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Designing the big fridge

-Sabina Griffith

Last week, leaders from various technical sections within the ITER Organization and experts from other international labs convened in Cadarache to take another close look at the design and requirements of the ITER Cryoplant and its cryodistribution system.

"The goal of this exercise was not only to look at the design and main features of the plant, but also to check if the assumptions made concerning the boundary conditions such as operations over time and maintenance intervals are realistic, said the chairman of the review, Guenter Janeschitz. "Experiences with operational features gained at other labs such as CERN thus make valuable contributions to ITER", he explains. "Although the highly flexible heat loads due to magnetic filed variations and the neutron production during operations make fusion machines so much more difficult to handle compared to accelerators", says Janeschitz.

The refrigeration capacity of the ITER Cryogenic System will be equivalent to 65 kW at 4.5 K. The coolant is distributed via a complex cryogenic distribution system, providing the cooling of the superconducting magnets, their current leads, the huge vacuum pumps and many other small components. All loops will use helium as cooling liquid. In addition, a 1300 kW nitrogen plant will provide the 80 K atmosphere to cool down ITER's thermal shields.

Recent results from the physics front recommend that the cooling power of the ITER Cryoplant might have to be increased by 10 kW. Another review is scheduled for later this year in view of the procurement lead times.


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