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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D Tibbets
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Postby D Tibbets » Tue Nov 08, 2011 11:04 pm

Joseph Chikva wrote:
D Tibbets wrote:I couldn't find the Battleship explosion I mentioned, so it cannot be confirmed.

Alternately, a small quench in an MRI machine

http://www.youtube.com/watch?v=1R7KsfosV-o

And an apparent submarine steam explosion (sort of). The effects are surprising, especially when the resultant tidal wave reaches the ship!

http://www.youtube.com/watch?v=Jw--eCJi4P4

Dan Tibbets :)
So, you are not answering on question. I know about threat. But it's solvable and solved. TOKAMAK as concept has less problems with magnetic field. TOKAMAK unlike to all other approaches has reached already Lawson criterion. But triple product has not been reached and very unlikely that ITER with his claimed 3keV from ohmic heating 20MW RF source and 1MeV NBI injector will reach desired 15keV temperature. That is a problem. Also problem is in joining of NBI injector with vacuum chamber. You are searching problems in wrong place.


I'm not sure where you are going. The topic is the stored energy in a superconducting magnet and the consequences of a sudden release of this energy. This has nothing to do with your above comments about the performance gains thus far achieved. Just like the LHC there are thoughtful safegards in place or planed. The point is that these planed for safeguards and construction details are not necessarily appropriate. This is very apparent from what happened at the Japanese power plants after the earthquake and tsunami. They thought, or at least claimed that all the safegaurds were adiquate. As I mentioned I suspect the consequences of a major failure does not have the consequences of a fission nuclear reactor meltdown , but neither is it trivial. If nothing else it could lead to a multibillion dollar damage to a very expensive and big Tokamak plant.
I don't know which Tokamak experimental reactors have used superconductors, but the biggest so far (?) did not- JET.

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

Joseph Chikva
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Postby Joseph Chikva » Wed Nov 09, 2011 3:52 am

Stoney3K wrote:Isn't that a bit beyond the scope of the discussion?

What I'm interested in is whether or not a tokamak (or any other fusion facility, for that matter) could be operated safely.

Remember, if we manage to get fusion going in the coming decade, it means commercial deployment, and it also means that fusion plants stop being science facilities, but start becoming utilities which need to operate efficiently.

Operating efficiently means operating on a tighter budget than university research grants. So it may involve cutting corners during maintenance, operation and construction... which means serious safety risks.

I wonder how long it will take for the first fusion facility to go 'boom', either through an accident or due to deliberate (possibly politically motivated) sabotage, and what safety mechanisms would be implemented to make the facility go 'fizz' instead.
No I do not think that my statement that TOKAMAK or any other device storing big amount of energy in magnetic field is not so dangerous (as stated here - kilotons TNT equivalent) is beyond the scope of the discussion.
Also I unlike you I am not so optimistic that commercial fusion reactors we can get already in the coming decade. I do not see corresponding financing and I do not see the concept proving its viability. Yes, TOKAMAK has overcome Lawson criterion but that also too far from net power production capability. Ignition of self-sustained reaction has not been achieved. ITER program is scheduled till 2030 and I do not see assets in ITER might to increase the temperature till desired 15keV requiring for ignition.
After overcoming of real breakeven very large volume of engineering challenges should be solved, some of those will regard optimization of operational regime, some materials and some - certainly, industrial safety.
As subprograms some of those are included in large ITER program.

If you are interested particularly in industrial safety, let's first of all recall that even HPP plant is a source of some threats. Such as e.g. dam breaking, etc.
Certainly, the object using high voltage, high current, high field, flammable lithium, vacuum and pressure vessels (in heat transfer loops) is sorce of many threates. So, commercialization of such complex reactors can be conducted only by large companies or state research and engineering organization. No garage enthusiasts.
But that's feasible.

Regarding radioactive threat, that is much lower than for fission reactors case. As charge of e.g. radioactive tritium is current (several grams order) and not a few years storing. Unlike heavy metals tritium is excreted from the body within several days. Secondary radiation only from short-living isotopes, etc.

