The key to carbon neutrality is the massive
electrification of our way of life. This means powering not just our homes and
cars but every sector of the world economy with carbon-free electricity. But there’s a problem. You see, not all sectors of our economy CAN
be electrified, and in those cases, we usually need to burn fuel to produce thermal energy. This calls for clean, carbon-free fuel to
burn but, where do we find it? For Japan, the answer is hydrogen. But not just any hydrogen… Red Hydrogen produced with nuclear energy. I’m Ricky, and this is Two Bit da Vinci. When you think of Japan and nuclear power,
I’ll wager that hydrogen isn’t the next thing to pop into your head. Yet Japan is a world leader both in hydrogen
technology and nuclear energy production, and recently they tied both expertise together
in a technological breakthrough that has been decades in the making. Japan has been one of the strongest proponents
of hydrogen adoption in the international scene, working to create hydrogen supply chains
and developing the hydrogen fuel cell electric vehicle industry. They house the world’s largest green hydrogen
plant, the Fukushima Hydrogen Energy Research Field (FH2R) [1]. However, clean hydrogen produced from renewable
sources is very expensive and unlikely to be a cost-effective alternative in the next
several decades, so Japan’s energy policy regarding hydrogen seems somewhat like a gamble
[2]. Even Elon Musk once joked that hydrogen-powered
vehicles ran on fools’ cells… instead of fuel cells… get it? Regardless, “...establishing elemental technologies
for hydrogen production…” is still one of Japan’s core Green Growth Strategies
to reach carbon neutrality by 2050, something the government confirmed just last year. Now… we’ve covered hydrogen before on
this channel (links in the description), so I won’t go too deep into the pros and cons
here, but hydrogen has plenty going for it. After nuclear energy, hydrogen has the highest
specific energy density of any known fuel, packing 33.3 kWh/kg, which is three times
more punch in the same amount of mass as the best fossil fuels. Additionally, we can burn hydrogen to generate
heat and use a fuel cell to generate electricity, in both cases releasing nothing more than
water vapor, so it’s carbon-free. On the flip side, being a gas, hydrogen has
very poor volumetric energy density, so we have to compress it at very high pressures
to make it practical. This brings all sorts of problems that go
from storage and transportation to safety issues, none of which are trivial, and which
have helped make batteries and not hydrogen, the key technology for the EV industry. But why does Japan seem so hell-bent on pursuing
hydrogen, and how does this affect you and me? The main reason is that Japan is a very small
island with few resources but with a big appetite for energy. This makes energy security a BIG DEAL in Japan,
especially after the oil crisis of the 70s. So, they’ve been pushing hydrogen technology
as a more sustainable and reliable option ever since. They also turned to nuclear energy, by the
way! In fact, nuclear energy is at the core of today’s topic, and
not because of what you’re probably thinking. But we’ll get back to that in a minute. [Ad Break] The second and equally important reason is
that many heavy industries like steel, heavy transportation, the chemical industry, and
even in the aerospace industry CAN NOT run on electricity alone and require burning some
form of fuel, where hydrogen is the perfect replacement for fossil fuels. This makes hydrogen imperative to reach our
global carbon neutrality goals. Take steel making, for example, which accounts
for roughly 8-9% of our total worldwide greenhouse gas emissions [3]. A Swedish company called H2GS, as in hydrogen
green steel, will use hydrogen instead of coal to produce steel and is set to start
operations in 2024, producing five million tons of high-quality steel per year with 95%
fewer carbon emissions than traditional steel mills [4]. Additionally, if used in the heavy transportation
sectors, hydrogen could help cut down as much as 13-14% of our total carbon emissions [5,6]. Image Source [6] Image Source [5]
So, clean hydrogen could help us cut down almost a quarter of the world’s emissions,
which is a huge step forward toward carbon neutrality. But There’s a catch. Notice how I said “clean” hydrogen and
not simply hydrogen? The problem is that, though hydrogen itself
burns cleanly, hydrogen is only as clean as the energy and processes we use to make it. And the sad truth is that 90% of the world’s
hydrogen, including the one Japan, mostly uses is made by burning fossil fuels. As it turns out, even if we captured those
emissions, producing what we call blue hydrogen, this hydrogen’s carbon footprint is actually
worse than just burning fossil fuels, to begin with [7]. So, how can Japan use dirty hydrogen and then
have the nerve to say that it’s all with the aim to decarbonize by 2050? As you may have already guessed, there’s
still more to unpack. In essence, Japan needs a stable hydrogen
supply chain to keep its hydrogen industry growing until they find an economically viable
alternative. And that they did! Ok, so, the first thing that comes to mind
when putting Japan and nuclear energy together is the nuclear disaster at Fukushima Daiichi
Nuclear Power Plant. The disaster caused the meltdown and explosion
