
The Fusion Reactor Next Door - pinewurst
https://www.nytimes.com/2019/05/13/business/fusion-energy-climate-change.html
======
fareesh
Isn't there a new generation of nuclear reactors that promise to work
exceptionally well, without all the negative outcomes associated with the
earlier generations? Bill Gates has been advocating this technology of late.

From my limited reading it sounds like this does a pretty great job of solving
energy and climate to a large extent.

Why aren't more people excited about this? I feel like this can be a very
politically viable solution that pleases most of the clout wielding sides of
the political spectrum.

What am I missing?

~~~
ttul
Fusion power is in between the research stage and the commercial stage. It’s
tough to find investors who are willing to put their capital up for something
which has a good chance of _eventually_ succeeding, but where you have very
little confidence in how long it will take to succeed.

General Fusion - one of the first private fusion companies - has been going
for 12 years without revenue and might need another ten. That’s a long time
for venture capital.

~~~
chefkoch
>Fusion power is in between the research stage and the commercial stage.

The commercial stage ist decades away, there isn't even energy surplus
generated in research. No reactor can run longer than some miliseconds, i
think you are overly optimistic. Fusion is 20 years away since 50 years.

~~~
Symmetry
The story, for the last 40 years, has always been more "We'll have fusion in
20 years if you fund us" and as far as I can tell might have been true since
the funding asked for didn't arrive until ITER was finally funded and it
hasn't used up its 20 years yet. The big difference is that advances in
superconducting magnets that spun off from MRI research have reduced what
"fully funded" can mean, meaning smaller players are getting involved.

~~~
nick_kline
Humans aren't really capable of making 20 year plans to invent new
technologies and implement them on a schedule. We don't know enough about how
it works, we don't know what of many choices to make. What you can do is keep
working to improve it and hope you'll get something useful. But it's silly,
obviously not something you can do, to make such a large research project with
a 20 year goal and so many unknowns and say we will have it with high
likelihood.

Research has to work toward broad goals and investigate new areas. In 1900
could you have made a 20 year plan to invent cell phones and all the
technology needed for what we have today? No one would suggest that, but you
can invest in basic science and engineering and you'll get some useful things
along the way, radios, maybe repeaters, ever smaller ones and better
batteries. But you don't necessarily get a specific thing.

------
credit_guy
Top 4 reasons why nuclear fusion is an incredibly bad idea:

4\. The power density of the Sun is surprisingly low, it's about 276 W/m3 [1].
If we would ever be able to create fusion similar to the one that's happening
in the Sun, we'd need a few million m3 to get to the power generated by a
typical large power plant (1 GW). Imagine what type of containment vessel you
need to enclose a few million m3 of hot (100 million degrees) stuff. For
comparison, the largest oil tankers in the world can hold about 300,000 m3 of
oil.

3\. Even assuming we can build such a humongous fusion based power plant, what
happens if, you know, something goes unplanned? Anti-nuclear people point to
Chernobyl and Fukushima, what could happen with a fusion power plant? You
would not have radiation, that's true, but you would have an explosion that
would make the Tsar Bomba look like firecrackers. Why? All that hydrogen that
is supposed to undergo fusion needs to first be heated to about 100 MM
degrees. That's a lot of energy. How much? Here's very rough back of the
envelope: density of Sun = 1 kg/m3; let's say we are looking at 10 MM m3 of
hydrogen (we account for some power conversion inefficiency), that's 10
Megatons of hydrogen. At about 15 kJ/kg.K specific heat, it takes about 1.5
billion kj to heat one kg of hydrogen, or 1500 GJ. This is about 0.3 T TNT
equivalent [2]. Overall, about 3 Gigatons TNT equivalent. That's 60 times
larger than the largest nuke ever tried (the Tsar bomba mentioned before). Or
200,000 larger than the Hiroshima bomb.

