will the new ITER fusion reactor actually work?

northernbear

I am hopeful that the new large ITER tokamak style fusion reactor will be successful.

According to wikipedia:

The ITER fusion reactor itself has been designed to produce 500 MW of output power for 50 MW of input power, or ten times the amount of energy put in. Hereby the machine is expected to demonstrate the principle of getting more energy out of the fusion process than is used to initiate it, something that has not been achieved with previous fusion reactors. Construction of the facility began in 2008 and first plasma is expected in 2018.[6] When ITER becomes operational it will surpass the Joint European Torus which is the current largest magnetic confinement plasma physics experiment in use.
http://en.wikipedia.org/wiki/Iter

i would appreciate any comments on the chances of ITER actually producing more energy through fusion than the energy used to initiate fusion.

what is it about the design of ITER that leads researchers to predict a net production of energy, whereas other tokamak fusion reactors have as yet failed to pass the break even point?

jimgraber

ITER scientists are extremely hopeful and rather confident that it will work as planned, but no one knows for sure until it actually runs. The main difference between ITER and previous tokamaks is that ITER is larger. Experiments on previous tokamaks have shown and theoretical calculations predict that as the tokamak gets larger the energy out increases faster than the energy in. If this pattern continues to hold, ITER will produce more energy than it consumes. There are many complicated details, but that's the big picture.
Best,
Jim Graber

Macocio

So this is like a perpetual 'motion' machine or am I getting it wrong?

Pengwuino

No, perpetual motion machines do not require fuel. This does.

Think of how you would start a fire, you need just a little match, a little flame, and boom your fire is lit. You gave the fuel (paper and wood) a tiny bit of energy and it ignited to give a lot of energy. Fusion is really awful at this concept. So far we have to give massive amounts of energy for the fusion to give us energy back. It would be like having to set off a bomb just to lite your fire place.

Macocio

^^ Thanks i get it now =)

LuisVela

There is another fact besides size. Iter, like the SouthCorean Tokamak ''K-Star'' will use super conducting magnets, therefore the energy lost by Ohms law, and Ohms heating is literally out of the picture. Im sure that adds up to reducing the amount of input energy.

jimgraber

Yes, there are many engineering details to make tokamaks more reliable and more efficient that still need to be discovered and tested. It might not work, but I think that's very unlikely. In my mind, the riskiest part of the whole business is whether taxpayers around the world will keep putting out the big bucks until it is obvious that fusion in general and tokamaks in particular will eventually pay for themselves. At this point, it looks like ITER has enough backing to be completed, but more than ten years to a live-fuel break-even test is a long time in politics.
Best.
Jim Graber

phyzguy

[QUOTE=northernbear;3074497what is it about the design of ITER that leads researchers to predict a net production of energy, whereas other tokamak fusion reactors have as yet failed to pass the break even point?[/QUOTE]

The main reason that ITER is expected to have a net energy production while other tokamaks have not is that ITER is simply larger than past tokamaks. Since energy is lost through the surface (which scales as L^2), and energy is produced in the volume(which scales as L^3), scaling up the size of the reactor inevitably improves the ratio of energy produced to energy lost. The attached slide shows how much larger ITER is than past machines, and the impact that this is expected to have on energy loss rates (and hence confinement time).

Attached Files

ITER.pdf (93.2 KB, 77 views)

LuisVela

I would like to ask, where did you get that pdf about the sizes of tokamaks?

phyzguy

I downloaded it several years ago, but can no longer find the link. The entire presentation is very informative. I can't upload it to this forum, because it is too big. Try accessing it here on Google docs:

https://docs.google.com/viewer?a=v&p...uthkey=CJSG4n0

LuisVela

That is great!, thanks a lot. BTW, what do you know about the Erasmus Mundus program in Fusion, I just remebered it because I saw the Gent University logo. Is it only focused on engineering and technology of Fusion?..or it also includes theoretical work on plasma physics?

phyzguy

Sorry, I know nothing about it.

tentpole

As with all engineering processes, shutdown is a test of design.
How will ITER react to a shutdown or more seriously failure?
Most of us are aware that when stars die they do so catastrophically.
This is in fact a "star" which is going to die.
Maybe it's not big enough but everything dissappearing into a "black hole" is a superb plot for the next disaster movie! - Roland are you there?

mheslep

Is fusion the only component of a star? Are their other factors comprise a star that are lacking in a terrestrial fusion reactor? What factors combine to make a star explode?

etudiant

No expert, but the problem of fusion devices has never been getting fusion to start, but rather how to keep it going.
Indeed, in the early days of hydrogen bomb research, the summary report about the progress of the fusion reaction was 'icicles are beginning to form'.
The ITER is most likely going to join a long list of interesting and useful fusion devices which generate some fusion reactions, perhaps for as long as a few seconds if they are lucky.
Shutting it down will not be a problem, all it would take is a minute air leak to allow the atmosphere to chill the very thin plasma essential for the fusion reaction.
As for stellar type explosions, the inside of ITER holds a high class vacuum, not superdense matter crushed by the gravity of a star. It could not explode, although the powerful magnetic fields needed to focus the plasma do put big stresses on the ITER structure.

mheslep

I suppose there is some chance the ITER HTSC magnets might explode in a quench event, like CERN's LHC did at start up.

Drakkith

The amount of plasma in the reactor is on the order of a few grams. This will never explode or collapse into a black hole. If the reactor is suddenly shutdown, confinement is lost and the plasma simply impacts the wall of the reactor and cools instantly.