An innovative reactor in the UK is preparing to start a key fuel blending test, which will eventually power ITER, the world's largest nuclear fusion experiment.Nuclear fusion is a phenomenon that provides energy for the sun. If physicists can use it on the earth, it will be an almost unlimited energy source.
In June, jet will start fusing more tritium and deuterium, another isotope of hydrogen. ITER will use this fuel mixture to try to create more energy from fusion than it has ever been shown before. The reactor should heat and limit the plasma of deuterium and tritium, so that the isotopes can fuse into helium and generate enough heat to maintain further fusion reaction.
Jet's experiment will help scientists predict how the plasma in ITER Tokamak will work, and design the operating environment for this large-scale experiment. ITER will start to operate low power hydrogen reaction in 2025. But from 2035, it will operate on a 50:50 deuterium and tritium blend.
ITER and jet are both located at the Culham fusion energy center (CCFE) near Oxford University. They use extreme magnetic fields to confine the plasma in a ring and heat it until fusion occurs. The temperature in jet can reach 100 million degrees, which is many times higher than that of the sun's core.
The world's last tokamak fusion experiment with tritium was also conducted in jet. The goal at that time was to achieve peak power, and the facility successfully achieved a record output to input power ratio (called Q value) of 0.67. This record is still maintained, Q value of 1 is the balance of payments. But this year's goal is to maintain a similar level of fusion energy for five seconds or more, get as much data as possible from experiments, and understand the behavior of longer lasting plasma.
Dealing with tritium presents a unique challenge, and jet researchers spent more than two years re installing parts of the machine and preparing to deal with radioactive materials. This isotope decays rapidly, so only a small amount of tritium appears in nature, usually as a by-product of nuclear fission reactors; the world supply is only 20 kg.
Part of the challenge with tritium is that it reacts with deuterium to produce neutrons much faster than pure deuterium. Commercial reactors will capture the energy of these neutrons to generate electricity, but in jet, high-energy particles will spread all over the machine, destroying the diagnostic system. This meant that the jet team had to move cameras and other instruments behind the concrete shield.