Nuclear fusion breakthrough: ‘Holy grail’ of power production is closer to reality

For years, nuclear scientists have tried to recreate the fusion process that takes place in billions of stars to create clean energy on Earth.

Now a British team has reported that they have reached a major milestone in the quest, heating up a nuclear reactor to the “magic figure” of 100 million degrees Celsius.

This is the threshold where hydrogen atoms can begin to fuse into helium, releasing renewable energy in the process that could put an end to fossil fuels.

Described as the ‘holy grail’, the milestone was achieved using the ST40 ‘spherical tokamak’ – an Oxfordshire ‘apple core’ nuclear device – and the team is now working on a nuclear reactor that can be connected to the national electricity grid by 2030.

The milestone is lower than the record set by Chinese scientists in 2021, who ran their reactor at 120 million degrees Celsius.

However, the Oxfordshire-based experts, who worked with colleagues at the Princeton Plasma Physics Laboratory, say their reactor is smaller and operates with less plasma heating power, potentially paving the way for the first fusion power plants.

The research team described their promising results in a new paper published in the journal Nuclear fusion.

“Ion temperatures of over 100 million degrees have been produced in the ST40 high-field compact spherical tokamak,” they say in the study.

‘[Such temperatures] have not been achieved before in a spherical tokamak and have only been obtained in much larger devices with significantly more plasma heating power.

‘Ion temperatures relevant to commercial magnetic confinement fusion can be achieved in a compact, high-field spherical tokamak.’

Tokamak Energy, based in Milton, Oxfordshire, is working to replicate the fusion process that takes place in billions of stars across the universe, in their privately funded device, the ST40.

First started up in April 2017, the ST40 is a ‘spherical tokamak’, so it is more squashed and compact compared to other ‘doughnut’ shaped reactors that are flatter and can reach several kilometers in diameter.

Due to its design, the ST40 is ‘compact’ – less than a meter wide – and reaches approximately 4 meters high.

View of the ST40 ‘spherical tokamak’ from outside (left) and inside (right). A spherical tokamak traps plasma in tighter magnetic fields, making it look more like a cored apple than a donut

The researchers say temperatures of more than 100 million degrees (8.6 keV) have been produced in the ST40 spherical tokamak

In the ST40, hydrogen gas is heated to ‘plasma’ – a soup of positively charged particles (ions) and negatively charged particles (electrons).

Plasma — often referred to as the fourth state of matter after solid, liquid, and gas — covers more than 99 percent of the visible universe and makes up most of our sun.

Inside the tokamak, the plasma is trapped and pressurized by magnetic fields until the activated plasma particles begin to collide.

As the particles fuse to form helium, they release massive amounts of energy, mimicking the process that occurs naturally in the centers of stars.

To produce commercial energy, future fusion power plants will need to reach temperatures of 100 million degrees Celsius, according to Tokamak Energy.

Although our sun’s core burns at about 15 million degrees Celsius, reactor temperatures must be much higher because the sun has a much higher particle density.

While the cost of the ST40 reaching the milestone is reported to be less than £50 million ($66 million), other reactors are much more than this amount.

For example, the cost of the International Thermonuclear Experimental Reactor (ITER) being built in France is estimated at $22.5bn (£15.9bn).

The British researchers say their work is ‘advancing the physics base’ towards commercial fusion using the ST40 tokamak at ‘potentially lower cost’.

It could pave the way for the UK’s first commercially viable fusion power plant, referred to as Spherical Tokamak for Energy Production (STEP).

Fusion power works by colliding heavy hydrogen atoms to form helium – releasing huge amounts of energy in the process, as happens naturally in the centers of stars

Ratcliffe-on-Soar Power Station, one of three active coal-fired power stations in the UK. The closure is scheduled for September 2024

Funded by the UK government, STEP will be based at the existing West Burton power station in Nottinghamshire, it was announced last October.

A coal-fired power station at the site ceased production a few days before the announcement, as part of the UK’s effort to phase out fossil fuel and replace it with clean energy sources such as nuclear power.

There are two active coal-fired power stations in operation in the UK – in Kilroot, Northern Ireland, and Ratcliffe on Soar, Nottingham – but these will be decommissioned or converted to gas power by 2024.

Fusion power plants will reduce greenhouse gas emissions from the power generation sector, which is one of the major sources of carbon emissions globally.

In just a few decades, power plants that used to spew out harmful pollutants such as carbon dioxide, sulfur dioxide and particulate matter can be transformed into clean facilities that provide clean, renewable energy.

While fusion joins atomic nuclei to create massive amounts of energy, the opposite, fission, which is used in atomic weapons and nuclear power plants, splits them into fragments.

Unlike nuclear fission, fusion carries less risk of accidents or theft of atomic material, but both are extremely difficult and can be expensive.

HOW A FUSION REACTOR WORKS

Fusion is the process of heating up a gas and separating it into its component ions and electrons.

It involves light elements, such as hydrogen, colliding with each other to form heavier elements, such as helium.

For fusion to take place, 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 forms the basis for the design of many modern fusion reactors. The purple in the center of the diagram shows the plasma inside

When deuterium and tritium nuclei – contained in hydrogen – fuse together, 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 degrees Celsius and forming a hot plasma, a gaseous soup of subatomic particles.

Strong magnetic fields are used to keep the plasma away from the reactor walls so that it does not cool down and lose its energy potential.

These fields are produced by superconducting coils that surround the vessel and by an electric current passed through the plasma.

For energy production, plasma must be confined for a long enough period of time for fusion to occur.

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

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