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The International Thermonuclear Experimental Reactor (ITER) project has announced that defects have been found in the thermal shields and vacuum vessel sectors. The project administrators have warned that the consequences on schedule and cost “will not be insignificant”.
Pietro Barabaschi is the director General of ITER. He said, “If there is one good thing about this situation, it is that it is happening at a moment we can fix it. The know-how we are acquiring in dealing with ITER's first-of-a-kind components will serve others when they launch their own fusion ventures. It is in ITER's nature and mission, as a unique and ambitious research infrastructure, to go through a whole range of challenges and setbacks during construction. And it is therefore our task and duty to promptly inform the engaged scientific community so that they will take precautions when dealing with the same type of assemblies.”
ITER is a major international project to build a huge experimental tokamak fusion reactor in Cadarache, France. It is designed to prove the feasibility of fusion as a large-scale and carbon-free source of energy. The goal of ITER is to operate at five hundred megawatts continuously for at least four hundred seconds with fifty megawatts of plasma heating power input. An additional three hundred megawatts of electricity input may be required. No electricity will be generated at ITER.
Thirty-five nations are collaborating to construct ITER. The European Union (EU) is contributing almost half of the cost of its construction. The other six members (China, India, Japan, South Korea, Russia and the USA) are contributing equally to the rest. Construction started in 2010 and the original 2018 first plasma target date was pushed back to 2025 by the ITER council in 2016.
The vacuum vessel thermal shields are about three quarters of an inch thick. They contribute to insulating the superconducting magnet system operating at four degrees Kelvin or minus four hundred and fifty two degrees Fahrenheit. ITER said that in November of last year, helium tests detected a leak on an element of the vacuum vessel thermal shields that were delivered in 2020. The cause of the leak was found to be stress caused by the bending and welding of the cooling fluid pipes to the thermal shield panels “compounded by a slow chemical reaction due to the presence of chlorine residues in some small areas near the pipe welds. This had caused stress corrosion cracking and over time, cracks up to seven hundredths of an inch deep had developed in the pipes.” A total of about fourteen miles of piping are welded to the surface of the thermal shield panels. Investigative techniques including high-resolution CT scanning, scanning electron microscope, energy-dispersive X-ray spectrometer, and metallographic observation revealed cracks in the thermal shield cooling pipes.
There have been serious problems with substandard welds at nuclear reactors in France. Many welds had to be redone. Apparently ITER has inherited the lack of quality controls for welds that has plagued other nuclear projects in welds. Many nations have contributed components to the ITER project, but they are dependent on French welders to do a professional job in welding those components together.
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