Chamequa – Year 12 Student
Editor’s Note: Talented Year 12 student Chamequa writes here for the GSAL Science Magazine on the fascinating prospect of using nuclear fusion, through a technique called inertial confinement, to produce a plentiful source of renewable energy. Is this soon to be a reality, or will it forever remain ‘just 20 years away’? CPD
[Featured image: Laser beams causing ingition. (Wikipedia: Public Domain)]
Since nuclear fusion came into the realm of possibility in the 1930s[i], scientists all over the world have tried to unlock the power hidden in the stars. It has constantly thought to be ‘20 years away’, yet here we are in 2020 with no amazing renewable energy resource that solves the energy crisis. Despite this, we cannot rule out the prospect as impossible since the proof is sitting 152 million km away[ii] as our Sun. The possibility that this is achievable, if given enough time and funding, is too great an idea to ever truly give up on.
Currently, the two major experimental approaches for fusion is magnetic confinement and inertial confinement. The initial idea was magnetic confinement; it uses strong magnetic fields to contain heated plasma, as the reaction has to reach such high temperatures that no solid container could be used. After the invention of the laser in 1960[iii], inertial confinement began using the energy of laser beams to heat and compress atoms.
For inertial confinement, isotopes of hydrogen (deuterium and tritium used in micrograms) are placed into a multi-layered pellet inside a hohlraum, which is a gold cylinder with a cavity that helps regulate temperatures for the reaction. The lasers heat the hohlraum to over 100 million degrees – hotter than the Sun’s surface – ionising the pellet’s material. The ionisation of the surface of the pellet causes ablation, producing an inward force that implodes the inner layer; this recoil allows the nuclei to overcome electrostatic repulsion and fuse. For a viable fusion reaction, the time taken for the isotopes to fuse must be less than the time for the pellet to disassemble.
This method has no chain reaction like a normal fission reaction, which uses the decay of heavy elements such as uranium to produce energy, and therefore is more easily controlled and safer. The helium produced in this reaction is also unlike the radioactive waste produced after fission, so fusion has less impact environmentally.
A laboratory that has produced the highest fusion yield[v] is the National Ignition Facility (NIF) in California. It has 192 lasers for this type of fusion and is the largest in the world for its function. Yet its fusion reactions are still not commercially viable as the energy used in heating still exceeds that of the energy produced by the fusion reaction. This is mainly due to the asymmetrical ablation of the pellet. If this was uniform the reaction would be much easier to control as the energy drive of the lasers would be centered for perfect ignition of the fuel. The inefficiency of the short-wavelength laser beams used is still a hindrance to its success, therefore nuclear fusion may be just ‘20 years away’ forever. On the other hand the implosion may be controllable and finally we’ll have the answer to unlocking the power of the stars.
Scientists are not giving up on fusion yet as NIF is planning to construct a Laser Inertial Fusion Energy facility in the mid-2020s, that could finally make fusion economically viable with the expense of $4 billion.[vi]
Though, if fusion never comes into fruition, decades of research would not be wasted as the scientific progress made in this time has contributed to our understanding of physics. For example, it can be applied to further study the conditions of black holes and supernovas, and the simulation of nuclear weaponry without the need for testing the weapon itself. Therefore, if fusion never lives up to its potential as a virtually limitless energy source, the advancements made during the journey may lead us to a different scientific revolution. This could have the potential to change the world, perhaps through another renewable energy resource that can finally solve the energy crisis. This can only be brought about if governments continue to give scientists freedom, financially and academically, to pursue areas of interest even if there isn’t a clear goal like the inexhaustible energy source discussed.
All sources accessed in January 2020.