Tag Archives: Reactor

A startup proposes using autonomous microreactors fueled by nuclear waste to produce energy

Nuclear reactors are definitely powerful, but they also produce quite a lot of problematic, radioactive waste. A new Silicon Valley startup plans to change that through the introduction of small-scale reactors that run on waste from their conventional peers.

Rendering of the Aurora powerhouse, a concept developed by Oklo to test their reactor design currently ongoing in Idaho. Image credits Gensler / Wikimedia.

The startup Oklo plans to give us a reliable and cost-effective source of power while also solving the issue of radioactive waste, which needs to be stored and managed in particular conditions for hundreds of thousands of years. Their solution is to reuse the waste in autonomous reactors that don’t try to slow down the nuclear decay of the material. Effectively, such a reactor would be able to extract more power from fuel that has already been spent, giving us a use for the processes that happen naturally in a radioactive fuel dump, instead of letting them waste away as radioactive pollution.

No wasting power

“What we’ve done is take waste that you have to think about managing for 100,000 or a million years … and now changed it into a form where you think about it for a few hundred, maybe thousands of years,” Oklo’s co-founder Jacob DeWitte told CNBC.

If you’ve read our piece about nuclear reactors, you’ll know that their main purpose is to draw out the physical processes taking place within them as much as possible. This prevents the fuel from turning into a bomb — very nice — but also limits how much power can be extracted from it — not so nice.

Oklo’s plan is to use small-scale reactors that don’t use water or any other medium around the reaction chamber, mediums which work to slow down the neutrons released from the fuel. This would make them overall more efficient and allow the reactors to extract energy even from spent fuel rods. This approach wouldn’t work in a traditional reactor, however, because fresh fuel is too energetic, and would explode.

In order to keep everything cost-effective, the startup envisions their design to be autonomous, require no human supervision, and be quite small-scale. They would not provide nearly as much energy as a traditional reactor, but would still be enough to power an industrial site, a campus, or a whole company.

Their project started in 2013, with the company spending the last seven years trying to get access to nuclear waste to demonstrate their technology. Oklo was established in 2013 and spent the next seven years getting access to nuclear waste to demonstrate its technology. In 2019, the startup unveiled its plans for its microreactor with integrated solar panels, churning out 1.5 megawatts (MW) of power. Each one, it says, can be built in a year’s time.

The reactors run on spent fuel that’s meant for disposal, and each batch of radioactive waste can power the small-scale reactor for 20 years, according to the startup. In the end, the material they output is still radioactive, but to a much lesser extent than what goes in. This double-spent material will then be vitrified (turned to glass) and buried underground, just like typical nuclear waste.

Oklo is still awaiting a license to build its first microreactor, but the idea of an unsupervised nuclear device is definitely not something regulators will be keen on, no matter how cost-efficient it might be. Exactly where this story will go is still quite undecided, but it is exciting that we have this technology on hand.

Even if the microreactors don’t end up the way Oklo envisaged them initially, they could provide a great way for us to handle nuclear waste going forward. We could significantly slash the radiation our waste produces and the time it remains active after churning it through such a microreactor, and we’d get some energy out of it to boot.

Fukushima Daiichi.

Devastated Fukushima nuclear plant will run out of storage space for radioactive water in three years

The utility company that operates the tsunami-crippled Fukushima’s nuclear power plant will run out of space to store its contaminated water in three years.

Fukushima Daiichi.

Two IAEA experts examine recovery work on top of Unit 4 of TEPCO’s Fukushima Daiichi Nuclear Power Station on 17 April 2013 as part of a mission to review Japan’s plans to decommission the facility.
Image credits Greg Webb / IAEA via Flickr / IAEA Imagebank.

Fukushima Daiichi suffered extensive meltdowns (in three of its reactors) due to a massive 2011 earthquake and tsunami that devastated northeastern Japan. In a bid to contain the radioactive fallout, TEPCO (Tokyo Electric Power Company Holdings Inc.) has installed some 1,000 tanks to hold the treated — but still radioactive — water used to keep the reactors cool.

