Is There an Optimal Size for Magrid Casings?

MSimon · Post by **MSimon** » Fri Jun 27, 2008 1:58 am

David,

Good idea. It may have merit. It will need an R&D program to make it work. As of now we know how to do pumps. Crude but effective.

ravingdave · Post by **ravingdave** » Fri Jun 27, 2008 3:59 pm

MSimon wrote:David,

Good idea. It may have merit. It will need an R&D program to make it work. As of now we know how to do pumps. Crude but effective.

Even a blind squirrel finds an acorn once in a while !

David

charliem · Post by **charliem** » Sun Jun 29, 2008 12:29 am

MSimon wrote:The real world consideration is 1 MW/sq m and about 100 deg K delta T. Inlet of the cooling loop to outlet.

1.4 meters from a 100 MW machine center, each sq meter will receive about four times that figure (100MW/(4*pi*(1.4m)^2)

Still doable?

nferguso · Post by **nferguso** » Sun Jun 29, 2008 1:53 am

Are water jacket pressures comparable to pressurized light water reactors contemplated? Pressures of such are @ 150 atmospheres, operating temperature 350C (with Wikipedia disclaimer). Is the 100C delta T a magic number or an example?

MSimon · Post by **MSimon** » Sun Jun 29, 2008 6:39 am

nferguso wrote:Are water jacket pressures comparable to pressurized light water reactors contemplated? Pressures of such are @ 150 atmospheres, operating temperature 350C (with Wikipedia disclaimer). Is the 100C delta T a magic number or an example?

The pressure you have to operate at is strictly a function of temperature and whether or not you want bulk boiling. Lower temps and you get lower pressure. A steam table is your friend. It is a balance. The higher the delta temp you can do heat rejection the smaller the heat exchangers.

http://www.engineeringtoolbox.com/satur ... d_101.html

http://freesteam.sourceforge.net/

http://www.x-eng.com/Download_XSteam.htm

The 100 C number is a rule of thumb not a hard and fast number. It has to do with things like expansion/contraction and thermal shock. Think of water entering the reactor at 250 C and leaving at 350 C in a distance of a few meters.

In this particular case since we are not trying to extract any energy from the hot water the mixing of inlet and outlet water is not a problem. We may be able use that as an advantage.

District heating might come back into vogue. Or using the waste heat for warming a greenhouse in winter. Or process steam.

Billy Catringer · Post by **Billy Catringer** » Thu Feb 05, 2009 1:57 pm

Honest to goodness, guys, I think this is what you need for cooling the reactor internals.

http://www.therminol.com/pages/products/vp-1.asp

This is especially true for a p-B11 reactor. Water is always trouble.

MSimon · Post by **MSimon** » Thu Feb 05, 2009 7:13 pm

Billy Catringer wrote:Honest to goodness, guys, I think this is what you need for cooling the reactor internals.

http://www.therminol.com/pages/products/vp-1.asp

This is especially true for a p-B11 reactor. Water is always trouble.

Long experience with water in nuclear reactors. What happens to therminol under neutron bombardment? How good a moderator is it?

Billy Catringer · Post by **Billy Catringer** » Thu Feb 05, 2009 7:42 pm

MSimon wrote:
Billy Catringer wrote: Long experience with water in nuclear reactors. What happens to therminol under neutron bombardment? How good a moderator is it?

I do not doubt your experience one bit. You had a hairy-assed job and you did it well or you and I would not be having this correspondence. So lemme see if I can explain without giving offense, 'cause I'm tryin' to help, not hinder.

I don't know what will happen to Therminol under neutron bombardment save that it is likely that some of the carbon atoms will become C13 or C14 and certainly some molecular breakdown will occur. I would think, given that you have relatively little neutron bombardment in this type of reactor, that those problems could be cured with filtration in the cold side of the loop.

Two things bother me about using water in this unit. We are guaranteed to get a temperature excursion out of it when fusion starts. I can't see anyway it can be avoided. About all you can do is to anticipate it in your design.

Now, you work real hard to never have a temperature/pressure excursion in a fission plant, right? As you powered one up at dockside you took your time and let the thing warm up slow so that the containmenf vessel was never treated to any hard thermal shocks. How long did that take? At least a day, right?

