AbstractThe ARIES-RS tokamak power plant study developed a design approach which has the potential for high availability. One of the keys for high plant availability is a design that allows rapid replacement of the power core sectors. This is achieved by using large maintenance ports for each power core sector, enabling the removal of entire sectors composed of inboard and outboard blankets, neutron shields, and upper and lower divertors. Another important feature is the location of all connections to the cooling system inside the port area and outside the plasma chamber, avoiding contamination of the chamber by coolant leaks or handling operations. Any spread of radioactive particles (e.g. tritium or dust) is avoided by the use of flasks for the transfer of used sectors to the hot cells and return of new or refurbished sectors. It is estimated that the impact on availability is less than 5% for scheduled maintenance of the power core.