Fusion Reactor

[waitaminute]

I have a question:

 

 

Stars fuse hydrogen not heavy hydrogen. There is equilibrium between the energy
released from fusion and the pressure created by gravity. My understanding is what keeps all of the hydrogen from reacting or fusing is the temperature in the sun is too low to cause fusion, but as hydrogen migrates toward the center of the sun gravity brings hydrogen atoms close enough together for quantum tunneling to fuse the protons.

 

If my understanding of fusion in a star is correct then couldn't a scaled down version of a sun be constructed? Where a hefty chamber contains ordinary
hydrogen under very high pressure and therefore density and a small plutonium filament is detonated to cause fusion. The temperature of the system rises to heat the
hydrogen in the chamber to create very high pressures where hydrogen can get close enough for quantum mechanical tunneling to cause more fusion. The amount
or rate of fusion could be controlled by releasing or absorbing heat from the system. Eventually the chamber burns all of the hydrogen and the system has to
be re-initialized.

 

 

The idea seems simple so where is my thinking wrong?

 

[swansont]

How do you build the chamber to create such a pressure and withstand the temperature of the reaction?

[John Cuthber]

The pressure at the centre of the sun is something like 10^11 bar and the temperature is about 15,000,000K

 

What are you going to make the pressure vessel from?

 

 

Also, it's not often realised just how little heat the sun generates.

Overall it produces a lot of heat (10^26 Watts,)

But that's only because it is very big. (10^30Kg)

However a ton of material from the sun's centre generates (very roughly) about as much heat in a year as a compost heap of the same weight.

 

 

It's not sufficient to get fusion to work as well as the Sun, we need to do it thousands of times better

[waitaminute]

How do you build the chamber to create such a pressure and withstand the temperature of the reaction?

 

Well...A chamber made of thick titanium backed up with walls of lead say 50 to 100 feet thick which are then encased in re-enforced concrete walls 50 to 100 feet thick?

 

The pressure at the centre of the sun is something like 10^11 bar and the temperature is about 15,000,000K

 

What are you going to make the pressure vessel from?

 

 

Also, it's not often realised just how little heat the sun generates.

Overall it produces a lot of heat (10^26 Watts,)

But that's only because it is very big. (10^30Kg)

However a ton of material from the sun's centre generates (very roughly) about as much heat in a year as a compost heap of the same weight.

 

 

It's not sufficient to get fusion to work as well as the Sun, we need to do it thousands of times better

 

 

Then perhaps heavy hydrogen is needed?

Edited February 28, 2013 by waitaminute

[John Cuthber]

"Well...A chamber made of thick titanium backed up with walls of lead say 50 to 100 feet thick which are then encased in re-enforced concrete walls 50 to 100 feet thick"

Titanium melts at about 1700 C.

How long do you think it would last when 10,000 times hotter?

[waitaminute]

"Well...A chamber made of thick titanium backed up with walls of lead say 50 to 100 feet thick which are then encased in re-enforced concrete walls 50 to 100 feet thick"

Titanium melts at about 1700 C.

How long do you think it would last when 10,000 times hotter?

 

Well heat doesn't transfer instantly so there maybe a way to manage the hot plasma without a magnetic field, I mean other fusion reaction systems have to deal with that kind of heat as well, albeit radiated heat, where the walls of other fusion reactor proposals don't make contact with the plasma. So if heat is conducted out of the system it might create onion layers where temperature toward the walls of the chamber are cooler than temperatures at its center.

[John Cuthber]

The thing is that, if the walls are not in contact with the gas, how will they keep the pressure at 100,000,000,000 atmosphere's pressure?

 

Of course, that's a rhetorical question: nothing would stand that pressure or that temperature.

The idea won't work.

[swansont]

It's also usually not a winning play to assume that scientists, collectively, are dim. If it seems obvious to you and science doesn't do it that way, the odds are pretty good it's that you're missing something.

[waitaminute]

It's also usually not a winning play to assume that scientists, collectively, are dim. If it seems obvious to you and science doesn't do it that way, the odds are pretty good it's that you're missing something.

Who said anything about scientist being collectively dim? As for the second comment; I wouldn't put too much credence in following the status quo. It usually pays to follow your nose or gut feeling.

Edited March 1, 2013 by waitaminute

[swansont]

Who said anything about scientist being collectively dim? As for the second comment; I wouldn't put too much credence in following the status quo. It usually pays to follow your nose or gut feeling.

 

When you suggest a seemingly obvious, simple solution that's not being used. Fusion scientists would have to be idiots not to do this if it were possible.

[Enthalpy]

Supposing that human fellows are stupid is often a loosing bet... But the hope to find better solutions than the rest of Mankind has up to now is also a pre-requisite in the psychology of an inventor, which does bear consequences, hi bro.

