OT: For the Thorium enthusiasts!

[The Other John]

one-million-miles/

Enjoy!

TOJ.

[Chris Hogg]

[The Other John]

There's always someone waiting to rain on your parade! :(

TOJ.

[harryagain]

What a load of bollocks.

[Terry Fields]

"I have no clue what process Stevens is claiming to use that lets you bombard thorium with a laser and get energy out, especially since he said it?s sub-critical and thus not a nuclear fission reaction. Instead I?ll pretend he is doing nuclear fission, since that?s one of the more energy-productive reactions we can do and will set a good estimated upper bound on how much energy Stevens could extract from thorium".

[The Natural Philosopher]

well yes and no. That 8 grams of thorieum has the energy to take you quater of a million mile is beyond dispute.

but as they say 'if it were that easy, we would already be doing it'

Nevertheless the idea of using lasers to fission a thorium target is not impossible.

You could take a standard engine, put a few grams of thorium and say copperor lead as a spallation target in the piston centre and replace the spark plugs with petawatt lasers..

Exhaust would be a bit radioactive, mind...

[The Natural Philosopher]

the actual principle is not hard to guess.

Under ultra high power laser pulses, lead and other metals will undergo isotope decay and produce neutrons. Those neutrons cause the thorium to fission.

That obviates the need to have a uranium or plutonium chain reaction 'spark plug' for a thorium recator.

Sub critical means the thorium fission never generates enough neutrons by itself to sustain a chain reaction.

Ther are a lot of elentes - anything heavier than iron actually - that it split release more energy than that used to split them. very heavy ones produce a lot more and extremely heavy ones will produce enugh energy to split themselves in a massive nuclear blast. Which is they they no longer exist on earth.

The trick is to pick an element near the end of the periodic table and generate enough neutrons to split it.

lasers are a way to split heavy elements and produce neutrons, and then the neutrons split the very heavy elements and energy comes out.

[tony sayer]

I can see if this does become a reality it could do more then perhaps any other invention has done to change the world especially world politics.

Wonder what would happen if the demand for Oil dried up?..

Interesting...

[tony sayer]

In article , harryagain scribeth thus

Well that was very very predictable .. was it not?...

[newshound]

I can't be arsed to do the sums, but you have still got the fission products. I wouldn't be surprised if the quantities are similar to what we currently ship to Sellafield in 50 ton flasks. So it's going to be more like a thorium powered Challenger tank.

[polygonum]

What would be the effect on climate of every single person on the planet having many kilowatts of energy available to spill into the environment at next to no cost?

[Chris Hogg]

And presumably this 'petawatt laser' isn't going to be run off a car battery!

[newshound]

Solar panels on the roof.

[Terry Fields]

Thanks for the explanation - my point in quoting from the above crtitique was to illustrate the method used in it, namely "Stevens uses thorium, so I'll invent this straw man about uranium so I can rubbish his method (although I don't know what it is)".

[John Rumm]

Harry seems to have found his place as the groups new dribble... he seems to feel compelled to disagree with everything as a matter of principle now. Which is a shame really, since he could actually contribute useful information if a little less confrontational and better researched.

[tony sayer]

Then that would have to be regulated or dealt with..

But perhaps the reduction of CO2 if of course all that does add up?..

One way or the other we will have to do something, as the Oil will run right down .. one day of course..

[dennis]

Don't let TNP confuse you as if we had petawatt lasers available we would probably use them for fusion rather than thorium reactors.

What you need is a particle accelerator and how that is achieved using a laser is the question. It doesn't have to be petawatts all it has to do is deliver a stream of high energy particles (neutrons) to sustain the fission reaction.

Of course petawatt levels might compress the target to the point it becomes critical but I doubt if that's what is intended.

[The Natural Philosopher]

well again yes and no.

8 grams of thorium can't produce tonnes of fission products.

And laser ignition as a way to create neutrons by spallation doenst require a brreder pack of U238 and a U235 starter.

so really all you are going to get is a bit of U232 and a bit more U233, and both of those would decay fairly rapidly - especially in situations of high neutron flux, to the sort of lead/bismuth and radon type shit that you normally get anyway from natural radioactive decay.

