The accelerator is the first step of the accelerator driven system (ADS). A high power continuous wave accelerator is required for ADS applications. An essential aspect of accelerator for ADS is beam availability. It must be an order of magnitude better than current best systems. High availability may be achieved by fault tolerance and redundancy of the accelerator. Three factors play a key role here: use of components in a high MTBF regime, parallel and serial redundancy of components, ability to repair failing elements. In terms of accelerator controls system (CS) EPICS and Linux is chosen as proven technology. High availability will be achieved through making parts of the CS redundant. Subsystems shall be redundant by design. If failure of a subsystem is detected, pre-defined scenarios should kick-in. System model or "virtual accelerator" can be implemented to predict effects of parameter change, determine required configuration of set points for optimal performance or re-configuration in case of sub-system failure. Implementation of predictive diagnostics can harvest large amount of data created by archiving service. Prediction of failure allows for controlled shutdown as opposed to abrupt stop. ADS MYRRHA is a research reactor conceived as an Accelerator Driven System (ADS) and constituted by a subcritical core fed by an external neutron source. This source is obtained by spallation reaction through a high power proton accelerator, a superconducting LINAC, accelerating a high current proton beam up to 600 MeV. The MYRRHA project [1] aims to demonstrate the feasibility of the ADS concept and the operability of a safe and efficient long-lived radioactive waste transmuter, and moreover, to establish a multipurpose and flexible irradiation facility based on a fast neutron source. The most significant accelerator design requirements [2] include the Continuous Wave (CW) delivery of a high power beam accompanied to an outstanding design specification of 250 hours as Mean Time Between Failures (MTBF) being a failure a beam trip longer than 3 s corresponding to less than 10 failures over a 3 month operation cycle. The allowed beam trip frequency is significantly lower than observed on today's state-of-the-art comparable accelerators [3], therefore the issue of reliability is considered the main design challenge. Fault tolerance capability is addressed by design, implementing redundancy in both parallel and series manners: the parallel scenario is mandatory in the injector, while the serial scheme (replacing a missing element's functionality by retuning adjacent elements with equivalent functionalities) can be accomplished where high degree of modularity of the accelerating and focusing structures is present (main superconducting accelerator section). Reliability is increased with exploitation of components far from their performance limits, with adoption of reliable diagnostics and powerful and fast controls for fault detection and quick machine reconfiguration. Provisions for online repairability and short Mean Time to Repair (MTTR) are required to guarantee high system availability. CS A general-purpose control system is computer-based, hence consists of software and hardware. In the case of MYRRHA, special attention needs to be given to reliability.