 

Hydrogen fusion is easy. Fusors for instance do it:

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

But to harvest more energy from fusion than was invested - say in the acelerating field - the material must be held warm enough and dense enough for a time long enough: keywords "Lawson's criterion"

http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/lawson.html

http://www-fusion-magnetique.cea.fr/gb/fusion/physique/lawson2.htm

 

This criterion is really hard and makes fusion energy very difficult - far beyond thick metal and concrete. Temperature is in the many-million K, so if containing the matter, it can't be with engineer's materials; the one method up to now is a magnetic field, and then you end with a Tokamak or its Stellarator variant

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

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

or you don't contain the matter, but then it's a very short process that needs higher P and T according to Lawson. Current designs are laser fusion

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

Z-pinch machines

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

and at intermediate time scale, magnetized target fusion

http://www.generalfusion.com/

 

All are damned difficult. My suggestion would be to play a bit with Lawson's criterion and check its technological implications.

 

One more worry: the easiest reaction is D-T but Tritium is not available and can't be produced in proper amounts elsewhere, so a fusion reactor would have to regenerate it, but this needs a step of neutron multiplication, which is about as polluting as uranium fission to produce the same energy

http://saposjoint.net/Forum/viewtopic.php?f=66&t=2450

the least improbable approach to run without tritium instead would be the Z-pinch.

 

I've stopped thinking at fusion. Renewables are easier and we'll have them before.

 

-----

 

Why do you suggest a plutonium wire? Any wire can be exploded by a current surge to produce heat and pressure within, say, a piece of D-T ice. If you hope to start plutonium fission, it takes more than heat. Plutonium can combine well with deuterium (and possibly lithium) to ease a combined fusion+fission reaction, but

- You'll end with currents similar to the Z-machine if putting the proper figures, I bet

- The whole game of hydrogen fusion is to avoid the polluting fission products...

 

People who develop tritium regenation at ITER know perfectly that the neutron multiplier of choice is plutonium, followed by uranium... And they stick to lead because Pu and U would be a fission reactor - most heat would be made by fission, not fusion, and the reactor would require as much scarce uranium as presently.

 

Is there more in this proposal?

[waitaminute]

When you suggest a seemingly obvious, simple solution that's not being used. Fusion scientists would have to be idiots not to do this if it were possible.

I don't want to sound argumentative but you'd be surprise how when an idea is explained, many find it suddenly obivious, but never would have thought up the idea themselves. LOL

 

Supposing that human fellows are stupid is often a loosing bet... But the hope to find better solutions than the rest of Mankind has up to now is also a pre-requisite in the psychology of an inventor, which does bear consequences, hi bro.

 

Hydrogen fusion is easy. Fusors for instance do it:

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

But to harvest more energy from fusion than was invested - say in the acelerating field - the material must be held warm enough and dense enough for a time long enough: keywords "Lawson's criterion"

http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/lawson.html

http://www-fusion-magnetique.cea.fr/gb/fusion/physique/lawson2.htm

 

This criterion is really hard and makes fusion energy very difficult - far beyond thick metal and concrete. Temperature is in the many-million K, so if containing the matter, it can't be with engineer's materials; the one method up to now is a magnetic field, and then you end with a Tokamak or its Stellarator variant

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

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

or you don't contain the matter, but then it's a very short process that needs higher P and T according to Lawson. Current designs are laser fusion

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

Z-pinch machines

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

and at intermediate time scale, magnetized target fusion

http://www.generalfusion.com/

 

All are damned difficult. My suggestion would be to play a bit with Lawson's criterion and check its technological implications.

 

One more worry: the easiest reaction is D-T but Tritium is not available and can't be produced in proper amounts elsewhere, so a fusion reactor would have to regenerate it, but this needs a step of neutron multiplication, which is about as polluting as uranium fission to produce the same energy

http://saposjoint.net/Forum/viewtopic.php?f=66&t=2450

the least improbable approach to run without tritium instead would be the Z-pinch.

 

I've stopped thinking at fusion. Renewables are easier and we'll have them before.

 

-----

 

Why do you suggest a plutonium wire? Any wire can be exploded by a current surge to produce heat and pressure within, say, a piece of D-T ice. If you hope to start plutonium fission, it takes more than heat. Plutonium can combine well with deuterium (and possibly lithium) to ease a combined fusion+fission reaction, but

- You'll end with currents similar to the Z-machine if putting the proper figures, I bet

- The whole game of hydrogen fusion is to avoid the polluting fission products...

 

People who develop tritium regenation at ITER know perfectly that the neutron multiplier of choice is plutonium, followed by uranium... And they stick to lead because Pu and U would be a fission reactor - most heat would be made by fission, not fusion, and the reactor would require as much scarce uranium as presently.

 

Is there more in this proposal?

Wow Enthalpy, great post and wonderful cites, thanks for the info.

Edited March 1, 2013 by waitaminute

[howlingmadpanda]

You would need to recreate the heat, pressure and gravity of the sun, how do you plan to do that?