Joseph Chikva
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Postby Joseph Chikva » Wed Nov 09, 2011 4:01 am

D Tibbets wrote:I'm not sure where you are going. The topic is the stored energy in a superconducting magnet and the consequences of a sudden release of this energy. This has nothing to do with your above comments about the performance gains thus far achieved.
I asked and asking again now:
Please, explain the mechanism of energy releasing when superconducting magnet damages.
You have colorfully described consequences. I am sure that exaggerating. But have absolutely passed how energy flows to explosion point. And why that is explosion point and not all mass of magnet (365 tons in ITER case)
Thanks.

Joseph Chikva
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Postby Joseph Chikva » Wed Nov 09, 2011 4:32 am

By the way, Dan, describing explosive capabilities of helium you forgot answering also on a simple question:
Closed or opened loop is used for cooling?
And if you are so sure in capabilities of helium as explosive, have you offered to US Department of Defence to use helium artillery shells? Joke :)

bk78
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Postby bk78 » Wed Nov 09, 2011 12:06 pm

I think we are discussing 2 different things here.
For a dedicated energy storage device, quenches are a serious issue. In the 70s, they planned devices with several 100m diameter, for storage of some 10 TWh, so a quench could release the energy of a small atomic bomb.
For superconductors that are not meant for energy storage but to produce a magnetic field, i have to agree Josef, this is not an unsolvable problem (although i disagree that the energy is evenly heating the whole magnet. Instead of 17 degrees increase for the whole structure, it could be 1700 degrees for 1% of it). They can be built to release the energy safely. The quench-videos on youtube actually demonstrate this, they are doing as they were designed to. The magnets for a fusion reactor could be pumped separately, evaporation of helium and a overpressure ventile might already be sufficient. There will be repairs, it may cost a bit to have the reactor offline for a few days, but there will certainly not be a real hazard for people.
The comparison with fukushima is unfair, because that plant was designed for a tsunami of a certain height, and then a higher tsunami occured. In case of a magnet, in contrast, we know exactly how much energy it contains and can design it accordingly.

Joseph Chikva
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Postby Joseph Chikva » Wed Nov 09, 2011 1:55 pm

bk78 wrote:(although i disagree that the energy is evenly heating the whole magnet. Instead of 17 degrees increase for the whole structure, it could be 1700 degrees for 1% of it).
It does not matter you agree or not. Energy releases in the EDF form that resists to magnetic flux change and drives current. Regardless to what we agree current flows through conductor and not dielectric. In case of dielectric you are right. May be even less than 1% will be heated in breakdown of dielectric case, in which current flows only there where the weak area would be found.
In case of conductor matrix you have quite uniform heating. As matrix is resistive but well conductive too with only fraction of ohm resistivity. And so, 17 deg of temperature increase is realistic estimation for ITER’s parameters.

ladajo
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Postby ladajo » Wed Nov 09, 2011 2:27 pm

It would seem that the entire thread here has degenerated to refusal to take a step back.
I would offer that yes, high power magnetic systems can store tremendous amounts of energy. And that, if not properly designed, they can release this energy in a violent/uncontrolled manner. That said, it is not saying that one can not perform the proper design to contain and disspate the energy in a controlled manner.

I go back to my orignal comments where I discussed having uncontrolled failures, the energy being sourced from the collapse of magnetic fields, to modifying the design to provide a controlled manner to manage this energy as the fields collapsed, and thus preventing the previously observed violent failures.

Joseph Chikva
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Postby Joseph Chikva » Fri Nov 11, 2011 6:18 pm

D Tibbets wrote:I'm not sure where you are going. The topic is the stored energy in a superconducting magnet and the consequences of a sudden release of this energy.
Enjoy:
The PF coils are
designed for a normal operation current of 45 kA at an operating temperature of 5 K. In the backup mode, when one of the damaged double pancakes of a coil will be disconnected and bypassed, the coil current will be increased to 52 kA. The operating current of the PF 2 coil under normal conditions is 41 kA, although the conductor is designed for 45 kA. The PF 2 coil has 5 double pancakes only. In the backup mode, with one double pancake less, the coil current will exceed the maximum current limited to 52 kA. Therefore, normal operating current has to be limited to 41 kA. The detailed data of the PF coil conductors are summarised in Tab. 2.2.
Yes, here is described poloidal coils of ITER. But toroidal coils are desined similarly and probability of damage is not excluded.

