## What would happen if an energy storage device failed?

Point out news stories, on the net or in mainstream media, related to polywell fusion.

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Joseph Chikva
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mdeminico wrote:But, if as you state, the discharge of the energy takes place over a matter of seconds, rather than microseconds, the "explosion" doesn't really happen nearly as much.
Not several seconds but fractions of second. In any case much slower than energy release of high explosives. And yes, when superconducting condition stops first of all energy heats matrix of superconducting filaments.
Returning again to ITER's site and quoting the same text:
The 18 Toroidal Field (TF) magnets produce a magnetic field around the torus, whose primary function is to confine the plasma particles. The ITER TF coils are designed to have a total magnetic energy of 41 gigajoules and a maximum magnetic field of 11.8 tesla. The coils will weigh 6540 tons total; besides the Vacuum Vessel, they are the biggest components of the ITER machine.
I assumed 20 tons per coil but 6540/18=363.3 tons. Now energy stored per that coil 44 GJ/18=2.44 GJ divide on product of specific heat of copper 385 J/kg*K * 363300 kg.
This is only 17.44 deg of temperature increase. In case if all energy stored in mag field will released as a heat in toroidal coils.
This calculation is not quite correct as specific heat is function of temperature but gives right picture. May be not 17 but 20 deg.

KitemanSA
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mdeminico wrote: But, if as you state, the discharge of the energy takes place over a matter of seconds, rather than microseconds, the "explosion" doesn't really happen nearly as much.
When I asked Joe how long it would take for the field to collapse, he said he didn't know. So his "seconds" or even fractions of a second may be orders of magnitude high (though one could always cover his butt by saying 1/10000 of a second is still a "fraction".

Anyone? How long would it take for a field storing that kind of energy to collapse?

KitemanSA
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Joseph Chikva wrote: I assumed 20 tons per coil but 6540/18=363.3 tons. Now energy stored per that coil 44 GJ/18=2.44 GJ divide on product of specific heat of copper 385 J/kg*K * 363300 kg.
This is only 17.44 deg of temperature increase. In case if all energy stored in mag field will released as a heat in toroidal coils.
This calculation is not quite correct as specific heat is function of temperature but gives right picture. May be not 17 but 20 deg.
Totally different assumption. I think M's assumption (energy dumps at a point) is a lot more likely to be correct than Joe's (spread evenly throuout the mass).

D Tibbets
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I think there are two elements to consider. First is the thermal heating, melting of structure to consider. Then there is the helium steam explosion. I suspect this this second process would do most of the damage, at least outside of the magnet casing itself. Also, in [EDIT- LHC, not ITER's case (the magnets and cooling system is probably separate for each magnet(?)). In LHC the helium coolent may be shared in a common system] the explosive decompression when/ if the vacuum wall is breached might cause significant damage to other internal structures upstream and down stream of the failed magnet.

Dan Tibbets
Last edited by D Tibbets on Tue Nov 08, 2011 5:43 pm, edited 1 time in total.
To error is human... and I'm very human.

Joseph Chikva
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KitemanSA wrote:
mdeminico wrote: But, if as you state, the discharge of the energy takes place over a matter of seconds, rather than microseconds, the "explosion" doesn't really happen nearly as much.
When I asked Joe how long it would take for the field to collapse, he said he didn't know. So his "seconds" or even fractions of a second may be orders of magnitude high (though one could always cover his butt by saying 1/10000 of a second is still a "fraction".

Anyone? How long would it take for a field storing that kind of energy to collapse?
"Anyone" will not help. Get data of real indutance and real resistivity and let's calculate. It's easy. Fractions of sec is several milliseconds. It's quite slow for such a process. In any case you sould not be worried. Even all energy released in heat form and only in the coil the temperture increase of 17 deg we have estimated. Are you disagree with this result?

Joseph Chikva
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D Tibbets wrote:Then there is the helium steam explosion. I suspect this this second process would do most of the damage, at least outside of the magnet casing itself.
Have ever seen teapot with whistling valve? Relax Dan.

Joseph Chikva
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KitemanSA wrote:I think M's assumption (energy dumps at a point)
Via which mechanism? Who has fed you with such fairy tales?

