Impact of plasma thermal transients on the design of the EU DEMO first wall protection

The protection of the EU-DEMO first wall (FW) during plasma transients represents one of the main challenges of the current pre-concept design phase. While the present DEMO FW design heat load capability is of the order of ≈1−2 MW/m2 in steady state, this limit is overcome during plasma transients for both normal and off-normal events leading to a plasma-wall contact. A strategy to protect the FW is being developed, considering the inclusion of discrete limiters, designed also to maintain the integrity of their cooling system during transients. The present investigations include electromagnetic modelling and plasma simulations on a list of critical transient events. The plasma equilibria are designed to ensure that the plasma impact, in case of loss of plasma control, is located, when possible, close to maintenance ports, to allow for replacement of the limiters. Charged particles and radiation heat load calculations are performed to evaluate the surface design and the required number of limiters. Finally, simplified thermal analyses are run to verify the integrity of the limiter plasma-facing components, and propose their design.