From Fiction to Reality: the thrilling Journey of Arc Reactor


You have probably heard of an fusion reactor before…whether you are  a hard core  marvel fan or just wondering about the lack of energy fuels. You also know that despite of many attempts, it is not invented yet.   There is a joke saying that it will be invented in the next 30 years, which never comes.  The waiting-to-be-invented fusion reactor is caused by the lack of its chain reaction, unlike fission reactor. In real world physics, that is possible, besides the fact that it is impossible.   Confused?  Well,  then  we  have  something  to  save  the  human  race  from  further confusing – “ arc reactor”!!!

What is an” arc fusion reactor”?

It is a fusion reactor which is “ Affordable, Robust, Compact” or ARC reactor .The thing which kept Tony Stark alive, and the suit charged in fiction.  The arc reactor is a theoretical design for a compact fusion reactor which aims to achieve an engineering breakdown  of three ( affordable  , robust, compact)   while being about half the diameter of  ITER  reactor and cheaper to build. The arc reactor has the ability to generate an electromagnetic field. It is small, but large enough to produce a net gain of energy. It mashes  two heavy isotopes of hydrogen  , deuterium and tritium,  together at such high energies that they combine into one atom.  When they fuse, the reaction produces  helium and free neutron .  Helium+ neutron have less mass than deuterium +tritium, so the missing mass converts to energy. The energy is the form of heat that run a traditional stream, driving turbine like power plant. 

How does it work?

The said reactor is planned to be donut shaped, or more truthfully, like a TOKAMARK.  It can generate the same amount of energy as much as larger designs. It uses superconductors made of rare earth barium copper oxide.  Because of the stronger magnetic field generation, arc reactors are able to contain better plasma, allowing the reactor to be smaller, cheaper and easier to build.

It contains a palladium core (usually, but metals or isotopes  with specific capture or decay properties   can be used instead . Besides , palladiam is usually damaged by neutron-energy force , so the specific isotope is needed). It has electromagnetic coils in a toros and emits a low whitish blue glow (creaters can also hide those enchanting lights).  Palladium isotope pd-13 produces Rh-103(rhodium) via electron capture and the said reactor has fuel consumed charge. This means an inner electron is absorbed by the nucleus, merging with a proton to produce a neutron and an energetic photon –a gamma ray. Another isotope, Pd-107, produces Ag-107 (silver) via beta decay, releasing an electron when a neutron turns into proton. (this is the opposite reaction to the one above.)

Now,  in real- world physics, the electrons balance  the resulting atomic nuclei-silver and rhodium  have different numbers of protons from palludiam, and the produced/consumed electrons just balance out the proton count so there is  no net flow of electricity. To utilize the beta decay of Pd107 ions as an electron source for the electron capture of Pd-103, thereby producing an electric circuit between two different radioactive isotopes.Pd-103 is very radioactive (17-day half life) compared to Pd-107 (6.5 million-year half life) so there would need to be dramatically more of the heavier isotope to compensate for the disparity in decay rates. Since we know the device uses charged particles travelling within a ring of electromagnets, tiny amount of Pd-103 is ionized by an electric arc, which then allows Pd-103+ to be circulated at high velocity within the outer ring of the device.

The ionization acts to delay the electron capture step until the atom encounters a free electron, and the high kinetic energy due to velocity increases the chances of electron capture occurring once an electron is encountered. In effect, the radioactive decay of Pd-103 can be started, stopped, and throttled by the device simply by controlling the ionization and circulation of the Pd-103. The palladium core of the device would most likely be Pd-107, which emits high-energy electrons as it decays into silver. This is a pretty stable isotope that we would expect to be present in the normal (non-separated) palladium. The device’s geometry and electromagnetic fields route the high-energy electrons from the Pd-107 core towards the outer ring. There the electrons are captured by high energy Pd-103 ions. This electron capture process emits gamma rays, which are deflected inward to catalyze the beta decay of the Pd-107 core. Normally, the gamma rays are directed inward to catalyse the device’s operation, but they can be directed outward in a concentrated energy beam Electrons project outward from the inner core, and gamma rays project inward from the outer ring. Because this electron/photon counter flow creates a deficit of electrons (relative to protons) in the core, a massive electrostatic potential is developed and the palladium core attracts lower-energy weapon.

The ejection of electrons from the core towards the rim of the device produces an electrical cell capable of generating enormous voltage and current. Reactor start-up process: Using external power, Pd-103 is ionized by an electric arc, and accelerated to high velocity in the outer ring. There may also be some externally powered gamma ray production to jump-start the inner core. The electrical current through an external load relieves the electrostatic charge accumulations that initially slowed the reactions. Pd-107 in the inner core starts to emit high-energy electrons as it decays to Ag-107. The electrons escape the core and are directed by magnetic fields into the outer ring.

