science

Energy: Experimental fusion reactor in the UK successfully produces its first super-hot 'plasma'

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In a step towards cleaner and safer nuclear energy using the same reactions that power the Sun, a UK experimental fusion reactor has powered on for the first time.

Fusion power works by colliding heavy hydrogen atoms to form helium — releasing vast amounts of energy in the process, as occurs naturally in the centre of stars.

In such stellar furnaces, it is gravity that overcomes the tendency of the charged hydrogen atoms to repel away from each other, like two positive ends of a magnet.

On Earth, however, the same can be achieved by creating a ring of charged, super-hot gas called a plasma, which is held in place by powerful magnetic fields.

The Oxfordshire-based ‘MAST Upgrade’ achieved this feat for the first time on October 29, producing plasma heated to some 1.8 million degrees Fahrenheit.

Eventually, however, the test reactor — which cost some £55 million to construct — will bring plasma to ten times this temperature.

While the experiment will not produce power itself, MAST Upgrade will allow experts to gather key data and test a new exhaust system for future fusion power plants.

For the same amount of fuel, fusion produces around four time the energy of a conventional nuclear power station — which uses atom-splitting, fission, reactions. 

Unlike conventional, fission-based nuclear reactors, fusion uses easy-to-source fuel and provides cheap, clean and safe energy without creating radioactive waste.

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In a step towards cleaner and safer nuclear energy using the same reactions that power the Sun, a UK experimental fusion reactor has powered on for the first time. Pictured, plasma is generator in the core of the MAST Upgrade reactor for the first time

 In a step towards cleaner and safer nuclear energy using the same reactions that power the Sun, a UK experimental fusion reactor has powered on for the first time. Pictured, plasma is generator in the core of the MAST Upgrade reactor for the first time

The Oxfordshire-based 'MAST Upgrade' (pictured here in cutaway) produced plasma for the first time on October 29, reaching internal temperatures around 1.8 million degrees Fahrenheit

The Oxfordshire-based ‘MAST Upgrade’ (pictured here in cutaway) produced plasma for the first time on October 29, reaching internal temperatures around 1.8 million degrees Fahrenheit

‘We want the UK to be a world leader in fusion energy and to capitalise on its amazing potential as a clean energy source that could last for hundreds of years,’ said UK Science Minister, Amanda Solloway in a statement.

‘Backed by £55 million of government funding, powering up the MAST Upgrade device is a landmark moment for this national fusion experiment.’

This, she added, ‘takes us another step closer towards our goal of building the UK’s first fusion power plant by 2040.’ 

As its name suggests, MAST Upgrade is a refinement of a previous experimental reactor facility, MAST — short for ‘Mega Ampere Spherical Tokamak’ — which operated from 1999 to 2013.

Although built at the same site, around 90 per cent of MAST Upgrade’s hardware is completely new — and it is capable of realising greater heating power, magnetic fields and plasma currents than its forebear. 

The key new feature of the upgrade, however, is the introduction of an experimental ‘Super-X’ divertor’, which MAST Upgrade will be putting to the test.

In a tokamak reactor, divertors are responsible for funnelling off excess heat and any waste material — which, in a working power plant, would include both fusion products and impurities in the plasma that came from the reactor’s lining. 

At present, the exhaust mechanisms of fusion reactors face temperatures equivalent to those seen by spacecraft re-entering the Earth’s atmosphere — meaning that they require regular replacement, which increases the cost of reactor operation.

Fusion power works by colliding heavy hydrogen atoms to form helium — releasing vast amounts of energy in the process, as occurs naturally in the centre of stars. In such stellar furnaces, it is gravity that overcomes the tendency of the charged hydrogen atoms to repel away from each other, like two positive ends of a magnet. On Earth, however, the same can be achieved by creating a ring of charged, super-hot gas called a plasma, held in place by powerful magnetic fields. Pictured, an artist's impression of the plasma in MAST Upgrade

Fusion power works by colliding heavy hydrogen atoms to form helium — releasing vast amounts of energy in the process, as occurs naturally in the centre of stars. In such stellar furnaces, it is gravity that overcomes the tendency of the charged hydrogen atoms to repel away from each other, like two positive ends of a magnet. On Earth, however, the same can be achieved by creating a ring of charged, super-hot gas called a plasma, held in place by powerful magnetic fields. Pictured, an artist’s impression of the plasma in MAST Upgrade