The tanks hold over 1 million tons of the dirty water. While experts recommend that it is released into the sea in a controlled manner, locals vehemently oppose the plan. However, there is growing pressure to resolve the issue: TEPCO reports it will run out of storage room for this water in three years, according to The Japan Times.

Running out of tanks

Immediately after the tsunami, the Fukushima Daiichi nuclear plant’s reactors were leaking water with radioactive isotopes into the ocean. In an effort to contain these atoms, 960 tanks were built at the site to siphon the runoff. These tanks can hold roughly 1.15 million tons of water. TEPCO expects to secure enough extra tanks to hold 1.37 million tons in total by the end of 2020.

But, with an average 170 tons of contaminated water produced each day during fiscal 2018, those tanks are going to fill up fast. TEPCO aims to reduce the volume to 150 per day next year — but even that should only be enough for the next three years or so. Even at that reduced level, the tanks would reach full capacity in either the summer or fall of 2022, the company estimates.

TEPCO installed equipment to decontaminate the water, but it still contains tritium, a radioactive hydrogen isotope that also occurs in minute amounts in nature. A panel commissioned by the Ministry of Economy, Trade and Industry considered diluting and releasing the water into the ocean.

“Releasing tritium-tainted water into the sea in a controlled manner is common practice at nuclear power plants around the world, and it was generally considered the most viable option as it could be done quickly and would cost the least,” writes Kazuaki Nagata for The Japan Times.

“But people in Fukushima, especially fishermen, fear it will damage the region’s reputation.”

However, with the 2020 Summer Olympics in Tokyo fast approaching, the government doesn’t want to rock the boat too much and is delaying a decision. Prime Minister Shinzo Abe told the International Olympic Committee in his final pitch to secure the Games six years ago that the situation at Fukushima was “under control,” according to Reuters,

Clean-up plans are due for completion in 2021. The tanks pose flooding and radiation risks that will hamper efforts, however.

Comet-inspired reactor could create oxygen for astronauts

When it comes to space, oxygen has been famously known to be in short supply. This is why it was a very pleasant surprise when two researchers at the California Institute of Technology found a way to produce some.

Konstantinos P. Giapis with his reactor that converts carbon dioxide to molecular oxygen. Credit: Caltech.

In 2015, the European Space Agency’s Rosetta spacecraft unexpectedly found abundant levels of molecular oxygen in Comet 67Ps atmosphere. Molecular oxygen in space is highly unstable, as oxygen prefers to pair up with hydrogen to make water, or carbon to make carbon dioxide. When oxygen was detected streaming out of the comet, it was believed that the gas had been locked inside the comet for billions of years.

However, in 2017, Caltech researchers proposed that the oxygen was actually created by other compounds slamming into the comet at high speeds. After water or carbon dioxide are discharged from the comet, solar winds accelerate them back into the comet, which creates molecular oxygen.

Now Caltech scientists have created a reactor to reproduce this reaction originally found in outer space. Such technology is appealing, as it could provide future astronauts on Mars a way to generate their own air. It could even be utilized on our home planet to combat our little carbon dioxide problem. The process would remove CO2 from the atmosphere, converting it into O2, giving humans a leg-up in the war against climate change.

It works by crashing CO2 onto the inert surface of gold foil. The foil cannot be oxidized and theoretically should not produce molecular oxygen. However, through the experiment, O2 continued to be emitted from the gold surface. This meant that both atoms of oxygen come from the same CO2 molecule, effectively splitting it in extraordinary style.

“At the time we thought it would be impossible to combine the two oxygen atoms of a CO2 molecule together because CO2 is a linear molecule, and you would have to bend the molecule severely for it to work,” says Konstantinos P. Giapis, a professor of chemical engineering at Caltech. “You’re doing something really drastic to the molecule.”

Credit: Caltech.

Most chemical reactions require energy, which is most often provided as heat. However, Giapis’s research shows some unusual reactions can occur by providing kinetic energy. When water molecules are shot like extremely tiny bullets onto surfaces containing oxygen, such as sand or rust, the water molecule can rip off that oxygen to produce molecular oxygen.

