What is nuclear fusion

It is estimated that the sun releases 3. However, the issue with fusion is that it requires the fusing of nuclei, which are positive particles. As two nuclei approach each other, they will repel because they have the same charge.

The fusion of the nuclei has to happen quickly so that the repulsion of the charges does not have time to stop it from happening. A way that particles can travel that quickly is by being in a hot gas or in plasma , like in the Sun.

Nuclear fusion Nuclear fusion is when two small, light nuclei join together to make one heavy nucleus. As well as power generation, the company envisages material processing and chemical manufacturing applications. It focuses powerful laser beams into a small target in a few billionths of a second, delivering more than 2 MJ of ultraviolet energy and TW of peak power.

A completely different concept, the 'Z-pinch' or 'zeta pinch' , uses a strong electrical current in a plasma to generate X-rays, which compress a tiny D-T fuel cylinder.

Magnetized target fusion MTF , also referred to as magneto-inertial fusion MIF , is a pulsed approach to fusion that combines the compressional heating of inertial confinement fusion with the magnetically reduced thermal transport and magnetically enhanced alpha heating of magnetic confinement fusion.

A range of MTF systems are currently being experimented with, and commonly use a magnetic field to confine a plasma with compressional heating provided by laser, electromagnetic or mechanical liner implosion. As a result of this combined approach, shorter plasma confinement times are required than for magnetic confinement from ns to 1 ms, depending on the MIF approach , reducing the requirement to stabilize the plasma for long periods.

Conversely, compression can be achieved over timescales longer than those typical for inertial confinement, making it possible to achieve compression through mechanical, magnetic, chemical, or relatively low-powered laser drivers.

Due to the reduced demands on confinement time and compression velocities, MTF has been pursued as a lower-cost and simpler approach to investigating these challenges than conventional fusion projects. Fusion can also be combined with fission in what is referred to as hybrid nuclear fusion where the blanket surrounding the core is a subcritical fission reactor.

The fusion reaction acts as a source of neutrons for the surrounding blanket, where these neutrons are captured, resulting in fission reactions taking place. These fission reactions would also produce more neutrons, thereby assisting further fission reactions in the blanket. The concept of hybrid fusion can be compared with an accelerator-driven system ADS , where an accelerator is the source of neutrons for the blanket assembly, rather than nuclear fusion reactions see page on Accelerator-driven Nuclear Energy.

The blanket of a hybrid fusion system can therefore contain the same fuel as an ADS — for example, the abundant element thorium or the long-lived heavy isotopes present in used nuclear fuel from a conventional reactor could be used as fuel. The blanket containing fission fuel in a hybrid fusion system would not require the development of new materials capable of withstanding constant neutron bombardment, whereas such materials would be needed in the blanket of a 'conventional' fusion system.

A further advantage of a hybrid system is that the fusion part would not need to produce as many neutrons as a non-hybrid fusion reactor would in order to generate more power than is consumed — so a commercial-scale fusion reactor in a hybrid system does not need to be as large as a fusion-only reactor.

A long-standing quip about fusion points out that, since the s, commercial deployment of fusion power has always been about 40 years away. While there is some truth in this, many breakthroughs have been made, particularly in recent years, and there are a number of major projects under development that may bring research to the point where fusion power can be commercialised.

Much research has also been carried out on stellarators. It is being used to study the best magnetic configuration for plasma confinement.

At the Garching site of the Max Planck Institute for Plasma Physics in Germany, research carried out at the Wendelstein 7-AS between and is being progressed at the Wendelstein 7-X, which was built over 19 years at Max Planck Institute's Greifswald site and started up at the end of In the USA, at Princeton Plasma Physics Laboratory, where the first stellarators were built in , construction on the NCSX stellerator was abandoned in due to cost overruns and lack of funding 2.

There have also been significant developments in research into inertial fusion energy IFE. Both are designed to deliver, in a few billionths of a second, nearly two million joules of light energy to targets measuring a few millimeters in size.

Between and , the initial designs were drawn up for an International Thermonuclear Experimental Reactor ITER, which also means 'a path' or 'journey' in Latin with the aim of proving that fusion could produce useful energy. The four parties agreed in to collaborate further on engineering design activities for ITER. Canada and Kazakhstan are also involved through Euratom and Russia, respectively.

The envisaged energy gain is unlikely to be enough for a power plant, but it should demonstrate feasibility. In , the USA rejoined the project and China also announced it would join. The deal involved major concessions to Japan, which had put forward Rokkasho as a preferred site.

India became the seventh member of the ITER consortium at the end of The total cost of the MW ITER comprises about half for the ten-year construction and half for 20 years of operation. Site preparation works at Cadarache commenced in January First concrete for the buildings was poured in December Experiments were due to begin in , when hydrogen will be used to avoid activating the magnets, but this is now expected in The first D-T plasma is not expected until ITER is large because confinement time increases with the cube of machine size.

The vacuum vessel will be 19 m across and 11 m high, and weigh more than tonnes. The goal of ITER is to operate with a plasma thermal output of MW for at least seconds continuously with less than 50 MW of plasma heating power input. No electricity will be generated at ITER. It is focused on the divertor structure to remove helium, testing the durability of tungsten materials used. A 2 GW Demonstration Power Plant, known as Demo, is expected to demonstrate large-scale production of electrical power on a continual basis.

The conceptual design of Demo was expected to be completed by , with construction beginning around and the first phase of operation commencing from It has since been delayed, with construction now planned for after JET is the largest tokamak operating in the world today. JET produced its first plasma in , and became the first experiment to produce controlled fusion power in November , albeit with high input of electricity.

