Should EMC2 publish reasons to go over Rider´s limitation?

Discuss how polywell fusion works; share theoretical questions and answers.

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rexxam62
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Post by rexxam62 »

jlumartinez wrote:Fusion has much more advantages than fission, not only radiation. Aneutronic fusion has another else advantage because it doesn´t produce radiation. But even the radiation of a normal neutronic fusion is x1000 lower than fission because it doesn´t produce radioactive sub-product . In case of D-T fusion the helium produced is just radioactive for 10-20 years, not thousands of years as happens with fission. It only radiate the metal of the fusion reactor.

We are expecting direct aneutronic fusion from Polywell just from the first moment. First it has to conquest normal D-T or D-D fusion. Even this, it will be a great step forward!!! Later the aneutronic fusion will be the next challenge.
BORING! That aneutronic stuff better work. The Sun works so Fusion must work. Just need to learn how to get there.

Zixinus
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Post by Zixinus »

um whats the point with fusion and radiation? you can just do fission then
What's the point of fission in the first place?
But even the radiation of a normal neutronic fusion is x1000 lower than fission because it doesn´t produce radioactive sub-product . In case of D-T fusion the helium produced is just radioactive for 10-20 years, not thousands of years as happens with fission. It only radiate the metal of the fusion reactor.
Not quite correct.

First off, radiation is stronger, because the neutrons are more energetic. But countering radiation is easy: just build a thick, concrete wall between the reactor and everything else.

How much radioactive waste is produced obviously depends on many things, but a neutron fusion reactor has higher neutron flux then a fission reactor of equal strength.

The quality and cool-down time of non-aneutronic fusion varies according to the components of the reactor. The heavier elements are used, the more likely radioactive waste will be generated with significant half-life.

The helium produced by fusion is not radioactive. At all. It's stable. In fact, there is no such thing as radioactive helium, because any non-stable isotope of helium will decay quickly (http://ie.lbl.gov/education/parent/He_iso.htm , higherst is 119 miliseconds).

One last thing: neutrons will make ANYTHING unstable and radioactive, its just the question of how long. Miliseconds or centuries. Fission produces long-lived radioactive waste because it uses very heavy isotopes that are "cut" into smaller isotopes, but not my much. It should be noted that by further neutron bombardment it is possible to make these materials give allot of energy in very a very short time, and thus use them as a heat source.

I even recall a IV generation design that would naturally bombard fuels during normal operation, and by the time fuel would have to be changed, very little radioactive waste would have to be handled.
BORING! That aneutronic stuff better work. The Sun works so Fusion must work. Just need to learn how to get there.
You have no idea how complicated the "just" is. Right now, everyone would cry with joy if economic breakeven is done with D-T.

drmike
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Post by drmike »

If you have to play with neutrons, fission has the advantage of being surrounded with water. Fusion needs a vacuum so it's hard to stop the neutrons and absorb their energy.

In tokamaks it's called the "first wall" problem, and if you are going to use DD or DT in an IEC device you have the same problem.

For fusion to beat fission in terms of economic viability it will have to go aneutronic. Otherwise you get just as many radioactive buildings and components even if you don't have radioactive fuel. The problem of radioactive fuel has been solved for fission with metal fuels and breeder reactors.

Zixinus
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Post by Zixinus »

If you have to play with neutrons, fission has the advantage of being surrounded with water. Fusion needs a vacuum so it's hard to stop the neutrons and absorb their energy.
In the case of the tokamaks, where they are trying to put helium between the cryogenic-cooled superconducting magnets and molten lithium, that may be a significant problem. However, in the case of Polywell, not all neutrons hit the grid, depending on what coil-configuration is used.

That means that neutrons are free to fly into a wall where their energy can be absorbed by neutron-killer material. I recall that for the neutron-based Polywell, boron-based components would be used, as they are the most potent neutron killers.
In tokamaks it's called the "first wall" problem, and if you are going to use DD or DT in an IEC device you have the same problem.
The problem of shielding the device is there, however due the reason mentioned before (that the electromagnets are in there in the form of coils, and are not the reactor room and reactor itself), this problem is different. Also, I think Polywell doesn't need to produce tritium (if tritium is used at all) in-situ.

