Equatorial electron cyclotron port plug neutronic analyses for the EU DEMO

Abstract

Within the Power Plant Physics and Technology (PPPT) programme in the EUROfusion Consortium design activities are currently in progress for the development of a DEMOnstration Fusion Power Plant (DEMO). The design of the machine and the integration of in-vessel components require neutronics analyses to verify the tritium selfsufficiency, the shielding requirements, and the structural integrity of its components. In particular, the effect of penetrations in the blanket and in equatorial port plug introduced by the electron cyclotron (EC) heating system, namely due to openings for the antenna waveguides (WGs), were analyzed. In this study three-dimensional MCNP calculations were conducted for the pre-conceptual designs of the EC port plugs and shielding optimization were performed in order to ensure that the DEMO design limits are not exceeded. Two configurations of the EC heating system were performed using a DEMO Water Cooled Lithium Lead (WCLL) with integrated EC configurations model of a half of the sector (i.e. 10° model) and relevant ones repeated with a full sector model (i.e. 20° model) to test the reliability of results. Additionally, the effect of the radiation on the WGs closest to the plasma was analyzed as well as the impact on Tritium Breeding Ratio (TBR).

EU DEMO EC equatorial launcher pre-conceptual performance studies

“…These dimensions seem not compatible with engineering constraints as the neutron shielding, nuclear heating of toroidal field coils, the TBR and the port occupation. In fact, the analysis performed in [17] for two configurations of RSA without mirrors (considering the gap in BB due to the RSA steering) showed results at the limit or over the acceptable values, in particular for nuclear heating of toroidal field coils. The smallest identified surface identified for the fixed focusing mirror is more than twice larger than the one mentioned in the analysis, therefore we expect a worsening with larger apertures in front of the RSA mirrors.…”

The EU DEMO equatorial outboard limiter — Design and port integration concept

“…The results from the neutron transport calculations shown before are promising. Neutronic studies on other equatorial port plugs approximately verify these results [16]. For the SDDR the situation is different.…”

Integration concept of an Electron Cyclotron System in DEMO

“…A high availability is needed, and for this reason the port plug was designed in a way that the replacement of the M2 mirrors (SMs) is possible without dismantling the waveguides as highlighted in section 7. Also, the figures that are found in [33] give on the mirrors a maximum dpa per fpy of 2.36 dpa, implying 14.2 dpa at DEMO lifetime, after 6 fpy. If a dpa level of 6 dpa would be assumed for the mirror materials as end of life value, this would mean that one would have to replace the mirrors once in the DEMO lifetime, which would be acceptable in terms of the defined requirements.…”