Nuclear powered trains

[Big Mac]

Apologies if this has been covered before, but I did search this forum and it didn't seem to return any threads addressing this question.

I was idly wondering how practical it would be to construct a train powered directly by a nuclear reactor. I was thinking such a thing would be a locomotive hauling a rake of some sort.

Surely it would be technically possible? The necessay radiation shielding might be quite heavy, but as locomotives can be 100 tons+, I think it could be technically possible to make such a thing.

I'm no expert in reactors or locomotives, so I'd be very interested in the views of more knowledgeable forum members on such a proposal.

Obviously the initial cost of such a project would be very high, but given some modern types of nuclear reactors of the type typically found in submarines can go 25 years without refuelling, in the longer term it could be worthwhile.

Given such a locomotive could theroetically operate anywhere on the NR metals, over time, it could make economic sense; on the Uckfield branch for example.

Thank you for your input.

 

[HSTEd]

The minimum size of a nuclear reactor is proportional to the enrichment of fissile material.

Lightweight reactors like submarine cores or even aircraft reactor testbeds have used highly enriched material, often as much as bomb grade (90% 235U).
Various treaty restrictions prohibit greater than 20% enrichment in most civilian applications.

It is highly unlikely a viable reactor could be built that would physically fit inside the loading gauge.

A nuclear powered train is however perfectly feasible..... its called an electric train.
Most TGVs are essentially nuclear powered for example.

 

[Philip Phlopp]

Nuclear reactors are one thing, how are we getting electric out of it though ?

 

[Darandio]

Nuclear reactors are one thing, how are we getting electric out of it though ?

Well, presumably we need a pressurizer and a steam generator, that is going to make the consist 3-4 car lengths already. Don't forget the turbine, another couple of car lengths? Oh, we then have to probably transfer it through some kind of propshaft as well?

There is a reason why a submarine is quite long.

 

[Big Mac]

The minimum size of a nuclear reactor is proportional to the enrichment of fissile material.

Lightweight reactors like submarine cores or even aircraft reactor testbeds have used highly enriched material, often as much as bomb grade (90% 235U).
Various treaty restrictions prohibit greater than 20% enrichment in most civilian applications.

It is highly unlikely a viable reactor could be built that would physically fit inside the loading gauge.

A nuclear powered train is however perfectly feasible..... its called an electric train.
Most TGVs are essentially nuclear powered for example.

Many thanks for your reply. I appreciate that the UK loading gauge is quite restrictive, I didn't know about the treaty restrictions you mentioned.

Sounds like those might be the biggest impediment rather than the limitations of the technology.

 

[D365]

Sounds like those might be the biggest impediment rather than the limitations of the technology.

To say nothing of the evil and greed of mankind...

 

[Big Mac]

Not withstanding Darandio's points about the mechanism of converting the heat output of the nuclear reactor into something which might actually power the train, how about the use of thorium pebble bed type reactors, which as these can't produce material for use in nuclear weapons, presumably this gets around HSTED's treaty restriction argument?

 

[najaB]

There have been at least two aircraft that carried working nuclear rectors. If you can make one fly, you can make it run on the rails.

 

[broadgage]

The smallest nuclear reactors available at present are those that power nuclear submarines, they are too large to fit within any likely loading gauge.

They produce electricity, not directly from the reactor but by boiling water and raising steam to operate a steam turbine.

 

[RepTCTC]

Ignoring the obvious cost issue...

Nuclear reactors aren't the most responsive things in terms of the way they generate heat, so aren't really conducive to efficient operation in the railway "lots of power, not a lot of power, no power for a while, repeat and rinse" mode of operation, so in order to use them efficiently you'd really need a system of transmitting the electricity generated from the otherwise wasted heat to other trains. In other words, you'd need the infrastructure associated with electrification, and with that in place why bother carting the reactor about on a train?

 

[edwin_m]

Well, presumably we need a pressurizer and a steam generator, that is going to make the consist 3-4 car lengths already. Don't forget the turbine, another couple of car lengths? Oh, we then have to probably transfer it through some kind of propshaft as well?

There is a reason why a submarine is quite long.

Just build a couple more of the bottom half of Tornado and pipe the steam there. Or is the steam radioactive?

 

[JN114]

Not withstanding Darandio's points about the mechanism of converting the heat output of the nuclear reactor into something which might actually power the train, how about the use of thorium pebble bed type reactors, which as these can't produce material for use in nuclear weapons, presumably this gets around HSTED's treaty restriction argument?

