Iter: five years of delay in sight for the construction of the nuclear fusion reactor

Iter: five years of delay in sight for the construction of the nuclear fusion reactor
Iter: five years of delay in sight for the construction of the nuclear fusion reactor

Posted Nov 24, 2022 12:37 PMUpdated Nov. 24, 2022, 4:41 p.m.

Same causes, same effects: as on the Flamanville EPR, welding defects are in turn undermining the international Iter programme. Suspected by the Nuclear Safety Authority (ASN) in January, these anomalies have just been confirmed by Iter Organization, the coordinating body for the gigantic construction site of the experimental nuclear fusion reactor located in Cadarache in the Bouches-du- Rhone.

The problem was identified on two key components of the installation delivered by South Korea and installed at the bottom of an inaccessible area. It requires taking out an 18-meter-high sector weighing 1,350 tonnes, dismantling the assembly and repairing or repairing the defective parts.

In a press release, the new general manager of Iter, Pietro Barabaschi, has already estimated that the consequences in terms of schedule and cost “will not be negligible”. The experts evoke a delay of at least two years, which is added to an additional period of 35 months granted by the Iter council meeting last week, due to the impact of the health crisis and the war. The additional cost has not yet been quantified, but, depending on the options chosen, it could increase the bill by more than one billion euros on a budget which has already more than tripled (20 billion euros according to the latest estimates ).

Design issue

The engineers will indeed have to review their copy. Because it is a problem of design even of the way in which the welds are carried out which is at the origin of these difficulties. The defective part is the first of the 9 sectors making up the circular vacuum chamber which must confine the plasma at 150 million degrees resulting from the nuclear reaction. It consists of three sectors: a vacuum chamber, heat shields and superconducting magnets which contain the assembly. The first two are problematic.

In the vacuum chamber, the welds caused a larger structural deformation than had been anticipated, preventing the assembly of the other parts of the ring to come. On the thermal protection screens, chlorine particles used to clean the surfaces remained trapped in the silver protective layer, causing corrosion cracks over a few millimeters on the cooling circuit.

As a precaution, Pietro Barabaschi announced that the magnet coils – which have not been identified as defective – would be tested before being installed. A new vacuum cryogenic chamber will therefore have to be installed. Its cost and development time are currently being assessed.

Cascading problems

These new difficulties add another stone to the management of this site, which has been battered for several months. In a letter dated February, the ASN notably asked Iter Organization for clarifications on the calculations concerning the facility’s radiological shielding devices. “The elements transmitted concerning the radiological maps do not make it possible to demonstrate control of the limitation of exposure to ionizing radiation, a major issue for a nuclear fusion installation”, estimated the regulator.

According to Michel Claessens, former spokesperson for Iter, now retired, “the tightness of the reactor is compromised” due to structural defects on the walls and the very foundations of the three nuclear buildings. “Radiation protection could be reduced by a third,” he says. However, it is not certain that the slab, designed to support a load of 400,000 tonnes, can support an additional sealing load without breaking.

The costing of all these repairs will be presented to the member nations of Iter (European Union, China, India, Japan, Korea, Russia, United States) at the next Council meeting scheduled for June. Meeting last week, they unanimously renewed their commitment.

The article is in French

Tags: Iter years delay sight construction nuclear fusion reactor

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