The setbacks of the international ITER reactor project

Part of the ITER reactor vacuum chamber, in the assembly hall.

On the pharaonic construction site of the prototype of the ITER nuclear fusion reactor at the Cadarache site (Bouches-du-Rhône), it is not just the workers who are busy. The engineers had to change their priorities to respond quickly to the long list of requests from the Nuclear Safety Authority (ASN), so that the assembly of this unique machine in the world continues on schedule.

ASN’s requests, in the form of a letter addressed by its chairman to the director general of the international organization ITER, were revealed on 21 February by the information site New Energy Times, very critical on fusion energy. The missive is not good news. It indicates that, as it stands, the assembly of the reactor cannot begin, in particular the key and irreversible stage of welding the first two elements together, out of nine, constituting the vacuum chamber 19.4 meters in diameter and 11.4 meters high, in which the fusion reactions must take place.

Unlike nuclear fission, which breaks uranium nuclei to release energy, here, as in stars, light hydrogen nuclei are forced together. For this fusion to take place, it is necessary to bring the nuclei together and heat them to 150 million degrees long enough to produce more energy than that necessary to initiate the reaction. This technique, called “tokamak”, uses intense magnetic fields to confine matter.

The ITER project, decided in 2006 and which brings together six countries and the European Union, must demonstrate the viability of this large-scale solution from 2025, at a construction cost of around 20 billion euros. In 2012, when the ASN agreed to start the work, three so-called “stopping points” were planned as so many appointments to be honored for the continuation of operations. In 2014, for the pouring of the concrete screed (the slab), and in 2016, for the external heating devices, these steps had been completed.

Guarantee safety

But, on January 25, a year after his request for “lifting of the third stopping point”, ITER received the negative response from ASN: “The breakpoint related to the tokamak assembly will not be able to be lifted (…). As a result, the tokamak assembly cannot be engaged. » The latter was to take place “towards the end of 2022”, explains Laban Coblentz, ITER Communications Director. He adds : “The construction site is not stopped. This mail does not interrupt work. This is a usual phase of dialogue with the regulator. It must also be said that we are dealing with a machine which is the first of its kind and which is very complex. »

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