But nor do they generate anywhere near the same level of heat...

A nuclear reactor, in any power-generation application - be it HMS Astute or Sizewell B is just a source of heat, replacing fuel-oil and previously coal burners. These super-heat water in much the same way the fire does on a steam locomotive - the high-pressure steam resulting being used to either directly propel the vehicle or drive an electric generator.

In principal there is nothing stopping a very small Nuclear reactor being used in lieu of a firebox on a modern steam locomotive. The problem is as mentioned above - a small reactor either won't produce enough heat or will end up having to contain weapons-grade material. Then there's security concerns, safety/crash worthiness concerns... It quickly becomes more hassle than it's worth.

Better to put a very large nuclear reactor in a massive building, relatively remote location, high security, connect it to the national grid and use it to power trains that way.

 

[Ediswan]

A nuclear powered train is however perfectly feasible..... its called an electric train.
Most TGVs are essentially nuclear powered for example.

+1 to that.

Maybe one day there will be no/low maintenance nuclear reactors. Maybe one day these will be small enough. Maybe one day people will be happy with them running round the countryside at speed. Until then, EDF+TGV looks like a good option.

 

[Big Mac]

Good point, but carting about the reactor on the the negates the need for OHLE, so gives flexibility.

I fully appreciate the initial costs and technical difficulties probably rule out nuclear powered trains for the forseeable future, but it's interesting to discuss all these points.

As technology progresses, there may come a point in the future when this idea comes to pass.

Many thanks to all who have contributed to this discussion; the weath of technical knowledge of members of this forum, and their willingness to share it is what makes this site.

Thank you.

 

[Philip Phlopp]

Good point, but carting about the reactor on the the negates the need for OHLE, so gives flexibility.

It's a damned stupid idea, the only flexibility you get is choosing which isotope kills people when it goes horribly wrong.

 

[Big Mac]

It's a damned stupid idea, the only flexibility you get is choosing which isotope kills people when it goes horribly wrong.

But why would it go horribly wrong?

Provided correct operating procedures are followed, it should all be fine.

Why be so negative about a theoretical proposal?

No risks, no progress, right?

 

[bangor-toad]

Hi there,
The Russians were working on a nuclear powered loco in the 1950's. If you search you can find some of the proposed schematics online.

The purpose was to roam the northern tundra without the need to refuel. It took advantage of the very generous Russian loading gauge and I'm sure a fairly worrying slapdash approach to shielding.

The plans were resurrected again about 4 years ago. Link
I've no idea if this has progressed...

Mind you, having read up recently for a project on the new super thin composite radiations shields eg link you may not need lots of lead. A thin 10cm lightweight composite will see you good...

Mind you, I *really* don't think we'll ever see one in the UK!
Cheers,
Mr Toad

 

[6Gman]

There was IIRC some semi-serious talk of this in the USA in the late 50s/ early 60s?

Mind you, it was about this time that helicopters were being touted as the future of inter-city travel in the UK and we would all have personal powerpacks to allow us to fly ourselves to the heliports!

 

[HSTEd]

Just build a couple more of the bottom half of Tornado and pipe the steam there. Or is the steam radioactive?

If this is a direct cycle, like a boiling water reactor - then yes the steam will be radioactive for roughly a minute after it leaves the reactor assembly.
This is due to radioactive nitrogen being produced by interaction of neutrons with oxygen in the coolant.
Its half life is in seconds though.

 

[Domh245]

But why would it go horribly wrong?

Provided correct operating procedures are followed, it should all be fine.

Why be so negative about a theoretical proposal?

No risks, no progress, right?

For much the same reasons that a nuclear power station might go horribly wrong. But until we have mastered the art of generating electricity directly from the byproducts of fission instead of by steam turbine, the best bet is generating electricity off-shore and then transmitting it to the train by OHLE.

 

[Trog]

If the loco had a towering plume of glowing exhaust steam, at least we would not have to worry about it not having a yellow front end.

 

[Philip Phlopp]

But why would it go horribly wrong?

Provided correct operating procedures are followed, it should all be fine.

Why be so negative about a theoretical proposal?

No risks, no progress, right?

Oh, I don't know. A derailment or level crossing collision, running out of coolant during a landslip or other disruption, a failure of a critical component and so it goes on.

