How much does liquid helium cost?

[Mark R]

Just wondering.

The new MRI scanner at our local hospital is liquid helium cooled. One of the technicians pointed at the big red switch on the wall marked 'emergency magnet shutdown'. He warned, that it wouldn't be a good idea to press it, because it will cause to magnet to dump it's load of liquid helium.

I was rather stunned at the claimed cost to refill the scanner - $75k (and that's not including several days of labor charges for the manufacturer to recomission the machine).

I'm guessing that the scanner probably holds about 150-200 gallons of helium. Does it really cost $500 per gallon?

 

[stonecold3169]

If thats the number that the tech quoted you, he may be right. Keep in mind that if they are really refilling the machine and not purifying what was dumped, well, you now have 200 gallons of hazerdous waste to get rid of. OSHA regulations means an authorized company needs to come to dispose of it, hell 200 gallons of hazmat pickup could easily cost $20k by itself

 

[Howard]

Too bad it doesn't use HTS materials, which only need liquid nitrogen to function properly.

EDIT: Helium liquefies at 4K, which is pretty damn close to absolute zero. From what I hear, you can't pressurize it to raise the boiling point.

 

[OrganizedChaos]

i've got a stupid question.

where does the helium go or how do they keep it from suffocating people?

 

[0]

Originally posted by: stonecold3169
If thats the number that the tech quoted you, he may be right. Keep in mind that if they are really refilling the machine and not purifying what was dumped, well, you now have 200 gallons of hazerdous waste to get rid of. OSHA regulations means an authorized company needs to come to dispose of it, hell 200 gallons of hazmat pickup could easily cost $20k by itself

What are you talking about? Liquid Helium will boil off into the atmosphere, there is nothing to "get rid of".

 

[Hyperion042]

I'm a structural biologist with experience in NMR/MRI (same thing):
The cost lies in replacing the system. Typically, you just fill the thing with liquid helium to induce the formation of superconducting electron pairs, creating a superconducting magnet. In NMR systems, you fill the system once under very controlled conditions to make the magnetic field start up and stabilize - BUT it doesn't always stabilize, and so you have to do things very carefully and usually multiple times. While LHe is expensive, the primary cost there lies in setup and configuration, since once you dump the He, the magnet is no longer superconductive and must be reconfigured from scratch.

Yes, LN2 is about the same price per unit volume as milk, but for the most part the cost of getting High Temp Superconductors set up and in quantity far exceeds the cost of the magnet's coolant. Plus, for the LHe you usually have it inside a jacket of LN2 anyway, if I recall my courses on spectroscopy correctly.

 

[FoBoT]

w0w, Hyperion042 must have wandered into the wrong forum, a helpful informative post is so rare! :thumbsup:

 

[zoiks]

Originally posted by: Hyperion042
I'm a structural biologist with experience in NMR/MRI (same thing):
The cost lies in replacing the system. Typically, you just fill the thing with liquid helium to induce the formation of superconducting electron pairs, creating a superconducting magnet. In NMR systems, you fill the system once under very controlled conditions to make the magnetic field start up and stabilize - BUT it doesn't always stabilize, and so you have to do things very carefully and usually multiple times. While LHe is expensive, the primary cost there lies in setup and configuration, since once you dump the He, the magnet is no longer superconductive and must be reconfigured from scratch.

Yes, LN2 is about the same price per unit volume as milk, but for the most part the cost of getting High Temp Superconductors set up and in quantity far exceeds the cost of the magnet's coolant. Plus, for the LHe you usually have it inside a jacket of LN2 anyway, if I recall my courses on spectroscopy correctly.

Great information. But the OP said that the 75k doesnt include the labor charges to recommision the machine.

 

[Mark R]

Originally posted by: OrganizedChaos
i've got a stupid question.

where does the helium go or how do they keep it from suffocating people?

The helium evaporates.

When the electromagnet is running, it stores a huge amount of energy in the magnetic field. But during a shutdown that energy has to be dumped. It ends up getting dumped as heat in the magnet coils. The coils are immersed in the helium coolant.

This causes the helium to boil and evaporate. Outside the building there's a huge vent pipe (about 1 foot across) where the helium vapors are supposed to be discharged during a shutdown.