Stoney3K
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Postby Stoney3K » Tue Nov 15, 2011 2:00 pm

Joseph Chikva wrote:
D Tibbets wrote:I'm not sure where you are going. The topic is the stored energy in a superconducting magnet and the consequences of a sudden release of this energy.
Enjoy:Yes, here is described poloidal coils of ITER. But toroidal coils are desined similarly and probability of damage is not excluded.


I don't see any mention here of monitoring or automatic shunting or shutoff mechanisms which would shunt the excess current in case of a sudden quench in one of the coils.

Furthermore, if the coils are running at the rated 41kA each and one would fail during operation, shunting would mean the other coil gets the full current load of 82kA in an instant. I doubt it would be able to handle such a current in steady state, let alone the shunting process which would introduce some serious magnetic forces (think Lorentz force and Lenz' Law here) that could rip the coil apart.

The mechanism you're talking about here would work if one of the coils is marked as faulty before they are energized.
Because we can.

Joseph Chikva
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Postby Joseph Chikva » Tue Nov 15, 2011 2:15 pm

Stoney3K wrote:
Joseph Chikva wrote:
D Tibbets wrote:I'm not sure where you are going. The topic is the stored energy in a superconducting magnet and the consequences of a sudden release of this energy.
Enjoy:Yes, here is described poloidal coils of ITER. But toroidal coils are desined similarly and probability of damage is not excluded.


I don't see any mention here of monitoring or automatic shunting or shutoff mechanisms which would shunt the excess current in case of a sudden quench in one of the coils.

Furthermore, if the coils are running at the rated 41kA each and one would fail during operation, shunting would mean the other coil gets the full current load of 82kA in an instant. I doubt it would be able to handle such a current in steady state, let alone the shunting process which would introduce some serious magnetic forces (think Lorentz force and Lenz' Law here) that could rip the coil apart.

The mechanism you're talking about here would work if one of the coils is marked as faulty before they are energized.
There is not any other bypass except conductive matrix. In that paper/book i written
In the backup mode, when one of the damaged double pancakes of a coil will be disconnected and bypassed, the coil current will be increased to 52 kA.
And that is reserve but projected mode. I do not understand from where you get nomber of 82kA. Regarding so high currents and acting forces do not worry too. I have a book in Russian in which pulse magnets with currents 1.5MA are discribed with pulse duration of milliseconds order and fields 40T and higher. Have ever heard about Bitter and High Fields Lab?
Largest Bitter magnetAs of 2011 the National High Magnetic Field Laboratory in Tallahassee, Florida, USA, houses the current world's largest resistive magnet. This system has a maximum output of 36.2 teslas and consists of hundreds of separate Bitter plates. The system consumes 19.6 megawatts of electric power and requires about 139 litres of water pumped through it per second for cooling.[2] . This magnet is mainly used for material science experimentation. For similarly designed examples of bitter coils see the external links below.
This is not easy but this is quite solvable.

D Tibbets
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Postby D Tibbets » Wed Nov 16, 2011 3:11 am

Joseph Chikva wrote:By the way, Dan, describing explosive capabilities of helium you forgot answering also on a simple question:
Closed or opened loop is used for cooling?
And if you are so sure in capabilities of helium as explosive, have you offered to US Department of Defence to use helium artillery shells? Joke :)


Who ever said helium was explosive. I repeat - I am talking about steam explosions. Any liquid, whether helium, water, alcohol, oil,liquid nitrogen,etc behaves the same.The mechanism is the volume occupied by the substance in liquid and gas form. also a point is that the fluid is super heated when it breaches the pressure vessel ( due to the quenching of the superconductor and the release of heat into the cryostat). Whether the pressure vessel is at low or high initial pressure plays a role in how fast the liquid boils when the pressure is released. If the helium is flowing through an open system with wide ports/ valves, the explosion would be mitigated to a small or large extent. But, I'm under the impression is that helium blankets are mostly closed systems. It is much too expensive for open systems. CT scanners for example operate with a cryostat/ tank of helium surrounding the superconducting magnets, and this sealed system lasts for months, if not years between servicing- venting and /or topping off. Actually a safety feature would be simply large pressure release valves so that as the temperature and thus pressure increases in the tank is limited before the boiling liquid vents into a secondary container vessel. There are various ways the process could be contained, diverted. But it would be very difficult and perhaps foolish to keep the heated helium in its small container. Also difficult (probably not impossible?) is to very quickly divert the circulating current so that it does not overheat the now non superconducting magnet. It should be manageable, we agree on that. But, also I point out that management has often been assumed when it was actually not adequate. Thus the explosion in the LHC, the 2 out of 3 Japanese reactor building demolitions, and many other steam explosions. For that matter I think most of the damage at the Russian nuclear plant accident was a steam explosion. The reactor heated up- rapidly heating the water in the containment vessel, the boiling increased, the pressure increased unti the heavy lid was lifted off. At that point the pressure dropped rapidly and the large volume of superheated water flashed into steam/ water vapor, and this rapid volume expansion demolished the reactor and building. This was not a chemical explosion, it was due to the very rapid phase change of the water from liquid to gas.

