The DEMOnstration fusion power plant (DEMO) is being developed within EUROfusion and one of the challenges is the integration of all the systems into a fusion reactor by designs that meet strict design criteria required for safe and reliable long-term reactor operation. Neutronics analyses are required as an important contribution to this effort.

The work described here has analysed the equatorial port plugs of the electron cyclotron (EC) system in terms of neutronic aspects. The EC port plugs are needed for heating the fusion plasma and for plasma control. Necessary openings in the breeding blanket and port plug structures foreseen for the mm-wave heating beams of microwaves coming from launchers of the EC system in equatorial port plugs are a challenge in terms of neutron shielding. Both the neutron streaming through the EC port and nuclear loads in its critical components like mirrors have to be considered in the system design and integration.