In the event that the main vent is blocked (apparently, birds occasionally get in and build nests in them), then helium will vent into the scanner room. There are oxygen level alarms and automatic poweful extract fans to make sure that people don't get suffocated if the helium does get into the room.


Unfortunately, I don't actually know how much helium is needed. No one knew when I asked, and the specs aren't publicly available.

Liquid nitrogen isn't normally used in MRI scanners because the temperature isn't low enough to allow sufficient magnetic field strength. Something to do with high-temperature superconductors not being able to tolerate the magnetic field. Hybrid designs (helium insulated with nitrogen) are also not used - not quite sure why; might be something to do with space constraints. Adding an extra cryogen reservoir would mean either less space in the scanner, or making the whole thing bigger and much more expensive (and possibly of lower quality).

 

[Antisocial Virge]

According to google "liquid helium cost" is around $5 a liter.

 

[grohl]

amazing...a thread that's interesting AND educational.

 

[RLN]

Re: Cost of LHe and MRI magnets

There are several surveys online - the latest being from 2009 when the average cost per liter - world wide - was given as $8.65/+- $3.25 and that of LN2 was $0.41/+-$0.17.

Clearly if competitively priced/performance high temperature superconductors - HTcs (superconducting at LN2 temperatures) were readily available they would be a benefit for MRI magnets and overall cost and while there is ongoing research to make more formable/ductile, cost effective HTc wire it does not get the funding needed to push the envelope into commercial applications/uses to date. Useful HTcs would have a big impact on power transmission and transportation too.

A typical human MRI magnet holds about 1000 to 1400 liters for filling - hence the cost to recover from a 'quench' (the rapid boil off of LHe) is high and frequently poses damage risks to the magnet. In some cases this is fatal or unrecoverable damage because the wire heats up in this process and it may melt or the potting or insulation fails and the wire 'touches' creating shorts in the windings so the magnet cannot be 're-energized' properly. Manufacturers attempt to mitigate this by using so-called 'dumping resistors' but the designs are far from fool-proof. At $8.65 a liter it would be more like $10 to 12K to refill (a bit more actually since the process of transferring from a shipping vessel into the magnet is not perfect and 'bottled dry' He gas is used to push the LHe into the magnet) and frequently (depending on the temperature in the magnet chamber itself post 'quench') the magnet will need to be cooled first with LN2 just to bring the magnet's superconducting windings down to LN2 temperature to make the LHe cooling more efficient before starting the LHe transfer to get to the low temperature superconductor (LTc) wire to the temperature need to put power back into the magnet. This all takes time and the bigger cost is that of the service engineer to do this and re-adjust the homogeneity of ("re-shim") the magnet to make it suitable for doing MRIs. This is complicated and costly. And the original 'shim' parameters are lost in the quench process.

MRI magnets also hold a lot of stored energy in the superconducting wire - this can be on the order of a few sticks of dynamite so a lot of energy is stored therein as well. But this works because the wire effectively has 'zero' resistance at the superconducting temperature and current put into it will last 'forever' as long as the wire is kept superconducting cold. The current can be quite high - hundreds of amps at very low or 'no' volts. So a special power supply is needed for this process and is normally shipped in for the initial installation/energization process and then it is sent elsewhere for other installations or re-energizations -- since these power supplies are expensive to make and make safe. And they need not remain 'on-site' once the magnet is operational

TMI- sorry.

 

[rivan]

w0w, Hyperion042 must have wandered into the wrong forum, a helpful informative post is so rare! :thumbsup:

Elite with 53 posts? :hmm:

In the event that the main vent is blocked (apparently, birds occasionally get in and build nests in them), then helium will vent into the scanner room. There are oxygen level alarms and automatic poweful extract fans to make sure that people don't get suffocated if the helium does get into the room.

What a simultaneously hilarious and horrifying way to die.

You're suffocating, but can breathe easily. All the while, you can be shouting for help with your high pitched voice.

 

[wirednuts]

its weird to me because helium is a finite resource. were actually lucky to even have it on this planet as far as i knew. we basically just found large pockets of it underground and once we use that up, its gone. im guessing those are just really large pockets though because ive never heard anyone worry about it... and we still fill up baloons with that stuff all the time

 

[Jeff7]

Welcome back, ancient thread.


