Tuesday, June 04, 2013

An "Economically Viable" Fusion Device?

          by Brian Orlotti 
For decades, large government research programs around the world have struggled to develop nuclear fusion, a power source with world-changing potential. Decades of effort, however, has failed to achieve an economically viable fusion device. Now, a group of small firms are working toward this holy grail of energy using a smaller-scale approach.

Fusion is a type of nuclear reaction in which two or more atomic nuclei collide at very high speed and merge to form a new nucleus, releasing great amounts of energy in the process. In space, fusion reactions power stars like our Sun by the collision of hydrogen nuclei to form helium.

Fusion energy research currently consists of two main branches: inertial confinement fusion (ICF) and magnetic confinement fusion (MCF). In ICF, high-energy laser, electron or ion beams are used to compress and heat a small pellet of fuel. This compression creates shock waves that travel through the fuel to the centre, heating it so greatly that fusion reactions are triggered. In MCF, fuel is fed into a vacuum chamber where magnetic fields compress and heat it to about 150 million °C, forming a hot plasma (a gaseous state of matter).
The National Ignition Facility, part of the Lawrence Livermore National Laboratory.

The two largest government-funded government fusion research projects are the National Ignition Facility (NIF) in the US and the International Thermonuclear Experimental Reactor (ITER) multinational facility currently being built in southern France. The NIF creates ICF fusion with ultra-powerful lasers while the ITER will create MCF fusion via a device called a tokamak (a doughnut-shaped vacuum chamber). At both these facilities, the reactors are massive machines requiring large support staffs and budgets. Because of their large size and cost, these facilities have been years behind schedule and billions of dollars over budget. Being government projects, they are also hamstrung by politics. In the case of the ITER, its participating nations spent 10 years alone debating where the reactor would be built.
The Joint European Torus, located in Oxfordshire, UK.

In addition to their fiscal and political issues, the devices being developed by the government programs have had questions raised concerning their utility. Owing to their physics, laser-based fusion devices and tokamaks cannot be made small and light enough to be portable, severely limiting their use. Finally, after decades of research, no fusion device has ever achieved ‘energy breakeven’. Energy breakeven describes the moment when a fusion device produces as much energy output as input. The current record-holder for energy output is the Joint European Torus (JET), which succeeded in generating 70 percent of its input power.

Given the current climate of fiscal restraint and the developmental issues with government fusion programs, the possibility of cutbacks and cancellations is high. Anticipating this, a small group of innovative companies is exploring different paths to fusion power. These firms include:
  • EMC2 which is based in Santa Fe, New Mexico. Continuing the work of the late physicist Robert Bussard, EMC2’s work is focused on a device called a polywell, which uses a series of ring magnets to trap electrons and ions. The negatively charged electrons then attract positively charged ions, which accelerates the ions. If they collide at high speeds in the center, they fuse in a form of inertial confinement fusion. Since 2007, EMC2 has done contract work for the US Navy and has built several experimental polywell units, but has been under a publishing embargo. As a result, little hard data on the Polywell has been made public.
Michel Laberge, president and chief technology officer of General Fusion. Photo c/o Brent Beadle for NPR.
  • General Fusion which is based out of Burnaby, BC. General Fusion’s reactor will be a three-meter-diameter steel sphere filled with spinning molten lead and lithium. Super-heated plasma would be injected into the vortex, then the outside of the sphere would be hit with 200 computer-synchronized pistons travelling 100 meters per second. The resulting shock waves would compress the plasma and spark a fusion reaction for a few microseconds. General Fusion has received roughly $50Mln CDN in funding from Cenovus Energy, Amazon founder Jeff Bezos, and the Business Development Bank of Canada (BDBC). General Fusion is aiming to produce a net energy gain device later this year. If the early stage efforts are successful, the first commercial scale unit could be available in 2016-2018.
  • Lawrenceville Plasma Physics (LPP), which is based in based in Middlesex, New Jersey. The LPP approach uses a device called a dense plasma focus (DPF) to burn fusion fuels that make no radioactive waste, a combination LPP calls “focus fusion.” The dense plasma focus device consists of two cylindrical copper or beryllium electrodes nested inside each other. The electrodes are enclosed in a vacuum chamber with a low pressure gas filling the space between them. An electric pulse from a capacitor bank (an energy storage device) is discharged across the electrodes. For a few millionths of a second, an intense current flows from the outer to the inner electrode through the gas. This current starts to heat the gas and creates an intense magnetic field. Guided by its own magnetic field, the current forms itself into a thin sheath of hot plasma. This sheath travels to the end of the inner electrode where the magnetic fields produced by the currents pinch and twist the plasma into a tiny, dense ball only a few thousandths of an inch across called a plasmoid. The magnetic fields very quickly collapse, and these changing magnetic fields induce an electric field which causes a beam of electrons to flow in one direction and a beam of ions (atoms that have lost electrons) in the other. The electron beam heats the plasmoid to extremely high temperatures, the equivalent of billions of degrees Celsius. The company has raised $2Mln US from private investors and hopes to have a prototype in the next two years.
    Charles Chase and his team at Lockheed have developed a high beta configuration, which allows a compact reactor design and speedier development timeline.
  • Lockheed Skunkworks Fusion. US aerospace heavyweight Lockheed is developing a trailer-sized fusion reactor that uses radio waves to heat deuterium and tritium gas inside tightly controlled magnetic fields, creating a high temperature plasma. Utilizing modular components and assembly line techniques to cut development time and costs, Lockheed is promising a 100mW prototype by 2017 with commercial 100mW systems available by 2022. 
  • Tri-Alpha Energy which has received over $50Mln US in funding and is developing colliding beam fusion. This is building upon the work of fusion researcher Norman Rostoker and is using a field reversed configuration. The project is highly secretive but has mentioned 2015-2018 target dates.
Fusion has always been sold as a panacea of limitless opportunity and for good reason.

The fuel for the process is extracted from seawater, making it both cheap and free from control by any single nation or group of nations so the advent of economically viable fusion power could radically alter both global economics and geopolitics. Fusion would also enable spacecraft propulsion at 1% to 20% of light speed, enabling easy access to anywhere in our solar system.

But that's only if one of the ideas listed above roll out successfully. The longtime joke among space enthusiasts is that fusion reactors have always been "10 to 20 years away" for the past 50 years.

Let's hope that we don't have to wait another 50 years to find out for sure.

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