Nuclear FusionFusion - The ultimate source of energy?

Nuclear fusion, the energy source of the stars, is primarily a reaction where two or more atomic nuclei combine, or fuse, together to form a single heavier nucleus.  This fusion is accompanied by energy absorbtion or release (depending on the weight of the nuclei that fuse together).  Within the sun it is primarily hydrogen nuclei that are colliding and fusing togther, producing helium, a heavier element, and large amounts of energy as well.  ITER ReactorThe extra energy is released because the helium, whilst being heavier than the hydrogen nuclei, is actually lighter than the combined mass of the hydrogen nuclei that created it and the difference in mass between the initial and resulting nuclei is released as energy.

Therefore nuclear fusion promises a low pollution route to generating massive amounts of energy sustainably and cleanly.  However, the fusion reaction active in stars relies on the massive gravitational forces within stars that overcome the natural electrostatic repulsion that exists between the positive charges of the nuclei that are required to combine to fuse and produce energy.  For this reason spontaneous fusion does not occur on Earth, and creating artificial fusion requires large and complex machines (called reactors) to try and encourage or force nuclei to fuse together. The scientific and engineering challenges in designing such a reactor are formidable and commercial power plants are not expected before 2050.

Current Fusion Technology

Without the ability to use gravitational confinement for fusion (as stars do) two different technological approaches have been taken to attempt to create stable fusion reactions on earth; magnetic and inertial confinement.

JET PlasmaInertial confinement aims to create the very high pressure required to overcome the  electrostatic repulsion of nuclei by apply a large amount of energy to a pellet of fusion fuel causing it to simultaneously collapse and heat to very high pressure and temperature. If the reaction is hot enough and the fuel is sufficiently dense then the fusion reaction will be high enough to burn a significant fraction of the fuel before it has exploded and dissipated.  Currently a large inertial confinement reactor is being constructed by the National Ignition Facility which uses high powered lasers to a pellet of deuterium and tritium.

Magentic confinement fusion devices exploit the fact that electrically charged particles, such as those used as the fuel for fusion reactors, will follow magnetic field lines and therefore can be contained by strong magnetic fields.  Extremely strong magnetic fields are used to contain fusion plasmas, enabling very high pressures and temperatures to be acheived in the gas within the magnetic field and therefore fusion to occur.  There are two main types of fusion reactor currently under investigation, tokamaks and stellerators.  They both use the same principles to generate fusion but differ in how they create and mantain the magnetic field required to create the fusion reactor.   Tokamak reactors use a torus shape which simplifies construction of the reactor but does lead to issues with the magnetic field's shape (the magnetic field is not uniform within a torus).  Stellerators aim to address the issues with the magnetic field that tokamaks encounter by balancing the magnetic field around the devices (and thus achieving a more uniform field across the whole reactor).  However, this greatly increases the design and engineering complexities of building the reactor.

The Nu-FuSE project's focus is magnetic confinement fusion, particularly tokamak fusion reactors, and we are working towards supporting the design and development of the ITER and DEMO reactors.