2\. The accident discussed above assumes nothing goes really bad. It's simply
a rapid release of some thermal energy. But what if instead of this, we have
an accelerated fusion reaction? Then we have at hand many orders of magnitude
more fusion fuel than all the thermonuclear bombs ever build. I don't want to
do any calculations, but there's a chance that could be the end of the humans,
or maybe all multicellular life on earth. 1\. All this hope for clean nuclear
energy means a lot of people don't want to even consider practical solutions
for the fission-based nuclear energy, such as waste reprocessing or next
generation nuclear reactors (like Bill Gates's Terrapower). Why would they, if
clean nuclear energy is just around the corner? That kills what is probably
our most realistic tool to reduce carbon emissions.

[1] [https://physics.stackexchange.com/questions/370899/suns-
powe...](https://physics.stackexchange.com/questions/370899/suns-power-
density-compared-to-a-compost-heap) [2]
[https://en.wikipedia.org/wiki/TNT_equivalent](https://en.wikipedia.org/wiki/TNT_equivalent)

~~~
pdonis
_> The power density of the Sun is surprisingly low_

That's because the Sun is very different from an Earthbound fusion reactor. It
runs at a very different temperature and density, using very different
reactions. The analogy you are trying to draw is invalid.

 _> you would have an explosion that would make the Tsar Bomba look like
firecrackers_

No, you wouldn't, because only a very small amount of fuel is inside the
reactor at any given time. The inside of a fusion reactor is very different
from a nuclear bomb. The analogy you are trying to draw is invalid.

 _> what if instead of this, we have an accelerated fusion reaction?_

You can't. If anything goes wrong the injection of fuel into the reactor stops
and the reactor shuts down.

~~~
scottlocklin
> That's because the Sun is very different from an Earthbound fusion reactor.
> It runs at a very different temperature and density, using very different
> reactions. The analogy you are trying to draw is invalid.

No, the analogy he draws is the correct one: the sun actually works.
"Earthbound" controlled nuclear fusion doesn't in any meaningful way relating
to energy production. There's no reason physics should cooperate with us and
make it possible; "wouldn't it be nice" wishful thinking isn't good enough,
and the results thus far are all complete and total crap. It isn't that we
haven't spent enough: we simply don't know how to do this -there is no reason
to believe it is possible. All the results from inertial confinement,
tokomaks, fusors, whatever indicates we really don't know WTF we're doing.

His other concerns are legit as well. If you _can_ do controlled nuclear
fusion, you have a really, really scary weapon.

~~~
pdonis
_> the analogy he draws is the correct one: the sun actually works_

Under, as I said, very different conditions from those which Earthbound fusion
reactors are attempting. The only meaningful similarity between the two is
that both are fusion reactions. You certainly cannot use numbers for the Sun
to make any valid estimates about Earthbound fusion reactors, as the poster I
responded to was attempting to do.

 _> Earthbound" controlled nuclear fusion doesn't in any meaningful way
relating to energy production._

It hasn't yet, but that doesn't mean it never will. If it does, it certainly
will not be by reproducing conditions similar to those that produce fusion in
the Sun. And if your criticisms of fusion power turn out to be valid and it
never works, then everything the poster I responded to said is irrelevant
anyway, since he was assuming fusion power _would_ work.

 _> If you can do controlled nuclear fusion, you have a really, really scary
weapon._

No, you don't, because, as I said, only a very small amount of fuel is in the
reactor at any given time--enough for a few seconds' worth of energy
production. That equates to the energy equivalent of a few tons of TNT, not a
few megatons. And since the entire system is designed to remove that amount of
energy at that rate, concerns about even that few tons of TNT energy
equivalent "exploding" are invalid--that amount of fuel undergoing complete
fusion and liberating all that energy is what the reactor is _designed_ for,
not an abnormal condition. And, as I said, all you need to do to stop energy
production is stop injecting fuel, and the reactor shuts down.

Again, a fusion reactor is very different from a fusion bomb.

