactor-grade plutonium (pu+239 + pu-240).

Alright, if we somehow lose reactor grade plutonium (> 19% Pu-240) that's been in an operational reactor, what's the difficulty in separating out the Pu-239 to weapons grade Pu? We want that to be at least hugely difficult if not impossible. Would it require a separation process on a grand scale requiring the resources of a nation state?

As for making a reactor sturdy enough to survive conditions related to warfare, I'd imagine some sort of self-contained metal cooled reactor would be best. But no matter what the design is, even if heavily shielded and protected, a direct hit from a big bomb or armor penetrating shell or what have you will ruin your day. :p

Well some of these small reactors (http://www.world-nuclear.org/info/inf33.html" ) are designed so that the fission reaction stops by default if the reactor gas/liquid metal flow stops for any reason, so that should eliminate the run away case. Then we're left with the escape to the atmosphere of what products? What dosage is possible?

 

[QuantumPion]

Alright, if we somehow lose reactor grade plutonium (> 19% Pu-240) that's been in an operational reactor, what's the difficulty in separating out the Pu-239 to weapons grade Pu? We want that to be at least hugely difficult if not impossible. Would it require a separation process on a grand scale requiring the resources of a nation state?

Separating Pu-240 from Pu-239 is much much harder than separating U-235 from natural uranium. If you had the technology to do isotopic separation to begin with you wouldn't bother trying to separate highly radioactive reactor fuel when you can dig uranium out of the ground.

Well some of these small reactors (http://www.world-nuclear.org/info/inf33.html" ) are designed so that the fission reaction stops by default if the reactor gas/liquid metal flow stops for any reason, so that should eliminate the run away case. Then we're left with the escape to the atmosphere of what products? What dosage is possible?

Depends on many factors, such as the fuel composition, burnup, and how it is dispersed. I wouldn't want to be anywhere nearby though. :p

 

[MadRocketSci2]

What about if they boost the efficiency of a beta-voltaic type battery, or nuclear thermal battery. You might eventually reach a power density where it could propel a car or something, without having to worry about a full reactor that can runaway. Just crazy drivers and accident lawsuits.


If my deadly nuclear tank gets hit on enemy territorry, dosage from leaking fuel elements is their problem. (evil laugh).

 

[mheslep]

Separating Pu-240 from Pu-239 is much much harder than separating U-235 from natural uranium. If you had the technology to do isotopic separation to begin with you wouldn't bother trying to separate highly radioactive reactor fuel when you can dig uranium out of the ground.

This seems to suggest that reactor grade Pu presents no proliferation risk. Yet Pu output from commercial nuclear operations is cited as a proliferation risk, by e.g. the MIT Nuclear report.

Depends on many factors, such as the fuel composition, burnup, and how it is dispersed. I wouldn't want to be anywhere nearby though. :p

Well I wouldn't want to be anywhere near a 500,000 gal fuel depot that was attacked, but we consider that an acceptable risk - a baseline if you will. I'm curious in weighing the risk against such a baseline for smallish reactors.

 

[theCandyman]

This seems to suggest that reactor grade Pu presents no proliferation risk. Yet Pu output from commercial nuclear operations is cited as a proliferation risk, by e.g. the MIT Nuclear report.

There's still a large amount of Pu-239 in reactor grade fuel, more than 50% if I remember right. It would be very difficult and require a lot of energy, but it could be separated out. Also, Pu-240 is fertile, so if it could potentially be used as well.

 

[WhoWee]

Other than reducing the need to re-fuel, why would you want a nuclear fueled tank? It seems the risks would outweigh the benefits.

 

[mheslep]

There's still a large amount of Pu-239 in reactor grade fuel, more than 50% if I remember right. It would be very difficult and require a lot of energy, but it could be separated out.

I'm sure its possible given the resources. The idea here is to assess the risk, level of difficulty. [/QUOTE]I believe it is safe to say from what I've read here that if one tossed a lump of mixed Pu into Bin Laden's cave, it would utterly useless to him as a fissile weapon.

Also, Pu-240 is fertile, so if it could potentially be used as well.

Well the only useful decay path is to Pu-241. Then given a small reactor w/ a small fuel load of 240, one would have to wait ~6000 years to get half as much 241. Maybe neutron bombardment in a reactor would accelerate that route?

 

[ensabah6]

Other than reducing the need to re-fuel, why would you want a nuclear fueled tank? It seems the risks would outweigh the benefits.

