A logistical simulation tool to quantitatively evaluate the effect of different maintenance solutions on the total maintenance downtime for fusion reactors

Abstract The goal of the DEMO project is to demonstrate that a profitable nuclear fusion power plant is viable. The high level of neutron activation, however, implies time-consuming maintenance processes occurring during the reactor shutdown, which lower the reactor availability and economic viability. As part of the design process, different concepts are continuously proposed and quantitatively evaluated to optimise the plant performance, a key component of which is maintenance duration. One accurate way to quantitatively evaluate and compare different concepts is to simulate the occurrence of the maintenance activities across the time with a logistical simulation tool. This work aims to present the logistical simulation tool, which has been developed within the DEMO project, along with the methodology used to quantitatively evaluate and compare maintenance concepts. We use the self-developed methodology to assess two example concepts. The first one, called Cask Concept, is based on the utilization of vertical maintenance system casks to replace the In-Vessel components. The casks are remote handling containers that are docked on the upper ports of the machine and provide the interface to extract and insert the pieces of hardware without contamination of the area above the upper ports. The second one, called Hot Cell Concept, is based on an overhead crane system situated above the upper ports of the tokamak using the complete area as a Hot Cell. The results show clear and interesting differences between the two concepts and demonstrate the relevance of the developed methodologies to assessing maintenance durations for new or modified plant concepts.