Lawrence Livermore lab repeats fusion breakthrough – yep, still kinda works

Researchers at the Lawrence Livermore National Laboratory in California have repeated their breakthrough fusion experiment, which nominally produced more energy than it consumed.

The US security-linked institution claimed a world-first in December last year when it produced 3.15 megajoules of fusion energy as output, exceeding the 2.05 megajoules delivered by the 192 lasers that kickstarted the nuclear fusion reaction.

Researchers have since been working to refine the technique and learn more about the field. On July 30, it repeated the feat. "As is our standard practice, we plan on reporting those results at upcoming scientific conferences and in peer-reviewed publications," a spokesperson told the Financial Times.

The most recent experiment achieved a higher energy yield than the earlier breakthrough, the institution said.

The lab's National Ignition Facility (NIF) relies on laser fusion – as opposed to the magnetic confinement fusion approach used elsewhere – whereby 192 lasers focus on a cylindrical container or hohlraum. This 120mm x 6mm jar converts laser energy into x-rays which heat a tiny plasma capsule at its center. The capsule's high-density carbon (diamond) walls are 80μm (micrometers) thick and houses the nuclear fuel, a mixture of hydrogen isotopes deuterium and tritium.

The breakthrough has attracted global attention as the world struggles to find clean energy alternatives to damaging fossil fuels on which global economies rely.

Such enthusiasm must be tempered by the fact that the energy from the reaction is only greater than the laser energy entering the capsule, rather than the total energy required to run the facility, which could be a hundred times more.

Since the 1950s, the world has been waiting for cheap, clean and abundant power resulting from nuclear fusion, the process of combining lighter atoms into heavier ones, which releases energy via the strong nuclear force. As the saying goes, the practical application of the technology seems to remain 20 years into the future, although there has been a heightened interest in the field in the last couple of years.

• Beyond the hype, AI promises leg up for scientific research
• Aspiration to deploy new UK nuclear reactor every year a 'wish', not a plan
• A room-temperature, ambient-pressure superconductor? Take a closer look
• UK's dream of fusion power by 2040s will need GPUs

If the aim is a viable energy source – the NIF project is a physics experiment – then there are other hurdles to overcome regarding scale, reliability, and affordability.

Dame Sue Ion, former chair of the UK Nuclear Innovation Research Advisory Board, told Parliament last year: "There's a difference between confidence that it will work and confidence that it will work 24 hours a day, seven days a week, 365 days a year and satisfy an economic environment in which it's got to live."

While nuclear fusion still needs to overcome considerable barriers before it is a viable energy source, nuclear fission continues to develop and merit attention, at least from some investors. Microsoft co-founder and philanthropist Bill Gates is the biggest investor in UK startup TerraPower, which achieved a $750 million funding round last year.

The company claims its Natrium technology is one of the lowest-cost paths to advanced clean energy and promises a 345MW_e reactor that can be optimized for specific markets. It also uses a molten salt energy storage system to compensate for grid shortages owing to the variability of renewable energy such as wind and solar. ®