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18th March 2021

Is unlimited clean energy too good to be true?

The first stage of bringing fusion power to the national grid is underway
Is unlimited clean energy too good to be true?
Photo: aglet @ Flickr

The Spherical Tokamak for Energy Production (STEP) is an ambitious project. It aims to build the world’s first prototype nuclear fusion power station. Overseen by the UK Atomic Energy Authority (UKAEA), they hope to start construction in 2030. After that, they want the plant operational by 2040.

The step towards commercially viable fusion power is crucial. It will play a key role in meeting the goal for net zero carbon dioxide emissions by 2050. This goal was enshrined in UK law in 2019. If successful, it will provide a reliable and continuous clean energy accompaniment to other more variable renewable energy sources, such as wind and solar.

Why is it ‘clean’?

The fuel needed for fusion reactions are light nuclei. Specifically, deuterium and tritium. Which, when fused together to create heavier nuclei, release energy.

Deuterium can be extracted from water. Tritium can be produced from lithium, which is plentiful in seawater, and the Earth’s crust. This means the fuel supplies for fusion could be extracted for thousands of years with minimal harm to the environment.

The fusion reaction produces no radioactive waste, as the main product of the reaction is helium. This is non-toxic and can be used for other purposes.

There is also no risk of a ‘meltdown’, as if anything goes wrong, the plasma cools and the reaction stops.

How does it work?

The tokamak is a magnetic chamber. It contains the superheated plasma of deuterium and tritium, in which the fusion reactions occur. This happens once the temperature of the plasma is high enough to force the nearby positive ions to react.

It is usually in the shape of a torus or doughnut. However, the STEP tokamak will more closely resemble a cored apple. The UKAEA states this is because the spherical shape “improves efficiency in the magnetic field and potentially reduces the plant’s cost”.  

There are many tokamak facilities around the world. The largest of which is currently under construction in France. The International Thermonuclear Experimental Reactor (ITER) will come online in 2025, and aims to produce 500 MW of output power from 50 MW of input.

STEP is aiming for a more modest input into the national grid of 100 MW. Its main goal, however, is to research how to best integrate a fusion power plant into the grid. The aim is to improve and duplicate the plant, helping make fusion power commercially viable.

Hopefully, in the five years between ITER firing up and STEP initiating construction, discoveries and developments from ITER will be found. These could then be integrated into the design of STEP.

Where will it be?

The UKAEA has asked for the submission of potential sites across the UK, mainly due to its home site at Culham in Oxfordshire being full. The deadline for this is the end of March 2021. A site will be chosen by the end of 2022.

Sites in Nottingham and Cumbria are known to have been put forward so far. The University of Manchester is part of the Centre for Doctoral Training in the Science and Technology of Fusion Energy. PhD students following this programme have access to the fusion facilities at Culham.

It therefore seems likely that Manchester students will be collaborating on future research to develop the STEP project, helping lead the charge towards net zero emissions in the UK.

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