Once the reactor was up to power you always kept an eye on the temperature and pressure inside the primary loop, never allowing any sudden excursions if it could possibly be helped. In fact, if you did see such an excursion begin, you scrammed the plant.

I don't see how you can operate BFR that way. You will have to pump coolant through the magnets like crazy just to keep resistance down. When fusion starts, your going to see a rapid increase in temperature. See what I'm saying? The cooling system around the magets is never going to be as robust as the containment and primary coolant loop of a fission plant. Using mineral oil or Therminol would greatly reduce the likelyhood of destructive pressure excursion.

Granted, there is a tradeoff in the need for a filtration system, but that is simpler than a demin water system and with either system you have to have a pretty good cooling plant. So, at a relatively small cost, a shielded filtration system, you avoid the possibility of a coolant system leak or rupture inside the reactor.

MSimon · Post by **MSimon** » Thu Feb 05, 2009 9:00 pm

Water is the best inexpensive heat transfer fluid known to man in terms of joules/kg*degC.

BTW I need good moderation properties. It is part of shielding the SCs from the neutron flux.

Billy Catringer · Post by **Billy Catringer** » Thu Feb 05, 2009 9:22 pm

MSimon wrote:Water is the best inexpensive heat transfer fluid known to man in terms of joules/kg*degC.

Yes, that's true. It also has some rather nasty habits.

MSimon wrote:BTW I need good moderation properties. It is part of shielding the SCs from the neutron flux.

I hear and understand, especially if you are dealing with d-d or d-t reactions, but I really do think you'd be better off with a sacrificial shield of B10 on the inward facing parts of the electromagnets when using either of those reactions.

Now, answer me this, how are you going to cool SC's w/ water? Is the water going to be in an outer jacket? Either way, it will have to have a relief system. After thinking about it a little more, you're not worrying about something like a fission plant's core being exposed, so water loss would not be immediately fatal.

Even so, heat rejection from this type of reactor is starting to look like a major issue. With superconductors, you have to use LN2 or something colder, right? Producing that stuff and recycling it for re-chilling is going to be a big consumer of energy. And, if your magnets require both water and a liquified gas like N2 or He2, the start up sequence is going to be a bear.

MSimon · Post by **MSimon** » Thu Feb 05, 2009 9:29 pm

I hear and understand, especially if you are dealing with d-d or d-t reactions, but I really do think you'd be better off with a sacrificial shield of B10 on the inward facing parts of the electromagnets when using either of those reactions.

That is the point of the water. Thermalizing the neutrons so B10 can capture them. And we want the shortest slowing down distance possible to keep the machine small. It is a geometry problem.

MSimon · Post by **MSimon** » Thu Feb 05, 2009 9:31 pm

It is a multijacket system:

SC + LHe, vacuum, LN2, vacuum, H2O 300K, vacuum, H2O 600K, vacuum chamber.

Billy Catringer · Post by **Billy Catringer** » Thu Feb 05, 2009 10:29 pm

Holy smokes! At those temperatures you may as well let the water flash to steam at the outlets and run it through a pair of turbines and a dump condensor. You might get enough power to maintain the vaccum jackets AND drive the feedwater pump.

But that trips yet another alarm and I may well be misconstruing something here. Doctor Bussard said that the coils have to be gapped rather precisely from one another. The gap has to be a certain number of times the gyro radius. Now your coils are buried inside three insulating jackets and three cooling jackets. If am understanding Doctor Bussard correctly, those coils need to be spaced some number times the radius of the barrel rolls the electrons execute as they follow the magnetic lines of force. Is that right? If so the structure holding the magnet array together is going to be a really neat trick.

MSimon · Post by **MSimon** » Fri Feb 06, 2009 1:02 am

If so the structure holding the magnet array together is going to be a really neat trick.

Yes it will be.

krenshala · Post by **krenshala** » Fri Feb 06, 2009 2:51 am

MSimon wrote:It is a multijacket system:

SC + LHe, vacuum, LN2, vacuum, H2O 300K, vacuum, H2O 600K, vacuum chamber.

Taking this into account, what do you think the minimum diameter (outer layer down through the SC and back to the outer layer) would need to be for the torii? If we have that, it should point to a desired device size, yes?