When something goes wrong, I want it to be under the critical eye of physicists and nuclear engineers, not some of the dippy engineers who lurk about in the far recesses of the rail network.

 

[najaB]

When something goes wrong, I want it to be under the critical eye of physicists and nuclear engineers, not some of the dippy engineers who lurk about in the far recesses of the rail network.

It is possible to build self-contained, self-regulating reactors that need very little in the way of hands-on operation. The US Peace Corps (edit: It wasn't the Peace Corps, but the idea was the same) had ideas of using them in the late 1960's to provide power and fresh water in remote areas. The designs they were proposing weren't small enough to fit in a locomotive, but would be delivered by a couple of trucks, run for a few years on site and then replaced by another unit. The whole thing would then be taken back to the factory for refuelling, etc. They wouldn't need any input from 'the natives' and were more or less sealed units that shut down if tampered with.

I think the Army were also interested for using them in remote operations as well - for example in the high Arctic. No idea what the current state of the art is though.

 

[dcsprior]

It is possible to build self-contained, self-regulating reactors that need very little in the way of hands-on operation. The US Peace Corps (edit: It wasn't the Peace Corps, but the idea was the same) had ideas of using them in the late 1960's to provide power and fresh water in remote areas. The designs they were proposing weren't small enough to fit in a locomotive, but would be delivered by a couple of trucks, run for a few years on site and then replaced by another unit. The whole thing would then be taken back to the factory for refuelling, etc. They wouldn't need any input from 'the natives' and were more or less sealed units that shut down if tampered with.

I think the Army were also interested for using them in remote operations as well - for example in the high Arctic. No idea what the current state of the art is though.

Is this one of the above experiments: https://en.wikipedia.org/wiki/SL-1

 

[Big Mac]

Oh, I don't know. A derailment or level crossing collision, running out of coolant during a landslip or other disruption, a failure of a critical component and so it goes on.

When something goes wrong, I want it to be under the critical eye of physicists and nuclear engineers, not some of the dippy engineers who lurk about in the far recesses of the rail network.

Provided the type of reactor does not have a characteristic termed a positive void coeffecient (like the old RBMK type designs), and has appropriate safety systems in place, (together with safe operating procedures) I can't really see a problem with it.

 

[Taunton]

London Underground is also effectively nuclear powered ever since they did the current supply deal with EdF who bring power across from their French nuclear stations via the under-Channel Interconnector.

It's much more effective to generate in a nuclear station and transmit electricity. The same thing was discovered 70 years ago, that instead of bringing coal by rail down through Britain and burning it in local power stations, it was much more efficient to burn it in large stations on the Yorkshire coalfield and transmit the electricity down instead. It was a curious feature, however, that in recent times it was then discovered it was EVEN MORE efficient to mine the coal in Australia, ship it halfway round the world, then rail it all the way from Hunterston to the Yorkshire stations!

 

[najaB]

Is this one of the above experiments: https://en.wikipedia.org/wiki/SL-1

I think that was one of the early designs, yes. The later ones were much smaller - capable of being transportable. And also this accident led to them using fail-safe design concepts.

 

[Philip Phlopp]

I think that was one of the early designs, yes. The later ones were much smaller - capable of being transportable. And also this accident led to them using fail-safe design concepts.

It's not fail-safe if it's lying upside down leaking radioactive material after the locomotive has hit an HGV on a crossing though.

 

[DarloRich]

Listen - why don't we just skip a generation and wait until they perfect propulsion powered by Dilithium crystals?

They never go wrong

 

[coppercapped]

Good point, but carting about the reactor on the the negates the need for OHLE, so gives flexibility.

I fully appreciate the initial costs and technical difficulties probably rule out nuclear powered trains for the forseeable future, but it's interesting to discuss all these points.

As technology progresses, there may come a point in the future when this idea comes to pass.

Many thanks to all who have contributed to this discussion; the weath of technical knowledge of members of this forum, and their willingness to share it is what makes this site.

Thank you.

I remember the possibility of nuclear-powered trains (and other things) being discussed in the early 1950s at the dawn of the atomic age.

It was bonkers then and it's bonkers now.

I suggest that you do some reading on the physics of fission and the technology needed to make it safe in populated areas and why you would want to pay orders of magnitude more money per horsepower.

It will not 'come to pass' - the physics of radioactivity is the same now as it was then. It is likely to remain the same in the future.