of the reactor, releasing tons of radioactive material into the atmosphere, displacing hundreds
of thousands of Japanese residents, and unleashing a worldwide anti-nuclear energy movement. The aftermath affected all of us. In the United States, nuclear has been declining
ever since, with 26 of the 96 operational nuclear reactors either scheduled to or already
being decommissioned and only two reactors currently under construction. Japan closed down all its nuclear reactors
and was forced to go back to coal and oil to cover the energy gap. Image Source [8]
However, the energy crisis caused by the war in Ukraine caused oil and gas prices to skyrocket,
making the Japanese reconsider, and now, nuclear is making a big comeback in Japan thanks to
a cutting-edge nuclear reactor called the High-Temperature Gas-Cooled Reactor or HTGR
for short, and the implications are huge! We’ve been testing HTGRs since 1964, but
only as small-scale experimental reactors or pilot plants. Image Source [9] Yet HTGRs are “almost” the holy grail
of nuclear energy. They could prove to be the solution to cut
down a significant portion of our carbon emissions and make hydrogen a real game-changer that
could rival lithium-ion in some market segments. But what exactly is a High-Temperature Gas-cooled
Nuclear Reactor and how is it different from all the others we have today? To answer that, let’s put our engineering
hats on and do a nose dive into the nuclear reactor… well, not literally, but… you know what
I mean. Nuclear energy is pretty straightforward. All current reactors use fission energy from
the breakup of heavy atoms like uranium or plutonium to generate heat. We use that heat directly or we use it to
boil water and drive steam turbines and generate electricity. This reaction needs a neutron to start but
releases three other neutrons, which leads to a sustained chain reaction that constantly
produces heat and power. It’s crazy hard to maintain and control
this chain reaction without it running away and blowing to smithereens. The big problem is heat, so we need to drain
it out as fast as possible to avoid the core from melting. The vast majority of the 440 operational reactors
worldwide are light water reactors that use liquid water as coolant. But in the case of the HTGR, the coolant isn’t
water, it’s a gas! A gas? As in, air-cooled? Now that I think about it, the HTGR is the
VW Beatle of nuclear power plants! Anyway, using gas as the coolant has many
challenges because gases have very low thermal conductivities (in the range of 0.01 to 0.03
W/m.K at room temperature) [10] an order of magnitude lower than liquid water’s (0.598
W/m.K), and also low specific heats. For example, air has a specific heat of only
1.005 J/g.K, which is a fourth of liquid water’s 4.186 J/g.K. This means that gases absorb heat at a slower
rate than water, and can hold less heat for the same temperature difference, making them
less effective as coolants in general. But Japan’s new HTGR reactor isn’t cooled
by air. They chose helium, which has an unusually
large thermal conductivity of 0.15 W/m.K [10] and a specific heat at room temperature that
is actually greater than water’s. While still not as good as water at cooling
the core, using helium has other more important advantages: We can heat helium to much higher temperatures
than liquid water and since it’s an inert gas, it won’t corrode the piping. This allows us to operate the nuclear reactor
at over 1,800 °F (approx. 1,000 °C) compared to light water reactors that barely reach
600 °F (315 °C). This temperature opens a world of opportunities
in terms of what we could use HTGRs for, besides generating electricity, including many heavy
industries. Image Source [11]
With adequate coupling technology, we could use this heat directly to power heavy industrial
processes like iron making, oil refining, and even the petrochemical industry. In comes hydrogen
So, to summarize, HTGRs are amazing. But what does this all have to do with hydrogen? The answer is EVERYTHING! Notice that several of the potential applications
of HTGR heat have to do with hydrogen production. In the first place, HTGR heat is enough to
drive the steam reforming process used to make hydrogen from methane and other components
of natural gas. This means we can use HTGR heat to produce
hydrogen without burning fossil fuels. However, because gas reforming still produces
carbon monoxide and dioxide as by-products of the chemical reactions, hydrogen’s carbon
footprint is only reduced by about 40% [9]. But there are two other hydrogen production
technologies that require high temperatures but that don’t generate any carbon emissions
at all, making the resulting hydrogen completely clean. Those are high-temperature steam electrolysis
(HTSE) and thermo-chemical cycles like the thermochemical water-splitting iodine-sulfur
(IS) process. This is exactly where Japan’s potentially
genius plan comes in. They’re the first in the world to attempt
coupling an operational HTGR called Hight-Temperature Engineering Test Reactor or HTTR, with a thermochemical
cycle hydrogen production plant. The HTTR test reactor achieved its first criticality
on November 10th, 1998, and started operating at its full 30 megawatts of thermal power
on April 19th, 2004. It was then successfully run for 50 consecutive
