Three research reactors are currently in operation in Germany – one of them is in Mainz and is celebrating its 50th anniversary this year. On August 3, 1965, Fritz Straßmann commissioned the facility on the grounds of Johannes Gutenberg University Mainz (JGU) for the first time. Routine operation began in 1967 with the official inauguration by Nobel laureate Otto Hahn. Since then, hundreds of scientists from Germany and all over the world have come to the reactor with the strong neutron source to conduct basic research in nuclear chemistry, nuclear physics and physics. Some of these academic papers are unique in the world. The Mainz Institute of Nuclear Chemistry celebrated its anniversary with around 200 guests from science and politics, looking back over the past 50 years, but also looking forward.

The TRIGA Mark II research reactor, as it is officially known, has been in use 200 days a year since 1967. In continuous operation, it can be operated with a maximum thermal output of 100 kilowatts. Measured by this, TRIGA Mainz is one of the smallest research reactors in the world. The output is around 30,000 times smaller than that of a typical nuclear power plant. In addition to continuous operation, however, pulsed operation is also possible, in which a peak output of 250,000 kilowatts is achieved for around 30 milliseconds. This produces blue Cherenkov radiation, caused by charged particles that move faster than light in the water-filled reactor pool. The bluish Cherenkov glow, the characteristic feature of the reactor, will often be seen in the future.

The TRIGA Mainz has been pulsed around 20,000 times since its inception. Apart from a brief conversion phase in 1995 to renew the cooling circuits, it has run without interruption. Due to the fuel material used, passing a special alloy with less than 20 percent uranium-235, the reactor type is inherently safe, i.e. uncontrollable chain reactions or a core meltdown are physically impossible. Following the reactor accident in Fukushima, additional safety checks were carried out in 2012 with the result that the research reactor poses no risk to the population.

TRIGA Mainz is used as a neutron source for precision experiments in nuclear chemistry, nuclear physics and physics as well as for medical and biological questions. It is also used to analyze solar cells for trace elements or to examine archaeological finds. By irradiating moon dust with neutrons, for example, it has been possible to precisely determine the composition and age of the moon. This sometimes unique work is often carried out in cooperation with partners in Germany and abroad. TRIGA also serves as a training center in nuclear and radiochemistry, radiation protection and reactor physics for scientists, students, teachers, engineers and technicians.

A new chapter in the history of the Mainz research reactor began with its success in the 2012 Federal Excellence Initiative: the TRIGA reactor plays a central role in the approved PRISMA cluster of excellence. The facility is being expanded into a user facility where national and international research units can conduct experiments with very slow, so-called ultracold neutrons (UCN). Mainz has one of the most powerful sources for UCN. A second source is currently being set up together with the Technical University of Munich and is due to go into operation in 2016.

This is not the end of the TRIGA reactor’s range of uses: in the TRIGA-SPEC experiments, also part of the PRISMA cluster of excellence, short-lived atomic nuclei are produced and studied in order to investigate the structure and form of nuclear matter. For many years now, TRIGA has been developing and applying fast separation methods to study short-lived fission products and the so-called superheavy elements produced in particle accelerators in collaboration with the GSI Helmholtz Center for Heavy Ion Research and the Helmholtz Institute Mainz (HIM). The operators, led by operations manager Dr. Christopher Geppert, inform 600 to 800 visitors a year about this and the further use of the facility during public tours.