Lack of electrons creates a net positive charge in the core, which slows further emission (preventing run-away decay) until the electrons can be externally replenished. The electron flow from the inner core to the outer core creates an electric potential difference. When a circuit is created through the suit’s electrical loads, the outer ring has an excess of electrons and the inner core has a shortage of electrons. This creates current. In the outer ring, the high-energy free electrons collide with high-energy Pd103+ions. This causes instantaneous electron capture and gamma ray emission. The gamma rays are deflected inward towards the core, thus catalyzing further electron emission and producing self-sustaining reaction. Note that the reaction is self-sustaining, but very slow while the reactor is idle. The palladium slowly converts to Rh-103 and Ag-107, and the reactor runs out of power when the palladium is fully consumed.

Expert’s words

ARC reactor designed to have 500 MW fusion power at 3.3 m major radius.

  • Compact, simplified design allowed by high magnetic fields and jointed magnets.
  • ARC has innovative plasma physics solutions such as inboardside RF launch
  • High temperature superconductors allow high magnetic fields and jointed magnets.
  • Liquid immersion blanket and jointed magnets greatly simplify tokamak reactor design.

The affordable, robust, compact (ARC) reactor is the product of a conceptual design study aimed at reducing the size, cost, and complexity of a combined fusion nuclear science facility (FNSF) and demonstration fusion Pilot power plant. ARC is a ∼200–250 MWe tokamak reactor with a major radius of 3.3 m, a minor radius of 1.1 m, and an on-axis magnetic field of 9.2 T. ARC has rare earth barium copper oxide (REBCO) superconducting toroidal field coils, which have joints to enable disassembly. This allows the vacuum vessel to be replaced quickly, mitigating first wall survivability concerns, and permits a single device to test many vacuum vessel designs and divertor materials. The design point has a plasma fusion gain of Qp ≈ 13.6, yet is fully non-inductive, with a modest bootstrap fraction of only ∼63%. Thus ARC offers a high power gain with relatively large external control of the current profile. This highly attractive combination is enabled by the ∼23 T peak field on coil achievable with newly available REBCO superconductor technology. External current drive is provided by two innovative inboard RF launchers using 25 MW of lower hybrid and 13.6 MW of ion cyclotron fast wave power. The resulting efficient current drive provides a robust, steady state core plasma far from disruptive limits. ARC uses an all-liquid blanket, consisting of low pressure, slowly flowing fluorine lithium beryllium (FLiBe) molten salt. The liquid blanket is low-risk technology and provides effective neutron moderation and shielding, excellent heat removal, and a tritium breeding ratio ≥ 1.1. The large temperature range over which FLiBe is liquid permits an output blanket temperature of 900 K, single phase fluid cooling, and a high efficiency helium Brayton cycle, which allows for net electricity generation when operating ARC as a Pilot power plant. ( all rights are reserved to  respective researchers)

Expectation  vs Reality

Although it seems pretty  ridiculous to have one in real life,  it will be possible  soon. MIT took a page from Tony Stark!  For the past 20 years , MIT’s  Plasma Science and Fusion Center (PSFC)’ has been experimenting with nuclear fusion through the world’s smallest tokamark-type nuclear fusion device- the ‘Alcator C-Mod’ .Their goal is to produce the world’s smallest fusion reactor – one that crushes a doughnut-shaped fusion reaction into a 3.3 meter radius—three of which could power a city the size of Boston.  MIT’s previous smaller Alcator C-Mod  fusion device has enabled  researchers  including  MIT’s Ph.D candidate Brandon Sorbom and  PSFC  Director Dennis Whyte, to develop the conceptual ARC reactor.  “We wanted to produce  something  that could produce power, but be as small as possible,” Sorbom said.

Now, Europe’s working tokamark reactor named ‘JET ‘ holds the world’s record for power creation; it generates 16MW of fusion power but requires 24MW of electricity to operate.  MIT’s researchers, however , believe  they  have  the  answer  to  the  net  power  problem  and it’ll be available in a relatively tiny package compared to today’s  nuclear fission power plants . Also, it would be modular, allowing its many parts to be removed for repairs to upgrades, something not previously achieved. 

A big part of human population is doing their best to save our mother earth. If ARC reactor becomes real, many of these problems will be solved.   We hope that  soon  MIT   will be  able  to  make the ARC  reactor, and make our earth a better place. We have our fingers crossed scientists! Wish you buona fortuna!(good fortune!).

Koushiki Das

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