The executive in charge of the €20bn ($21.9bn) International Thermonuclear Experimental Reactor (Iter) nuclear fusion project in France is hoping to rehire retired engineers, who possess knowledge that is critical to advancing the prospects for development and deployment of fusion reactors.

Pietro Barabaschi, Iter’s director general, told the International Atomic Energy Agency’s Fusion Energy Conference in London: “The knowledge is available somewhere but it is not consolidated. We have to get some retired people on board again.”

“What it takes to integrate a facility like Iter and design it from scratch has been lost,” Barabaschi said.

He said one of the most important outcomes of Iter – the world’s biggest fusion project – will be the consolidation of information.