How close are we to powering the world with nuclear fusion? - George Zaidan
In the time it takes to snap your fingers,
the Sun releases enough energy to power
our entire civilization for 4,500 years.
So naturally, scientists and engineers
have been working to build
a miniature star here on Earth...
to plug into our power grid.
And the thing is, we already kind of have.
It just doesn’t look like a tiny star
floating in a lab.
The stars are made of an almost
incomprehensible number of particles,
which gravity compresses
into a super dense core.
This core is hot and dense enough
to force atomic nuclei together,
forming larger, heavier nuclei
in a process known as fusion.
The reverse process, where one atom
splits into two, is called fission.
In both processes, the mass of the end
products is slightly less
than the mass of the initial atoms.
But that lost mass doesn’t disappear—
it’s converted to energy according
to Einstein’s famous equation.
And since c² is such
a massive number,
both fission and fusion
generate a lot of energy.
Fusion in our Sun mostly
produces helium nuclei.
In the most common pathway, two protons
fuse to form a deuterium nucleus,
which then fuses with another proton
to form a helium-3 nucleus,
which then fuses with another helium-3
nucleus to form a helium-4 nucleus.
But there’s a catch—
that first step is incredibly rare.
Only 1 in 100 septillion collisions
between protons
results in a deuterium nucleus.
In the Sun this isn’t a problem
because there are so many protons
that even a reaction this rare
happens all the time.
But on Earth, researchers rely
on a more easily reproducible reaction,
where a deuterium nucleus fuses
with a tritium nucleus
to form a helium-4 nucleus and a neutron.
We’ve actually been doing reactions
like this one inside particle accelerators
since the 1930s.
But these accelerators are not designed to
harness the energy this reaction releases.
Rather, they’re used to generate neutrons
for a variety of scientific
and military purposes.
Whereas if we want to use fusion
to produce limitless energy,
we’d need a device that can
harness the energy released,
channel enough of that energy back into
the device to keep the reaction going,
and then send the rest
out to our power grid.
And for that job,
we need a nuclear fusion reactor.
Like a particle accelerator, a reactor
would generate helium nuclei and neutrons.
But that reaction would happen
in a superhot core
and the resulting neutrons
would shoot outward
to heat up a layer of lithium metal.
That heat would then boil water,
generating steam to run turbines
and produce electricity.
Meanwhile, the helium nuclei
would stay in the core
and slam into other nuclei
to keep the reaction going—
and the electricity flowing.
This tech has many practical challenges,
including how to confine a swirling
mass of million-degree matter.
But the biggest hurdle is achieving
what's called ignition.
An energy technology is only
commercially viable
if it puts out more energy than it uses.
And a fusion reactor needs a lot of energy
to get the core hot enough
for fusion to occur.
So there’s a tipping point:
a moment when the fuel is hot
enough to start the reaction
and release more energy than is needed
to reach and maintain that temperature.
This is ignition.
Stars reach ignition under the force
of huge amounts of gravity,
but this approach is impossible on Earth
since you’d need thousands of times
the mass of, well, the entire Earth.
So researchers typically rely
on vast arrays of lasers,
or methods that combine magnets
with high energy particles
or electromagnetic waves similar
to those in your microwave oven.
In 2022, scientists at the
US National Ignition Facility
demonstrated ignition
for the first time ever,
using 192 lasers to heat deuterium
and tritium to 100 million degrees.
While this was a huge step forward,
we’re still a ways off from a
self-sustaining, long-running reactor
that produces more energy than it uses.
But once operational, these relatively
small reactors could power a city
of a million people for a year
with just two pickup trucks of fuel.
Today, you’d have to burn
roughly 3 million tons of coal
to produce that much energy.
That is the promise of fusion:
limitless, on-demand energy
with almost no emissions.
True star power, right here on Earth.
