Accelerator-driven sub-critical reactor

[ohiovr]

This is interesting,

http://en.wikipedia.org/wiki/Accelerato ... al_reactor

They use a particle accelerator to make neutrons for burning wastes or thorium in a sub critical assembly. Although the energy amplification factor of the beam products is at least 8 times, isn't the beam itself rather horribly inefficient?

[ohiovr]

According to this article:

http://www.theguardian.com/science/blog ... ar-reactor

"But surely that particle accelerator needs a lot of energy to operate? Yes, it does. However, you get far more power out at the other end. That's where the ADSR's unofficial name – Energy Amplifier – comes from. The Thorium Energy Amplifier Association, ThorEA, calculates that an ADSR would generate 600MW of electrical power – pretty much the same as a conventional power station.

Yes, the accelerator will require power input – around 20MW – but that power can be taken from the ADSR's own output, leaving an excess 580MW of electric power."

[hanelyp]

A key factor in such a reactor is the pile of fuel being only marginally below critical mass when cool, and shifting slightly away from critical mass as it heats. That way a single injected neutron can produce several fissions, but the reaction will always die out when the accelerator is stopped.

[ohiovr]

I think it's pretty exciting because:

It can burn U238, which we got a hell of a lot of (1.5 million tons).
It can make weapons grade materials but not in normal operation for a power plant so there shouldn't be any proliferation concern.
You could burn Thorium, but since its a pita to get out of the ground (its a rare earth), burn the waste we got. I think we should have
enough nuclear garbage to power the world for at least 100 years. After that there is at least 900 years worth of thorium. I would hope
that polywell will be figured out within that time Ok joke I know but you get the picture. If the human race can survive:

one or more nuclear wars
genetic engineering disasters
germ warfare
catastrophic damage to the food chain
etc

within 900 years there will be plenty of time to figure out additional sources of energetic fuels including fusion of hydrogen and boron.

900 years is a very long time in today's years. Technology is advancing faster than ever before. Therefor the misuse of technology will also increase
at a faster rate.

But at least it could be possible in theory to decouple our energy production from the environment almost entirely for 100 years or more.

If we burn waste, there is nothing to mine. If we don't have to enrich anything, then its going to be cheap and safer to workers around the plants.
You can locate these new plants on site of the older waste producing reactors so that waste does not need to be transported and you might be able
to utilize some of the existing plant's machines like turbo generators and cooling towers.

[KitemanSA]

As an aside, a 2.2+ fluid Liquid Fluoride Thorium Reactor can burn U238 too. The U238 would be an addition to the Th232 bred U233 and would be controlled to assure the reactor stayed in sustainment mode rather than be a breeder.

[ohiovr]

I think either of those concepts show that we do in fact have a ton of energy out there in our stockpiles of spent fuel. By the time fracking has made most of the aquifers in the USA undrinkable or unusable for livestock, thorium or beam fission could also come online with far less serious environmental impact.

[MSimon]

I think either of those concepts show that we do in fact have a ton of energy out there in our stockpiles of spent fuel. By the time fracking has made most of the aquifers in the USA undrinkable or unusable for livestock, thorium or beam fission could also come online with far less serious environmental impact.

Well the oil is about a half mile or more below the water. And wells properly installed do not leak. And there is an incentive to properly install them. Only oil that reaches the surface and is collected there can be sold.

[ohiovr]

lotta improperly made wells out there according to the youtube videos

[MSimon]

lotta improperly made wells out there according to the youtube videos

A lot of oil leaks out of the ground naturally. Natural gas too. Anti-fracking people use this as "evidence".

Fracking has been used since 1947. Only recently when it became a significant factor in the oil market did the antis start up. Now in whose interest is reduced American oil production? There is a ME country behind it. Look it up.

[ohiovr]

lotta improperly made wells out there according to the youtube videos

A lot of oil leaks out of the ground naturally. Natural gas too. Anti-fracking people use this as "evidence".

Fracking has been used since 1947. Only recently when it became a significant factor in the oil market did the antis start up. Now in whose interest is reduced American oil production? There is a ME country behind it. Look it up.

