The post Could Fusion Reactors Use Lithium Vapour Caves As Chamber Coolants? appeared first on Techso Mogro.
]]>Controlling hot plasmas created through the fusing of atoms has proven to be much harder than fusion itself. How do you keep hot plasmas stable and where do you keep them?
The most common designs include tokamaks that look like fat doughnuts, and stellarators that are like bagels wrapped in spaghetti. Then there is Vancouver-based General Fusion with a spherical chamber surrounded by giant hammers.
At the Princeton University Plasma Physics Laboratory (PPPL), scientists have proposed using a lithium vapour cave and porous plasma-facing wall within a tokamak. PPPL envisions adding a lithium vapour cave containing liquid lithium metal to fusion reactor designs. The liquid lithium would go through a phase change turning into vapour when exposed to the heat of the plasma contained within the reaction chamber.
A paper published in the journal IOPScience on July 2, 2024, describes the concept, calling it a lithium vapour cave with “a detached divertor design.” The cave keeps the liquid lithium contained within the boundary structure of the tokamak while being close enough to absorb the heat from the plasma causing lithium atoms to boil off and become vapour.
PPPL has done simulations testing two proposed locations: a“private flux region” and a “common flux region.” The former would be located in the bottom centre of the tokamak while the latter would encase the outer edge. Simulations of both have concluded that the private flux region would prove to be a better option. States Eric Emdee, Associate Research Physicist at PPPL, “You don’t want your core plasma to get dirty with lithium and cool, but you also want the lithium to do some heat mitigation before it leaves the cave.”
Originally, the lithium vapour cave was described as a full, four-sided metal box with a small opening at the top. It has since evolved (see illustration below) to be described as a cave with solid walls on top, bottom, and one side, with the opposite side facing the tokamak’s plasma chamber made of porous tile material. Liquid lithium would penetrate the porous wall and vaporize when exposed to heat, acting as a coolant.
The lithium liquid-to-vapour exchange could serve future fusion reactors as a solution for keeping their plasma cores from eroding or melting the tokamak’s walls. This type of heat management within fusion reactor containment vessels could accelerate the development of this zero-emission, zero-pollution sustainable energy source. Now, the PPPL team needs to translate the conceptual design to reactor scale to determine its practicality and maybe become the game-changer for commercial fusion energy to come of age sooner than later in the 21st century.
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]]>The post Creeping Closer But Not Fast Enough to Harness Nuclear Fusion appeared first on Techso Mogro.
]]>The potential to realize commercial nuclear fusion energy has been a receding target 30 years in the future for as long as I can remember. The promise for humanity of harnessing the power used by the sun and other stars here on Earth is seen as the ultimate clean energy solution. It would be revolutionary, zero polluting, with an almost unlimited supply of fuel based on plentiful hydrogen. Nuclear fusion energy if not deployed in a bomb is the dream for a clean, and safe energy future.
To know nuclear fusion you need to remember the chemistry taught in high school. In Grade 11 we were introduced to the periodic table of elements plastered on the wall of the chemistry lab.
We learned that hydrogen with the symbol H is the first element in the periodic table with an atom that contains one electron circling a nucleus containing a single proton. H is the most abundant element in the Universe.
Isotopes of H include protium, H1, deuterium, H2 and tritium, H3. It is the latter two that are critical elements for nuclear fusion. H2 atoms contain one electron and a nucleus with one proton and one neutron. H3 atoms contain one electron and a nucleus containing a proton and two neutrons. The natural ratio of H1 to H2 and H3 is 99.98%/0.016%/<0.01%.
Fusing H2 and H3 at temperatures of over 100 million Celsius (212 million Fahrenheit) degrees produces an electrically charged gas called plasma which is a million times less dense than air and thus needs to be contained. That’s where the engineering behind commercial nuclear fusion comes in. The technology requirements are complex involving developing materials to confine the plasma in a containment vessel wrapped by powerful magnets and superconducting coils. High-powered lasers are used to target a pellet of D-T to initiate fusion.
Kyoto Fusioneering Ltd. (KF) is one of several Japanese nuclear fusion startup companies working on components needed for fusion reactors. Earlier this year the company announced a partnership with Canada’s premier nuclear science research centre, the Canadian Nuclear Laboratories (CNL). The new venture Fusion Fuel Cycles Inc. (FFC), plans to develop and deploy deuterium-tritium (D-T) fusion fuel cycle technologies. KF is providing silicon carbide composite for tritium breeding blankets to up production of the hydrogen isotope. The target delivery date for the tritium processing facility is 2026.
Japan is looking to differentiate its industrial base which today tends to be largely dominated by automobile manufacturers and a supporting supply chain. KF is one of the companies that hopes to participate in an initiative established earlier this year called the Japan Fusion Energy Council or J-Fusion. It is designed to build synergies among many companies in the country with USD 6.2 billion available in investment capital. So far, KF’s share of the pot is $91 million.