~~~
scottlocklin
Yes, "earthbound" fusion reactors are attempting very different conditions
from the sun: that's what I said. The sun is the only reason anyone thinks a
sustained, controlled fusion reaction is possible: there are no other
examples, and the idea that we can do arbitrary (and high) energy densities of
sustainable controlled fusion is wishful thinking. All the results thus far
are that we don't know how to do this. Nature may prevent it completely.

If we do figure out how to do this, _of course_ the possibility of a
controlled fusion reactor can be used as an absurdly powerful weapon. You've
basically invented something that can make gigawatts of energy appear in a
small volume. Sure, a power-generating fusion reactor won't make as big a mess
as a fission reactor if there is a fault. That's not the point. If you know
how to do this, you can design a system where you can open a hole in one end
and point it at things you don't like. And people most certainly will do this
if they can. Making the non-proliferation aspects of such a postulated
technology absurd. Imagine you could build a NIF type device that actually was
sustainable, and you could fit into a truck. Just the neutron flux from the
thing would be absurdly murderous, and even using NIF figures (~200MJ), being
able to direct the energy of some fraction of a ton of TNT worth of energy at
things you don't like, fueled by a tiny amount of hydrogen seems pretty
dangerous to me.

~~~
pdonis
_> The sun is the only reason anyone thinks a sustained, controlled fusion
reaction is possible_

No, it isn't. We think it's possible because we have extensive experimental
data on fusion reactions from Earthbound experiments. From those experiments
we know a wide range of possible conditions that can produce sustained,
controlled fusion. The conditions inside the Sun are only a very narrow part
of that range.

 _> You've basically invented something that can make gigawatts of energy
appear in a small volume._

You do realize that _any_ power plant that is making gigawatts of energy has
the same amount of fuel energy content inside it as a fusion reactor, right? A
coal plant that is making a gigawatt of energy has a ton or so of TNT's worth
of fuel energy inside it at any given time, just like a fusion reactor. There
is no difference between them in terms of weapon potential. It's true that the
amount of fusion fuel needed to make a ton or so of TNT's worth of energy
occupies a much smaller volume than the amount of coal or oil or natural gas
needed to make that amount of energy, but so what? It's the energy content
that matters, not the volume.

 _> Imagine you could build a NIF type device that actually was sustainable,
and you could fit into a truck._

That means you're building a laser capable of short pulses of gigawatts of
power that can fit into a truck. If you can build that, you don't need to
include a pellet of fusion fuel with it to make it a weapon.

Also, nobody is talking about building gigawatt fusion reactors that can fit
into trucks. They're large facilities, just like other power plants.

 _> being able to direct the energy of some fraction of a ton of TNT worth of
energy at things you don't like_

We already have weapons that can do this, and are much cheaper than building a
fusion reactor with a hole in the side of it would be. They're called
missiles.

~~~
scottlocklin
>No, it isn't. We think it's possible because we have extensive experimental
data on fusion reactions from Earthbound experiments. From those experiments
we know a wide range of possible conditions that can produce sustained,
controlled fusion.

There is zero evidence sustained, controlled, above break-even fusion works at
the types of energy densities people talk about for power plants. None; keine,
zero, zilch: there is arguably as much evidence for this as the existence of
ghosts or leprechauns. The models don't work! I ain't saying we shouldn't try,
but there are by now reasonable arguments to be made that it's a big waste of
time and money better spent on something boring that we know will work, like
thorium.

To make another technological analogy from nature: if the earth's
gravitational potential well were larger, we wouldn't have been able to
achieve orbit using chemical rockets. The specific impulse of fuels which
exist in the periodic table of the elements would have been insufficient to
achieve this. For example:
[https://arxiv.org/abs/1804.04727](https://arxiv.org/abs/1804.04727)
-similarly, the properties of plasmas may make it impossible to achieve
controlled, above break-even nuclear fusion in a conveniently small and dense
volume. There is at present no evidence that it can be achieved. They've been
working on it for 65 or 70 years now depending on how you count things, you'd
think there would be some positive indications by now beyond optimistic press
releases.