This is the most information I could find on the actual shit

"a. Neutron absorption by Th-232 produces Th-233 which beta-decays (with a half-life of about 22 minutes) to protactinium-233 (Pa-233) ? and this decays to U-233 by further beta decay (with a half-life of 27 days). Some of the bred-in U-233 is converted to U-234 by further neutron absorption. U-234 is an unwanted parasitic neutron absorber. It converts to fissile U-235 (the naturally occuring fissile isotope of uranium) and this somewhat compensates for this neutronic penalty. In fuel cycles involving the multi-recycle of thorium-U-233 fuels, the build up of U-234 can be appreciable.

b. A U-233 nucleus yields more neutrons, on average, when it fissions (splits) than either a uranium-235 or plutonium-239 nucleus. In other words, for every thermal neutron absorbed in a U-233 fuel there are a greater number of neutrons produced and released into the surrounding fuel. This gives better neutron economy in the reactor system."

So the initial products are proactinium and uranium 233, the uranium 234 and then possibly uranium 235.

All these would essentially stay inside the reactor vessel. And it would be in the case of a car 'fuelled for life'.

I think that is where the excitement is: to get to critical mass with uranium or plutonium requires at least kilograms of pure, or tonnes of enriched, nuclear fuel, of which very little is burnt up at all before it becomes poisoned with decay products that stop it working. Then you need new fuel. And tonnes of fuel to reprocess and re-refine, and a lot of muck you have to be very careful about on account of paranoid regulations.

With laser ignition of sub critical masses it really is all easier. You burn up a lot more of the fuel and you dont need kilograms to get the energy out, and it cant go critical on you.

And the raw fuel - thorium - is so low in radioactivity that it simply is no more hazardous than say lead.

Its a bit like comparing a bonfire to an acetylene torch. one is big and messy and produces a lot of muck, the other is small precise and doesnt.

Remember we have had nuclear reactors longer than we have had lasers. Initially the only way to fire a ubcritical reactor was to use a uranium or plutonium neutron source which doesnt actually achive what you want - small and clean. Or a massive particle beam from a cyclotron, and that isn't very portable either.

you still need a petawatt laser to use spallation to generate the neutrons BUT you dont need to opearte it continously. Fire a high energy pulse in - get a higher energy pulse out. That's the principle.

It's very like what they are trying with fusion..except this looks an easier way to tackle the problem. Use fission instead.

I dont think the car is remotely relaistc for years, but it COULD make a bloody handy boat system. If a boat witha few grammes of radioactivity sinlks, who cares? its got access tyo an effectively infinite amnmnout of cooling water, and slow start up is nota big problem.

Use pure water in the reactor to generate steam, run that round a turbine and condense using a sea water heat exchanger. And with power levels from zero to max available simply by adjusting the duty cycle on the laser. With a small primary steam circuit like a flash steam unit, warm up times are minutes, not hours.

Youi could do that in a car, but you would need a massive air cooled condenser - probably fan cooled. And power response would not be at the press of a pedal. More likely you would run the thing as an electric hybrid vehicle with batteries and electric propulsion with a small steam turbine to charge it up and handle the cruise power. That way the battery does the instant response bit, and the nuclear turbine does the sheer grunt work.

flash steam is a pretty amazing way to generate a lot of power from a small engine and no real boiler at all.

I think someone even built a flash steam model aircraft once, just to see if they could :-)

and a real one too

The problem is carrying all the water and the fuel if you cant condense..but with a thorium boiler the fuel is not the problem, just the water.

With say a car on cruise at 35bhp and a thermal efficiency of 35% you need to dump 60bhp - or around 50KW - of heat to somwehere. and not as a high temperature exahust, but as sub 100C heat to get the water to condense.

[The Natural Philosopher]

Not a lot. No more than they currently do anyway. cities are heat islands that actually raise local tempeatures by several degrees. In fact a large part ofte attack on the 'climate change' scare is to pont out that most temeparture sensors around the country are not stuck out in the wilds but stuck near cites and airports...that have seen a massive increase in waste energy over the past 50 years.

I hink I did the sums once - UK energy use in toto which all ends up as heat anyway, was about 1% of what it gets from the sun over the UK surface area. And we are the worst case - very high population desnity, with high per capita energy use and not a lot of sun.

Thermal efficiency of a nuclear car would not be markedly worse than an IC car so similar amouunts of heat dumped ..would be overall far less polluting though. No NOx., carbon or sulphur compounds. All of whch have known atmopspheric effects.

Its a lovely idea, and might actually work in 30 years time..

[John Stumbles]

Article dated August 16th, 2011

Where is it then?!