“In general, excited molecules can lead to unusual chemistry, so we started with that,” Tom Miller, a professor of chemistry at Caltech, says. “But, to our surprise, the excited state did not create molecular oxygen. Instead, the molecule decomposed into other products. Ultimately, we found that a severely bent CO2 can also form without exciting the molecule, and that could produce O2.”

The device the Caltech team devised works like a particle accelerator. It converts carbon dioxide molecules into ions by giving them a charge and then fast-tracking them using an electric field, though at drastically lower energies than you’ll find in a particle accelerator. The device generates only one or two oxygen molecules for every 100 carbon dioxide molecules.

“You could throw a stone with enough velocity at some CO2 and achieve the same thing. It would need to be traveling about as fast as a comet or asteroid travels through space,” said Giapis but stresses this is not the final product. “Is it a final device? No. Is it a device that can solve the problem with Mars? No. But it is a device that can do something that is very hard,” he says. “We are doing some crazy things with this reactor.”

The study was published in the journal Nature Communications

Hand Plasma Lamp.

New theoretical framework will keep our fusion reactors from going ‘boom’

New theoretical work finally paves the way to viable fusion reactors and abundant energy for all.

Hand Plasma Lamp.

Hand touching a plasma lamp.
Image credits Jim Foley.

A team of physicists from the U.S. Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) at Princeton University’s Forrestal Campus, New Jersey, may have finally solved a long-standing problem in physics — how to tame fusion for energy production. Their work lays down the groundwork needed to stabilize the temperature and density levels of plasma in fusion reactors, an issue that plagued past efforts in this field.

Wild and energetic

Plasma is one of the four natural states of matter. That may sound confusing since we’re all thought that stuff is either a gas, a liquid, or a solid, but there’s a good explanation for this: plasma is such a violent and energetic state of matter that it simply doesn’t exist freely on Earth. It is, however, the stuff that most stars are made of.

Think of plasma as a soup, only instead of veggies, it’s full of protons and electrons (essentially, highly-energized hydrogen atoms) that smack together to create helium. For a less-culinary explanation, see here. This process requires a lot of energy to get going — you need to heat the hydrogen to about 100 million degrees Celsius — but will generate monumental amounts of energy if you manage to keep it running.

It’s easy to understand, then, why fusion is often hailed as the harbinger of infinite, free energy for everybody — ever. So far, we’ve successfully recreated plasma in fusion reactors — the donut-shaped tokamaks or funky stellarators, for example — but we’ve yet to find a way of keeping this super-heated soup of charged particles stable for more than a few seconds.

One of the biggest hurdles we’ve encountered is that plasma in fusion reactors tends to fluctuate wildly in terms of temperature and density. Such turbulence is very dangerous, as any inkling of runaway plasma will eat through a reactor’s wall like a lightsaber through butter. Faced with such odds, researchers have little choice but to shut down experimental reactions before they run amok.

Plasma MAST Tokamak.

Plasma confined in the MAST tokamak at the Culham Centre for Fusion Energy in the UK. Magnetic field lines that combine to act like an invisible bottle for the plasma.
Image credits ITER / CCFE.

The most frustrating thing is that we know what we have to do, but not how to do it. We need to contain the plasma in an orderly fashion and keep the reaction going long enough for it to start being net-energy-positive — i.e. generate more energy than we put in.

Stars can cash in on their sheer mass to press plasma into playing nice, but we don’t have that luxury. Instead, we use massively-powerful magnetic fields (some 20,000 times stronger than that of the Earth) to keep it away from the reactor’s walls.

Go with the flow

This is where the present paper comes in. Certain types of plasma flows (like those inside stars) have been found to be very stable over time, without dangerous turbulence. We didn’t know how to make plasma flow like this, but the PPPL researchers report it comes down to a mechanism called magnetic flux pumping forcing the flow at the core of the plasma body to stay stable.

According to the flow simulations the team ran, magnetic flux pumping can take place in hybrid scenarios — a mix of the standard flow regimes currently known from theoretical and experimental models. These standard regimes include high-confinement mode (H-mode) and low-confinement mode (L-mode).

