Livio Bettinali

DESIGN ISSUES OF THE PRE‐COMPRESSION RINGS OF ITER

The pre‐compression system is the keystone of ITER. A centripetal force of ∼30 MN will be applied at cryogenic conditions on top and bottom of each TF coil. It will prevent the ‘breathing effect’ caused by the bursting forces occurring during plasma operation that would affect the machine design life of 30000 cycles. Different alternatives have been studied throughout the years. There are two major design requirements limiting the engineering possibilities: 1) the limited available space and 2) the need to hamper eddy currents flowing in the structures. Six unidirectionally wound glass‐fibre composite rings (∼5 m diameter and ∼300 mm cross section) are the final design choice. The rings will withstand the maximum hoop stresses <500 MPa at room temperature conditions. Although retightening or replacing the pre‐compression rings in case of malfunctioning is possible, they have to sustain the load during the entire 20 years of machine operation. The present paper summarizes the pre‐compression ring R&D carri...

Experience and lessons from the JET 4.0 T assessment

Raising the JET maximum toroidal field from 3.45 to 4.0 T results in increased forces and stresses in the key machine components during normal operations and disruptions. These forces and stresses have been predicted for 4.0 T operation and compared with allowable values derived from tests on used and spare JET coils. In this assessment significant lessons related to the design, manufacture and operation of key Tokamak components have also been learnt.