And a little bit of $ for ITER

TallDave · Post by **TallDave** » Mon Sep 21, 2009 2:27 pm

Yes there are: transmuting long lived nuclear waste.

Oh goody. We've done ~$100B research to replace the shovel.

Anwyays, the goal is economic power production.

There's already a start up company looking into this application.

It's just a PowerPoint slide. Anyways, FRCs are looking at the same thing.

Tokamaks are the best performing fusion devices to date.

Again, it's easy to be the best at something when you have orders of magnitude more resources. This should not be regarded as an endorsement of the technology path.

There was a time when steam engines were the best performing engines.

You want to divert funding away from something that does work and spend it on something that doesn't work with no proof it will?

Tokamaks don't "work" in any commercial sense of the word. They're just nice science projects with no economic value.

A better question: why waste even more money on a path that we know, after $100B, cannot lead to economic fusion power, when alternatives exist that can be researched at a fraction of the cost?

In anycase 100B over 50 years to research a limitless source of infinite energy is not too bad.

We already have one that's practically limitless: fission. That will last at least a thousand years. Tokamak fusion is too expensive to compete. If we can't find something better in 500 years, maybe we can dust off those ITER plans.

There's nothing wrong with that but don't try to make out its any different or better than tokamaks.

It is different. It's high beta. That has implications for the size, which has implications for the cost, which has implications for the commercialization.

93143 · Post by **93143** » Mon Sep 21, 2009 2:43 pm

TallDave wrote:Tokamaks don't "work" in any commercial sense of the word. They're just nice science projects with no economic value.

...so what's wrong with the fission/fusion hybrid again? Tokamaks are awesome neutron sources, and they don't need to be huge monstrosities for this application.

TallDave · Post by **TallDave** » Mon Sep 21, 2009 2:45 pm

93143 wrote:
TallDave wrote:Tokamaks don't "work" in any commercial sense of the word. They're just nice science projects with no economic value.
...so what's wrong with the fission/fusion hybrid again? Tokamaks are awesome neutron sources, and they don't need to be huge monstrosities for this application.

Economics. Why build a hybrid when straight fission is cheaper?

I haven't seen anything suggesting these are economically competitive, but if there is point me toward it.

I wouldn't mind seeing one built anyway. It's a neat science project.

Anyways, my point is not to bash tokamaks gratuitously. I just find the claims of superiority as a path to economic power to be on shaky ground, given what we know.

chrismb · Post by **chrismb** » Mon Sep 21, 2009 4:12 pm

TallDave wrote: Why build a hybrid when straight fission is cheaper?

Availability of the fuel. With a hybrid design you do not need outright fissile material. In particular, thorium will do. About 4 times as abundant as uranium.

A good pre-processing scheme, or fast-breeder reactor, would be great and save on the uranium for sure. I've no issue with not worrying too much about fusion yet whilst fission is so successful - why d'you think the politicos aren't too worried either? But some time will come in mankind's history that fusion will become required, or we will no longer be a techological species. Maybe 1Ma, maybe a millenium, maybe a hundred year, but sometime it will be essential that we crack it.

D Tibbets · Post by **D Tibbets** » Mon Sep 21, 2009 4:29 pm

93143 wrote:
TallDave wrote:Tokamaks don't "work" in any commercial sense of the word. They're just nice science projects with no economic value.
...so what's wrong with the fission/fusion hybrid again? Tokamaks are awesome neutron sources, and they don't need to be huge monstrosities for this application.

One problem with Tokamaks for fusion- fission hybirds is that thay can only operate wityh tritium so nearly all D-T fusion produced neutrons need to be used to produce new tritium (depending on the efficiency of the lithium blanket and the tritium amplifier system (lead, beryllium, etc.)) and would not be aviable for driving fission. Perhaps the D-T neutrons can be dedicated to driving the fission reactions, and the fision reactions would produce enough neutrons to make the replacement tritium, though I suspect this would negate some, if not most of the control/ safty advantages. Perhaps it could be engeenered to work with thorium, otherwise it might be only a more expensive option than conventional or breeder fision reactors

Dan Tibbets

MSimon · Post by **MSimon** » Mon Sep 21, 2009 8:50 pm

D Tibbets wrote:
93143 wrote:
TallDave wrote:Tokamaks don't "work" in any commercial sense of the word. They're just nice science projects with no economic value.
...so what's wrong with the fission/fusion hybrid again? Tokamaks are awesome neutron sources, and they don't need to be huge monstrosities for this application.

One problem with Tokamaks for fusion- fission hybirds is that thay can only operate wityh tritium so nearly all D-T fusion produced neutrons need to be used to produce new tritium (depending on the efficiency of the tritium amplifier system (lead, buryllium, etc.)) and would not be aviable for driving fission. Perhaps the D-T neutrons can be dedicated to driving the fission reactions, and the fision reactions would produce enough neutrons to make the replacement tritium, though I suspect this would negate some, if not most of the control/ safty advantages. Perhaps it could be engeenered to work with thorium, otherwise it might be only a more expensive option than conventional or breeder fision reactors

Dan Tibbets

Excellent point. BTW it is an honor to be in such august company. chris included. And every one else who comments.

I'm always reminded of angles I hadn't considered.

Or as Eric Raymond says: All bugs are shallow wit enough eyeballs.

jmc · Post by **jmc** » Tue Sep 22, 2009 2:46 pm

Talldave:

At present Tokamaks don't have high beta, but there's no reason to believe that will not change in the future. Tokamak technology is just as capable of evolving as anything else.

Regarding steam engines at the time diesel engines were developed there were plenty of other wack job ideas that had no chance of success around. Your looking at this from the benefit of hindsight. The way you do research is you give those champoning concepts that have high risk high payoff just enough money to demonstrate the validity of their claims and if they can, then you pour in more. Polywells are behind tokamaks, both concepts are capable of developing further but until Polywells produce more neutrons they'll simply be given enough funding to stay alive to demonstrate the proof of principle of their operation.

Regarding hybrids:

I've spoken to people who design the blankets who state that even without fissile fuels you can get a tritium breeding factor of 2. It's just noboby wants this factor because tritium is highly toxic and radioactive so you only want to produce as much as you need.

With fissile fuel producing extra neutrons breeding tritium would be child's play.

Art Carlson · Post by **Art Carlson** » Tue Sep 22, 2009 4:13 pm

jmc wrote:I've spoken to people who design the blankets who state that even without fissile fuels you can get a tritium breeding factor of 2. It's just noboby wants this factor because tritium is highly toxic and radioactive so you only want to produce as much as you need.

I can only imagine getting such a generous breeding ratio by using massive neutron multipliers. Beryllium? Lead? Uranium?!

jmc · Post by **jmc** » Wed Sep 23, 2009 4:21 pm

Berylium and lead I believe