In L-mode, an electrically-balanced scenario — meaning it has a perfect ratio of positive to negative charged-particles — formed at lower temperatures, turbulence allows the plasma to leak away some of its energy. L-mode is unstable as high-temperature plasma at the core is thrown out to the surface, destabilizing the reaction. If this mode can be surpassed and the reaction enters H-mode, the overall temperature of the plasma body is increased and the reaction stabilizes. H-mode is an energy-imbalanced mode, but the plasma is kept stable and confined by electrical fields it itself generates (T. Kobayashi et al., Nature, 2016).

In a hybrid scenario, however, the flow is kept orderly only at the plasma body’s core. This generates an effect similar to that encountered inside the Earth, the team reports, where the solid iron core acts as a ‘mixer’, generating a magnetic field. The interactions between this field, the one applied by the generator, and the two types of plasma flow stabilize the reaction.

Even better, this magnetic flux pumping mechanism is self-regulating, the simulations show. If the mixer becomes too strong, the plasma’s current drops just below the point where it would go haywire.

And, even better #2, the authors suggest that ITER — widely held to be the most ambitious nuclear fusion project, currently under construction in Provence, France — may be suited to experiment with developing magnetic flux pumping by using the same hardware it employs to heat up the plasma.

The paper “Magnetic flux pumping in 3D nonlinear magnetohydrodynamic simulations” has been published in the journal Physics of Plasmas.

The U.S. plans to build the most advanced fusion reactor ever

The US government has put its weight behind efforts to create an economically viable fusion reactor, endorsing a new category of designs that could become the most efficient and viable yet.

Test cell of the NSTX-U.
Image credits Elle Starkman / PPPL Office of Communications.

Re-creating the atom fusing processes that sustain the sun on Earth has long been one of the holy grails of modern physics. Hydrogen fusion has been powering out Sun for the past 4.5 billion years now, and it’s still going strong — a machine that could safely and stably harvest these processes would offer humanity safe, clean, and virtually endless energy.

But, at the risk of stating the obvious, making a star isn’t easy. Physicists have seen some progress in this field, but a viable fusion reactor still remains out of their grasp. We’re inching forward, however, and in an effort to promote progress the US government has just backed plans for physicists to build a new kind of nuclear fusion device that could be the most efficient design yet.

Harnessing the atom…again

Our nuclear plants today rely on nuclear fission — the splitting of an atom into tinier atoms and neutrons — to produce energy, and they’re really good at it. Per unit of mass, nuclear fission releases millions of times more energy than coal-burning. The downside is that you have to deal with the resulting radioactive waste, which is really costly and really hard to get right.

But merging atoms, in nuclear fusion, produces no radioactive waste. If you heat up the nuclei of two lighter atoms to a high enough temperature, they merge into a heavier one releasing massive amounts of energy, with the only reaction product being the fused atom. It’s an incredibly efficient process, one that sustains all the stars in the Universe, our sun included.

So there’s understandably a lot of interest into taking that process, scaling it down, and harvesting it to power our lives. Physicists have been trying to do just that for the past 60 years and still haven’t succeeded, a testament to how hard it can be to put “a star in a jar.” The biggest issue, as you might have guessed, is that stars are incredibly hot.

While fission can be performed at temperatures just a few hundred degrees Celsius, fusion takes place at star-core temperatures of several millions of degrees. And because our would-be reactors have to jump-start the reaction from scratch, they need to generate temperatures in excess of that. A successful reactor should be able to resist at least 100 million degrees Celsius. Which is a lot.

“During the process of nuclear fusion, atoms’ electrons are separated from their nuclei, thereby creating a super-hot cloud of electrons and ions (the nuclei minus their electrons) known as plasma,” Daniel Oberhaus said for the Motherboard.

“The problem with this energy-rich plasma is figuring out how to contain it, since it exists at extremely high temperatures (up to 150 million degrees Celsius, or 10 times the temperature at the Sun’s core). Any material you can find on Earth isn’t going to make a very good jar.”

