Structural Finite-Element Analysis for Fusion
Finite-element structural codes predict stress, deformation, and fatigue in fusion components under mechanical, thermal, and electromagnetic loads.
The finite-element method
Finite-element analysis divides a component into a mesh of small elements, approximates the displacement field within each, and assembles the elements into a large system of equations enforcing equilibrium. Solving it yields the stress and deformation everywhere, letting engineers check that a component stays within material limits.
Fusion-specific loads
- Electromagnetic forces from currents in fields, especially during disruptions
- Thermal stress from steep temperature gradients and cyclic heating
- Coolant pressure and dead weight in large structures
- Neutron-induced swelling and property changes over the component life
Coupled analysis
Fusion loads are rarely purely mechanical. Structural codes are coupled to electromagnetic codes that supply the forces from eddy and halo currents, and to thermal codes that supply temperature fields. This multiphysics chain is why structural analysis of a fusion device is more involved than for a conventional pressure vessel.
Fatigue and lifetime
Many components see cyclic loading as the machine pulses. Beyond peak stress, codes assess fatigue: how many cycles a part survives at its stress range. Neutron irradiation complicates this by embrittling and swelling materials, so lifetime assessment couples structural results to irradiation-damage predictions.
Verification
Structural predictions are checked against analytic solutions for simple cases, mesh-refinement studies for numerical convergence, and, where possible, experimental tests. Design codes and standards then apply safety factors to the computed stresses to set allowable loads.
For a device with intense magnetic fields and neutron flux, such as the Hyperion breeder, structural analysis is central to confirming that magnets, vessel, and internals can bear their loads over the intended life.