KitemanSA
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Joseph Chikva wrote:"Anyone" will not help. Get data of real indutance and real resistivity and let's calculate. It's easy. Fractions of sec is several milliseconds.
But plenty fast for effecting an explosion like response.

Joseph Chikva
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KitemanSA wrote:
Joseph Chikva wrote:"Anyone" will not help. Get data of real indutance and real resistivity and let's calculate. It's easy. Fractions of sec is several milliseconds.
But plenty fast for effecting an explosion like response.
If designed by amateurs.

KitemanSA
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Joseph Chikva wrote:
KitemanSA wrote:I think M's assumption (energy dumps at a point)
Via which mechanism? Who has fed you with such fairy tales?
Putting a break in a suerconductive wire in a SC electro-magnet. Pretty much what they described in smaller scale at the LHC.

KitemanSA
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Joseph Chikva wrote:
KitemanSA wrote:
Joseph Chikva wrote:"Anyone" will not help. Get data of real indutance and real resistivity and let's calculate. It's easy. Fractions of sec is several milliseconds.
But plenty fast for effecting an explosion like response.
If designed by amateurs.
Yup, like tha amateurs who designed the LHC?

Joseph Chikva
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KitemanSA wrote:Yup, like tha amateurs who designed the LHC?
Nothing has exploded there. As I see the picture 0.5 m of machine with 27 km circumference has been damaged. I am explaining one more time dipole magnet (bending magnet) does not store big energy as magnetic field there has 1.5T order and volume occupied by that field is only the gap of magnetic conductor. See the picture: http://www.esrf.eu/Accelerators/Groups/ ... ry/steerer See the gap and please answer what energy can be stored there.
kilojoules, mega or gigajoules?

For your note pressure vessels of steam turbines much more dangerous than designed properly magnetic system. I do not understand what are you attempting to say. If you do not like TOKAMAK and seek its weaknesses, I said you what weaknesses that has. Heating issue. They have achieved Lawson criterion, achieved confinement time 3-5 sec, but now according different sources ITER should achieve confinement time on 2-3 orders of magnitude longer. Not interested why? Because of low reactivity of cold plasma. There is not effective enough way how to achieve desired 15keV.

But no explosion during not less than 50 years of experiment.

D Tibbets
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Joseph Chikva wrote:
D Tibbets wrote:Then there is the helium steam explosion. I suspect this this second process would do most of the damage, at least outside of the magnet casing itself.
Have ever seen teapot with whistling valve? Relax Dan.
Have you ever seen a Steam Locomotive explosion (at least a film of it). Despite all of the safety measures...
And of course, have you looked at the damage from the LHC failure. I doubt the visible damage was from heating a few Kg of metal to molten temperatures. In fact I doubt if there was much inductive/ ohmic heating of structure. What it would do is vaporize some of the helium liquid while heating (even modestly) additional liquid helium. Once the wall was breached, the pressure would drop, and the now superheated liquid helium would flash into helium steam, producing plenty of 'hot' explosively expanding gas .

Dan Tibbets
Last edited by D Tibbets on Tue Nov 08, 2011 2:17 am, edited 1 time in total.
To error is human... and I'm very human.

D Tibbets
Posts: 2775
Joined: Thu Jun 26, 2008 6:52 am
Joseph Chikva wrote:
KitemanSA wrote:Yup, like tha amateurs who designed the LHC?
Nothing has exploded there. As I see the picture 0.5 m of machine with 27 km circumference has been damaged. I am explaining one more time dipole magnet (bending magnet) does not store big energy as magnetic field there has 1.5T order and volume occupied by that field is only the gap of magnetic conductor. See the picture: http://www.esrf.eu/Accelerators/Groups/ ... ry/steerer See the gap and please answer what energy can be stored there.
kilojoules, mega or gigajoules?

For your note pressure vessels of steam turbines much more dangerous than designed properly magnetic system. I do not understand what are you attempting to say.
...

But no explosion during not less than 50 years of experiment.
I disagree about water steam and helium steam dangers. One will cook you and the other will freeze you. The explosive overpressure may be similar, and the shrapnel danger would be similar.
What is important is the scale of the contained pressure and the volume. The LHC was a small accident which as you point out, with small volume and modest B field. A Tokamak like ITER may have magnets with hundreds of times larger volumes and at least several times as much strength/ unit of volume. Take the explosive damage that occurred at the LHC and multiply it by ~ 1000 or more. And as I pointed out earlier, consider the hot liquid lithium blanket (this may make a pretty good explosive by itself- dispersed in a cloud by a quenching explosion, it may make an excellent fuel air explosive. Add to that nearby large water steam plumbing...

