Breakeven with D-T?

[opensource]

I just listened to this: https://www.youtube.com/watch?v=bDzZwVtMxg8 (Solve For x, 30 min scientific presentation at Fusion Brainstorming Conference).

At the very end Lerner said, “… It would be break-even with D-T by extrapolation.”

Theoretically, the current FF setup LPP runs would break even if running with D-T? Really?
Have to ask! Thanks!

[zapkitty]

It’s very neat that LPP has exceeded D-T fusion requirements but D-T is not a good fuel for a Focus Fusion generator.

Deuterium-Tritium (D-T) is a neutronic reaction with a radioactive fuel component. The cost of gearing up the LPP lab to handle tritium would be considerable and the Focus Fusion setup in general isn’t good for the kind of neutron flux or the resulting thermal load that D-T produces.

And thus Eric has stated that LPP will not be doing any D-T testing.

[dennisp]

Which doesn’t answer the question.

A similar situation holds for the JT-60 tokamak in Japan…conditions achieved with D-D which would surpass breakeven if it were D-T. This seems to be considered a pretty significant result, so if LPP has done something comparable that would really be something.

Or is there some scaling involved with the plasma focus that makes it more of an extrapolation?

[opensource]

So I posted this about a week ago… If there’s a mountain of evidence anywhere for this stuff, then I think is should be demonstrable via this forum, right?

[JimmyT]

Since you can’t capture the rather large fraction of total fusion energy from a DT reaction which is imparted to the neutrons it really is merely a theoretical point.

[asymmetric_implosion]

There are publications by LPP that suggest the temperature was achieved. The measurement leaves some questions but it is a good first look at it. They used the hard x-rays generated by the pinch to estimate a temperature. The potential problem is the high energy gamma rays created when neutrons interact with the stainless steel vacuum vessel. I’ve encountered it in the past and it can screw up measurements. The measurement I’m waiting to see is the soft x-ray spectrum of continuum radiation from the deuterium. Folks have done it before and it provides a pretty reasonable estimation of the temperature. It tends to be a little on the cold side so it is a good lower bound. The density again has been estimated. You really need to do an x-ray transmission measurement to measure the line density and infer the actual density from x-ray images of the pinch itself. Nether has been done so the conditions for D-T breakeven have been inferred rather than measured. This does not mean the results to date are not promising, but more needs to be done. The other option is to load the machine with DT and go for it. It would be a huge political win to show breakeven. The cost of the experiment would be enormous as T is involved but a successful demonstration might eliminate some of the funding problems. Big risk, big reward. The other option would be to move the machine to a national lab for the test. It would be distracting and difficult but again, big risk, big reward. You could also get some DOE buy in as their lab made fusion viable.

[JimmyT]

Don’t forget Eric has time of flight on the neutrons too.

[Tulse]

JimmyT wrote: Since you can’t capture the rather large fraction of total fusion energy from a DT reaction which is imparted to the neutrons it really is merely a theoretical point.

But it’s a theoretical point that has huge implications for the validity of the FF approach.

I think the very large downside of doing a DT run is that it would make FF-1 radioactive. That’s apart from the problems of handling tritium. (Is LPP even licensed to handle a radioactive substance like tritium?)

[delt0r]

The radioactivity from neutron activation is overplayed a bit. Its quite manageable if you keep the shot count low. Even without careful materials choices. The real problem is the amount of shielding you need for the neutrons in the first place. Its really quite a bit if you expect +1J of neutrons in a shot. I have though that water tanks with borated water etc would be a good temporary way of dealing with neutrons. Added advantage of reducing activation since the Boron absorbs most of the neutrons.

[JimmyT]

delt0r Please note the thread title. We are specifically discussing running a Focus Fusion device on DT, NOT boron and protium. I think the neutron count and radation would be considerable.

While running on Boron -protium, you are right, of course.

[delt0r]

Please read what i said. What does * shielding materials* have to do with fuel?

A break even DT or even better a burn with DT produces a lot of neutrons, probably well over 1J worth. You need to deal with them in a way that doesn’t produce secondary gammas or activation as much as possible. Typically this is borated concrete. Boron has a large neutron cross section. Boron salts can be added to water and the hydrogen is effective at moderating the 14MeV neutrons so that they get absorbed in shorter distances. You can run the numbers and you can get most of the neutrons absorbed by the boron (or Li ). Thus mittigating activation problems.

[Tulse]

Shielding would help with protecting the general area, but wouldn’t the actual FF device itself become radioactive? I think the main concern with doing D-T runs is practical — LPP only has enough financial resources for the one FF-1 device, and if they make it too hot to handle easily, that becomes problematic for them to work on further. (I also don’t know if such residual radiation would have any impact on the actual p-B11 reaction when they would move to that fuel.)

[delt0r]

As i said before, it can be minimized to the point of being manageable. If we are talking 100s of DT shots for a year and total T inventory needs to be large (aka 1g or so) then its a licencing nightmare, and activation is a serious problem (assuming you get burns). But if its much smaller and you don’t need to do so many shots, it really shouldn’t be a problem, at least not a big one. The radioactivity from a single shot would decay quickly (hours or so) But do tend to be gammas. Again its manageable.

If what you wanted to do was show breakeven or even burn with DT, then such a program does not need 100s of shots. And if done…. well i don’t think your going to have problems with grants again. At least for a while.

[Tulse]

Given what you’ve said, it certainly sounds like D-T radioactivity wouldn’t be an issue, and I agree that theoretical D-T breakeven would be a big achievement. But I’m not sure if it would necessarily bring in the funding bonanza, since as far as I know an FF device is unsuited to using D-T as a practical, power-generating fuel. At the very least, the current design is not set up to capture any reasonable amount of neutron energy for power production (I don’t know how easy it would be to reconfigure a basic FF design for such purpose.)

If I were a potential investor, I’d see D-T breakeven with FF as a neat trick, but that doesn’t really indicate if it can do the much harder p-B11 breakeven.

[delt0r]

I think you underestimate just how much of a big deal it would be. Especially in a small device. Real Nobel prize level of big. Currently there is no method of extracting energy. Its in the science phase. You don’t bother with collecting anything but diagnostics.

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