Producing the energy over a number of seconds is essential for understanding the heating, cooling and movement happening inside the plasma that will be crucial to run ITER, says Rimini.įive seconds “is a big deal”, adds Proll. The improvement took 20 years of experimental optimization, as well as hardware upgrades that included replacing the tokamak’s inner wall to waste less fuel, she says. Although the 1997 experiment still retains the record for ‘peak power’, that spike lasted for only a fraction of a second, and the experiment’s average power was less than half that of the latest test, says Fernanda Rimini, a plasma scientist at the CCFE who oversaw last year’s experimental campaign. In an experiment on 21 December 2021, JET’s tokamak produced 59 megajoules of energy over a fusion ‘pulse’ of 5 seconds - more than double the 21.7 megajoules released in 1997 over around 4 seconds. (It’s quite good with the sound on, too.) Credit: UKAEA
The record-breaking pulse in action inside JET’s doughnut-shaped internal vessel. “I am sure I am not alone in the fusion community in wanting to extend very hearty congratulations to the JET team.” The experiments - the culmination of almost two decades of work - are important for helping scientists to predict how ITER will behave, and will guide its operating settings, says Anne White, a plasma physicist at the Massachusetts Institute of Technology in Cambridge who works on tokamaks, reactors that, like JET, have a doughnut shape. “It’s a really, really good sign and I’m excited.” Two decades’ work The same modelling now says ITER will work,” says fusion physicist Josefine Proll at Eindhoven University of Technology in the Netherlands, who works on a different kind of reactor called a stellarator. JET’s results do not change that, but they suggest that a follow-up fusion-reactor project that uses the same technology and fuel mixture - the ambitious US$22-billion ITER, scheduled to begin fusion experiments in 2025 - should eventually be able to reach this goal.
But so far, no experiment has generated more energy than has been put in. The values above are the total energy yield, not the energy delivered to a consumer.If researchers can harness nuclear fusion - the process that powers the Sun - it promises to provide a near-limitless source of clean energy. This figure is dated and probably high, but it gives a basis for comparison. Then they are expressed in terms of a nominal per capita U.S. Both the single event energy and the energy per kilogram of fuel are compared. Nuclear binding energy curveĭeuterium-tritium fusion and uranium-235 fission are compared in terms of energy yield. Its average binding energy per nucleon is exceeded only by 58Fe and 62Ni, the nickel isotope being the most tightly bound of the nuclides. Iron-56 is abundant in stellar processes, and with a binding energy per nucleon of 8.8 MeV, it is the third most tightly bound of the nuclides. The iron limitThe buildup of heavier elements in the nuclear fusion processes in stars is limited to elements below iron, since the fusion of iron would subtract energy rather than provide it. Whereas an atomic transition might emit a photon in the range of a few electron volts, perhaps in the visible light region, nuclear transitions can emit gamma-rays with quantum energies in the MeV range. The binding energies of nucleons are in the range of millions of electron volts compared to tens of eV for atomic electrons. The fact that there is a peak in the binding energy curve in the region of stability near iron means that either the breakup of heavier nuclei (fission) or the combining of lighter nuclei (fusion) will yield nuclei which are more tightly bound (less mass per nucleon). The binding energy curve is obtained by dividing the total nuclear binding energy by the number of nucleons. The nuclear binding energies are on the order of a million times greater than the electron binding energies of atoms. The comparison of the alpha particle binding energy with the binding energy of the electron in a hydrogen atom is shown below.
The enormity of the nuclear binding energy can perhaps be better appreciated by comparing it to the binding energy of an electron in an atom. This binding energy can be calculated from the Einstein relationship: Nuclear binding energy = Δmc 2įor the alpha particle Δm= 0.0304 u which gives a binding energy of 28.3 MeV. The difference is a measure of the nuclear binding energy which holds the nucleus together. Nuclei are made up of protons and neutrons, but the mass of a nucleus is always less than the sum of the individual masses of the protons and neutrons which constitute it. Nuclear Binding Energy Nuclear Binding Energy