Description
The TRIGA Mark-II reactor was installed by General Atomic (San Diego, California, USA) in the years 1959 through 1962, and went critical 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 a research reactor of the swimming-pool type that is used for training, research and isotope production.
The reactor 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 20–40°C) and a secondary coolant circuit (ground water at 12–18 °C) the two circuits being separated by a heat exchanger.
Since the moderator has the special property of moderating less efficiently at high temperatures, the
TRIGA-reactor Vienna can also be operated in a pulsed mode (with a rapid power rise to 250 MW for roughly 40 milliseconds). The power rise is accompanied by an increase in the maximum neutron flux density from
1x1013 cm-2s-1 (at 250 kW) to 1x1016 cm~1 (at 250 MW). This negative temperature coefficient of reactivity brings the power level back to approximately 250 kW after the excursion, the maximal pulse rate being 12 per hour, since the temperature of the fuel elements rises to about 360°C during the pulse and, therefore, the fuel is subjected to strong thermal stress.