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

D Tibbets
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Postby D Tibbets » Wed Nov 16, 2011 3:23 am

Copper Bitter magnets are not superconducting. They are chilled to liquid nitrogen temperatures to improve conductivity 6-8 X, but they are not superconducting.

And pulsed magnets are presumably innapropriate for Tokamaks, and I think innapropriate for superconducting magnets in general. superconducting magnets are vunerable to large magnetic fields. There are limits. Liquid helium temperature superconductors do better than high temperature superconductos, but still there are limits. Currently the limits for high temperature superconductors is in the few thousand Amps range. I'm not sure if running superconductor magnet wires in parellel would help, I doubt it as the they would still be within the overall magnetic field.

Why would the current increase in other magnets if one failed? I assume each magnet would be wired in isolation. Are you talking about current induction in other magnets as the failed magnetic field collapses?

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

KitemanSA
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Postby KitemanSA » Wed Nov 16, 2011 3:34 am

bk78 wrote:I think we are discussing 2 different things here.
For a dedicated energy storage device, quenches are a serious issue. In the 70s, they planned devices with several 100m diameter, for storage of some 10 TWh, so a quench could release the energy of a small atomic bomb.
For superconductors that are not meant for energy storage but to produce a magnetic field, i have to agree Josef, this is not an unsolvable problem (although i disagree that the energy is evenly heating the whole magnet. Instead of 17 degrees increase for the whole structure, it could be 1700 degrees for 1% of it). They can be built to release the energy safely. The quench-videos on youtube actually demonstrate this, they are doing as they were designed to. The magnets for a fusion reactor could be pumped separately, evaporation of helium and a overpressure ventile might already be sufficient. There will be repairs, it may cost a bit to have the reactor offline for a few days, but there will certainly not be a real hazard for people.
But if you have one of these 10TWhr units and a terrorist comes along and shoots a shaped charge missile at it, and the shaped charge penetrates across the worst case number of strands of the SC magnet, what will happen to all that energy? KaBOOM, no?

Joseph Chikva
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Postby Joseph Chikva » Wed Nov 16, 2011 3:53 am

D Tibbets wrote:Copper Bitter magnets are not superconducting. They are chilled to liquid nitrogen temperatures to improve conductivity 6-8 X, but they are not superconducting.

And pulsed magnets are presumably innapropriate for Tokamaks, and I think innapropriate for superconducting magnets in general. superconducting magnets are vunerable to large magnetic fields. There are limits. Liquid helium temperature superconductors do better than high temperature superconductos, but still there are limits. Currently the limits for high temperature superconductors is in the few thousand Amps range. I'm not sure if running superconductor magnet wires in parellel would help, I doubt it as the they would still be within the overall magnetic field.

Why would the current increase in other magnets if one failed? I assume each magnet would be wired in isolation. Are you talking about current induction in other magnets as the failed magnetic field collapses?

Dan Tibbets
Bitter magnet as example of magnet conducting hundreds amperes and withstanding fields 40T.
The strongest quazi-stationary fields are created with hybrid magnets with outer superconducting coil and inner - resistive.

Joseph Chikva
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Postby Joseph Chikva » Wed Nov 16, 2011 3:57 am

KitemanSA wrote:But if you have one of these 10TWhr units and a terrorist comes along and shoots a shaped charge missile at it, and the shaped charge penetrates across the worst case number of strands of the SC magnet, what will happen to all that energy? KaBOOM, no?
KaBOOM in which form?
Please describe. If you can without poetry.


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