[Nuke]

even with both thorium and uranium fuel cycles you still cant breed forever. theres that pesky third law of thermodynamics.

[Dragon]

Well, but you can breed more than long enough to develop cheap hydrogen fusion alternatives. Hydrogen has one big advantage: Most of the Earth is covered with substance that has two atoms of it in each particle. And it has also enough Deuterium to support early fusion technologies long enough to get pure Hydrogen-Hydrogen plants up and running (IIRC, ITER and DEMO are both going to run on a slightly less efficient Deuterium-Tritium fusion).

[Herra Tohtori]

The result of proton-proton fusion is a diproton, or He-2, which is extremely unstable and thus this is not a viable fusion reaction.

In fact, there is no way you can use only individual protons as fusion fuel - you must have SOME neutrons in the mix. However if you have extra neutrons, they will end up producing neutron flux which will irradiate and activate the materials it hits.

If you use Tritium-Deuterium fuel cycle, you can line your reactor walls with Lithium-7 which will produce tritium under neutron bombardment; this would mean the reactor would replenish its tritium from its inner walls, which would have to be replaced from time to time. Regardless, neutron flux is not exactly ideal if you want to eliminate radioactive waste products.


There are two fusion reactions that produce no neutron flux (well, to be sure there are more but these two are the easiest to accomplish): Helium-3 - Deuterium reaction, and proton-boron reaction. Of these, the former is easier to accomplish (lower optimal energy level to initiate the fusion) but the fuel is sparse (Helium-3 is rare isotope on Earth), and the latter requires about 500 times more powerful confinement to run the fusion reaction at the required, high temperature, but the fuel is practically unlimited - hydrogen is plentiful, while boron is a reasonably abundant element. The Tritium-Deuterium reaction also offers about 2500 higher energy density than proton-boron reaction...

There is a third aneutronic reaction achievable with light elements: proton-Lithium-6 reaction, but its energy yield is rather pathetic.

[redsniper]

you still cant breed forever

Dekker can.

[Dragon]

The result of proton-proton fusion is a diproton, or He-2, which is extremely unstable and thus this is not a viable fusion reaction.

Sorry, you're right, I confused it with proton-proton cycle, which, while indeed the most energy efficient, is a whole different can of worms (it's what powers stars, and does involve deuterium as one of the stages). While a proton-proton fusion can and does occasionally produce deuterium (that's how the cycle can work), it mostly results in a rather useless and short lived He-2 (a good thing too, since if it produced deuterium more often, the sun would've fizzled out long ago). I'm not sure if this cycle could be replicated in a reactor in a way that would be good for something, but the answer is likely "no", given the unlikelihood of getting deuterium from a proton-proton reaction.

[Droid803]

If you want a proton-proton fusion plant you might as well just capture some red dwarf in a Dyson Sphere. Just sayin'.
That's about the smallest scale that it's known to work at.

(Helium-3 is rare isotope on Earth)

It's plentiful in SPAAAAAAACE though.

[Beskargam]

But we're not in space. also relevance




looking through my notes for what a Q is specifically defined as

EDIT: found it

1 Q = 10^21 Joules
1/2 Q per year = Total energy used for the world
1/10 Q per year = US total use per year

for perspective sun produces 100 Q/wk




this a bit late, but is response to any "but we're finding more oil"

[Nuke]

you still cant breed forever

Dekker can.

why did i know someone was going to say that

[Dragon]

If you want a proton-proton fusion plant you might as well just capture some red dwarf in a Dyson Sphere. Just sayin'.
That's about the smallest scale that it's known to work at.

While it's a great way to power an antimatter plant in science fiction, I doubt it's a viable solution to the current energy generation problems.

[Mikes]

you still cant breed forever

Dekker can.

why did i know someone was going to say that

Viable Power Source?

[Nuke]

hey dekker we want to implant some large magnets in your pecker. and we have a bunch of sluts wrapped in magnet wire. we want you to generate the power neccisary to run a small city.

[headdie]

hey dekker we want to implant some large magnets in your pecker. and we have a bunch of sluts wrapped in magnet wire. we want you to generate the power neccisary to run a small city.

Im sure with plenty of booze and takeaway all out problems would be solved

[jr2]

What's the deal with potential He3-He3 fusion?  Read about it somewherez.

[watsisname]

This seems like a relevant article for you.

