(Bloomberg) -- Cracks in a key silver-lined component are creating new delays and cost overruns in the $23 billion project to prove whether nuclear fusion can generate limitless clean energy.

The International Thermonuclear Experimental Reactor, or ITER, under construction in southern France is being funded by the European Union and countries including China, India, Japan, Russia and South Korea. The world’s biggest experiment aims to show that mimicking the power that makes stars shine can produce clean energy that could help slow global warming on Earth.

But new ITER Director-General Pietro Barabaschi warned members this week the project faces problems that are potentially “extensive,” along with new requirements for time and money that “will not be insignificant.” 

The project has been plagued by unexpected challenges over the past 12 months. Just as it started sorting out logistics disrupted by the pandemic, Moscow’s invasion of Ukraine complicated the supply of critical components manufactured in Russia. In May, the project’s long-time chief Bernard Bigot died. The first task of his replacement, the Italian engineer Barabaschi, has been to investigate problems that will prevent the reactor from starting up in 2025. 

At issue are two South Korean-made components: thermal shields built by SFA Engineering Corp. and vacuum vessel sectors made by Hyundai Heavy Industries Co. Neither company responded to Bloomberg requests for comment outside of business hours. 

The thermal shield, which is lined with 5 tons of pure silver and designed to contain heat 10 times hotter than the sun, showed cracks along cooling pipes, ITER reported. The vacuum vessel sectors, each weighing the equivalent of 300 cars and as tall as a telephone pole, show slight differences in manufacturing that complicates the welding process used to put them together. 

So far, ITER’s governing board has taken the setbacks in its stride. At an extraordinary meeting convened this month, it ordered Barabaschi to come up with a new budget and time line to be presented next year. 

“What was remarkable at the ITER council was the lack of finger pointing,” ITER spokesman Laban Coblentz said Friday in an interview. “It has been a very solutions-oriented discussion.”

More than 10 kilometers (6.2 miles) of pipe will need to be ripped out and reassembled on site, with engineers forced to figure out new ways of putting together the dizzyingly complex reactor. More than a million individual pieces have been commissioned to go into the project, which ITER figured was close to 70% complete before the defects were discovered. 

The delay at ITER will give a new generation of closely held fusion startups time to catch up. Bill Gates, Jeff Bezos and Peter Thiel are among a group of billionaires pursuing fusion privately. The National Academies of Science this year called on the US to accelerate plans to build a pilot fusion reactor capable of generating electricity by 2035. 

“Companies have been learning enormously from this first-of-its kind project,” said ITER’s Coblentz, dismissing suggestions that the delays could dampen enthusiasm. “The goal here isn’t to build just a single machine but to show that fusion power is feasible and to make that happen.”

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