Our Changing World: A New Zealand approach to nuclear fusion

For Dr Ratu Mataira the problem he's tackling is simple: our reliance on fossil fuels as an energy source. But the solution he's working on is anything but simple.

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Ratu founded Wellington-based OpenStar Technologies in 2021 with the goal of developing an efficient nuclear fusion reactor. Unlike nuclear fission, which creates long-lasting radioactive waste, fusion offers the promise of abundant clean energy - if scientists can get it right.

The technological difficulties in achieving nuclear fusion on Earth are immense. But with their unique approach, backed by New Zealand scientific discoveries, Ratu thinks his company is in with a shot.

Nuclear fusion in the lab

Nuclear fusion happens in the sun, and other stars, due to their massive sizes - gravity creates intense pressure that squeezes atoms in the star's core together, forcing them to fuse and release huge amounts of energy.

The sun itself is a big ball of plasma - a heated, charged gas. Here on Earth, the approach favoured by many nuclear fusion scientists is to create plasma out of isotopes of hydrogen gas and then coax it to incredibly high temperatures - hundreds of millions of degrees Celsius - much hotter than the core of the sun.

Under these conditions, the heat energy causes the atoms to collide, and at the right speed they can fuse together. When the two hydrogen isotopes fuse, they produce helium and release a high-energy neutron in the process.

In the blueprint for how fusion powerplants would work, 'blanketing' material is then used to capture this neutron and its energy. The energy is converted to heat and then used to power steam engines to produce electricity.

Lasers or magnets

Because of its promise as an energy source, there are many efforts internationally to investigate nuclear fusion, which can be broken down into two main approaches - using lasers or using magnets.

For example, the US Department of Energy's National Ignition Laboratory uses lasers, and over the past few years they have achieved 'ignition'. This is a term for when the nuclear fusion reaction can sustain itself and create more energy than the energy put into the experiment. It was a big milestone - however their current approach is not suitable for developing energy powerplants.

One of the big international efforts using magnets, ITER, involves 35 different nations and is based in the south of France at a massive purpose-built complex. ITER was dreamed up in the 1980s, the collaboration formed in 2006 and construction began in 2010, with a focus very much on energy production.

But last year, the project announced that the reactor would not turn on until 2034, nine years later than planned. It has been a slow-moving effort with issues, delays and growing costs. In the meantime, because of recent scientific advances, dozens of private companies have popped up around the world, each hoping to be the first to crack this tricky nuclear fusion powerplant problem.

New Zealand enters the race

"Publicly, you can find about 50 companies, there are probably a few more than that, and we all differ," says Ratu.

"Just like any company in any industry, we all have our kind of unique advantages and our pitch as to why we exist… But the interesting thing is that none of us have a product yet. And so, we're really competing on our choice of technology and our ability to make that technology work."

The US-based Commonwealth Fusion Systems (CFS), a 2018 spinoff from the Massachusetts Institute of Technology, recently hit the headlines when they announced a new agreement with Google. The tech giant signed a power purchase agreement for half of the output of a yet-to-be-built nuclear fusion powerplant that CFS says will be online in the early 2030s.

They use a magnet approach known as a tokamak, where the hydrogen plasma sits inside a doughnut shaped chamber built out of magnets. They have yet to achieve ignition, which they say they are aiming for in 2027.

OpenStar Technologies' unique point of difference is their levitated dipole magnet design, in which a very powerful magnet floats within a vacuum chamber, creating a strong magnetic field that holds the fusion plasma in place.

The vacuum chamber where they run their current experiments looks like a big steel spaceship. Measuring 5.2 metres in diameter, it sits supported by large metal beams in their warehouse space in Ngauranga Gorge. Off to the side is the magnet workshop, where the team can wind superconducting material into coils to build the all-important magnet in-house.

Some of the magnet materials and power supply design that they are using have stemmed from groundbreaking New Zealand research at the nearby Robinson Research Institute. Several of OpenStar Technologies' 60 staff members have previously trained or worked there. Ratu himself completed his PhD there, in superconducting magnet science.

In their levitating dipole magnet plan, a magnet attached to the top of the chamber attracts the core magnet by a 'goldilocks' amount - not too much, not too little, so that it floats within the chamber.

Hydrogen isotope fuel is put into the chamber, heated to create plasma, and then the plasma is held in a halo by the magnetic field of the core magnet while more heat energy is added, until fusion is achieved.

The team reached a major milestone last year, called 'first plasma'. In late October they created a helium plasma in the chamber and heated and constrained it at 300,000 °C for 20 seconds using a supported magnet. Their next step is to attempt this again, but with the magnet fully levitating.

There is still a long way to go, but Ratu believes they are well in the race. "We think that we can effectively catch up to where some of the other concepts are as long as we can keep moving fast enough and make the progress that we need to."

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