In short, it has the benefit of giving out much less radiation, but the downside is it's more difficult / less efficient, because of the increased temperature requirement.  A better option might be D-3He fusion.  3He is also pretty rare on earth and would be best mined from the moon.

[666maslo666]

even with both thorium and uranium fuel cycles you still cant breed forever. theres that pesky third law of thermodynamics.

Indeed, but if burning the sea (seawater extraction) and burning the rocks (mining of fissionables from granite with positive EROEI) are viable, then we are talking about billions of years worth of energy. Nuclear could power humanity long after the Sun burns out.

[Dragon]

What's the deal with potential He3-He3 fusion?  Read about it somewherez.

In general, fusing He3 with anything is an expensive option. If we were to build a fusion powered lunar colony, then by all means, it'd be a great fuel, but on Earth it's a bit too rare. You're better off working with Deuterium.

[Nuke]

even with both thorium and uranium fuel cycles you still cant breed forever. theres that pesky third law of thermodynamics.

Indeed, but if burning the sea (seawater extraction) and burning the rocks (mining of fissionables from granite with positive EROEI) are viable, then we are talking about billions of years worth of energy. Nuclear could power humanity long after the Sun burns out.

i like to think of nuclear as an interim power source to cover us till we can get fusion off the ground. its coming, its just taking longer than we though. even then nuclear reactors, especially thorium cycle reactors will still have their place, probibly for space applications (depending on which works better in zero g). for now we should focus on can haz now technologies like lftr and hif.

[jr2]

This seems like a relevant article for you.

In short, it has the benefit of giving out much less radiation, but the downside is it's more difficult / less efficient, because of the increased temperature requirement.  A better option might be D-3He fusion.  3He is also pretty rare on earth and would be best mined from the moon.

What's the deal with potential He3-He3 fusion?  Read about it somewherez.

In general, fusing He3 with anything is an expensive option. If we were to build a fusion powered lunar colony, then by all means, it'd be a great fuel, but on Earth it's a bit too rare. You're better off working with Deuterium.

What I got from reading the article is, He3-He3 is awesome, if they can figure it out (no radiation, direct electrical production), however, they don't know how to contain it yet, and, we aren't going mining in spaaace anytime soon, so He3 fuel is a problem.  So, basically, He3-He3 would be a showstopper for other forms of energy production if it ever took off, which, it's not likely to in the near future.  Based on the potential, though, if we ever found an economical way to get into space...

[MP-Ryan]

this a bit late, but is response to any "but we're finding more oil"

Citations for images needed.

Data does not appear to include non-conventional shale gas reserves located in Canada (though the portion in the north-central US does appear to be listed) nor a complete representation of the bitumen located in the non-surface mined portions of the Athabascan oil sands to be recovered with SAGD, CSS, and future extraction methods to be devised.

Data also fails to account for the following:  oil price goes up - technology improves - previously uneconomical deposits become economical.  There are several millions of barrels of conventional oil stuck in Alberta alone (Turner Valley) which remain unextractable because they were not properly drilled when they were first exploited decades ago.  The trick isn't that there isn't enough oil/natural gas or even finding it, it's getting it out of the ground.

Anyone who says we're running out of petroleum in the next several decades is selling something.  Not to say we shouldn't be working toward alternative energy sources, just that the situation is nowhere near as dire as some source would have you believe.

[TwentyPercentCooler]

even with both thorium and uranium fuel cycles you still cant breed forever. theres that pesky third law of thermodynamics.

Indeed, but if burning the sea (seawater extraction) and burning the rocks (mining of fissionables from granite with positive EROEI) are viable, then we are talking about billions of years worth of energy. Nuclear could power humanity long after the Sun burns out.

Yeah, this is what I was getting at. There are no laws of thermodynamics being violated in breeder reactors - they're simply using some of their potential output to shift around some isotopes and "breed" new nuclear fuel. One of the first operational reactors was a breeder, it's certainly not new technology by any stretch of the imagination.

Liquid fluoride thorium reactors are probably one of my favorite designs. It was first proposed in the 1960s. So far, commercial plants haven't bothered with breeder reactors for the same reason we haven't bothered replacing fossil fuels - the people in charge are morons. "Uranium is cheap ENOUGH, let's just keep using it until it runs out, then we can panic and run around like a chicken with its head cut off."