Part 1 of 2 Parts
Scientists at the Culham Centre Fusion for Fusion Energy laboratory in England have broken the record for the amount of energy produced during a controlled, sustained fusion reaction. The Joint European Torus (JET) in England produced fifty-nine megajoules of energy over five seconds. Some media outlets have called the experiment a “breakthrough” and it has caused a lot of excitements among physicists.
The JET experiment demonstrates a remarkable advancement in understanding the physics of nuclear fusion. It also shows that the new materials used to construct the inner walls of the fusion reactor worked as the scientists intended.
Nuclear fusion is a merging of two atomic nuclei into a single compound nucleus. In this process, a great deal of energy is released. A fusion power plant would capture the energy in the form of heat and use it to generate electricity. Our Sun and the stars are powered by nuclear fusion.
There are several different ways to create reactors that can safely control the fusion process on Earth. In the approach taken for the JET, powerful magnetic fields are used to confine atoms until they reach a high enough temperature for them to fuse. The fuel used in many experimental fusion reactors consists of two different isotopes of hydrogen. They are called deuterium which has a neutron in the nucleus in addition to the proton and tritium which has two neutrons in the nucleus in addition to the proton.
In order for a fusion reaction to be successful, the fuel atoms must become so hot that electrons are expelled from the atom. The result is a plasma which is a collection of positive ions and electrons. The plasma is heated until it reaches temperature of over two hundred million degrees Fahrenheit.
To control fusion on Earth, one of the first and most popular reactor designs is called a tokamak which uses magnetic fields to confine the plasma. Magnetic field lines wrapping around the inside of the donut behave like train tracks that the ions and electron follow. The injection of energy into the plasma heats it. When adequate temperatures are reached, the fuel particles are accelerated to such high speeds that when they collide, they fuse. The energy that is released is primarily in the form of fast neutrons.
During the fusion process, fuel particles can gradually drift away from the hot, dense core and eventually collide with the inner wall of the fusion containment vessel. In order to prevent the degradation of the wall due to these collisions, reactors are constructed so that they channel the wayward particles towards a heavily armored chamber called the divertor. This pumps out the diverted particles. It also removed excess heat to protect the tokamak.
A major limitation of past tokamaks has been the fact that divertors cannot survive the constant bombardment of the particles for more than a few seconds. To construct a tokamak that will be able to produce continuous power, engineers need to build a tokamak containment vessel that will be able to survive for years at the extreme temperatures and pressures necessary for fusion.
Please read Part 2