As for your wishful thinking that a controlled nuclear fusion technology
_couldn 't_ be used as a weapon, well, there you go again with that wishful
thinking. Controlled fusion is a non-proliferation nightmare. Should this
actually come to pass and become routine enough to be a meaningful part of the
power grid, it will be a hell of a lot easier to build a fusion howitzer than
an ICBM with H bomb at the business end of it.

I mean, you're a nuclear physicist, man!

~~~
pdonis
_> There is zero evidence sustained, controlled, above break-even fusion works
at the types of energy densities people talk about for power plants._

This is just another way of saying we haven't gotten it to work yet. That's
true, we haven't. The same could have been said about controlled fission in
1941.

 _> there are by now reasonable arguments to be made that it's a big waste of
time and money better spent on something boring that we know will work, like
thorium._

I agree there are reasonable arguments to be made about this. But comparing
controlled fusion to ghosts and leprechauns is not one of them.

 _> it will be a hell of a lot easier to build a fusion howitzer_

I have no idea where you're getting this from. Again, I really don't think
you've grasped the implications of the fact that the energy content of the
fuel inside a reactor producing, say, a gigawatt of power, is _the same_
whether the reactor is fueled by coal, oil, natural gas, or fusion. So a
"fusion howitzer" based on a fusion reactor would have no more explosive power
than a chemical explosive howitzer (which is not based on a coal, oil, or
natural gas plant anyway, it's a very different thing).

Nuclear fission is a unique case here because of the historical accident of
fission power developing in such a way that multiple years' worth of fuel,
containing orders of magnitude more stored energy than was being burned at any
given time, was all inside the reactor core at once, instead of the reactor
having fuel continually injected just in time to be burned, like every other
kind of reactor. All of the downsides of fission--the possibility of meltdown,
decay heat removal, huge spent fuel pools containing lots of long-lived
radioisotopes, even an accident like Chernobyl--are due to this unique
attribute. Newer designs like pebble bed reactors have shown that this is not
a necessary attribute of fission power. But it won't be an attribute of fusion
power at all.

~~~
scottlocklin
People claim to have seen ghosts and leprechauns. Nobody's claiming to have
seen break even. Only "if you give me enough money you'll see it." Which one
could say about ghosts and leprechauns also.

The difference between the energy content of a coal reactor and a hypothetical
fusion reactor: you can store a lot more gigawatts in the back of a pickup
truck for one of them, and that is the one that makes enough neutrons to
sterilize a city block when you burn them up. I mean, how many pounds of
fusion fuel does it take to level a city?

~~~
pdonis
_> Nobody's claiming to have seen break even._

Huh? That milestone was reached some years ago.

[https://www.livescience.com/43318-fusion-energy-reaches-
mile...](https://www.livescience.com/43318-fusion-energy-reaches-
milestone.html)

What has not yet been achieved is ignition--a self-sustaining reaction that
does not require continuous energy input.

 _> how many pounds of fusion fuel does it take to level a city?_

We already know how to make a fusion reaction that will level a city. Having a
working controlled fusion reactor would not affect our capability to level
cities. So I really don't understand why you keep harping on this.

~~~
scottlocklin
Because you can put the energy required to level a city in the back of a
pickup truck, then level a city with it using the same technology has a
hypothetical fusion reactor possible, that's why. I don't know why you _can
't_ see the destructive potential of a project Daedelus with the business end
aimed at Los Angeles.

