Lifecycle of the ESS Moderator and Reflector System

The European Spallation Source (ESS) will be a 5 MW class spallation neutron research facility. An important part of the target station is the Moderator and Reflector (MR) System including structure and handling. The primary function of the MR Plugs is to efficiently reflect and moderate fast neutrons from the spallation target to thermal and cold neutrons suitable for the neutron scattering systems. However, the MR System need to fulfil many operational functions as well, which include cooling of radiation heat in liquid and metal bodies, positioning and structural support, capability of handling of active components and confinement, shielding and avoidance of streaming. Depending on the design, the accumulated neutron flux and irradiation induced material degradation mechanism limit the lifetime of the MR Plug. At full beam power of 5 MW, the MR Plugs need to be changed yearly. That imposes high demands on logistics, manufacturing and handling on the system. This paper presents the lifetime criteria of the MR System, in view of radiation induced material degradation. The complete MR System lifecycle is presented, which ranges from purchase of raw materials (aluminium alloy, stainless steel and beryllium), manufacturing, factory acceptance test FAT), transport, delivery control, pre-installation test until a new MR System is ready for installation.