Lessons learnt from MAST Upgrade will aid the development of the Spherical Tokamak for Energy Production — or 'STEP' — the UK's first prototype fusion power plant. This £220 million, government-funded project is to be completed in the year 2040, and also borrows from MAST Upgrade the latter's more compact and efficient internal shape, pictured, which is more spherical than the classic ring-doughnut-like tokamak design

Lessons learnt from MAST Upgrade will aid the development of the Spherical Tokamak for Energy Production — or ‘STEP’ — the UK’s first prototype fusion power plant. This £220 million, government-funded project is to be completed in the year 2040, and also borrows from MAST Upgrade the latter’s more compact and efficient internal shape, pictured, which is more spherical than the classic ring-doughnut-like tokamak design

By sending the plasma exhaust whizzing around in long spirals within the reactor core — but away from the main plasma flow — it is hoped that the Super-X divertor will be able to cool the exhaust to a less destructive level .

Researchers aim to ultimately lower the temperature so that it matches that which might find in a car’s exhaust — allowing the reactor to require less maintenance and run continuously for longer. 

Should the Super-X prove effective, it will be just one lesson that experts will be able to take from MAST Upgrade into the development of the Spherical Tokamak for Energy Production — or ‘STEP’ — the UK’s first prototype fusion power plant.

This £220 million, government-funded project is to be completed in the year 2040, and also borrows from MAST Upgrade the latter’s more compact and efficient shape, which is more spherical than the classic ring-doughnut-like tokamak design. 

By sending plasma exhaust whizzing around in long spirals within the reactor core — but away from the main plasma flow — it is hoped that the MAST Upgrade's Super-X divertor, pictured, will be able to cool the reactor's exhaust to a more manageable level

By sending plasma exhaust whizzing around in long spirals within the reactor core — but away from the main plasma flow — it is hoped that the MAST Upgrade’s Super-X divertor, pictured, will be able to cool the reactor’s exhaust to a more manageable level

As its name suggests, MAST Upgrade, pictured, is a refinement of a previous reactor, MAST — short for 'Mega Ampere Spherical Tokamak' — which operated from 1999 to 2013

As its name suggests, MAST Upgrade, pictured, is a refinement of a previous reactor, MAST — short for ‘Mega Ampere Spherical Tokamak’ — which operated from 1999 to 2013

‘MAST Upgrade will take us closer to delivering sustainable, clean fusion energy,’ said UK Atomic Energy Authority CEO, Ian Chapman.

‘This experiment will break new ground and test technology that has never been tried before,’ Professor Chapman added.

‘It ensures the UK is in the premier league of countries working on fusion — and will be vital in achieving UKAEA’s goal of building the STEP fusion power plant.’

Data collected by experiments with MAST Upgrade will also help to inform the development and operation of the world’s largest nuclear fusion project, the International Thermonuclear Experimental Reactor — or ITER, for short.

This project — a collaboration between various nations including China, Europe, India, Japan, Russia, South Korea and the US — is expected to reach full fusion by full fusion by 2023 and start delivering energy in the year 2035.

HOW A FUSION REACTOR WORKS

Fusion is the process by which a gas is heated up and separated into its constituent ions and electrons. 

It involves light elements, such as hydrogen, smashing together to form heavier elements, such as helium. 

For fusion to occur, hydrogen atoms are placed under high heat and pressure until they fuse together.

The tokamak (artist's impression) is the most developed magnetic confinement system and is the basis for the design of many modern fusion reactors. The purple at the center of the diagram shows the plasma inside 

The tokamak (artist’s impression) is the most developed magnetic confinement system and is the basis for the design of many modern fusion reactors. The purple at the center of the diagram shows the plasma inside 

When deuterium and tritium nuclei – which can be found in hydrogen – fuse, they form a helium nucleus, a neutron and a lot of energy.

This is done by heating the fuel to temperatures in excess of 150 million°C and forming a hot plasma, a gaseous soup of subatomic particles.

Strong magnetic fields are used to keep the plasma away from the reactor’s walls, so that it doesn’t cool down and lose its energy potential.

These fields are produced by superconducting coils surrounding the vessel and by an electrical current driven through the plasma.

For energy production, plasma has to be confined for a sufficiently long period for fusion to occur.

When ions get hot enough, they can overcome their mutual repulsion and collide, fusing together. 

When this happens, they release around one million times more energy than a chemical reaction and three to four times more than a conventional nuclear fission reactor.

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