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

Mechanical support concept of the DEMO breeding blanket

“…On the outboard side up to 16mm are predicted at the equatorial plane. However, the presence of plasma limiters on the outboard side that protrude the BB FW [40] and its relatively large distance to the last closed flux surface of 225mm on the midplane is expected to prevent excessive heat loads on any leading edges of the BB FW.…”

European DEMO first wall shaping and limiters design and analysis status

“…The main candidates are tungsten monoblock PFCs that are cooled by CuCrZr heat sink. The armour will be thick [6] to limit the heat conducted to the heat sink during the transients. According to our current knowledge the CuCrZr heat sink is likely to have an irradiation lifetime (possibly around 1-2 full power years (fpy) [11]) that is lower than the plant life (~6fpy).…”

“…The maximum envisaged heat flux is 5-10 MW/m 2 for tens of seconds (20-60s). During the ramp-up the plasma will touch the OML [6]. We foresee 4 of such limiters periodically placed 90 degrees apart (alternatively it is studied to use only 3 to save equatorial ports).…”

“…Avoiding disruptions and VDEs cannot be guaranteed based on present plasma scenarios. The energy released during the upward VDE is huge: ~1.3 GJ during the thermal quench in ~4 ms [21], followed by the current quench with ~1 GJ within ~250 ms [6]. This enormous heat load would destroy the BB FW.…”

“…This paper focuses on the latest development in the engineering solutions to deal with these events. The physics behind the above transient scenarios in the EU DEMO is detailed in [6].…”