Nuclear synthi-jetfuel plants wanted for US Afghan bases

Original URL: https://www.theregister.com/2010/03/31/darpa_portable_fuel_reactors/

Porta-reactors to make diesel from soldiers' poo?

Posted in Science, 31st March 2010 12:09 GMT

In a potentially controversial move, US military tech chiefs have decided to investigate the idea of using mobile nuclear reactors to provide power and synthetic jet fuel at forward bases overseas.

In a request for information issued yesterday, Pentagon scientists say they would like to hear proposals for "deployable nuclear reactor technologies for the generation of electrical power and military logistic fuels (JP-8) in forward land based and maritime military operations".

JP-8 is standard US forces jet fuel, regarded as relatively easy to synthesise from commonly available ingredients compared to the other main military fuel, diesel.

Boffins at the US Naval Research Laboratory have already developed processes by which it would be possible to make JP-8 using carbon dioxide and hydrogen extracted from sea water. The process would require a lot of energy, but in a US naval context this might not be a problem: American aircraft carriers have powerful nuclear reactors to drive their propulsion and catapults, which would have plenty of surplus grunt whenever full-speed launch operations weren't in progress.

This would be well worth doing, as the onboard supply of jet fuel is the main limiting factor on how long a nuclear carrier can keep operating its planes: the reactor's uranium lasts for years.

At the moment, the naval boffins' process produces large amounts of methane as a byproduct. Methane is a potentially useful fuel, but probably not in a military context; however, it could simply be dumped into the atmosphere, or more likely burned off in a flare stack for environmental* and safety reasons.

So the "maritime military operations" part of the plan is quite sensible. But what about "forward land based" reactors?

Well, from the point of view of a military supply officer, the idea could be an attractive one. At the moment, a military base in Afghanistan is likely to be powered by generators running on diesel. Its planes and helicopters will be burning through huge amounts of JP-8.

All this fuel has to be brought in by road convoys, along dangerous routes plagued by ambushes and bombings. It would be great if instead of diesel generators, the base's electricity came from a reactor that wouldn't need refuelling for years on end - probably not until after the war was over, in fact. It would be even greater if the reactor could also top up the base's supplies of JP-8 for its thirsty choppers and planes.

The problem here, though, is one of getting hold of the necessary hydrogen and carbon feedstocks with which to synthesise the jet juice. There's no limitless supply of seawater here.

Hydrogen could still be obtained from river or lake water, by using reactor power to crack it using electrolysis. Getting hold of the necessary carbon could be difficult, however, as huge - probably prohibitive - amounts of water would need to be processed to extract useful amounts of CO₂.

The Pentagon RFI has this to say:

Technical approaches to fuel production should accommodate a broad range of hydrogen and carbon feedstocks (water/seawater, biomass, waste materials, etc). Concepts that involve carbon capture or sequestration should be well justified in terms of technical feasibility given known carbon concentrations in the proposed carrier stream.

OK, where are we going to find a whole lot of carbon waste here at Kandahar? Hey, what's that horrible smell?

"Biomass/waste materials" most probably alludes to the huge, odorous lakes of sewage which have accumulated next to some of the bigger bases in Afghanistan, much complained of by the resident servicemen. This could potentially be an excellent carbon source, and turning it into jetfuel would have the added benefit of making the bases pleasanter to be in.

That said, such a base's aircraft use huge amounts of fuel: if the local reactor were supplying all or most of it, even thousands of gutsy troops' output might not be enough to keep it supplied. Logistics officers might find that they had to run just as many troublesome convoys to get hold of enough feedstock (sewage, wood, crops, coal, whatever) as they formerly did to bring in fuel - probably more, in fact, as the feedstocks would be bulkier and heavier than the resulting JP-8.

But the electrical power savings would still be there: and any fuel which could be produced using local materials would ease the burden on the supply chain. It might even be possible, perhaps, to make diesel for ground vehicles as well as JP-8 for aircraft:

It may be assumed that the desired fuel end product is JP-8; however, responders should discuss the degree to which their fuel production technology could be used to produce other mobility fuels including gasoline and diesel fuels.

