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Comment by theantidote | Hacker News Reader

Here is the treehugger side of me, not the pragmatic side: where do we dispose of the waste? At the end of the day there's still waste created.

Here's some pragmatism: Why spend any money investing in a new short term solution when we could spend the same amount on renewable energy that never runs out such as wind, solar, tidal and for the most part hydrogen? In another few hundred years we will start running low on uranium (edit: Wikipedia says it can be reprocessed and used an estimated thousands of years). I think if we're going to transition from oil and coal we shouldn't just go to a new stop-gap solution. The next energy source needs to be renewable so we never run into the same problem again.

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A 'properly designed' DT fusion reactor creates much less waste than an equivalently powered nuclear reactor, and moreover, the waste doesn't last as long: with a half life of a dozen years, not thousands. This means that you can store the waste just about anywhere where the higher isotopes of the surrounding material are stable, and keep it there for a hundred years, and cycle it out. Since there's not much waste, and you don't need to keep it contained effectively 'forever', there's not much storage that one needs in order to power the world at a steady state.

Of course, the problem is what form a 'properly designed' DT reactor would take. This involves a materials problem that hasn't yet been solved: how to maintain structural integrity under massive magnetic and temperature stresses, while keeping enough lithium around to breed tritium out of outgoing neutrons. Not easy.

There are other forms of fusion, so called 'aneutronic' fusion, that would avoid these materials and waste problems almost entirely, but in exchange for a much harder plasma physics problem. Bussard, the one talking in the video, believed that the Polywell might be able to achieve aneutronic fusion, between protons and boron-11. This is generally regarded as difficult; if the electrons and ions thermalize, they'll lose energy faster than the fusion could create it. The Polywell could conceivably avoid this though (I worked on a similar project in aneutronic fusion while I was at Princeton).

There are two main technical reasons fusion power is still being pursued: it remains a possibility that it's cheaper at ultrahigh capacities (many GW) than coal or solar or wind (we don't really know, but it is in fact quite a possibility), and it's portable, meaning it could be used on submarines and ships (Bussard had funding from the US Navy, for example) and spacecraft.

The third, of course, is that academic and engineering disciplines, and especially those federal funded, have astonishing momentum. :-)

Thousands of years from now, we will be far more technologically advanced. When we run out of uranium, it will be orders of magnitude simpler to develop alternatives on the off chance that we haven't yet. I don't think finiteness of nuclear is a practical concern. When our energy needs exceed what our Dyson sphere can provide, we'll need an alternative to solar as well.

As for the waste issue... shoot it into the sun? I don't know what the tradeoffs are between renewables and nuclear, but if nuclear is far more feasible at the moment as I suspect, it seems pretty reasonable to go for it. I'm pretty sure we'll have a good solution to the waste issue within the next century or two.

(tl;dw, so I don't know if the video mentions any of this.)

"As for the waste issue... shoot it into the sun?"

Ah, if the rocket explodes, which does happen, waste everywhere!

Also, strangely, it takes quite a lot of energy to get to the sun (you might think one could just 'fall into it', but you have to fight against the earth's orbital velocity!)

This is exactly why they don't put the fate of humanity in my hands.

Finding a way to deal with nuclear waste just doesn't seem like an insurmountable problem to me. In the meantime, reprocessing the waste and storing the remaining waste somewhere safe seems like a prudent enough plan. If we can't find a way to get rid of it by the time we start running out of space, we stop using nuclear energy. We'll be far better prepared to switch over to solar et al at that point, assuming that nuclear is currently significantly more cost-effective than the alternatives.

Waste disposal is a much smaller problem than people think. It's really not that much waste - you can store the waste of every plant ever made in the space that a single large coal mine and tailings takes.

I think the personal lifetime waste size for each person was something like a cup - we can find space for that somewhere on this very large earth.

Plus if you allow nuclear reprocessing, you can burn the fuel almost to nothing at all.

Right now renewable energy will not going to work. It's not enough, and it's not consistent enough. The only source with enough energy is sun, but that would require massive amounts of land use - I'd rather use a millionth of a percent of that land to store some nuclear waste.

On top of that storing the energy for use at night is problematic.

Except for sun, renewable will never be enough - there just isn't enough energy. And sun has it's own problems: it can be done if you use enough land (like all of texas), but that's not practical. You can put collectors on each roof, but that doesn't work, because right now they use almost as much energy to make as they produce over a reasonable time.

Today renewable is not going to work, and it probably never will. Don't wait for them, there are very large problems that will almost certainly make it impossible to supply energy solely with renewables.

The solution is this: nuclear for now. When materials science improves enough to put in a space tether you put in a collector in orbit and send power down the tether.

Sun power from space is the future, but without a tether it's too dangerous to send the power to earth.

Right now it's nuclear is the only realistic power source.

And besides, if we can be OK for right now, fusion power might eventually work.

You mentioned hydrogen. Hydrogen is a joke, it is totally unsuitable as a fuel. It's all but impossible to store. People have mostly given up on it, and if they didn't they should.

Hydrogen will leak out of just about any container ever made, and if it doesn't leak it will react with the material and damage it.

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