The TRIGA Mark II reactor was installed by General Atomic (San Diego, California, USA) in the years 1959 through 1962, and went into operation for the first time on march 7, 1962. Operation of the reactor since that time has averaged 220 days per year, without any long outages.

The TRIGA-reactor is purely a research reactor of the swimming-pool type that is used for training, research and isotope production (Training, Research, Isotope Production, General Atomic = TRIGA). Throughout the world there are about 38 TRIGA-reactors in operation, Europe alone accounting for 8 of them. The TRIGA-reactor Vienna has a maximum continuous power output of 250 kW (thermal). The heat produced is released into a channel of the river Danube via a primary coolant circuit (deionized, distilled water at temperatures between 20 and 30 °C) and a secondary coolant circuit (ground water at temperatures between 12 and 18 °C), the two circuits being separated by a heat exchanger.