Fusion Power Question

[History_Buff]

I understand the mechanics of the actual fusion reaction pretty well, as well as how you achieve the conditions necessary. What I don't understand is how you actually harvest power from such a reaction.

It seems that it must be from discharged heat energy, but since you would likely need to keep all the heat isolated from the reaction chamber walls to prevent them from melting, just how do you extract useful energy?

 

[Gogf]

The heat could be isolated from the chamber walls by having the reaction be water coaled. This water would naturally be turned to steam, which could power a turbine. As far as I know, this is how nuclear fission works.

 

[cairo140]

Although I don't know the physics of nuclear fusion above the basic subatomic theory, but I can answer your question.

Prospectively, nuclear fusion plants would work the same way as nuclear fission plants do. You said that heat energy is discharged. This is correct. In fission plants (and in all other non-mechanical power plants), the heat discharge is used to heat water to create fast-moving steam to spin the turbines.

I assume a fusion reaction would occur, and water could pass through a heating coil to change state and accelerate upwards. Hope that clears it up for you.

 

[El_Machinae]

These people are correct.

Some of the energy would be used to maintain the containment field, the rest would be piped out.

 

[History_Buff]

Alright, so your cooling water would be continuously cycled in and out of the actual reaction chamber, and then drive a turbine.

I knew that's how a fission plant worked, but for some reason it didn't occur to me that you could use the same system for a Fusion reactor

 

[capslock]

Yeah, I'm not sure it would be that simple. I'm a nuke n00b, but I'm taking an intro to nuke course this semester, for non nuclear engineers (I'm an EE).

My professor use to do his research in fusion, and he doesn't know how to harvest the power, or how it might be done. In his words, "Its anybody's guess."

From what I've learned, it doesn't seem anything like a fission reactor, and I also have trouble seeing how to harvest the energy.

Are you guys just assuming some unkown future technology that would allow it to work like a fission reactor? If you have some links, that would be nice, I'm kind of curious about this too.

 

[taper]

The vast majority of power plants work by heating water into steam, and then sending that pressurized steam through a turbine. Fission, coal, oil, natural gas, biomass, and even some solar plants do this. Hydro skips the steam part and sends water through the turbine. Wind skips all the middle men. Tried and true method. I'm not aware of any other method to extract power out of fusion

 

[HawkeyeGS]

I remember that it one way it may work in the future is that you could use the energy from a fission reaction (splitting of atoms) to join up some atoms (fusion) and the atoms would split again. That way you have a large cycle of splitting and joining atoms and if they could get energy requirements down then the energy lost due to incomplete fusions would be taken away to heat water leading on to what other posters have said. I can't remember where I was reading this but you never know how they will do it.

 

[GarretSidzaka]

the great thing about fusion (if properly developed) is that is it potentially completely clean, and safe from the meltdowns that plague the fission reactors.

I have heard a off-hand estimate in a publication that a glass of water would power New York City for a year.

 

[Mise]

Physicists don't know how to create a "controlled" reaction, hence the details of how the heat gets from the plasma to the water is still anybody's guess. But it will probably be heat -> heats water -> steam -> turn turbines -> electricity.

 

[Lotus49]

We are already harvesting power from a fusion reactor.

 

[El_Machinae]

We just put more energy in, than we're taking out. ITER is designed to determine if a larger reaction will put out more energy than is required to maintain it (since it might get large enough to feed itself)

 

[Sidhe]

We are already harvesting power from a fusion reactor.

Solar power is naff in England you'd probably get enough power to get a 40 watt bulb to run for a few weeks, if you were lucky

 

[Tank_Guy#3]

The heat could be isolated from the chamber walls by having the reaction be water coaled. This water would naturally be turned to steam, which could power a turbine. As far as I know, this is how nuclear fission works.

This is how I also envision it.

 

[capslock]

The vast majority of power plants work by heating water into steam, and then sending that pressurized steam through a turbine. Fission, coal, oil, natural gas, biomass, and even some solar plants do this. Hydro skips the steam part and sends water through the turbine. Wind skips all the middle men. Tried and true method. I'm not aware of any other method to extract power out of fusion

Yeah, I'm aware that electricity is generated by running steam, or water, through a turbine. I have trouble visualizing how to accomplish this with a fusion reactor. Answering the OP by saying, it will generate steam like all other power plants is very basic, and can be a bit misleading.

From what I've gathered in class:

A D-T reactor using magnetic confinement produces high energy neutrons (this means the reactor is radioactive). The energy for creating electricity, as far as I understand, comes from these neutrons. They are captured in a blanket (heat transfer and coolant medium) surrounding the reactor. They are used to breed more Tritium, for use as fuel, and the heat from capturing them can be used to create steam to generate electricity. Lithium is used as the blanket around the reactor, since it is a reactant used to create tritium. Li + n -> T + He

We didn't go into this much detail for inertial confinement reactors, but basically the high energy neutrons need to be taken care of, and their energy can be used to create electricity.

This is for the reaction D + T -> He + n, which is used in H-bombs, and will likely be the reaction used in the first fusion reactors.

If I'm wrong or misunderstand any of this, please correct me, I'm just learning about it.

 

[Urederra]

the great thing about fusion (if properly developed) is that is it potentially completely clean, and safe from the meltdowns that plague the fission reactors.

That is if you don't take into account the heat produced by the fussion itself, which will increase the so-called global warming. Or not?

 

[El_Machinae]

It will, but not significantly. Not as much as continuing to emit CO2.

What makes a house warmer? Lighting a candle, or closing the windows?

 

[Masquerouge]

It was one of the greatest disappointment in my scientific life to learn that no matter how advanced your energy producing device is, it will always come down to heating water for the steam.
Fusion ! Yeeha ! Now let's boil some water

 

[El_Machinae]

Well, we still have solar and OTEC

 

[History_Buff]

It was one of the greatest disappointment in my scientific life to learn that no matter how advanced your energy producing device is, it will always come down to heating water for the steam.
Fusion ! Yeeha ! Now let's boil some water

Not PV solar cells. You can use the photo-voltaic effect to create straight electricity. Nor in Hydro, where naturally falling water spins a turbine. The boiled turbine is only used when heat is produced in the reaction.

And as for the harvesting critics: would it be wrong to assume the outside of the reaction chamber would be heated? Although the plasma is contained within electric fields, heat would spread anyway, and be running water or another fluid along the reactor walls, wouldn't that heat it?