This sort of technology could also have serious implications outside the military, of course. Any nation with nuclear powerplants and a desire to cut carbon emissions and/or fossil fuel imports could use it for aviation; and potentially road transport too. Even if synthi-diesel and petrol can't be achieved, it would be a simple matter to make a road fleet run on jetfuel (compared to making it run on batteries or hydrogen, anyway).

A lot of people would rather be reliant on uranium supplies from Australia or Canada than on Gulf oil or Russian gas: and it would be possible to get a lot more reactor fuel by reprocessing existing waste stockpiles, though this might well face stiff opposition from people concerned over nuclear weapons proliferation**. Another advantage of uranium over fossil is that several years' national requirements can be stockpiled in quite small facilities, meaning that supply crises can easily be coped with.

Then, there would be massive carbon reductions for those primarily worried about global warming.

Some science-fiction writers have long assumed that the future human race would turn to this sort of technology. H Beam Piper, for one, wrote that "thermoconcentrate" juice would be made using reactors on worlds unfortunate enough not to have convenient underground reservoirs of almost ready-made fuel.

Even if you manage to steal a porta-reactor, you can't make a bomb with it

Given that there's a sci-fi feel about this plan, then, it's no surprise that it comes to us courtesy of DARPA, the Pentagon tech bureau which is always seeking to achieve regime change in the state of the art. The US warboffins, however, say that this is no longer the stuff of sci-fi.

Recent advances in high temperature materials science suggest that an investigation of compact, deployable nuclear reactor technologies may be timely. The goal would be to create a fieldable design that could be deployed to maritime and/or ground based forward operations to provide on-site power and fuel production capability in regions not connected to a robust grid and/or not easily accessible for fuel resupply. Preferred reactor designs would allow for several years of operation without refueling.

DARPA would like to see porta-reactor proposals able to carry a 5 to 10 megawatt electrical load in addition to producing 15,000 gallons of JP-8 or road fuel daily - enough to fill up a Chinook helicopter around a dozen times. They also want designs which are "inherently safe (negative temperature coefficient)", ie ones which can't suffer a runaway if damaged and melt their way down out of the base into a glowing tunnel in the Earth's crust.

As for size, DARPA doesn't offer any detailed requirements, but it does say that the reactor and its associated generators, fuel plant etc should be "readily deployable". That probably won't be too hard; existing submarine reactors in the same power range are only dustbin-sized.

The Pentagon tech-heads also aim to deal with proliferation fears by specifying that neither the reactor's fuel nor its wastes should be of any use in making weapons: thus, even if enemy forces managed to overrun a US base or steal its power'n'jetfuel plant they'd be no further foward toward making a bomb (or anyway no further than any nation with a civil nuclear programme).

Even so, given the general level of fear and misunderstanding that exists around nuclear technology, you have to say that the kit might never take the field with the landbased US military even if it succeeds technically. Naval deployment on ships which already have reactors would be much more plausible.

And, of course, for countries such as France or Switzerland which make serious use of civil reactors (which often produce a lot of waste power at times of low demand; reactors don't like being throttled up and down much) the fuel-making tech could offer major carbon cuts and freedom from fossil imports.

It'll be interesting to see how this pans out: though there's the usual caveat here that not many DARPA projects ever succeed. ®

Bootnotes

*Methane is a hugely more powerful greenhouse gas than CO₂, and one molecule of methane burns to make one of carbon dioxide: thus reducing its ecological burden by a factor of 25 as it does so.

This is why anyone who is truly concerned about the environment should always, without exception, light their farts. Failure to do so is colossally irresponsible in a global warming context.

**Reprocessed fuels, unlike freshly-mined uranium, are often of a grade that could also be used in weapons as well as reactors. The fear is that such material might be lost or stolen, therefore it should not be created. The USA follows this policy rigidly, and as a result has a very large waste stockpile. Other nations sometimes reprocess, but in general the cost - in large part resulting from the proliferation fears and associated precautions - are so large that it's generally cheaper to mine new fuel.