Design of the monorail crane system for remote handling of the ITER neutral beam cell

•The monorail crane system is introduced which is part of the ITER Neutral Beam (NB) Remote Handling (RH) system.•The MCS provides means for lifting and transportation of the components and the RH tools in the NB cell during maintenance period.•The concept of operation of the monorail crane system is described covering the storage in the hot cell complex to the NB cell. Its deployment sequences are described.•The mechanical design of the key subsystems of the monorail crane are described such as the railway, rail switching mechanism, crane trolley, and lifting frame.•The railway is composed of two rails mounted underneath the ceiling of the NB cell. It has eight rail switching mechanisms to direct the crane trolley to various locations.•The crane trolley moves underneath the railway by two long travel units, and lifts a payload by two independent hoisting units.•The electrical design such as the layout of the controller and cable routings are described. This paper describes the preliminary design result of the Monorail Crane System (MCS), which is a subsystem of the ITER Neutral Beam Remote Handling System. Since the concept design of the MCS, the design is elaborated further detail considering new maintenance requirements, updated interfaces with the components to be maintained, and the latest configurations in the NB cell. The main design updates are described as follows. First, the railway is changed from the one monorail with two side reaction rails to a dual rail system, which has better load distribution within the crane trolley and the building mountings. Second, additional railway and a switching mechanism are added between the HNB#1 and #2 to access to the VVPSS components, which are newly added in the NB cell. Third, the mounting of the transversal beams supporting the dual rails onto the embedded plates are updated and further elaborated. Forth, the crane trolley is designed to have independent redundant kinematic chains so that it is recoverable from a single point failure. Fifth, series of braking systems such as a service brake, an auxiliary brake, and an emergency brake are integrated in each kinematic chain to cope with normal and accidental loads. Sixth, seismic uncoupling devices are integrated to protect the mechanical components of the crane itself and the building structure. Lastly, detailed cabling design is implemented from the control cubicle to the locations where the subcomponents are located.