The first of the reactors built by INVAP was the RA-6 Reactor. This facility was built in San Carlos de Bariloche on the premises of the Centro Atómico Bariloche belonging to the Argentine Nuclear Authority, the CNEA. This 500 kW thermal power reactor for research and training was inaugurated in 1982. It is an MPR type open-pool reactor, designed to use 20% enriched Uranium fuel, and is moderated and cooled by light water.

Its operation is simple, the design is safe and the cost was moderate. It is operated, maintained, reformed and repaired by its own personnel, which includes Nuclear Engineering students of the Balseiro Institute of Physics and Nuclear Engineering.

The reactor building consists of two separate units, each constructed in compliance with seismic structural regulations which apply to the construction site. One of the buildings houses the reactor while the other houses the ancillary systems, laboratories and other facilities.

The starting point for RA6 was a basic design by the Reactor Design Department of CNEA. From that point on, INVAP was responsible for managing the construction of the reactor. INVAP designed and made key systems for the reactor, including all the components pertaining to the electronic control chains, both nuclear and conventional, the instrument bridge, the mechanics of the control rod movement, as well as the neutron and gamma detection systems.