So what scientists usually do to keep the plasma from vaporizing the device is to contain it through the use of magnetic fields. So far, the closest anyone’s gotten to sustainable fusion is a team of physicists at the Wendelstein 7-X stellarator in Greifswald, Germany, and researchers at China’s Experimental Advanced Superconducting Tokamak (EAST) – both of which have been trying to hold onto the super-heated plasma that results from the fusion reaction.

The German device managed to heat hydrogen gas to 80 million degrees Celsius and sustain a cloud of hydrogen plasma for a quarter of a second last year. That doesn’t sound like a lot but it was a huge milestone in the world of physics. Back in February, the Chinese team reported that it successfully generated hydrogen plasma at 49.999 million degrees Celsius, and held onto it for 102 seconds. Neither of these devices has proved that fusion can produce energy — just that it is possible in a controlled environment.

Physicists at the US Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) think that progress has been so slow because we’ve been working with the wrong jar. They plan to redesign the fusion reactor to incorporate better materials and a more efficient shape — instead of using the traditional tokamak to contain the plasma in a doughnut-like shape, they suggest employing spherical tokamaks, more akin to a cored apple. The team writes that this spherical design halves the size of the hole in the doughnut, meaning we can use much lower energy magnetic fields to keep the plasma in place.

Traditional tokamak.
Image credits Matthias W. Hirsch / Wikimedia.

The smaller hole could also allow for the production of tritium – a rare isotope of hydrogen – which can fuse with another isotope of hydrogen, called deuterium, to produce fusion reactions.

They’ve also set their sights on replacing the huge copper magnets employed in today tokamak designs with high-temperature superconducting magnets that are far more efficient because electricity can flow through them with zero resistance.

To save development time, the team will be applying these improvements to two existing spherical tokamaks – UK’s Mega Ampere Spherical Tokamak (MAST), which is in the final stages of construction, and the PPPL’s National Spherical Torus Experiment Upgrade (NSTX-U), which came online last year.

“We are opening up new options for future plants,” one of the researchers behind the study, NSTX-U program director Jonathan Menard, said in a statement.

“[These facilities] will push the physics frontier, expand our knowledge of high temperature plasmas, and, if successful, lay the scientific foundation for fusion development paths based on more compact designs,” added PPPL director Stewart Prager.

Right now, all we can do is wait and see the results. But if this works, we’ll be one step closer to creating stars right here on Earth — then plugging them right into the grid to power our smartphones.

The full paper titled “Fusion nuclear science facilities and pilot plants based on the spherical tokamak” has been published in Nuclear Fusion.

Advances in magnet technology could bring cheaper, modular fusion reactors from sci-fi to sci-reality in less than a decade

Advances in magnet technology have allowed MIT scientists to design a cheaper, more compact, modular and highly efficient fusion reactor that is efficient enough to use commercially. The era of clean, practically inexhaustible energy may be upon us in as little as a decade, scientists report.

MIT PhD candidate Brandon Sorbom holds REBCO superconducting tapes (left), enabling technology behind the ARC reactor.
When cooled to liquid nitrogen temperature, the superconducting tape can carry as much current as the large copper conductor on the right, enabling the construction of extremely high‑field magnets, which consume minimal amounts of power.
Photo: Jose‑Luis Olivares/MIT

The team used newly available rare-earth barium copper oxide (REBCO) superconducting tapes to produce high-magnetic field coils.

“[The implementation of these magnets] just ripples through the whole design,” says Dennis Whyte, professor of Nuclear Science and Engineering and director of MIT’s Plasma Science and Fusion Center. “It changes the whole thing.”

Bigger bang for your magnet

But how do magnets help us build a mini-star? Well, fusion reactors generate electricity by using the same physical process that powers stars. In such a reactor, two lighter atoms are mushed together to create heavier elements. And just like natural stars, they generate immensely hot plasma – a state of matter similar to an electrically charged gas.

The stronger magnets and the stronger magnetic fields they generate allow the plasma to be contained in a much smaller space than previously possible. This translates to less materials and space necessary to build the reactor, and less hours of work, meaning a cheaper, more affordable reactor.