There are however, to my limited knowledge two main issues when it comes to simple fuels with fusion: the neutrons destroying the reactor/magnets and cooling.

In the case of fission, there are no need for magnets or anything, the fuels themselves produce reactions, one merely has to control it with control rods. The control rods require nothing else but (relatively) simple mechanics.
As for cooling, the magnets have to be cool in order to provide a sufficiently powerful magnetic field that would (in the case of Polywell, indirectly) produce fusion. In the case of fission, cooling is what gives power: that's what the thermal cycle is about. However, getting rid of the grid's waste heat is a much more difficult task.
For fusion to beat fission in terms of economic viability it will have to go aneutronic. Otherwise you get just as many radioactive buildings and components even if you don't have radioactive fuel. The problem of radioactive fuel has been solved for fission with metal fuels and breeder reactors.
Not quite. The waste produced by fusion is much lower half-life and radioactivity, although this very much depends on what components do the neutrons hit.

Dr.Bussard also has ideas of using neutron-based fusion. Look at the video at 59:00-60:00.

MSimon
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Post by MSimon »

Putting a water blanket around a D-D Polywell would be very effective. About 6" would capture most of the neutron energy.


A fission reactor run continuously for months is "cool" enough radioactivity wise to allow people in the reactor compartment with no radiation protection after 10 days of cool down.

The system is made mostly of 404 Stainless Steel.

rexxam62
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Post by rexxam62 »

Dr Bussard is how old? And he said on the space show something like this: Someone will build it and when its built it will work and then it will replace all other forms of energy.

I like the good ol Doctor and I hope he is correct. Humanity really needS it now. And thank god for the internet where we can have forums and discuss these things.

drmike
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Post by drmike »

I guess the best thing to do is build it and see!

rexxam62
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Post by rexxam62 »

drmike wrote:I guess the best thing to do is build it and see!
I totaly agree. After having read hundreds of pages about people who are for or against that fusion can work i have discovered people who are for have wishful thinking it should work and people who are against it probably fear it will be competition to them in some way.

>>>So yes just freakin build it and see if it works or not<<<

MSimon
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Post by MSimon »

drmike wrote:If you have to play with neutrons, fission has the advantage of being surrounded with water. Fusion needs a vacuum so it's hard to stop the neutrons and absorb their energy.

In tokamaks it's called the "first wall" problem, and if you are going to use DD or DT in an IEC device you have the same problem.

For fusion to beat fission in terms of economic viability it will have to go aneutronic. Otherwise you get just as many radioactive buildings and components even if you don't have radioactive fuel. The problem of radioactive fuel has been solved for fission with metal fuels and breeder reactors.
Dr. Mike,

As you well know the problem with fission is not activated materials. It is fission products.

The first wall problem is over rated. In any case since a Polywell is small relative to ITER you could replace the reactor vessel periodically without a lot of cost vs. ITER.

drmike
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Post by drmike »

If you can avoid D-T I think that's a good thing. Chemistry for processing fuel or walls is pretty similar, so I think in terms of public relations it's still a problem. I agree with you the magnitude of the problem is far less, but for now public perception of radioactive materials is a far larger problem than the engineering associated with reprocessing. The French reprocess breeders with few problems and have lots of fuel for their LWR's. So it's clear we know how to deal with radioactive stuff.

Iter was on the drawing boards 25 years ago when I was a student. It's amazing to me it's taken this long to just get it built, let alone tested. I would love to see a polywell design from someone's basement blow them out of the water!

:)

MSimon
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D-T

Post by MSimon »

I see no reason to use D-T in a Polywell. Ever.

D-D should work fine at from 15 KV to 40 KV drive.

At 55 KV drive pB11 starts giving good reaction rates.

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