Up to 16 MW of fusion power for one second and 5 MW sustained has been achieved in D-T plasmas using the device, from 24 MW of power injected into its heating system, and many experiments are conducted to study different heating schemes and other techniques. JET has been very successful in operating remote handling techniques in a radioactive environment to modify the interior of the device and has shown that the remote handling maintenance of fusion devices is realistic.

It has been significantly upgraded in recent years to test ITER plasma physics and engineering systems. Further enhancements are planned at JET with a view to exceeding its fusion power record in future D-T experiments. MAST Upgrade is focused on designing a plasma exhaust system or divertor that would be able withstand the intense power loads created in commercial-sized fusion reactors.

It achieved first plasma in October The technical objectives of STEP are: to deliver predictable net electricity greater than MW; to exploit fusion energy beyond electricity production; to ensure tritium self-sufficiency; to qualify materials and components under appropriate fusion conditions of neutron flux; and to develop a viable path to affordable life-cycle costs.

STEP is scheduled for completion in Tokamak Energy in the UK is a private company developing a spherical tokamak, and hopes to commercialize this by The company grew out of Culham laboratory, home to JET, and its technology revolves around high temperature superconducting HTS magnets, which allow for relatively low-power and small-size devices, but high performance and potentially widespread commercial deployment.

It produced plasma temperatures of 15 million degrees Celsius in and after the commissioning of further magnetic coils. Chief executive of Tokamak Energy David Kingham said: "The ST40 is designed to achieve million degrees C and get within a factor of ten of energy break-even conditions. The funds will contribute to core development work on high temperature superconducting HTS magnets and plasma exhaust system divertor technologies. The divertor must handle high levels of heat and particle bombardment while removing impurities and waste from the system.

It aims to have a prototype delivering electricity to the grid by It is a pilot device for ITER, and involves much international collaboration. The tokamak with 1. Its first stage of development to was to prove baseline operation technologies and achieved plasma pulses of up to 20 seconds. For the second phase of development , KSTAR was upgraded to study long pulses of up to seconds in H mode — the s target was in — and embark upon high-performance AT mode.

It achieved 70 seconds in high-performance plasma operation in late , a world record. This is a steep pressure gradient in the core of the plasmas due to the enhanced core plasma confinement. Phase 4 will test DEMO-related prior arts. The device does not have tritium handling capabilities, so will not use D-T fuel.

According to the PPPL, it would generate "some 1 billion watts of power for several weeks on end", a much greater output than ITER's goal of producing million watts for seconds by the late s. K-DEMO is expected to have a 6. About KRW billion of that spending has already been funded. The government expects the project to employ nearly 2, people in the first phase, which will last throughout K-DEMO is expected to have an initial operational phase from about to to develop components for the second stage, which would produce electricity.

In November it achieved million degrees Celsius for 10 seconds, with input of 10 MW of electric power. In May it set a new world record of achieving a plasma temperature of million degrees Celsius for seconds. The experiment also realized a plasma temperature of million degrees Celsius, lasting 20 seconds. The following year TFTR produced TFTR set other records, including the achievement of a plasma temperature of million degrees centigrade in However, it did not achieve its goal of break-even fusion energy where the energy input required is no greater than the amount of fusion energy produced , but achieved all of its hardware design goals, thus making substantial contributions to the development of ITER.

Alcator C-Mod is claimed to have the highest magnetic field and highest plasma pressure of any fusion reactor, and is the largest university-based fusion reactor in the world. It operated In September it achieved a plasma pressure of 2. The plasma produced trillion fusion reactions per second and had a central magnetic field strength of 5.

It carried 1. The reaction occurred in a volume of approximately 1 cubic metre and the plasma lasted for two seconds. Having achieved this record performance for a fusion reactor, government funding ceased. A scaled-up version planned to be built at Triotsk near Moscow in collaboration with the Kurchatov Institute is Ignitor, with 1. LHD produced its first plasma in and has demonstrated plasma confinement properties comparable to other large fusion devices.

It has achieved an ion temperature of Following a year of tests, this started up at the end of , and helium plasma briefly reached about one million degrees centigrade. In it progressed to using hydrogen, and using 2 MW it achieved plasma of 80 million degrees centigrade for a quarter of a second.

At the Australian Plasma Fusion Research Facility at the Australian National University the H-1 stellarator has run for some years and in was upgraded significantly. H-1 is capable of accessing a wide range of plasma configurations and allows exploration of ideas for improved magnetic design of the fusion power stations that will follow ITER. Using its laser beams, NIF is able to deliver more than 60 times the energy of any previous laser system to its target e.

This is because it has been difficult for scientists to create a controllable, non-destructive way of harnessing the energy released during fusion.

First, fusion requires both extremely high temperatures to give hydrogen atoms enough energy to overcome repulsion between the protons. Energy from microwaves or lasers must be used to heat hydrogen atoms to the necessary temperatures. At these temperatures, hydrogen is a plasma , and this plasma must be sufficiently contained for fusion to continue, and safety.

This process is done by using intense magnetic fields , lasers, or ion beams. For potential nuclear energy sources, the deuterium-tritium fusion reaction is most likely because the conditions are less extreme. This reactor began construction in and uses a confinement method known as a Tokamak. This Tokamak provides a way to magnetically confine the hot plasma required for fusion. The experimental phase of ITER is expected to begin in Fossil Fuels.

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