What is the primary function of the RAR?

The primary function of the Reactor Auxiliary System (RAR) is to produce steam and facilitate the interaction between the reactors and the steam generators. This system is critical for the operation of a nuclear propulsion plant, where the reactor generates heat through nuclear fission. That heat is then used to generate steam, which drives the turbines that propel the ship. The RAR enables efficient steam generation by managing the flow and processing of water and steam between the reactor and steam generators, ensuring that the propulsion system operates effectively under various conditions.

In contrast, the other choices focus on functions that do not accurately reflect the role of the RAR. While a backup power source is important for many systems aboard a ship, it is not the primary function of the RAR. Similarly, while controlling ship navigation and providing repair facilities for reactors are crucial for overall ship operations and maintenance, these tasks are not within the purview of the RAR's intended design and responsibilities. Thus, the correct choice accurately encapsulates the essential function of the RAR in the nuclear propulsion system.