days in 2010 at full power, with an outlet helium coolant temperature of 1,742 °F (950
°C). Everything was shut down and put on hold after
the 2011 Fukushima disaster. But ten years later, after passing all the
new safety standards, the reactor was restarted on July 30th, 2021, and has been operating
at full power ever since. With the HTTR in full swing, things start
falling into place for Japan’s strategy for carbon neutrality by 2050. On February 8th this year, Mitsubishi Heavy
Industries was commissioned to spearhead the nation's biggest bet on hydrogen to date:
the construction of the first-ever large-scale hydrogen production plant coupled to direct
heat drawn from the HTTR nuclear reactor. The plant will use a new way to produce hydrogen
using a two-step thermochemical cycle called the iodine-sulfur or IS cycle. In essence, this runs two separate chemical
reactions that produce hydrogen and oxygen and a third one that consumes water and regenerates
the fuel for the first two reactions. So, the only input is water and the only outputs
are hydrogen and oxygen. Fun fact, many mistakingly refer to hydrogen
produced this way as pink hydrogen, but it’s actually called red hydrogen, as it’s a
form of high-temperature catalytic splitting of water that uses nuclear heat as a source
of energy [12]. But why is this game-changing? The significance of Japan’s test reactor
for all of us is three-fold. It’ll be the first time ever we manage to
produce large quantities of totally clean hydrogen in a constant, reliable, and economical
way, with costs far below green hydrogen. This could seriously change the game in the
quest for carbon neutrality worldwide, as it could be the answer heavy industries were
looking for to decarbonize their operations, something renewables just haven’t been able
to pull off. Secondly, these reactors can be built right
next to industries anywhere, since they don’t require vast amounts of nearby running water. So, we could see heavy industries moving further
away from power grids and closer to raw materials, lowering operational costs and further cutting
down carbon emissions due to less transportation. HTTR Safety
The third benefit is related to safety. Or, did you think that I was about to cut
the video short without addressing something as important and meaningful for nuclear energy? Hydrogen and carbon emissions aside, I have
to say that the biggest and most significant benefit of Japan’s HTTR reactor is how it
fixes one of the biggest and most notorious flaws of nuclear energy: the risk of a nuclear
meltdown! These new reactors have a series of inherent
safety features that make a nuclear meltdown almost impossible, and it starts with the
fuel. HTTR uses Tri-structural isotropic fuel or
TRISO fuel. This is made of tiny ceramic kernels with
6% uranium oxide covered with four layers of highly resistant ceramics. Image Source [13] This encapsulation traps all the radioactive
waste inside it and makes it almost impossible for this waste to be released into the atmosphere
even in case of an accident. But the best part is that these ceramics are
incredibly heat resistant and require temperatures of several thousand degrees Fahrenheit to
decompose making a meltdown almost impossible. Additionally, its high thermal conductivity
coupled with a high heat capacity helps the TRISO fuel lose heat passively to the surroundings
very quickly, which means that even in the unlikely case that there was no active cooling
(like what happened in Fukushima) the reactor wouldn’t melt down. You’re probably going like… Yeah right! Prove it! I get it! I felt the same way! Most Japanese did, in fact. But you wanna know what Japan did? They proved it! As in, they simulated catastrophic failure
of the cooling system and control rods in an experiment while the reactor was opperating
at full capacity. Spoiler alert! It didn’t blow up! In fact, it never even got close to the safety
limits. The reactor fuel initially reached a scorching
2,400 °F (1,320 °C) and then slowly cooled passively to 2,372 °F (1,300 °C). This would’ve been doomsday in any other
nuclear reactor, yet the reactor survived unscathed and is still opperating today. The test’s results suggest that we could
have Hommer Simpson running the reactor and we’d be fine. Jokes aside, though, we have a safety margin
of at least one full week without human intervention and without risk of meltdown or radioactive
contamination. Not bad at all! If you’re thinking, “that’s in Japan! What does this have to do with me?” Well, a lot! This success is unprecedented and it could
mean the return of nuclear power worldwide in all its glory, bringing clean hydrogen
along for the ride. Not everything is perfect
But of course, there’s always a tradeoff. First of all, though HTGRs almost completely
solve safety, they still produce as much nuclear waste as all the old technologies do. So, we still have to ask ourselves how are
we going to manage all that waste for the next couple of thousand years. Furthermore, we don’t know if this technology
will scale as they predict. But, we have our fingers crossed! It’s encouraging to think that most of the
remaining challenges are related to design-specific details and coupling technology [13] and we
can almost surely overcome these with clever engineering as we always have, proving, once
again, that the future is going to be awesome!