Kiyoshi Seko, director and chief operating officer at KF notes that the growing threat of human-caused climate change requires greater urgency. He states, “We cannot wait 30 or 40 or 50 years to make fusion happen. We have to make it within at least 25 or 20.” In my opinion, even 20 years will be problematic considering our global continuing dependence on fossil fuels for the energy we consume and the pollution that results.
To frustrate environmentalists even further regarding nuclear energy as a climate mitigation energy solution, the fusion project called ITER, a joint venture involving the European Union, Japan and many other countries, and forever delayed, in the last week announced it won’t be until 2039 at the earliest before the reactor is operational and it isn’t even designed to be a commercial operating facility.
Let’s hope that J-Fusion can light a fire while other nascent fusion reactor designs come to market much sooner.
The Princeton Plasma Physics Laboratory (PPPL) is proposing a kitchen-sized nuclear fusion appliance a fraction of the size of ITER. States Masayuki Ono, one of the research physicists at PPPL, “A compact, spherical tokamak plasma looks like a cored apple with a relatively small core.”
The design eliminates massive heating coils needed for other reactor vessel designs. The idea is to aim microwaves at the tokamak that get generated from outside the container. The idea is to create an electron cyclotron current drive to heat the plasma using as little power as possible.
The PPPL team have written two programs, one called TORAY and the other TRANSP, to find the most efficient ways to direct the current and to avoid any of the power being put into the plasma from finding its way out.
The hope is to design the reactor and launch a pilot power plant. One senior technical advisor describes the design as “the future for tokamak heating systems.” Tokamaks are what the industry calls the reactor vessels being used in fusion experiments. They are doughnut-shaped. This one, however, is like a cored apple, taller and rounder than a doughnut. The Princeton physicists believe the cored apple may prove to be better.
In a press release from Princeton, no timelines are mentioned. So we wait and wait and wait…..
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]]>The post If We Plan to Make Mars Our Second Home We Need Faster Propulsion – Magnetic-Plasma Rockets May Be The Answer appeared first on Techso Mogro.
]]>The largest tokamak fusion device is ITER, located in Europe. The timetable for ITER has dramatically slipped with 2040 now the estimated date for proof of concept. Will it become the model for nuclear energy in the near future. If so it will join solar, wind, geothermal and tidal energy as zero-emission technologies that can replace fossil fuels.
But Ebrahimi sees something else coming out of the NSTX-U. She sees the utility of the technology for rocket propulsion. Instead of enhanced magnets containing the plasma produced within a tokamak, the energy could be directed out the back of a rocket.
Ebrahimi, in an interview in January of this year, described how she arrived at the concept. “I had the idea in 2017…thinking about the similarities between a car’s exhaust and the high-velocity exhaust particles created by PPPL’s National Spherical Torus Experiment. During its operation, this tokamak produces magnetic bubbles called plasmoids that move at around 20 kilometres per second, which seemed…a lot like thrust.”
A prototype has yet to be built but the concept represents an advance on what NASA already uses with satellites called pulsed plasma thrusters (PPTs). These low-powered electric thrusters use two high voltage electrodes placed close to the propellant source. When the fuel, usually xenon gas, is ignited the thrusters produce a small plasma discharge guided by the electric fields to discharge out the back of a thruster. The amount of thrust produced is small, no more than you blowing on a piece of paper. But over time, if operated continuously, a PPT can attain speeds of near 7 kilometres per second.
What Ebrahimi is proposing replaces the electrodes with magnets and uses almost any type of gas, not just xenon, as the propellant. The magnets concentrate and channel the gas plasma to form bubbles containing lots of kinetic energy which can propel a rocket at speeds minimally exceeding 72,000 kilometres (44,730 miles) per hour. Note I said minimally, equivalent to 20 kilometres (12 miles) per second. That’s almost three times faster than existing chemical rocket propulsion systems today. But it gets better. By adjusting the magnetic field Ebrahimi’s plasma rocket can theoretically reach speeds of 1.8 million kilometres (1.1 million miles) per hour, 70 times faster than what Elon Musk’s Starship can produce to fly to Mars. Musk’s rocket journey of six to eight months would be dramatically reduced to as little as a couple of weeks making it possible to visit Mars not just when it is conveniently aligned with Earth, about every two years, but regularly.
Ebrahimi describes her propulsion system in an article that appeared in December of last year in the Journal of Plasma Physics. She argues that the only practical form of propulsion that will allow humans to explore the Solar System beyond the Moon and Mars is a rocket that uses magnetic reconnection, the physical process that occurs in the interaction between highly conducting plasmas and magnetic fields to produce kinetic energy — velocity. This is the energy behind coronal mass ejections erupting from the Sun’s surface at high speed.
Ebrahimi calls the output of her engine (see schematic below), Alfvenic, named after Hannes Alfvén, who first described waves produced by the interaction of magnetic fields with plasmas or fluids.
With this type of rocket engine, Ebrahimi envisions humans exploring the Solar System with little fear of exposure to cosmic radiation. She believes we could even go interstellar reaching solar systems within a few light-years from ours. She hopes to build a prototype soon.
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