UK’s fusion energy production approach took shape with the announcement of STEP (Spherical Tokamak for Energy Production) programme in 2019. Its first phase (2019-2024) has come to an end with the release of a concept design for the integrated fusion prototype powerplant. It will be based on use of magnetic field for confining plasma using tokamak machine however UK’s STEP will use a spherical tokamak instead of traditional doughnut shaped tokamak being used at ITER. A spherical tokamak is thought to have several advantages. The plant will be built in Nottinghamshire and is expected to be operational in the early 2040s.
The need for a dependable source of clean energy to meet the burgeoning energy demand of growing population and world economy that could quickly help meet challenges (posed by exhaustible fossil fuels, carbon emission and climate change, environmental risks associated with nuclear fission reactors, and poor scalability of renewable sources) has never been felt so intensely than in the present time.
In nature, nuclear fusion powers stars including our sun which take place in the core of the stars where fusion conditions (viz. extremely high temperature in the range of hundreds of million degree centigrade and pressure) prevail. Ability to create controlled fusion conditions on earth is key to unlimited clean energy. This involve building a fusion environment with a very high temperature to provoke high-energy collisions, that has sufficient plasma density to increase probability of collisions and that could confine plasma for a sufficient duration to enable fusion. Obviously, infrastructure and technology to confine and control superheated plasma is the key requirement for commercial exploitation of fusion energy. Different approaches are being explored and applied across the world for plasma confinement towards commercial realisation of fusion energy.
Inertial Confinement Fusion (ICF)
In inertial fusion approach, fusion conditions are created by rapidly compressing and heating a small quantity of fusion fuel. The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) uses laser-driven implosion technique to implode capsules filled with deuterium-tritium fuel using high-energy laser beams. NIF achieved fusion ignition first in December 2022. Subsequently, fusion ignition was demonstrated on three occasions in 2023 which confirmed proof-of-concept that controlled nuclear fusion can be exploited to meet energy needs.
Magnetic confinement of plasma approach
Use of magnets to confine and control plasma for fusion is being tried at many places. IITER, the most ambitious fusion energy collaboration of 35 nations based in St. Paul-lez-Durance in southern France uses a ring torus (or doughnut magnetic device) called tokamak which is designed to confine fusion fuel for long periods at high enough temperatures for fusion ignition to take place. A leading plasma confinement concept for fusion power plants, tokamaks can keep fusion reaction going so long as there is plasma stability. ITER’s tokamak will be world’s largest.
UK’s STEP (Spherical Tokamak for Energy Production) Fusion Programme:
Like ITER, the STEP fusion programme of United Kingdom is based on magnetic confinement of plasma using tokamak. However, the tokamak of STEP programme will spherical shaped (instead of ITER’s doughnut shaped). A spherical tokamak is compact, cost effective and may be easier to scale.
STEP programme was announced in 2019. Its first phase (2019-2024) has come to an end with the release of a concept design for the integrated fusion prototype powerplant.
A themed issue of Philosophical Transactions A of Royal Society, titled “Delivering Fusion Energy – The Spherical Tokamak for Energy Production (STEP)” comprising 15 peer-reviewed papers was published on 26 August 2024 which detail the technical progress of the programme to design and build the UK’s first prototype plant to produce electricity from fusion. The papers capture complete snapshot of the design and outline technologies required and their integration into a prototype plant by early 2040s.
The STEP programme aims to pave the way for the commercial viability of fusion by demonstrating net energy, fuel self-sufficiency and a viable route to plant maintenance. It takes a holistic approach to delivering a fully operational prototype plant that also considers decommissioning as part of the design.
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References:
- UK Government. Press release – UK leading the world in fusion powerplant design. Published 03 September 2024. Available at https://www.gov.uk/government/news/uk-leading-the-world-in-fusion-powerplant-design
- ‘Delivering Fusion Energy – The Spherical Tokamak for Energy Production (STEP). The themed Royal Society edition of Philosophical Transactions A,. All 15 peer-reviewed articles in the theme issue published on 26 August 2024. Available at https://royalsocietypublishing.org/toc/rsta/2024/382/2280
- U.K. researchers reveal glimpse of designs for novel fusion power plant. Science. 4 September 2024. DOI: https://doi.org/10.1126/science.zvexp8a
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