The proposed reactor, using a tokamak (donut-ish) geometry is described in a paper in the journal Fusion Engineering and Design, co-authored by Whyte, PhD candidate Brandon Sorbom, and 11 others at MIT.

A cutaway view of the proposed ARC reactor. Thanks to powerful new magnet technology, the much smaller, less-expensive ARC reactor would deliver the same power output as a much larger reactor.
Illustration credits to the MIT ARC team

Power plant prototype

The basic concept of the reactor and its associated elements rely on well-tested and proven principles that have been developed over decades of study.

The new reactor is intended to allow basic research on fusion and to potentially function as a prototype power plant – that could produce significant quantities of power.

“The much higher magnetic field,” Sorbom says, “allows you to achieve much higher performance.”

The reactor uses hydrogen fusion to form helium, with enormous releases of energy. To sustain the reaction and make it energy efficient (to release more energy than the reaction consumes) the plasma has to be heated to temperatures hotter than the cores of stars. And here is where the new magnets come in handy – they trap the heated particles in the center of the tokamak.

Cutaway of the inner workings of the ITER reactor. Not much difference structurally in the tokamak, the increase in power comes from the magnets. Notice the solid cover over the reactor.
Image via nature

“Any increase in the magnetic field gives you a huge win,” Sorbom says.

This is because in a fusion reactor, changing the strength of the magnetic field has a dramatic effect on the reaction: available fusion power increases to the fourth power of the increase in the magnetic field. Doubling the field would thus produce a 16-fold increase in the power generated by the device.

Ten times more power

The new magnets do not quite produce a doubling of the field strength, but they are strong enough to increase the power generation of the reactor ten times over previously used superconducting technology, the study says. This opens up the path for a series of improvements to be done to the standard design of the reactor.

The world’s most powerful planned fusion reactor, a huge device under construction in France called ITER, is expected to cost around US$ 40 billion. This device was designed and put into production before the new superconductors became available. Sorbom and the MIT team believe that their new design would produce about the same power as the french reactor, while being only half the diameter, cost but a fraction of its price and being faster to construct.

But despite the difference in size and magnetic field strength, the proposed reactor, called ARC, is based on “exactly the same physics” as ITER, Whyte says.

“We’re not extrapolating to some brand-new regime,” he adds.

The team also plans to include a method for removing the fusion core from the reactor without having to dismantle the entire device. Being able to do this would lend well to research aimed at further improving the system by using different materials or designs of its core to improve performance.

In addition, as with ITER, the new superconducting magnets would enable the reactor to operate in a sustained way, producing a steady power output, unlike today’s experimental reactors that can only operate for a few seconds at a time without overheating of copper coils.

Molten core and liquid cover

Another key breakthrough the design of the reactor brings is that it replaces the blanket of solid materials that surrounds the fusion chamber with a liquid material, that can be easily circulated and replaced. This curbs operating costs associated with replacement of the materials that degrade over time.

“It’s an extremely harsh environment for [solid] materials,” Whyte says, so replacing those materials with a liquid could be a major advantage.

In its current state, the reactor should be capable of producing about three times as much electricity as is needed to keep the reaction going. Sorbom says that the design could probably be improved and fine-tuned to crank up to about five or six times that much power. So far, no completed fusion reactor has produced energy (well they did, but they use more juice than they make) so the kind of net energy production ARC is expected to deliver would be a major breakthrough in fusion technology, the team says. They estimate that the design should be able to produce electricity for about 100,000 people.

“Fusion energy is certain to be the most important source of electricity on earth in the 22nd century, but we need it much sooner than that to avoid catastrophic global warming,” says David Kingham, CEO of Tokamak Energy Ltd. in the UK, who was not connected with this research. “This paper shows a good way to make quicker progress,” he says.

The MIT research, Kingham says, “shows that going to higher magnetic fields, an MIT speciality, can lead to much smaller (and hence cheaper and quicker-to-build) devices.” The work is of “exceptional quality,” he says; “the next step … would be to refine the design and work out more of the engineering details, but already the work should be catching the attention of policy makers, philanthropists and private investors.”

The research was supported by the U.S. Department of Energy and the National Science Foundation.