The NIF result created 35000 neutrons, and you should know that press release
is the functional definition of a _scientific fraud_ -I wrote a couple of
articles on it which you can go find if you care about fraud.

~~~
pdonis
_> Because you can put the energy required to level a city in the back of a
pickup truck_

Yes, we can already do this, it's called a fusion bomb.

 _> then level a city with it using the same technology has a hypothetical
fusion reactor possible_

No, a bomb is not the same as a fusion reactor. A bomb burns a megaton of
TNT's worth of fusion fuel all at once. A fusion reactor outputting a gigawatt
of power burns the same amount of fuel in about a year. It's not at all the
same thing.

------
strainer
The "near limitless energy" claim of articles like these is very deceptive.
The true destination is perpetual _heat_ generation, which is low grade energy
and a potential pollutant on this planet.

The only thing we can do with such amounts of heat to produce the kind of
energy we need and consume is build thermo-electric power plants to generate
electricity. Here is the crunch:

> Thermoelectric power use has a significant impact on water resources and the
> power sector is highly dependent on these water resources; the United States
> Geological Survey (USGS) estimated on a national level that _41% of all
> freshwater withdrawals in the United States in 2005 were for thermoelectric
> power operations_ , primarily for cooling needs.[1]

[1] Operational water consumption and withdrawal factors for electricity
generating technologies -
[https://iopscience.iop.org/article/10.1088/1748-9326/7/4/045...](https://iopscience.iop.org/article/10.1088/1748-9326/7/4/045802/meta)

~~~
mrob
Heat pollution is a very minor concern. From "Sustainable Energy – without the
hot air" by David MacKay, pages 170 to 171:

"let’s assume that in 100 years or so, the world population is 10 billion, and
everyone is living at a European standard of living, using 125 kWh per day
derived from fossil sources, from nuclear power, or from mined geothermal
power. The area of the earth per person would be 51 000 m^2. Dividing the
power per person by the area per person, we find that the extra power
contributed by human energy use would be 0.1 W/m^2. That’s one fortieth of the
4 W/m^2 that we’re currently fretting about, and a little smaller than the
0.25 W/m^2 effect of solar variations. So yes, under these assumptions, human
power production would /just/ show up as a contributor to global climate
change."

[http://www.withouthotair.com/c24/page_170.shtml](http://www.withouthotair.com/c24/page_170.shtml)

~~~
epistasis
That's assuming that we use the same order of magnitude of energy.

If the promise of a technology is that we can use several orders of magnitude
more energy per person, then that .1W/m2 could become 10W/m2.

If we don't increase energy usage, sure, no big deal, but the entire point of
pursuing fusion is to enable fantastically more energy usage, at least as I
see it.

So we also need a second revolutionary technology, direct conversion of energy
rather than thermal energy conversion.

Fusion will never be a cost winner if it's using thermal energy conversion,
anyway. Solar and wind will soon undercut the steam turbine lifetime costs, so
even if the fusion part were free, there's no way for heat engines to compete
on cost.

~~~
llukas
> If the promise of a technology is that we can use several orders of
> magnitude more energy per person, then that .1W/m2 could become 10W/m2.

Depending on what type of energy you exactly have in mind.

It is totally possible to increase consumption of iee. electric energy and
reduce overall energy needs. We burn most of the fuels and use them very
inefficiently:

[https://en.wikipedia.org/wiki/Primary_energy](https://en.wikipedia.org/wiki/Primary_energy)

In short: you need to burn coal with 3x as much energy to generate 1x of
electricity. So when you switch from coal to nuclear (or renewable) and
increase 2x your energy usage you still come up ahead in total primary energy
consumption.

~~~
pdonis
This comparison isn't valid for nuclear; nuclear power plants use steam
turbines to convert heat to electricity, just like coal plants do, and the
thermal efficiency (fraction of energy from burning the fuel that actually
becomes electrical energy) is about the same.

~~~
llukas
OK, I double checked and you're right. Nuclear is counted properly difference
is only for renewables:

[https://energypost.eu/iea-underreports-contribution-solar-
wi...](https://energypost.eu/iea-underreports-contribution-solar-wind-factor-
three-compared-fossil-fuels/)