It was invented then but it was not widely used because it was not economical at the time.

[ohiovr]

A key factor in such a reactor is the pile of fuel being only marginally below critical mass when cool, and shifting slightly away from critical mass as it heats. That way a single injected neutron can produce several fissions, but the reaction will always die out when the accelerator is stopped.

BTW I thought particle accelerators were kind of inefficient.. how efficient are they really?

[hanelyp]

BTW I thought particle accelerators were kind of inefficient.. how efficient are they really?

What kind of particle energy are we talking? For the energy range I think we're dealing with for neutron production (several MeV) the accelerator itself can be fairly efficient. Knocking loose neutrons not so much. Making a guess, fissionable isotopes are favored for the target despite needing more energy to hit the target.

[prestonbarrows]

BTW I thought particle accelerators were kind of inefficient.. how efficient are they really?

Electrically, DC particle accelerators are basically just like running current through a resistor (a current running from a higher voltage to ground). The electrical efficiency is basically just limited by your high voltage power supply efficiency of converting mains power from the wall to DC high voltage power. This is usually in the 80-90% type range.

There are a number of auxiliary systems like pumps and magnets etc. but these generally use a small fraction of the power as the beam itself (again just given by Ohm's law and P = I * V like a simple resistor). So the beam itself is quite efficient.

The issue is, converting the electrical power in the beam to fusion power in nuclear reactions is incredibly inefficient. It takes in the ballpark of 50,000 W of beam power to release 1 W of fusion products i.e. energetic neutrons, protons etc. Almost all of the beam's particles just get randomized as heat in your target and effectively lost before reacting. So, beams can't produce power but can make boatloads of neutrons which open up many interesting applications.

It is my limited understanding that the main hurdles to sub-critical driven reactors are regulatory and economic ones. Somewhat similar to molten salt reactors, or fast breeders, or small modular reactors, or the host of other advanced reactors people want to play with, there is not a groundwork laid out for proving and licencing these new concepts at the NRC. Even licensing a run-of-the-mill reactor is a multi-million dollar and decade long process that often makes it economically nonviable compared to other power sources. Fully-functional and licensed reactors have been recently shut down due to economic pressure from other energy sources.

[choff]

I've been looking at sites claiming fracking costs $1.30 for every $1.00 profit, without high prices and cheap credit the whole thing goes bust. On the upside, the Saudi's can't sustain low prices for any great period without having financial problems themselves.

[ohiovr]

BTW I thought particle accelerators were kind of inefficient.. how efficient are they really?

Electrically, DC particle accelerators are basically just like running current through a resistor (a current running from a higher voltage to ground). The electrical efficiency is basically just limited by your high voltage power supply efficiency of converting mains power from the wall to DC high voltage power. This is usually in the 80-90% type range.

There are a number of auxiliary systems like pumps and magnets etc. but these generally use a small fraction of the power as the beam itself (again just given by Ohm's law and P = I * V like a simple resistor). So the beam itself is quite efficient.

The issue is, converting the electrical power in the beam to fusion power in nuclear reactions is incredibly inefficient. It takes in the ballpark of 50,000 W of beam power to release 1 W of fusion products i.e. energetic neutrons, protons etc. Almost all of the beam's particles just get randomized as heat in your target and effectively lost before reacting. So, beams can't produce power but can make boatloads of neutrons which open up many interesting applications.

It is my limited understanding that the main hurdles to sub-critical driven reactors are regulatory and economic ones. Somewhat similar to molten salt reactors, or fast breeders, or small modular reactors, or the host of other advanced reactors people want to play with, there is not a groundwork laid out for proving and licencing these new concepts at the NRC. Even licensing a run-of-the-mill reactor is a multi-million dollar and decade long process that often makes it economically nonviable compared to other power sources. Fully-functional and licensed reactors have been recently shut down due to economic pressure from other energy sources.

Some of the proposals use Linacs that are over 100 meters long, any chance we could get usable efficiency from a cyclotron or syncrotron for the same kind of effect?

I think the beam fission idea could potentially be easier to attain regulatory approval. But I maybe dreaming.