How would you power electro-magnetic armor, electro-magnetic shield, electro-magnetic guns, plasma guns, laser guns, microwave heat rays?

 

[MadRocketSci2]

You might be able to do it with separate gas turbine for power and a large fuel supply. It depends on what you want to do with it.

 

[WhoWee]

How would you power electro-magnetic armor, electro-magnetic shield, electro-magnetic guns, plasma guns, laser guns, microwave heat rays?

Maybe a space-based system would be better than a fleet of nuclear powered tanks?

 

[QuantumPion]

This seems to suggest that reactor grade Pu presents no proliferation risk. Yet Pu output from commercial nuclear operations is cited as a proliferation risk, by e.g. the MIT Nuclear report.

Reactor grade Pu cannot be made into a bomb. In order to get weapons-grade Pu from a commercial reactor, it has to be a plant type that allows for online-refueling. Mainly, a RBMK-type reactor (although it might be possible with a CANDU as well, I'm not sure).

Without having read the MIT report I would venture to say it is baloney. Why are they concerned about western nations (whom already have nuclear weapons) diverting reactor fuel for weapons (which no one does as far as I know). The real, actual risks for proliferation lie with Iran and North Korea, whom we know are trying to make weapons. Yet no one wants to do anything about them. How is banning reprocessing of fuel in the United States, while ignoring Iran's uranium centrifuges make sense? Ok I'm done ranting now. :)

 

[mheslep]

Reactor grade Pu cannot be made into a bomb. In order to get weapons-grade Pu from a commercial reactor, it has to be a plant type that allows for online-refueling. Mainly, a RBMK-type reactor (although it might be possible with a CANDU as well, I'm not sure).

Without having read the MIT report I would venture to say it is baloney. Why are they concerned about western nations (whom already have nuclear weapons) diverting reactor fuel for weapons (which no one does as far as I know). The real, actual risks for proliferation lie with Iran and North Korea, whom we know are trying to make weapons. Yet no one wants to do anything about them. How is banning reprocessing of fuel in the United States, while ignoring Iran's uranium centrifuges make sense? Ok I'm done ranting now. :)

Reprocessing inevitably increases the amount of stored Pu in the world. The current PUREX/MOX process produces weapons usable Pu. The authors associate some non-zero risk with each kg - that it can fall into the wrong hands. Small risk perhaps, but its not baloney.
http://web.mit.edu/nuclearpower/"
From the http://web.mit.edu/nuclearpower/pdf/nuclearpower-summary.pdf":

I posted a summary earlier:
https://www.physicsforums.com/showpost.php?p=1723712&postcount=201

BTW:

Iran and North Korea...Yet no one wants to do anything about them.

Hyperbole

 

[MATLABdude]

How about that for a deterrence weapon? "No, of course we're not carrying WMDs into battle. Yes, our nuclear tanks, when hit, will explode but it won't be like an atomic bomb. More like a dirty bomb, irradiating the land and rendering it unhabitable for the next thousand years."

 

[QuantumPion]

oops double post.

 

[QuantumPion]

Reprocessing inevitably increases the amount of stored Pu in the world. The current PUREX/MOX process produces weapons usable Pu. The authors associate some non-zero risk with each kg - that it can fall into the wrong hands. Small risk perhaps, but its not baloney.
http://web.mit.edu/nuclearpower/"
From the http://web.mit.edu/nuclearpower/pdf/nuclearpower-summary.pdf":

I posted a summary earlier:
https://www.physicsforums.com/showpost.php?p=1723712&postcount=201

Reprocessing doesn't magically create plutonium out of nothing. It extracts it from spent fuel, the isotopic mix of which is such that it can never be used for a bomb. In fact, if we were to reprocess fuel more, then that plutonium would become increasingly less capable of being used for a weapon each time it was recycled, as the relative concentration of Pu-242 would gradually increase.

BTWyperbole

So what argument do you have that my statement was hyperbole? You haven't addressed it at all.

Iran just announced they had even more uranium centrifuges then anyone (even the vaunted UN) knew about, on the eve of the United States president announcing his wish to get rid of all nuclear weapons. And no one has done anything about it. North Korea made a reactor to produce weapons plutonium after promising they would not, when the UN knew what they were up to nothing was done in that case either.

The UN clearly has no intention of acting to prevent other countries from producing weapons grade material and nuclear weapons. So why are they concerned about Western nations reprocessing reactor fuel?