IIt was a project that promised the Sun: researchers would use some of the most cutting-edge technology in the world to design machines capable of generating atomic fusion, the process that powers stars, to create a cheap, non-polluting source of electricity.

This was originally the purpose of the International Thermonuclear Experimental Reactor (Iter). Thirty-five countries, including European countries, China, Russia and the United States, agreed to build the reactor in Saint-Paul-lès-Durance in the south of France at an initial cost of $6 billion. Work began in 2010, with the promise of producing an energy-producing reaction by 2020.

Then reality set in: Cost overruns, the coronavirus, corrosion of key components, last-minute redesigns, and disputes with nuclear safety regulators have caused delays, and it was just announced that ITER won’t be ready for another decade. To make matters worse, the energy-producing fusion reaction won’t occur until 2039, adding another $5 billion to ITER’s already ballooning $20 billion budget.

Other estimates put the final cost much higher, the magazine said, potentially making ITER “the most delayed and costly scientific project in history.” Scientific American On the other hand, the journal Science It said only that ITER was currently facing “major problems”. Nature It noted that the project “has been plagued by a series of delays, cost overruns and management problems.”

Scientists warn that dozens of private companies are now threatening to develop fusion reactors on a shorter timeline, including Oxford-based Tokamak Energy and the US company Commonwealth Fusion Systems.

“The problem is that ITER has been going for so long and suffered so many delays that the rest of the world has moved on,” said Robbie Scott, a nuclear fusion expert at the UK Science and Technology Facilities Council. “A lot of new technology has come along since ITER was planned, and that has left the project with serious problems.”

Question marks now hang over the world’s most ambitious technological project, which seeks to understand the process that powers stars, in which two light atomic nuclei combine to form one heavy one, releasing a huge amount of energy – nuclear fusion, which only occurs at very high temperatures.

To generate this heat, doughnut-shaped reactors called tokamaks use magnetic fields to confine a plasma of hydrogen nuclei, then bombard it with particle beams and microwaves. When temperatures reach millions of degrees Celsius, a mixture of two hydrogen isotopes (deuterium and tritium) fuses to form helium, neutrons, and a huge amount of excess energy.

Containing plasma at such high temperatures is extremely difficult. “The original plan was to line the tokamak reactor with beryllium as a protective covering, but this proved extremely difficult and because beryllium is toxic, they ultimately decided to replace it with tungsten,” says David Armstrong, professor of materials science and engineering at the University of Oxford. “This was a major late design change.”

Then, after it was discovered that huge parts of the South Korean-made tokamak had not been fitted together properly, threatening to leak radioactive material, French nuclear regulators ordered construction of the plant halted. Further delays were announced as problems mounted.

Then came COVID-19. “The pandemic caused factories supplying components to close, resulting in related workforce cuts, backlogs in shipments and difficulties in carrying out quality-control inspections,” ITER Secretary General Pietro Barabaschi acknowledged.

So ITER has once again delayed completion until another decade. At the same time, researchers using other approaches to nuclear fusion are making breakthroughs. In 2022, the US National Ignition Facility in California announced that it had used a laser to superheat deuterium and tritium and fuse them to produce helium and surplus energy, which is ITER’s goal.

Other fusion projects also claim they too could soon achieve breakthroughs. “The past decade has seen a proliferation of private fusion companies promising to do things differently from ITER – faster, cheaper – and, to be fair, some of them have likely overpromised,” said Brian Aperbe, a research physicist at Imperial College London.

It remains to be seen whether ITER will weather these crises and whether backers will continue to fund it. Observer He argued that there was still promising work left to be done.

One example is research into how to produce tritium, a rare hydrogen isotope essential for fusion reactors. It can be made by bombarding lithium samples with neutrons produced in a fusion reactor, producing helium and tritium in the process. “That’s a worthwhile experiment in itself,” Aperbe said.

But it rejected claims ITER was “hugely problematic” and dismissed the notion it was a record-breaking science project in terms of cost overruns and delays – just look at the International Space Station or Britain’s HS2 rail link, a spokesman said.

Some have pointed out that fusion power’s limited carbon emissions could help the fight against climate change. “But fusion will be too slow to reduce carbon emissions in the short term,” says Aneeka Khan, a fusion researcher at the University of Manchester. “Only once fusion power plants are producing significant amounts of electricity later in the century will they help curb carbon emissions, which will be crucial in the fight against climate change.”