I don't know what kind of liquid helium sequestration the LHC had between magnets, apparently there was some, otherwise I suspect up to all of the magnets would have failed rather than 1-~12 that were destroyed or damaged. Or perhaps there was enough time for the more distant magnets to be shut down by safety mechanisms and the current was drained before the helium drained out and the magnets had a chance to quench.

Dan Tibbets
To error is human... and I'm very human.

Stoney3K
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D Tibbets wrote:I disagree about water steam and helium steam dangers. One will cook you and the other will freeze you. The explosive overpressure may be similar, and the shrapnel danger would be similar.
What is important is the scale of the contained pressure and the volume. The LHC was a small accident which as you point out, with small volume and modest B field. A Tokamak like ITER may have magnets with hundreds of times larger volumes and at least several times as much strength/ unit of volume. Take the explosive damage that occurred at the LHC and multiply it by ~ 1000 or more. And as I pointed out earlier, consider the hot liquid lithium blanket (this may make a pretty good explosive by itself- dispersed in a cloud by a quenching explosion, it may make an excellent fuel air explosive. Add to that nearby large water steam plumbing...

I don't know what kind of liquid helium sequestration the LHC had between magnets, apparently there was some, otherwise I suspect up to all of the magnets would have failed rather than 1-~12 that were destroyed or damaged. Or perhaps there was enough time for the more distant magnets to be shut down by safety mechanisms and the current was drained before the helium drained out and the magnets had a chance to quench.

Dan Tibbets
The LHe2 has enough energy stored in it to pack a mean punch. The important energy storage is because of the temperature differential between the liquid helium and the outside world.

Think of it like you're standing on a mountain. Lots of potential energy, but you're not moving. Unless you jump off a cliff, because that means there's a gap you can bridge and gain energy from it. Just make sure you bring your parachute.

Now if the liquid helium lines in the ITER facility were to fail somehow, there's enough bad things that can happen. Remember, not just the coolant lines are at a few Kelvin, but also the superconducting magnets.

Suppose there was some damage caused to the field magnets, causing a near instant quench. The quench area would heat up rapidly under the influence of Kiloamps of current, melting the superconducting coils and rupturing the LHe2 conduits inside.

Now the fun starts to build up. The coils are either in contact with the vacuum vessel directly or through the liquid lithium blanket. Very cold LHe2 coming in contact with very hot liquid lithium (or in case of Polywell, even direct plasma contact), means the liquid helium would flash evaporate into gaseous helium -- FAST. Not only that, but it would expand at a high rate, probably causing some part of the vacuum vessel to rupture.

This in turn would suck in outside air (because it's a vacuum chamber) and start to implode, probably not particularly fast because once a disaster of this magnitude hits the facility, vacuum pumping would have stopped already.

The whole situation starts to go downhill once you realize the helium explosion would scatter the liquid lithium blanket airborne over some distance, as D. Tibbets pointed out. Lithium + Air = bad news, burning very fast and intensely.

The steam plumbing would make the situation even more complicated, because lithium and water aren't very good friends. Especially not when mixed together in gaseous form in a cloud, which would add to the yield of the explosion even more. And cause some VERY nasty acid deposits in the direct vicinity. Imagine a laptop battery the size of a warehouse blowing up.... you don't want to be underneath that.

Now if it were regular lithium there would be less of a problem, but don't forget, if ITER is a running facility, this would be highly irradiated lithium, scattered across the countryside, in a burning fireball. Which means a release of radioactive fallout across miles.... starts to sound like Tsjernobyl, to be honest.

The whole thing complicates even more if the lithium blanket is also being used for tritium fuel breeding, which would make the radiation hazard even more acute. The half-life of lithium isotopes spread over the country would be a lot more manageable than the release of heavier radioactive isotopes like in fission reactors, but there's also the toxicity of airborne LiO2 dust to deal with...

I wonder what kind of safety measures the ITER crew has in mind to combat any catastrophic scenarios.
Because we can.