New idea for old threads: Still leave them accessible for new posts, lest we end up with more of this, but don't bump them to the top. Google will still find them.
(Seriously, I also hate those threads where no solution was ever found, and the thread is now close - or when the second post is "Nevermind, I figured it out" with no elaboration as to how that was done.)

its weird to me because helium is a finite resource. were actually lucky to even have it on this planet as far as i knew. we basically just found large pockets of it underground and once we use that up, its gone. im guessing those are just really large pockets though because ive never heard anyone worry about it... and we still fill up baloons with that stuff all the time

There is concern about it. Look around for information on "peak helium." Once those pockets are gone, I think our only option is distilling it out of the air, which I believe is done by cooling air until it liquefies, and then separate out the liquids by density. This of course would be a lot more expensive than tapping underground deposits. Or maybe that's how it's already done, but the underground deposits just have a lot more helium in them, making the process more efficient. I guess I've got reading to do too.

 

[silverpig]

I worked in a low-temperature physics lab where we used liquid helium extensively. The price of liquid helium depends a lot on where you are - if you are close to a production facility, you can get down to $5-6/L. In our lab, it was about $10, and it can go much higher than that.

Now, there is more to it than just filling the magnet chamber with LHe - you have to cool the magnet down and in the process boil off a ton of the liquid.

The general procedure is to fill the chamber with liquid nitrogen (dirt cheap), then blow the LN2 out with gaseous N2 (or He). Then, you put in the LHe. You'll boil a ton off as the magnet cools, and then once it hits 4.2K, most of the boil off will stop and you'll just have a little bit of evaporation.

 

[Soccerman06]

Wait a sec, 6 year necro by a new guy and hes actually adding something useful?

 

[wirednuts]

Wait a sec, 6 year necro by a new guy and hes actually adding something useful?

blame google. im sure he didnt even know what anadtech was until he searched google for helium. i dont know why, but anandtech much suck a lot of google dick because its not hard to make these threads show up at top of search results.

 

[rivan]

Hah, I didn't even notice the necro, with the total lack of free ipodz.

 

[PlasmaBomb]

Elite with 53 posts? :hmm:



What a simultaneously hilarious and horrifying way to die.

You're suffocating, but can breathe easily. All the while, you can be shouting for help with your high pitched voice.

This thread is pre-VB. Probably lost his count in the switch.

MarkR now knows lots more about MRIs too... :thumbsup:

I remember discussing them with him.

 

[PlasmaBomb]

Welcome back, ancient thread.

There is concern about it. Look around for information on "peak helium." Once those pockets are gone, I think our only option is distilling it out of the air, which I believe is done by cooling air until it liquefies, and then separate out the liquids by density. This of course would be a lot more expensive than tapping underground deposits. Or maybe that's how it's already done, but the underground deposits just have a lot more helium in them, making the process more efficient. I guess I've got reading to do too.

Nope we still get helium from natural gas deposits, distilling it is really difficult -

http://backreaction.blogspot.com/2008/07/liquid-helium.html


Just for fun -

Decomissioning an MRI machine -

http://www.youtube.com/watch?v=5z33ZcDgavY

Edit:

Pretty dramatic demonstration of why LHe is an asphyxiation hazard. You are now talking with a really squeeky voice and have no oxygen to breathe...

 

[Fausto]

WTF first post.

 

[Jeff7]

Nope we still get helium from natural gas deposits, distilling it is really difficult -

http://backreaction.blogspot.com/2008/07/liquid-helium.html


Just for fun -

Decomissioning an MRI machine -

http://www.youtube.com/watch?v=5z33ZcDgavY

Edit:

Pretty dramatic demonstration of why LHe is an asphyxiation hazard. You are now talking with a really squeeky voice and have no oxygen to breathe...

So I'd guess then that the concentrations of helium are higher in the natural gas deposits, which makes it more worthwhile to distill it out, right? (Versus distilling it out of plain air.)

 

[Analog]

the hazmat team could suck helium and talk like Donald Duck to each other....

D:

 

[Mark R]

So I'd guess then that the concentrations of helium are higher in the natural gas deposits, which makes it more worthwhile to distill it out, right? (Versus distilling it out of plain air.)

There is no helium in air. Any helium in the atmosphere rapidly escapes into space.

The only source of helium on earth is natural gas.