Scientists at a laboratory in the UK have surpassed the record for the amount of energy produced during a controlled, prolonged fusion reaction.
The production of 59 megajoules of energy in five seconds in a joint European torus or jet test in the UK has been called “a breakthrough” by some news organizations and has caused great excitement among physicists.
But the general line about fusion power generation is that it is “always 20 years away.”
We, a nuclear physicist and nuclear engineer, study how to create a controlled nuclear fusion for the purpose of generating electricity.
The JET results show significant advances in the understanding of fusion physics. But most importantly, it shows that the new materials used to build the interior walls of the fusion furnace worked purposefully.
The fact that the new wall construction also worked so well separates these results from previous milestones and elevates the magnetic link from a dream to reality.
Binding the particles together
Nuclear fusion is the union of two atoms into a single nucleus. The nucleus then splits and releases energy in the form of new atoms and particles, which are rapidly released from the reaction. A fusion power plant captures escape particles and uses their energy to generate electricity.
There are a number of different ways to safely control the joining of the earth. Our research focuses on the approach taken by JET – using powerful magnetic fields to control atoms until they are heated to a temperature high enough to melt.
The fuel for current and future reactors is two different isotopes of hydrogen – that is, they contain one proton, but different numbers of neutrons – called deuterium and tritium. Ordinary hydrogen has a proton and no nuclei in its nucleus. Deuterium has one proton and one neutron, tritium has one proton and two neutrons.
For a fusion reaction to be successful, the fuel atoms must first be very hot so that the electrons are released from the nuclei. It forms the plasma – the synthesis of positive ions and electrons.
You need to heat that plasma until it reaches a temperature of 200 million degrees Fahrenheit (100 million Celsius). These plasma fuel atoms must be kept in a confined space at a high density for long enough to collide with each other.
To control contact with the Earth, researchers have developed a donut-shaped device called a tomax – which uses magnetic fields to hold plasma. The magnetic field lines around the inside of the donut act as tracks for ions and electrons.
By injecting energy into the plasma and heating it, the fuel particles can accelerate at high speeds, and when they collide, the fuel cores stick together instead of jumping together. When this happens, they release energy, primarily in the form of fast-moving neutrons.
During the fusion process, the fuel particles gradually move away from the hot, dense core and eventually collide with the inner wall of the fusion vessel.
To prevent the walls from collapsing due to these collisions – which also contaminate the fusion fuel – the furnaces are built so that they direct the deflected particles into a large armored chamber called the diverter. It expels the distracted particles and removes excess heat to protect the tocopherol.
Walls are important
The main limitation of past furnaces was that the steering could not survive at constant particle bombardment for more than a few seconds. In order for the fusion power to work commercially, engineers must create a Tokomac vessel that will be used for many years under the conditions required for fusion.
The steering wall is the first consideration. Although the fuel particles are very cold when they reach the diverter, there is enough energy to loosen the atoms from the wall material of the diverter when they collide.
Previously, JET’s steering had a wall made of graphite, but graphite absorbs more fuel for practical use.
In 2011, JET’s engineers upgraded the diverter and inner ship walls to tungsten. Tungsten was selected as a component because it has the highest melting point of any metal – a very important characteristic when experiencing heat loads that are 10 times greater than the nozzle cone of a spacecraft re-entering the Earth’s atmosphere.
Tokamak’s inner ship wall was upgraded to beryllium from graphite. Beryllium has the best thermal and mechanical properties for a fusion furnace – it absorbs less fuel than graphite but still withstands higher temperatures.
It was the energy produced by the jet that made the headlines, but we would argue that it was actually the use of new wall materials that made the experiment truly impressive, as future devices would need these strong walls to run at high power. Time.
JET is a successful resource on how to build next generation fusion reactors.
Next fusion furnaces
JET tokamak is the largest and most advanced magnetic fusion furnace currently in operation. But the next generation of reactors are already in operation, especially the ITER test, which will be operational by 2027.
ITER – Latin for “way” – is under construction in France and is funded and operated by an international organization including the United States.
ITER is going to use many of the material improvements shown by JET. But there are also some important differences. First of all, ITER is huge. The fusion chamber is 37 feet (11.4 m) high and around 63 feet (19.4 m) – eight times larger than the JET.
In addition, ITER uses superconducting magnets capable of generating strong magnetic fields for long periods of time compared to JET’s magnets. With these updates, ITER is expected to break JET’s merger records – power output and how long the reaction will run.
ITER is expected to do something central to the idea of a fusion power plant: it produces more energy than it takes to heat fuel. Models predict that the ITER will produce 500 megawatts of power for 400 consecutive seconds when using only 50 megawatts of energy to heat the fuel.
This means that the reactor produces 10 times more energy than it uses – a huge improvement over JET, which required about three times more energy than the fuel produced for its latest 59 megajoule record.
JET’s latest record has yielded years of research in plasma physics and material science and has brought scientists to the threshold of using fusion for power generation. ITER will provide a tremendous improvement towards the goal of industrial-scale fusion power plants.
David Donovan, Associate Professor of Nuclear Engineering, University of Tennessee and Livia Kasali, Assistant Professor of Nuclear Engineering at the University of Tennessee.
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